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IB/srp: Add multichannel support

PATCH In review Bart Van Assche 15 participants 83 messages Oct 7, 2014 – Nov 5, 2014 33 messages not in the archive

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#0 lore raw

v2 cover IB/srp: Add multichannel support

Although the SRP protocol supports multichannel operation, although since considerable time RDMA HCA's are available that support multiple completion vectors and although multichannel operation yields better performance than using a single channel, the Linux SRP initiator does not yet support multichannel operation. Hence this patch series that adds multichannel support to the SRP initiator driver.

The changes compared to the previous version of this patch series are as follows:
* Added a function to the block layer that allows SCSI LLDs to query the blk-mq hardware context index chosen by the block layer. Removed the mq_queuecommand callback again.
* Added support for multiple hardware queues in the TCQ functions in the SCSI core.
* Split a few patches and elaborated the patch descriptions to make it easier to review this patch series.
* Added two new patches: one patch that makes the SRP initiator always use block layer tags and another patch that realizes a micro- optimization, namely elimination of the free requests list.

The patches in this series are:
0001-blk-mq-Use-all-available-hardware-queues.patch 0002-blk-mq-Add-blk_mq_unique_tag.patch 0003-scsi-mq-Add-support-for-multiple-hardware-queues.patch 0004-scsi_tcq.h-Add-support-for-multiple-hardware-queues.patch 0005-IB-srp-Move-ib_destroy_cm_id-call-into-srp_free_ch_i.patch 0006-IB-srp-Remove-stale-connection-retry-mechanism.patch 0007-IB-srp-Avoid-that-I-O-hangs-due-to-a-cable-pull-duri.patch 0008-IB-srp-Introduce-two-new-srp_target_port-member-vari.patch 0009-IB-srp-Separate-target-and-channel-variables.patch 0010-IB-srp-Use-block-layer-tags.patch 0011-IB-srp-Eliminate-free_reqs-list.patch 0012-IB-srp-Add-multichannel-support.patch

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#2 lore raw

PATCH v2 1/12 blk-mq: Use all available hardware queues

In reply to a message not in the archive

Suppose that a system has two CPU sockets, three cores per socket, that it does not support hyperthreading and that four hardware queues are provided by a block driver. With the current algorithm this will lead to the following assignment of CPU cores to hardware queues:

HWQ 0: 0 1
HWQ 1: 2 3
HWQ 2: 4 5
HWQ 3: (none)

This patch changes the queue assignment into:

HWQ 0: 0 1
HWQ 1: 2
HWQ 2: 3 4
HWQ 3: 5

In other words, this patch has the following three effects:
- All four hardware queues are used instead of only three.
- CPU cores are spread more evenly over hardware queues. For the above example the range of the number of CPU cores associated with a single HWQ is reduced from [0..2] to [1..2].
- If the number of HWQ's is a multiple of the number of CPU sockets it is now guaranteed that all CPU cores associated with a single HWQ reside on the same CPU socket.

---
 block/blk-mq-cpumap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
block/blk-mq-cpumap.c +1 -1
index 1065d7c..8e56455 100644
@@ -17,7 +17,7 @@
 static int cpu_to_queue_index(unsigned int nr_cpus, unsigned int nr_queues,
 			      const int cpu)
 {
-	return cpu / ((nr_cpus + nr_queues - 1) / nr_queues);
+	return cpu * nr_queues / nr_cpus;
 }
 
 static int get_first_sibling(unsigned int cpu)
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#33 lore raw

PATCH v2 2/12 blk-mq: Add blk_mq_unique_tag()

In reply to Bart Van Assche

The queuecommand() callback functions in SCSI low-level drivers need to know which hardware context has been selected by the block layer. Since this information is not available in the request structure, and since passing the hctx pointer directly to the queuecommand callback function would require modification of all SCSI LLDs, add a function to the block layer that allows to query the hardware context index.

---
 block/blk-mq-tag.c     | 27 +++++++++++++++++++++++++++
 block/blk-mq.c         |  2 ++
 include/linux/blk-mq.h | 22 ++++++++++++++++++++++
 3 files changed, 51 insertions(+)
block/blk-mq-tag.c +27 -0
index 88d512f..2c63a2b 100644
@@ -592,6 +592,33 @@ int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int tdepth)
 	return 0;
 }
 
+/**
+ * blk_mq_unique_tag() - return a tag that is unique queue-wide
+ * @rq: request for which to compute a unique tag
+ *
+ * The tag field in struct request is unique per hardware queue but not over
+ * all hardware queues. Hence this function that returns a tag with the
+ * hardware context index in the upper bits and the per hardware queue tag in
+ * the lower bits.
+ *
+ * Note: When called for a request that queued on a non-multiqueue request
+ * queue, the hardware context index is set to zero.
+ */
+u32 blk_mq_unique_tag(struct request *rq)
+{
+	struct request_queue *q = rq->q;
+	struct blk_mq_hw_ctx *hctx;
+	int hwq = 0;
+
+	if (q->mq_ops) {
+		hctx = q->mq_ops->map_queue(q, rq->mq_ctx->cpu);
+		hwq = hctx->queue_num;
+	}
+
+	return blk_mq_build_unique_tag(hwq, rq->tag);
+}
+EXPORT_SYMBOL(blk_mq_unique_tag);
+
 ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page)
 {
 	char *orig_page = page;
block/blk-mq.c +2 -0
index df8e1e0..bf1959c 100644
@@ -2018,6 +2018,8 @@ static int blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
  */
 int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
 {
+	BUILD_BUG_ON(BLK_MQ_MAX_DEPTH > 1 << BLK_MQ_UNIQUE_TAG_BITS);
+
 	if (!set->nr_hw_queues)
 		return -EINVAL;
 	if (!set->queue_depth)
include/linux/blk-mq.h +22 -0
index eac4f31..6050a23 100644
@@ -167,6 +167,28 @@ struct request *blk_mq_alloc_request(struct request_queue *q, int rw,
 		gfp_t gfp, bool reserved);
 struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag);
 
+enum {
+	BLK_MQ_UNIQUE_TAG_BITS = 16,
+	BLK_MQ_UNIQUE_TAG_MASK = (1 << BLK_MQ_UNIQUE_TAG_BITS) - 1,
+};
+
+u32 blk_mq_unique_tag(struct request *rq);
+
+static inline u32 blk_mq_build_unique_tag(int hwq, int tag)
+{
+	return (hwq << BLK_MQ_UNIQUE_TAG_BITS) | (tag & BLK_MQ_UNIQUE_TAG_MASK);
+}
+
+static inline u16 blk_mq_unique_tag_to_hwq(u32 unique_tag)
+{
+	return unique_tag >> BLK_MQ_UNIQUE_TAG_BITS;
+}
+
+static inline u16 blk_mq_unique_tag_to_tag(u32 unique_tag)
+{
+	return unique_tag & BLK_MQ_UNIQUE_TAG_MASK;
+}
+
 struct blk_mq_hw_ctx *blk_mq_map_queue(struct request_queue *, const int ctx_index);
 struct blk_mq_hw_ctx *blk_mq_alloc_single_hw_queue(struct blk_mq_tag_set *, unsigned int, int);
 
Signature · 1 line
1.8.4.5
#14 lore raw

PATCH v2 3/12 scsi-mq: Add support for multiple hardware queues

In reply to a message not in the archive

Allow a SCSI LLD to declare how many hardware queues it supports by setting Scsi_Host.nr_hw_queues before calling scsi_add_host().

Note: it is assumed that each hardware queue has a queue depth of shost->can_queue. In other words, the total queue depth per host is (number of hardware queues) * (shost->can_queue).

Cc Christoph Hellwig <[email protected]>
Cc Sagi Grimberg <sagig-VPRAkNaXOzVWk0Htik3J/[email protected]>
---
 drivers/scsi/scsi_lib.c  | 2 +-
 include/scsi/scsi_host.h | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)
drivers/scsi/scsi_lib.c +1 -1
index db8c449..f829c42 100644
@@ -2072,7 +2072,7 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
 
 	memset(&shost->tag_set, 0, sizeof(shost->tag_set));
 	shost->tag_set.ops = &scsi_mq_ops;
-	shost->tag_set.nr_hw_queues = 1;
+	shost->tag_set.nr_hw_queues = shost->nr_hw_queues ? : 1;
 	shost->tag_set.queue_depth = shost->can_queue;
 	shost->tag_set.cmd_size = cmd_size;
 	shost->tag_set.numa_node = NUMA_NO_NODE;
include/scsi/scsi_host.h +4 -0
index cafb260..d38cab9 100644
@@ -638,6 +638,10 @@ struct Scsi_Host {
 	short unsigned int sg_prot_tablesize;
 	unsigned int max_sectors;
 	unsigned long dma_boundary;
+	/*
+	 * In scsi-mq mode, the number of hardware queues supported by the LLD.
+	 */
+	unsigned nr_hw_queues;
 	/* 
 	 * Used to assign serial numbers to the cmds.
 	 * Protected by the host lock.
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#41 lore raw

PATCH v2 4/12 scsi_tcq.h: Add support for multiple hardware queues

In reply to Bart Van Assche

Modify scsi_find_tag() and scsi_host_find_tag() such that these fuctions can translate a tag generated by blk_mq_unique_tag().

Cc Christoph Hellwig <[email protected]>
Cc Sagi Grimberg <[email protected]>
---
 include/scsi/scsi_tcq.h | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)
include/scsi/scsi_tcq.h +11 -8
index e645835..ea1ca9c 100644
@@ -111,18 +111,21 @@ static inline int scsi_populate_tag_msg(struct scsi_cmnd *cmd, char *msg)
 }
 
 static inline struct scsi_cmnd *scsi_mq_find_tag(struct Scsi_Host *shost,
-		unsigned int hw_ctx, int tag)
+						 int unique_tag)
 {
-	struct request *req;
+	u16 hwq = blk_mq_unique_tag_to_hwq(unique_tag);
+	struct request *req = NULL;
 
-	req = blk_mq_tag_to_rq(shost->tag_set.tags[hw_ctx], tag);
+	if (hwq < shost->tag_set.nr_hw_queues)
+		req = blk_mq_tag_to_rq(shost->tag_set.tags[hwq],
+				       blk_mq_unique_tag_to_tag(unique_tag));
 	return req ? (struct scsi_cmnd *)req->special : NULL;
 }
 
 /**
  * scsi_find_tag - find a tagged command by device
  * @SDpnt:	pointer to the ScSI device
- * @tag:	the tag number
+ * @tag:	tag generated by blk_mq_unique_tag()
  *
  * Notes:
  *	Only works with tags allocated by the generic blk layer.
@@ -133,9 +136,9 @@ static inline struct scsi_cmnd *scsi_find_tag(struct scsi_device *sdev, int tag)
 
         if (tag != SCSI_NO_TAG) {
 		if (shost_use_blk_mq(sdev->host))
-			return scsi_mq_find_tag(sdev->host, 0, tag);
+			return scsi_mq_find_tag(sdev->host, tag);
 
-        	req = blk_queue_find_tag(sdev->request_queue, tag);
+		req = blk_queue_find_tag(sdev->request_queue, tag);
 	        return req ? (struct scsi_cmnd *)req->special : NULL;
 	}
 
@@ -174,7 +177,7 @@ static inline int scsi_init_shared_tag_map(struct Scsi_Host *shost, int depth)
 /**
  * scsi_host_find_tag - find the tagged command by host
  * @shost:	pointer to scsi_host
- * @tag:	tag of the scsi_cmnd
+ * @tag:	tag generated by blk_mq_unique_tag()
  *
  * Notes:
  *	Only works with tags allocated by the generic blk layer.
@@ -186,7 +189,7 @@ static inline struct scsi_cmnd *scsi_host_find_tag(struct Scsi_Host *shost,
 
 	if (tag != SCSI_NO_TAG) {
 		if (shost_use_blk_mq(shost))
-			return scsi_mq_find_tag(shost, 0, tag);
+			return scsi_mq_find_tag(shost, tag);
 		req = blk_map_queue_find_tag(shost->bqt, tag);
 		return req ? (struct scsi_cmnd *)req->special : NULL;
 	}
Signature · 1 line
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#22 lore raw

PATCH v2 5/12 IB/srp: Move ib_destroy_cm_id() call into srp_free_ch_ib()

In reply to a message not in the archive

The patch that adds multichannel support into the SRP initiator driver introduces an additional call to srp_free_ch_ib(). This patch helps to keep that later patch simple.

---
 drivers/infiniband/ulp/srp/ib_srp.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)
drivers/infiniband/ulp/srp/ib_srp.c +6 -5
index 62d2a18..d3c712f 100644
@@ -555,6 +555,11 @@ static void srp_free_target_ib(struct srp_target_port *target)
 	struct srp_device *dev = target->srp_host->srp_dev;
 	int i;
 
+	if (target->cm_id) {
+		ib_destroy_cm_id(target->cm_id);
+		target->cm_id = NULL;
+	}
+
 	if (dev->use_fast_reg) {
 		if (target->fr_pool)
 			srp_destroy_fr_pool(target->fr_pool);
@@ -868,7 +873,6 @@ static void srp_remove_target(struct srp_target_port *target)
 	scsi_remove_host(target->scsi_host);
 	srp_stop_rport_timers(target->rport);
 	srp_disconnect_target(target);
-	ib_destroy_cm_id(target->cm_id);
 	srp_free_target_ib(target);
 	cancel_work_sync(&target->tl_err_work);
 	srp_rport_put(target->rport);
@@ -3043,7 +3047,7 @@ static ssize_t srp_create_target(struct device *dev,
 	if (ret) {
 		shost_printk(KERN_ERR, target->scsi_host,
 			     PFX "Connection failed\n");
-		goto err_cm_id;
+		goto err_free_ib;
 	}
 
 	ret = srp_add_target(host, target);
@@ -3067,9 +3071,6 @@ out:
 err_disconnect:
 	srp_disconnect_target(target);
 
-err_cm_id:
-	ib_destroy_cm_id(target->cm_id);
-
 err_free_ib:
 	srp_free_target_ib(target);
 
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#23 lore raw

PATCH v2 6/12 IB/srp: Remove stale connection retry mechanism

In reply to a message not in the archive

Attempting to connect three times may be insufficient after an initiator system tries to relogin, especially if the relogin attempt occurs before the SRP target service ID has been registered. Since the srp_daemon retries a failed login attempt anyway, remove the stale connection retry mechanism.

---
 drivers/infiniband/ulp/srp/ib_srp.c | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)
drivers/infiniband/ulp/srp/ib_srp.c +3 -13
index d3c712f..9608e7a 100644
@@ -904,7 +904,6 @@ static void srp_rport_delete(struct srp_rport *rport)
 
 static int srp_connect_target(struct srp_target_port *target)
 {
-	int retries = 3;
 	int ret;
 
 	WARN_ON_ONCE(target->connected);
@@ -945,19 +944,10 @@ static int srp_connect_target(struct srp_target_port *target)
 			break;
 
 		case SRP_STALE_CONN:
-			/* Our current CM id was stale, and is now in timewait.
-			 * Try to reconnect with a new one.
-			 */
-			if (!retries-- || srp_new_cm_id(target)) {
-				shost_printk(KERN_ERR, target->scsi_host, PFX
-					     "giving up on stale connection\n");
-				target->status = -ECONNRESET;
-				return target->status;
-			}
-
 			shost_printk(KERN_ERR, target->scsi_host, PFX
-				     "retrying stale connection\n");
-			break;
+				     "giving up on stale connection\n");
+			target->status = -ECONNRESET;
+			return target->status;
 
 		default:
 			return target->status;
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#49 lore raw

PATCH v2 7/12 IB/srp: Avoid that I/O hangs due to a cable pull during LUN scanning

In reply to Bart Van Assche

If a cable is pulled during LUN scanning it can happen that the SRP rport and the SCSI host have been created but no LUNs have been added to the SCSI host. Since multipathd only sends SCSI commands to a SCSI target if one or more SCSI devices are present and since there is no keepalive mechanism for IB queue pairs this means that after a LUN scan failed and after a reconnect has succeeded no data will be sent over the QP and hence that a subsequent cable pull will not be detected. Avoid this by not creating an rport or SCSI host if a cable is pulled during a SCSI LUN scan.

Note: so far the above behavior has only been observed with the kernel module parameter ch_count set to a value >= 2.

Cc Sagi Grimberg <[email protected]>
Cc Sebastian Parschauer <[email protected]>
---
 drivers/infiniband/ulp/srp/ib_srp.c | 60 +++++++++++++++++++++++++++++++------
 drivers/infiniband/ulp/srp/ib_srp.h |  1 +
 2 files changed, 52 insertions(+), 9 deletions(-)
drivers/infiniband/ulp/srp/ib_srp.c +51 -9
index 9608e7a..a662c29 100644
@@ -1111,6 +1111,10 @@ static int srp_rport_reconnect(struct srp_rport *rport)
 	int i, ret;
 
 	srp_disconnect_target(target);
+
+	if (target->state == SRP_TARGET_SCANNING)
+		return -ENODEV;
+
 	/*
 	 * Now get a new local CM ID so that we avoid confusing the target in
 	 * case things are really fouled up. Doing so also ensures that all CM
@@ -2607,11 +2611,23 @@ static struct scsi_host_template srp_template = {
 	.shost_attrs			= srp_host_attrs
 };
 
+static int srp_sdev_count(struct Scsi_Host *host)
+{
+	struct scsi_device *sdev;
+	int c = 0;
+
+	shost_for_each_device(sdev, host)
+		c++;
+
+	return c;
+}
+
 static int srp_add_target(struct srp_host *host, struct srp_target_port *target)
 {
 	struct srp_rport_identifiers ids;
 	struct srp_rport *rport;
 
+	target->state = SRP_TARGET_SCANNING;
 	sprintf(target->target_name, "SRP.T10:%016llX",
 		 (unsigned long long) be64_to_cpu(target->id_ext));
 
@@ -2634,11 +2650,26 @@ static int srp_add_target(struct srp_host *host, struct srp_target_port *target)
 	list_add_tail(&target->list, &host->target_list);
 	spin_unlock(&host->target_lock);
 
-	target->state = SRP_TARGET_LIVE;
-
 	scsi_scan_target(&target->scsi_host->shost_gendev,
 			 0, target->scsi_id, SCAN_WILD_CARD, 0);
 
+	if (!target->connected || target->qp_in_error) {
+		shost_printk(KERN_INFO, target->scsi_host,
+			     PFX "SCSI scan failed - removing SCSI host\n");
+		srp_queue_remove_work(target);
+		goto out;
+	}
+
+	pr_debug(PFX "%s: SCSI scan succeeded - detected %d LUNs\n",
+		 dev_name(&target->scsi_host->shost_gendev),
+		 srp_sdev_count(target->scsi_host));
+
+	spin_lock_irq(&target->lock);
+	if (target->state == SRP_TARGET_SCANNING)
+		target->state = SRP_TARGET_LIVE;
+	spin_unlock_irq(&target->lock);
+
+out:
 	return 0;
 }
 
@@ -2982,6 +3013,12 @@ static ssize_t srp_create_target(struct device *dev,
 	target->tl_retry_count	= 7;
 	target->queue_size	= SRP_DEFAULT_QUEUE_SIZE;
 
+	/*
+	 * Avoid that the SCSI host can be removed by srp_remove_target()
+	 * before this function returns.
+	 */
+	scsi_host_get(target->scsi_host);
+
 	mutex_lock(&host->add_target_mutex);
 
 	ret = srp_parse_options(buf, target);
@@ -3044,18 +3081,23 @@ static ssize_t srp_create_target(struct device *dev,
 	if (ret)
 		goto err_disconnect;
 
-	shost_printk(KERN_DEBUG, target->scsi_host, PFX
-		     "new target: id_ext %016llx ioc_guid %016llx pkey %04x service_id %016llx sgid %pI6 dgid %pI6\n",
-		     be64_to_cpu(target->id_ext),
-		     be64_to_cpu(target->ioc_guid),
-		     be16_to_cpu(target->path.pkey),
-		     be64_to_cpu(target->service_id),
-		     target->path.sgid.raw, target->path.dgid.raw);
+	if (target->state != SRP_TARGET_REMOVED) {
+		shost_printk(KERN_DEBUG, target->scsi_host, PFX
+			     "new target: id_ext %016llx ioc_guid %016llx pkey %04x service_id %016llx sgid %pI6 dgid %pI6\n",
+			     be64_to_cpu(target->id_ext),
+			     be64_to_cpu(target->ioc_guid),
+			     be16_to_cpu(target->path.pkey),
+			     be64_to_cpu(target->service_id),
+			     target->path.sgid.raw, target->orig_dgid);
+	}
 
 	ret = count;
 
 out:
 	mutex_unlock(&host->add_target_mutex);
+
+	scsi_host_put(target->scsi_host);
+
 	return ret;
 
 err_disconnect:
drivers/infiniband/ulp/srp/ib_srp.h +1 -0
index e46ecb1..00c7c48 100644
@@ -73,6 +73,7 @@ enum {
 };
 
 enum srp_target_state {
+	SRP_TARGET_SCANNING,
 	SRP_TARGET_LIVE,
 	SRP_TARGET_REMOVED,
 };
Signature · 1 line
1.8.4.5
maintainer
#54 lore raw

PATCH v2 8/12 IB/srp: Introduce two new srp_target_port member variables

In reply to Bart Van Assche

Introduce the srp_target_port member variables 'sgid' and 'pkey'. Change the type of 'orig_dgid' from __be16[8] into union ib_gid. This patch does not change any functionality but makes the "Separate target and channel variables" patch easier to verify.

Cc Sagi Grimberg <[email protected]>
Cc Sebastian Parschauer <[email protected]>
---
 drivers/infiniband/ulp/srp/ib_srp.c | 39 ++++++++++++++++++++++---------------
 drivers/infiniband/ulp/srp/ib_srp.h |  4 +++-
 2 files changed, 26 insertions(+), 17 deletions(-)
drivers/infiniband/ulp/srp/ib_srp.c +23 -16
index a662c29..5685062 100644
@@ -262,7 +262,7 @@ static int srp_init_qp(struct srp_target_port *target,
 
 	ret = ib_find_pkey(target->srp_host->srp_dev->dev,
 			   target->srp_host->port,
-			   be16_to_cpu(target->path.pkey),
+			   be16_to_cpu(target->pkey),
 			   &attr->pkey_index);
 	if (ret)
 		goto out;
@@ -295,6 +295,10 @@ static int srp_new_cm_id(struct srp_target_port *target)
 	if (target->cm_id)
 		ib_destroy_cm_id(target->cm_id);
 	target->cm_id = new_cm_id;
+	target->path.sgid = target->sgid;
+	target->path.dgid = target->orig_dgid;
+	target->path.pkey = target->pkey;
+	target->path.service_id = target->service_id;
 
 	return 0;
 }
@@ -689,7 +693,7 @@ static int srp_send_req(struct srp_target_port *target)
 	 */
 	if (target->io_class == SRP_REV10_IB_IO_CLASS) {
 		memcpy(req->priv.initiator_port_id,
-		       &target->path.sgid.global.interface_id, 8);
+		       &target->sgid.global.interface_id, 8);
 		memcpy(req->priv.initiator_port_id + 8,
 		       &target->initiator_ext, 8);
 		memcpy(req->priv.target_port_id,     &target->ioc_guid, 8);
@@ -698,7 +702,7 @@ static int srp_send_req(struct srp_target_port *target)
 		memcpy(req->priv.initiator_port_id,
 		       &target->initiator_ext, 8);
 		memcpy(req->priv.initiator_port_id + 8,
-		       &target->path.sgid.global.interface_id, 8);
+		       &target->sgid.global.interface_id, 8);
 		memcpy(req->priv.target_port_id,     &target->id_ext, 8);
 		memcpy(req->priv.target_port_id + 8, &target->ioc_guid, 8);
 	}
@@ -2175,8 +2179,8 @@ static void srp_cm_rej_handler(struct ib_cm_id *cm_id,
 			else
 				shost_printk(KERN_WARNING, shost, PFX
 					     "SRP LOGIN from %pI6 to %pI6 REJECTED, reason 0x%08x\n",
-					     target->path.sgid.raw,
-					     target->orig_dgid, reason);
+					     target->sgid.raw,
+					     target->orig_dgid.raw, reason);
 		} else
 			shost_printk(KERN_WARNING, shost,
 				     "  REJ reason: IB_CM_REJ_CONSUMER_DEFINED,"
@@ -2464,7 +2468,7 @@ static ssize_t show_pkey(struct device *dev, struct device_attribute *attr,
 {
 	struct srp_target_port *target = host_to_target(class_to_shost(dev));
 
-	return sprintf(buf, "0x%04x\n", be16_to_cpu(target->path.pkey));
+	return sprintf(buf, "0x%04x\n", be16_to_cpu(target->pkey));
 }
 
 static ssize_t show_sgid(struct device *dev, struct device_attribute *attr,
@@ -2472,7 +2476,7 @@ static ssize_t show_sgid(struct device *dev, struct device_attribute *attr,
 {
 	struct srp_target_port *target = host_to_target(class_to_shost(dev));
 
-	return sprintf(buf, "%pI6\n", target->path.sgid.raw);
+	return sprintf(buf, "%pI6\n", target->sgid.raw);
 }
 
 static ssize_t show_dgid(struct device *dev, struct device_attribute *attr,
@@ -2488,7 +2492,7 @@ static ssize_t show_orig_dgid(struct device *dev,
 {
 	struct srp_target_port *target = host_to_target(class_to_shost(dev));
 
-	return sprintf(buf, "%pI6\n", target->orig_dgid);
+	return sprintf(buf, "%pI6\n", target->orig_dgid.raw);
 }
 
 static ssize_t show_req_lim(struct device *dev,
@@ -2826,11 +2830,15 @@ static int srp_parse_options(const char *buf, struct srp_target_port *target)
 			}
 
 			for (i = 0; i < 16; ++i) {
-				strlcpy(dgid, p + i * 2, 3);
-				target->path.dgid.raw[i] = simple_strtoul(dgid, NULL, 16);
+				strlcpy(dgid, p + i * 2, sizeof(dgid));
+				if (sscanf(dgid, "%hhx",
+					   &target->orig_dgid.raw[i]) < 1) {
+					ret = -EINVAL;
+					kfree(p);
+					goto out;
+				}
 			}
 			kfree(p);
-			memcpy(target->orig_dgid, target->path.dgid.raw, 16);
 			break;
 
 		case SRP_OPT_PKEY:
@@ -2838,7 +2846,7 @@ static int srp_parse_options(const char *buf, struct srp_target_port *target)
 				pr_warn("bad P_Key parameter '%s'\n", p);
 				goto out;
 			}
-			target->path.pkey = cpu_to_be16(token);
+			target->pkey = cpu_to_be16(token);
 			break;
 
 		case SRP_OPT_SERVICE_ID:
@@ -2848,7 +2856,6 @@ static int srp_parse_options(const char *buf, struct srp_target_port *target)
 				goto out;
 			}
 			target->service_id = cpu_to_be64(simple_strtoull(p, NULL, 16));
-			target->path.service_id = target->service_id;
 			kfree(p);
 			break;
 
@@ -3058,7 +3065,7 @@ static ssize_t srp_create_target(struct device *dev,
 	if (ret)
 		goto err_free_mem;
 
-	ret = ib_query_gid(ibdev, host->port, 0, &target->path.sgid);
+	ret = ib_query_gid(ibdev, host->port, 0, &target->sgid);
 	if (ret)
 		goto err_free_mem;
 
@@ -3086,9 +3093,9 @@ static ssize_t srp_create_target(struct device *dev,
 			     "new target: id_ext %016llx ioc_guid %016llx pkey %04x service_id %016llx sgid %pI6 dgid %pI6\n",
 			     be64_to_cpu(target->id_ext),
 			     be64_to_cpu(target->ioc_guid),
-			     be16_to_cpu(target->path.pkey),
+			     be16_to_cpu(target->pkey),
 			     be64_to_cpu(target->service_id),
-			     target->path.sgid.raw, target->orig_dgid);
+			     target->sgid.raw, target->orig_dgid.raw);
 	}
 
 	ret = count;
drivers/infiniband/ulp/srp/ib_srp.h +3 -1
index 00c7c48..8635ab6 100644
@@ -157,6 +157,7 @@ struct srp_target_port {
 	 * command processing. Try to keep them packed into cachelines.
 	 */
 
+	union ib_gid		sgid;
 	__be64			id_ext;
 	__be64			ioc_guid;
 	__be64			service_id;
@@ -173,8 +174,9 @@ struct srp_target_port {
 	int			comp_vector;
 	int			tl_retry_count;
 
+	union ib_gid		orig_dgid;
+	__be16			pkey;
 	struct ib_sa_path_rec	path;
-	__be16			orig_dgid[8];
 	struct ib_sa_query     *path_query;
 	int			path_query_id;
 
Signature · 1 line
1.8.4.5
#24 lore raw

PATCH v2 9/12 IB/srp: Separate target and channel variables

In reply to a message not in the archive

Changes in this patch:
- Move channel variables into a new structure (struct srp_rdma_ch).
- Add an srp_target_port pointer, 'lock' and 'comp_vector' members in struct srp_rdma_ch.
- Add code to initialize these three new member variables.
- Many boring "target->" into "ch->" changes.
- The cm_id and completion handler context pointers are now of type srp_rdma_ch * instead of srp_target_port *.
- Three kzalloc(a * b, f) calls have been changed into kcalloc(a, b, f) to avoid that this patch would trigger a checkpatch warning.
- Two casts from u64 into unsigned long long have been left out because these are superfluous. Since considerable time u64 is defined as unsigned long long for all architectures supported by the Linux kernel.

Cc Sagi Grimberg <sagig-VPRAkNaXOzVWk0Htik3J/[email protected]>
Cc Sebastian Parschauer <[email protected]>
---
 drivers/infiniband/ulp/srp/ib_srp.c | 674 +++++++++++++++++++-----------------
 drivers/infiniband/ulp/srp/ib_srp.h |  64 ++--
 2 files changed, 403 insertions(+), 335 deletions(-)
drivers/infiniband/ulp/srp/ib_srp.c +361 -313
index 5685062..cc0bf83b 100644
@@ -125,8 +125,8 @@ MODULE_PARM_DESC(dev_loss_tmo,
 
 static void srp_add_one(struct ib_device *device);
 static void srp_remove_one(struct ib_device *device);
-static void srp_recv_completion(struct ib_cq *cq, void *target_ptr);
-static void srp_send_completion(struct ib_cq *cq, void *target_ptr);
+static void srp_recv_completion(struct ib_cq *cq, void *ch_ptr);
+static void srp_send_completion(struct ib_cq *cq, void *ch_ptr);
 static int srp_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event);
 
 static struct scsi_transport_template *ib_srp_transport_template;
@@ -283,22 +283,23 @@ out:
 	return ret;
 }
 
-static int srp_new_cm_id(struct srp_target_port *target)
+static int srp_new_cm_id(struct srp_rdma_ch *ch)
 {
+	struct srp_target_port *target = ch->target;
 	struct ib_cm_id *new_cm_id;
 
 	new_cm_id = ib_create_cm_id(target->srp_host->srp_dev->dev,
-				    srp_cm_handler, target);
+				    srp_cm_handler, ch);
 	if (IS_ERR(new_cm_id))
 		return PTR_ERR(new_cm_id);
 
-	if (target->cm_id)
-		ib_destroy_cm_id(target->cm_id);
-	target->cm_id = new_cm_id;
-	target->path.sgid = target->sgid;
-	target->path.dgid = target->orig_dgid;
-	target->path.pkey = target->pkey;
-	target->path.service_id = target->service_id;
+	if (ch->cm_id)
+		ib_destroy_cm_id(ch->cm_id);
+	ch->cm_id = new_cm_id;
+	ch->path.sgid = target->sgid;
+	ch->path.dgid = target->orig_dgid;
+	ch->path.pkey = target->pkey;
+	ch->path.service_id = target->service_id;
 
 	return 0;
 }
@@ -447,8 +448,9 @@ static struct srp_fr_pool *srp_alloc_fr_pool(struct srp_target_port *target)
 				  dev->max_pages_per_mr);
 }
 
-static int srp_create_target_ib(struct srp_target_port *target)
+static int srp_create_ch_ib(struct srp_rdma_ch *ch)
 {
+	struct srp_target_port *target = ch->target;
 	struct srp_device *dev = target->srp_host->srp_dev;
 	struct ib_qp_init_attr *init_attr;
 	struct ib_cq *recv_cq, *send_cq;
@@ -462,15 +464,15 @@ static int srp_create_target_ib(struct srp_target_port *target)
 	if (!init_attr)
 		return -ENOMEM;
 
-	recv_cq = ib_create_cq(dev->dev, srp_recv_completion, NULL, target,
-			       target->queue_size, target->comp_vector);
+	recv_cq = ib_create_cq(dev->dev, srp_recv_completion, NULL, ch,
+			       target->queue_size, ch->comp_vector);
 	if (IS_ERR(recv_cq)) {
 		ret = PTR_ERR(recv_cq);
 		goto err;
 	}
 
-	send_cq = ib_create_cq(dev->dev, srp_send_completion, NULL, target,
-			       m * target->queue_size, target->comp_vector);
+	send_cq = ib_create_cq(dev->dev, srp_send_completion, NULL, ch,
+			       m * target->queue_size, ch->comp_vector);
 	if (IS_ERR(send_cq)) {
 		ret = PTR_ERR(send_cq);
 		goto err_recv_cq;
@@ -506,9 +508,9 @@ static int srp_create_target_ib(struct srp_target_port *target)
 				     "FR pool allocation failed (%d)\n", ret);
 			goto err_qp;
 		}
-		if (target->fr_pool)
-			srp_destroy_fr_pool(target->fr_pool);
-		target->fr_pool = fr_pool;
+		if (ch->fr_pool)
+			srp_destroy_fr_pool(ch->fr_pool);
+		ch->fr_pool = fr_pool;
 	} else if (!dev->use_fast_reg && dev->has_fmr) {
 		fmr_pool = srp_alloc_fmr_pool(target);
 		if (IS_ERR(fmr_pool)) {
@@ -517,21 +519,21 @@ static int srp_create_target_ib(struct srp_target_port *target)
 				     "FMR pool allocation failed (%d)\n", ret);
 			goto err_qp;
 		}
-		if (target->fmr_pool)
-			ib_destroy_fmr_pool(target->fmr_pool);
-		target->fmr_pool = fmr_pool;
+		if (ch->fmr_pool)
+			ib_destroy_fmr_pool(ch->fmr_pool);
+		ch->fmr_pool = fmr_pool;
 	}
 
-	if (target->qp)
-		ib_destroy_qp(target->qp);
-	if (target->recv_cq)
-		ib_destroy_cq(target->recv_cq);
-	if (target->send_cq)
-		ib_destroy_cq(target->send_cq);
+	if (ch->qp)
+		ib_destroy_qp(ch->qp);
+	if (ch->recv_cq)
+		ib_destroy_cq(ch->recv_cq);
+	if (ch->send_cq)
+		ib_destroy_cq(ch->send_cq);
 
-	target->qp = qp;
-	target->recv_cq = recv_cq;
-	target->send_cq = send_cq;
+	ch->qp = qp;
+	ch->recv_cq = recv_cq;
+	ch->send_cq = send_cq;
 
 	kfree(init_attr);
 	return 0;
@@ -552,98 +554,102 @@ err:
 
 /*
  * Note: this function may be called without srp_alloc_iu_bufs() having been
- * invoked. Hence the target->[rt]x_ring checks.
+ * invoked. Hence the ch->[rt]x_ring checks.
  */
-static void srp_free_target_ib(struct srp_target_port *target)
+static void srp_free_ch_ib(struct srp_target_port *target,
+			   struct srp_rdma_ch *ch)
 {
 	struct srp_device *dev = target->srp_host->srp_dev;
 	int i;
 
-	if (target->cm_id) {
-		ib_destroy_cm_id(target->cm_id);
-		target->cm_id = NULL;
+	if (ch->cm_id) {
+		ib_destroy_cm_id(ch->cm_id);
+		ch->cm_id = NULL;
 	}
 
 	if (dev->use_fast_reg) {
-		if (target->fr_pool)
-			srp_destroy_fr_pool(target->fr_pool);
+		if (ch->fr_pool)
+			srp_destroy_fr_pool(ch->fr_pool);
 	} else {
-		if (target->fmr_pool)
-			ib_destroy_fmr_pool(target->fmr_pool);
+		if (ch->fmr_pool)
+			ib_destroy_fmr_pool(ch->fmr_pool);
 	}
-	ib_destroy_qp(target->qp);
-	ib_destroy_cq(target->send_cq);
-	ib_destroy_cq(target->recv_cq);
+	ib_destroy_qp(ch->qp);
+	ib_destroy_cq(ch->send_cq);
+	ib_destroy_cq(ch->recv_cq);
 
-	target->qp = NULL;
-	target->send_cq = target->recv_cq = NULL;
+	ch->qp = NULL;
+	ch->send_cq = ch->recv_cq = NULL;
 
-	if (target->rx_ring) {
+	if (ch->rx_ring) {
 		for (i = 0; i < target->queue_size; ++i)
-			srp_free_iu(target->srp_host, target->rx_ring[i]);
-		kfree(target->rx_ring);
-		target->rx_ring = NULL;
+			srp_free_iu(target->srp_host, ch->rx_ring[i]);
+		kfree(ch->rx_ring);
+		ch->rx_ring = NULL;
 	}
-	if (target->tx_ring) {
+	if (ch->tx_ring) {
 		for (i = 0; i < target->queue_size; ++i)
-			srp_free_iu(target->srp_host, target->tx_ring[i]);
-		kfree(target->tx_ring);
-		target->tx_ring = NULL;
+			srp_free_iu(target->srp_host, ch->tx_ring[i]);
+		kfree(ch->tx_ring);
+		ch->tx_ring = NULL;
 	}
 }
 
 static void srp_path_rec_completion(int status,
 				    struct ib_sa_path_rec *pathrec,
-				    void *target_ptr)
+				    void *ch_ptr)
 {
-	struct srp_target_port *target = target_ptr;
+	struct srp_rdma_ch *ch = ch_ptr;
+	struct srp_target_port *target = ch->target;
 
-	target->status = status;
+	ch->status = status;
 	if (status)
 		shost_printk(KERN_ERR, target->scsi_host,
 			     PFX "Got failed path rec status %d\n", status);
 	else
-		target->path = *pathrec;
-	complete(&target->done);
+		ch->path = *pathrec;
+	complete(&ch->done);
 }
 
-static int srp_lookup_path(struct srp_target_port *target)
+static int srp_lookup_path(struct srp_rdma_ch *ch)
 {
+	struct srp_target_port *target = ch->target;
 	int ret;
 
-	target->path.numb_path = 1;
-
-	init_completion(&target->done);
-
-	target->path_query_id = ib_sa_path_rec_get(&srp_sa_client,
-						   target->srp_host->srp_dev->dev,
-						   target->srp_host->port,
-						   &target->path,
-						   IB_SA_PATH_REC_SERVICE_ID	|
-						   IB_SA_PATH_REC_DGID		|
-						   IB_SA_PATH_REC_SGID		|
-						   IB_SA_PATH_REC_NUMB_PATH	|
-						   IB_SA_PATH_REC_PKEY,
-						   SRP_PATH_REC_TIMEOUT_MS,
-						   GFP_KERNEL,
-						   srp_path_rec_completion,
-						   target, &target->path_query);
-	if (target->path_query_id < 0)
-		return target->path_query_id;
-
-	ret = wait_for_completion_interruptible(&target->done);
+	ch->path.numb_path = 1;
+
+	init_completion(&ch->done);
+
+	ch->path_query_id = ib_sa_path_rec_get(&srp_sa_client,
+					       target->srp_host->srp_dev->dev,
+					       target->srp_host->port,
+					       &ch->path,
+					       IB_SA_PATH_REC_SERVICE_ID |
+					       IB_SA_PATH_REC_DGID	 |
+					       IB_SA_PATH_REC_SGID	 |
+					       IB_SA_PATH_REC_NUMB_PATH	 |
+					       IB_SA_PATH_REC_PKEY,
+					       SRP_PATH_REC_TIMEOUT_MS,
+					       GFP_KERNEL,
+					       srp_path_rec_completion,
+					       ch, &ch->path_query);
+	if (ch->path_query_id < 0)
+		return ch->path_query_id;
+
+	ret = wait_for_completion_interruptible(&ch->done);
 	if (ret < 0)
 		return ret;
 
-	if (target->status < 0)
+	if (ch->status < 0)
 		shost_printk(KERN_WARNING, target->scsi_host,
 			     PFX "Path record query failed\n");
 
-	return target->status;
+	return ch->status;
 }
 
-static int srp_send_req(struct srp_target_port *target)
+static int srp_send_req(struct srp_rdma_ch *ch)
 {
+	struct srp_target_port *target = ch->target;
 	struct {
 		struct ib_cm_req_param param;
 		struct srp_login_req   priv;
@@ -654,11 +660,11 @@ static int srp_send_req(struct srp_target_port *target)
 	if (!req)
 		return -ENOMEM;
 
-	req->param.primary_path 	      = &target->path;
+	req->param.primary_path		      = &ch->path;
 	req->param.alternate_path 	      = NULL;
 	req->param.service_id 		      = target->service_id;
-	req->param.qp_num 		      = target->qp->qp_num;
-	req->param.qp_type 		      = target->qp->qp_type;
+	req->param.qp_num		      = ch->qp->qp_num;
+	req->param.qp_type		      = ch->qp->qp_type;
 	req->param.private_data 	      = &req->priv;
 	req->param.private_data_len 	      = sizeof req->priv;
 	req->param.flow_control 	      = 1;
@@ -722,7 +728,7 @@ static int srp_send_req(struct srp_target_port *target)
 		       &target->srp_host->srp_dev->dev->node_guid, 8);
 	}
 
-	status = ib_send_cm_req(target->cm_id, &req->param);
+	status = ib_send_cm_req(ch->cm_id, &req->param);
 
 	kfree(req);
 
@@ -763,28 +769,31 @@ static bool srp_change_conn_state(struct srp_target_port *target,
 
 static void srp_disconnect_target(struct srp_target_port *target)
 {
+	struct srp_rdma_ch *ch = &target->ch;
+
 	if (srp_change_conn_state(target, false)) {
 		/* XXX should send SRP_I_LOGOUT request */
 
-		if (ib_send_cm_dreq(target->cm_id, NULL, 0)) {
+		if (ib_send_cm_dreq(ch->cm_id, NULL, 0)) {
 			shost_printk(KERN_DEBUG, target->scsi_host,
 				     PFX "Sending CM DREQ failed\n");
 		}
 	}
 }
 
-static void srp_free_req_data(struct srp_target_port *target)
+static void srp_free_req_data(struct srp_target_port *target,
+			      struct srp_rdma_ch *ch)
 {
 	struct srp_device *dev = target->srp_host->srp_dev;
 	struct ib_device *ibdev = dev->dev;
 	struct srp_request *req;
 	int i;
 
-	if (!target->req_ring)
+	if (!ch->req_ring)
 		return;
 
 	for (i = 0; i < target->req_ring_size; ++i) {
-		req = &target->req_ring[i];
+		req = &ch->req_ring[i];
 		if (dev->use_fast_reg)
 			kfree(req->fr_list);
 		else
@@ -798,12 +807,13 @@ static void srp_free_req_data(struct srp_target_port *target)
 		kfree(req->indirect_desc);
 	}
 
-	kfree(target->req_ring);
-	target->req_ring = NULL;
+	kfree(ch->req_ring);
+	ch->req_ring = NULL;
 }
 
-static int srp_alloc_req_data(struct srp_target_port *target)
+static int srp_alloc_req_data(struct srp_rdma_ch *ch)
 {
+	struct srp_target_port *target = ch->target;
 	struct srp_device *srp_dev = target->srp_host->srp_dev;
 	struct ib_device *ibdev = srp_dev->dev;
 	struct srp_request *req;
@@ -811,15 +821,15 @@ static int srp_alloc_req_data(struct srp_target_port *target)
 	dma_addr_t dma_addr;
 	int i, ret = -ENOMEM;
 
-	INIT_LIST_HEAD(&target->free_reqs);
+	INIT_LIST_HEAD(&ch->free_reqs);
 
-	target->req_ring = kzalloc(target->req_ring_size *
-				   sizeof(*target->req_ring), GFP_KERNEL);
-	if (!target->req_ring)
+	ch->req_ring = kcalloc(target->req_ring_size, sizeof(*ch->req_ring),
+			       GFP_KERNEL);
+	if (!ch->req_ring)
 		goto out;
 
 	for (i = 0; i < target->req_ring_size; ++i) {
-		req = &target->req_ring[i];
+		req = &ch->req_ring[i];
 		mr_list = kmalloc(target->cmd_sg_cnt * sizeof(void *),
 				  GFP_KERNEL);
 		if (!mr_list)
@@ -844,7 +854,7 @@ static int srp_alloc_req_data(struct srp_target_port *target)
 
 		req->indirect_dma_addr = dma_addr;
 		req->index = i;
-		list_add_tail(&req->list, &target->free_reqs);
+		list_add_tail(&req->list, &ch->free_reqs);
 	}
 	ret = 0;
 
@@ -869,6 +879,8 @@ static void srp_del_scsi_host_attr(struct Scsi_Host *shost)
 
 static void srp_remove_target(struct srp_target_port *target)
 {
+	struct srp_rdma_ch *ch = &target->ch;
+
 	WARN_ON_ONCE(target->state != SRP_TARGET_REMOVED);
 
 	srp_del_scsi_host_attr(target->scsi_host);
@@ -877,10 +889,10 @@ static void srp_remove_target(struct srp_target_port *target)
 	scsi_remove_host(target->scsi_host);
 	srp_stop_rport_timers(target->rport);
 	srp_disconnect_target(target);
-	srp_free_target_ib(target);
+	srp_free_ch_ib(target, ch);
 	cancel_work_sync(&target->tl_err_work);
 	srp_rport_put(target->rport);
-	srp_free_req_data(target);
+	srp_free_req_data(target, ch);
 
 	spin_lock(&target->srp_host->target_lock);
 	list_del(&target->list);
@@ -906,24 +918,25 @@ static void srp_rport_delete(struct srp_rport *rport)
 	srp_queue_remove_work(target);
 }
 
-static int srp_connect_target(struct srp_target_port *target)
+static int srp_connect_ch(struct srp_rdma_ch *ch)
 {
+	struct srp_target_port *target = ch->target;
 	int ret;
 
 	WARN_ON_ONCE(target->connected);
 
 	target->qp_in_error = false;
 
-	ret = srp_lookup_path(target);
+	ret = srp_lookup_path(ch);
 	if (ret)
 		return ret;
 
 	while (1) {
-		init_completion(&target->done);
-		ret = srp_send_req(target);
+		init_completion(&ch->done);
+		ret = srp_send_req(ch);
 		if (ret)
 			return ret;
-		ret = wait_for_completion_interruptible(&target->done);
+		ret = wait_for_completion_interruptible(&ch->done);
 		if (ret < 0)
 			return ret;
 
@@ -933,13 +946,13 @@ static int srp_connect_target(struct srp_target_port *target)
 		 * back, or SRP_DLID_REDIRECT if we get a lid/qp
 		 * redirect REJ back.
 		 */
-		switch (target->status) {
+		switch (ch->status) {
 		case 0:
 			srp_change_conn_state(target, true);
 			return 0;
 
 		case SRP_PORT_REDIRECT:
-			ret = srp_lookup_path(target);
+			ret = srp_lookup_path(ch);
 			if (ret)
 				return ret;
 			break;
@@ -950,16 +963,16 @@ static int srp_connect_target(struct srp_target_port *target)
 		case SRP_STALE_CONN:
 			shost_printk(KERN_ERR, target->scsi_host, PFX
 				     "giving up on stale connection\n");
-			target->status = -ECONNRESET;
-			return target->status;
+			ch->status = -ECONNRESET;
+			return ch->status;
 
 		default:
-			return target->status;
+			return ch->status;
 		}
 	}
 }
 
-static int srp_inv_rkey(struct srp_target_port *target, u32 rkey)
+static int srp_inv_rkey(struct srp_rdma_ch *ch, u32 rkey)
 {
 	struct ib_send_wr *bad_wr;
 	struct ib_send_wr wr = {
@@ -971,13 +984,14 @@ static int srp_inv_rkey(struct srp_target_port *target, u32 rkey)
 		.ex.invalidate_rkey = rkey,
 	};
 
-	return ib_post_send(target->qp, &wr, &bad_wr);
+	return ib_post_send(ch->qp, &wr, &bad_wr);
 }
 
 static void srp_unmap_data(struct scsi_cmnd *scmnd,
-			   struct srp_target_port *target,
+			   struct srp_rdma_ch *ch,
 			   struct srp_request *req)
 {
+	struct srp_target_port *target = ch->target;
 	struct srp_device *dev = target->srp_host->srp_dev;
 	struct ib_device *ibdev = dev->dev;
 	int i, res;
@@ -991,7 +1005,7 @@ static void srp_unmap_data(struct scsi_cmnd *scmnd,
 		struct srp_fr_desc **pfr;
 
 		for (i = req->nmdesc, pfr = req->fr_list; i > 0; i--, pfr++) {
-			res = srp_inv_rkey(target, (*pfr)->mr->rkey);
+			res = srp_inv_rkey(ch, (*pfr)->mr->rkey);
 			if (res < 0) {
 				shost_printk(KERN_ERR, target->scsi_host, PFX
 				  "Queueing INV WR for rkey %#x failed (%d)\n",
@@ -1001,7 +1015,7 @@ static void srp_unmap_data(struct scsi_cmnd *scmnd,
 			}
 		}
 		if (req->nmdesc)
-			srp_fr_pool_put(target->fr_pool, req->fr_list,
+			srp_fr_pool_put(ch->fr_pool, req->fr_list,
 					req->nmdesc);
 	} else {
 		struct ib_pool_fmr **pfmr;
@@ -1016,7 +1030,7 @@ static void srp_unmap_data(struct scsi_cmnd *scmnd,
 
 /**
  * srp_claim_req - Take ownership of the scmnd associated with a request.
- * @target: SRP target port.
+ * @ch: SRP RDMA channel.
  * @req: SRP request.
  * @sdev: If not NULL, only take ownership for this SCSI device.
  * @scmnd: If NULL, take ownership of @req->scmnd. If not NULL, only take
@@ -1025,14 +1039,14 @@ static void srp_unmap_data(struct scsi_cmnd *scmnd,
  * Return value:
  * Either NULL or a pointer to the SCSI command the caller became owner of.
  */
-static struct scsi_cmnd *srp_claim_req(struct srp_target_port *target,
+static struct scsi_cmnd *srp_claim_req(struct srp_rdma_ch *ch,
 				       struct srp_request *req,
 				       struct scsi_device *sdev,
 				       struct scsi_cmnd *scmnd)
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&target->lock, flags);
+	spin_lock_irqsave(&ch->lock, flags);
 	if (req->scmnd &&
 	    (!sdev || req->scmnd->device == sdev) &&
 	    (!scmnd || req->scmnd == scmnd)) {
@@ -1041,40 +1055,38 @@ static struct scsi_cmnd *srp_claim_req(struct srp_target_port *target,
 	} else {
 		scmnd = NULL;
 	}
-	spin_unlock_irqrestore(&target->lock, flags);
+	spin_unlock_irqrestore(&ch->lock, flags);
 
 	return scmnd;
 }
 
 /**
  * srp_free_req() - Unmap data and add request to the free request list.
- * @target: SRP target port.
+ * @ch:     SRP RDMA channel.
  * @req:    Request to be freed.
  * @scmnd:  SCSI command associated with @req.
  * @req_lim_delta: Amount to be added to @target->req_lim.
  */
-static void srp_free_req(struct srp_target_port *target,
-			 struct srp_request *req, struct scsi_cmnd *scmnd,
-			 s32 req_lim_delta)
+static void srp_free_req(struct srp_rdma_ch *ch, struct srp_request *req,
+			 struct scsi_cmnd *scmnd, s32 req_lim_delta)
 {
 	unsigned long flags;
 
-	srp_unmap_data(scmnd, target, req);
+	srp_unmap_data(scmnd, ch, req);
 
-	spin_lock_irqsave(&target->lock, flags);
-	target->req_lim += req_lim_delta;
-	list_add_tail(&req->list, &target->free_reqs);
-	spin_unlock_irqrestore(&target->lock, flags);
+	spin_lock_irqsave(&ch->lock, flags);
+	ch->req_lim += req_lim_delta;
+	list_add_tail(&req->list, &ch->free_reqs);
+	spin_unlock_irqrestore(&ch->lock, flags);
 }
 
-static void srp_finish_req(struct srp_target_port *target,
-			   struct srp_request *req, struct scsi_device *sdev,
-			   int result)
+static void srp_finish_req(struct srp_rdma_ch *ch, struct srp_request *req,
+			   struct scsi_device *sdev, int result)
 {
-	struct scsi_cmnd *scmnd = srp_claim_req(target, req, sdev, NULL);
+	struct scsi_cmnd *scmnd = srp_claim_req(ch, req, sdev, NULL);
 
 	if (scmnd) {
-		srp_free_req(target, req, scmnd, 0);
+		srp_free_req(ch, req, scmnd, 0);
 		scmnd->result = result;
 		scmnd->scsi_done(scmnd);
 	}
@@ -1083,6 +1095,7 @@ static void srp_finish_req(struct srp_target_port *target,
 static void srp_terminate_io(struct srp_rport *rport)
 {
 	struct srp_target_port *target = rport->lld_data;
+	struct srp_rdma_ch *ch = &target->ch;
 	struct Scsi_Host *shost = target->scsi_host;
 	struct scsi_device *sdev;
 	int i;
@@ -1095,8 +1108,9 @@ static void srp_terminate_io(struct srp_rport *rport)
 		WARN_ON_ONCE(sdev->request_queue->request_fn_active);
 
 	for (i = 0; i < target->req_ring_size; ++i) {
-		struct srp_request *req = &target->req_ring[i];
-		srp_finish_req(target, req, NULL, DID_TRANSPORT_FAILFAST << 16);
+		struct srp_request *req = &ch->req_ring[i];
+
+		srp_finish_req(ch, req, NULL, DID_TRANSPORT_FAILFAST << 16);
 	}
 }
 
@@ -1112,6 +1126,7 @@ static void srp_terminate_io(struct srp_rport *rport)
 static int srp_rport_reconnect(struct srp_rport *rport)
 {
 	struct srp_target_port *target = rport->lld_data;
+	struct srp_rdma_ch *ch = &target->ch;
 	int i, ret;
 
 	srp_disconnect_target(target);
@@ -1124,11 +1139,12 @@ static int srp_rport_reconnect(struct srp_rport *rport)
 	 * case things are really fouled up. Doing so also ensures that all CM
 	 * callbacks will have finished before a new QP is allocated.
 	 */
-	ret = srp_new_cm_id(target);
+	ret = srp_new_cm_id(ch);
 
 	for (i = 0; i < target->req_ring_size; ++i) {
-		struct srp_request *req = &target->req_ring[i];
-		srp_finish_req(target, req, NULL, DID_RESET << 16);
+		struct srp_request *req = &ch->req_ring[i];
+
+		srp_finish_req(ch, req, NULL, DID_RESET << 16);
 	}
 
 	/*
@@ -1136,14 +1152,14 @@ static int srp_rport_reconnect(struct srp_rport *rport)
 	 * QP. This guarantees that all callback functions for the old QP have
 	 * finished before any send requests are posted on the new QP.
 	 */
-	ret += srp_create_target_ib(target);
+	ret += srp_create_ch_ib(ch);
 
-	INIT_LIST_HEAD(&target->free_tx);
+	INIT_LIST_HEAD(&ch->free_tx);
 	for (i = 0; i < target->queue_size; ++i)
-		list_add(&target->tx_ring[i]->list, &target->free_tx);
+		list_add(&ch->tx_ring[i]->list, &ch->free_tx);
 
 	if (ret == 0)
-		ret = srp_connect_target(target);
+		ret = srp_connect_ch(ch);
 
 	if (ret == 0)
 		shost_printk(KERN_INFO, target->scsi_host,
@@ -1167,12 +1183,12 @@ static void srp_map_desc(struct srp_map_state *state, dma_addr_t dma_addr,
 }
 
 static int srp_map_finish_fmr(struct srp_map_state *state,
-			      struct srp_target_port *target)
+			      struct srp_rdma_ch *ch)
 {
 	struct ib_pool_fmr *fmr;
 	u64 io_addr = 0;
 
-	fmr = ib_fmr_pool_map_phys(target->fmr_pool, state->pages,
+	fmr = ib_fmr_pool_map_phys(ch->fmr_pool, state->pages,
 				   state->npages, io_addr);
 	if (IS_ERR(fmr))
 		return PTR_ERR(fmr);
@@ -1186,15 +1202,16 @@ static int srp_map_finish_fmr(struct srp_map_state *state,
 }
 
 static int srp_map_finish_fr(struct srp_map_state *state,
-			     struct srp_target_port *target)
+			     struct srp_rdma_ch *ch)
 {
+	struct srp_target_port *target = ch->target;
 	struct srp_device *dev = target->srp_host->srp_dev;
 	struct ib_send_wr *bad_wr;
 	struct ib_send_wr wr;
 	struct srp_fr_desc *desc;
 	u32 rkey;
 
-	desc = srp_fr_pool_get(target->fr_pool);
+	desc = srp_fr_pool_get(ch->fr_pool);
 	if (!desc)
 		return -ENOMEM;
 
@@ -1223,12 +1240,13 @@ static int srp_map_finish_fr(struct srp_map_state *state,
 	srp_map_desc(state, state->base_dma_addr, state->dma_len,
 		     desc->mr->rkey);
 
-	return ib_post_send(target->qp, &wr, &bad_wr);
+	return ib_post_send(ch->qp, &wr, &bad_wr);
 }
 
 static int srp_finish_mapping(struct srp_map_state *state,
-			      struct srp_target_port *target)
+			      struct srp_rdma_ch *ch)
 {
+	struct srp_target_port *target = ch->target;
 	int ret = 0;
 
 	if (state->npages == 0)
@@ -1239,8 +1257,8 @@ static int srp_finish_mapping(struct srp_map_state *state,
 			     target->rkey);
 	else
 		ret = target->srp_host->srp_dev->use_fast_reg ?
-			srp_map_finish_fr(state, target) :
-			srp_map_finish_fmr(state, target);
+			srp_map_finish_fr(state, ch) :
+			srp_map_finish_fmr(state, ch);
 
 	if (ret == 0) {
 		state->npages = 0;
@@ -1260,10 +1278,11 @@ static void srp_map_update_start(struct srp_map_state *state,
 }
 
 static int srp_map_sg_entry(struct srp_map_state *state,
-			    struct srp_target_port *target,
+			    struct srp_rdma_ch *ch,
 			    struct scatterlist *sg, int sg_index,
 			    bool use_mr)
 {
+	struct srp_target_port *target = ch->target;
 	struct srp_device *dev = target->srp_host->srp_dev;
 	struct ib_device *ibdev = dev->dev;
 	dma_addr_t dma_addr = ib_sg_dma_address(ibdev, sg);
@@ -1292,7 +1311,7 @@ static int srp_map_sg_entry(struct srp_map_state *state,
 	 */
 	if ((!dev->use_fast_reg && dma_addr & ~dev->mr_page_mask) ||
 	    dma_len > dev->mr_max_size) {
-		ret = srp_finish_mapping(state, target);
+		ret = srp_finish_mapping(state, ch);
 		if (ret)
 			return ret;
 
@@ -1313,7 +1332,7 @@ static int srp_map_sg_entry(struct srp_map_state *state,
 	while (dma_len) {
 		unsigned offset = dma_addr & ~dev->mr_page_mask;
 		if (state->npages == dev->max_pages_per_mr || offset != 0) {
-			ret = srp_finish_mapping(state, target);
+			ret = srp_finish_mapping(state, ch);
 			if (ret)
 				return ret;
 
@@ -1337,17 +1356,18 @@ static int srp_map_sg_entry(struct srp_map_state *state,
 	 */
 	ret = 0;
 	if (len != dev->mr_page_size) {
-		ret = srp_finish_mapping(state, target);
+		ret = srp_finish_mapping(state, ch);
 		if (!ret)
 			srp_map_update_start(state, NULL, 0, 0);
 	}
 	return ret;
 }
 
-static int srp_map_sg(struct srp_map_state *state,
-		      struct srp_target_port *target, struct srp_request *req,
-		      struct scatterlist *scat, int count)
+static int srp_map_sg(struct srp_map_state *state, struct srp_rdma_ch *ch,
+		      struct srp_request *req, struct scatterlist *scat,
+		      int count)
 {
+	struct srp_target_port *target = ch->target;
 	struct srp_device *dev = target->srp_host->srp_dev;
 	struct ib_device *ibdev = dev->dev;
 	struct scatterlist *sg;
@@ -1358,14 +1378,14 @@ static int srp_map_sg(struct srp_map_state *state,
 	state->pages	= req->map_page;
 	if (dev->use_fast_reg) {
 		state->next_fr = req->fr_list;
-		use_mr = !!target->fr_pool;
+		use_mr = !!ch->fr_pool;
 	} else {
 		state->next_fmr = req->fmr_list;
-		use_mr = !!target->fmr_pool;
+		use_mr = !!ch->fmr_pool;
 	}
 
 	for_each_sg(scat, sg, count, i) {
-		if (srp_map_sg_entry(state, target, sg, i, use_mr)) {
+		if (srp_map_sg_entry(state, ch, sg, i, use_mr)) {
 			/*
 			 * Memory registration failed, so backtrack to the
 			 * first unmapped entry and continue on without using
@@ -1387,7 +1407,7 @@ backtrack:
 		}
 	}
 
-	if (use_mr && srp_finish_mapping(state, target))
+	if (use_mr && srp_finish_mapping(state, ch))
 		goto backtrack;
 
 	req->nmdesc = state->nmdesc;
@@ -1395,9 +1415,10 @@ backtrack:
 	return 0;
 }
 
-static int srp_map_data(struct scsi_cmnd *scmnd, struct srp_target_port *target,
+static int srp_map_data(struct scsi_cmnd *scmnd, struct srp_rdma_ch *ch,
 			struct srp_request *req)
 {
+	struct srp_target_port *target = ch->target;
 	struct scatterlist *scat;
 	struct srp_cmd *cmd = req->cmd->buf;
 	int len, nents, count;
@@ -1459,7 +1480,7 @@ static int srp_map_data(struct scsi_cmnd *scmnd, struct srp_target_port *target,
 				   target->indirect_size, DMA_TO_DEVICE);
 
 	memset(&state, 0, sizeof(state));
-	srp_map_sg(&state, target, req, scat, count);
+	srp_map_sg(&state, ch, req, scat, count);
 
 	/* We've mapped the request, now pull as much of the indirect
 	 * descriptor table as we can into the command buffer. If this
@@ -1520,20 +1541,20 @@ map_complete:
 /*
  * Return an IU and possible credit to the free pool
  */
-static void srp_put_tx_iu(struct srp_target_port *target, struct srp_iu *iu,
+static void srp_put_tx_iu(struct srp_rdma_ch *ch, struct srp_iu *iu,
 			  enum srp_iu_type iu_type)
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&target->lock, flags);
-	list_add(&iu->list, &target->free_tx);
+	spin_lock_irqsave(&ch->lock, flags);
+	list_add(&iu->list, &ch->free_tx);
 	if (iu_type != SRP_IU_RSP)
-		++target->req_lim;
-	spin_unlock_irqrestore(&target->lock, flags);
+		++ch->req_lim;
+	spin_unlock_irqrestore(&ch->lock, flags);
 }
 
 /*
- * Must be called with target->lock held to protect req_lim and free_tx.
+ * Must be called with ch->lock held to protect req_lim and free_tx.
  * If IU is not sent, it must be returned using srp_put_tx_iu().
  *
  * Note:
@@ -1545,35 +1566,36 @@ static void srp_put_tx_iu(struct srp_target_port *target, struct srp_iu *iu,
  * - SRP_IU_RSP: 1, since a conforming SRP target never sends more than
  *   one unanswered SRP request to an initiator.
  */
-static struct srp_iu *__srp_get_tx_iu(struct srp_target_port *target,
+static struct srp_iu *__srp_get_tx_iu(struct srp_rdma_ch *ch,
 				      enum srp_iu_type iu_type)
 {
+	struct srp_target_port *target = ch->target;
 	s32 rsv = (iu_type == SRP_IU_TSK_MGMT) ? 0 : SRP_TSK_MGMT_SQ_SIZE;
 	struct srp_iu *iu;
 
-	srp_send_completion(target->send_cq, target);
+	srp_send_completion(ch->send_cq, ch);
 
-	if (list_empty(&target->free_tx))
+	if (list_empty(&ch->free_tx))
 		return NULL;
 
 	/* Initiator responses to target requests do not consume credits */
 	if (iu_type != SRP_IU_RSP) {
-		if (target->req_lim <= rsv) {
+		if (ch->req_lim <= rsv) {
 			++target->zero_req_lim;
 			return NULL;
 		}
 
-		--target->req_lim;
+		--ch->req_lim;
 	}
 
-	iu = list_first_entry(&target->free_tx, struct srp_iu, list);
+	iu = list_first_entry(&ch->free_tx, struct srp_iu, list);
 	list_del(&iu->list);
 	return iu;
 }
 
-static int srp_post_send(struct srp_target_port *target,
-			 struct srp_iu *iu, int len)
+static int srp_post_send(struct srp_rdma_ch *ch, struct srp_iu *iu, int len)
 {
+	struct srp_target_port *target = ch->target;
 	struct ib_sge list;
 	struct ib_send_wr wr, *bad_wr;
 
@@ -1588,11 +1610,12 @@ static int srp_post_send(struct srp_target_port *target,
 	wr.opcode     = IB_WR_SEND;
 	wr.send_flags = IB_SEND_SIGNALED;
 
-	return ib_post_send(target->qp, &wr, &bad_wr);
+	return ib_post_send(ch->qp, &wr, &bad_wr);
 }
 
-static int srp_post_recv(struct srp_target_port *target, struct srp_iu *iu)
+static int srp_post_recv(struct srp_rdma_ch *ch, struct srp_iu *iu)
 {
+	struct srp_target_port *target = ch->target;
 	struct ib_recv_wr wr, *bad_wr;
 	struct ib_sge list;
 
@@ -1605,35 +1628,36 @@ static int srp_post_recv(struct srp_target_port *target, struct srp_iu *iu)
 	wr.sg_list  = &list;
 	wr.num_sge  = 1;
 
-	return ib_post_recv(target->qp, &wr, &bad_wr);
+	return ib_post_recv(ch->qp, &wr, &bad_wr);
 }
 
-static void srp_process_rsp(struct srp_target_port *target, struct srp_rsp *rsp)
+static void srp_process_rsp(struct srp_rdma_ch *ch, struct srp_rsp *rsp)
 {
+	struct srp_target_port *target = ch->target;
 	struct srp_request *req;
 	struct scsi_cmnd *scmnd;
 	unsigned long flags;
 
 	if (unlikely(rsp->tag & SRP_TAG_TSK_MGMT)) {
-		spin_lock_irqsave(&target->lock, flags);
-		target->req_lim += be32_to_cpu(rsp->req_lim_delta);
-		spin_unlock_irqrestore(&target->lock, flags);
+		spin_lock_irqsave(&ch->lock, flags);
+		ch->req_lim += be32_to_cpu(rsp->req_lim_delta);
+		spin_unlock_irqrestore(&ch->lock, flags);
 
-		target->tsk_mgmt_status = -1;
+		ch->tsk_mgmt_status = -1;
 		if (be32_to_cpu(rsp->resp_data_len) >= 4)
-			target->tsk_mgmt_status = rsp->data[3];
-		complete(&target->tsk_mgmt_done);
+			ch->tsk_mgmt_status = rsp->data[3];
+		complete(&ch->tsk_mgmt_done);
 	} else {
-		req = &target->req_ring[rsp->tag];
-		scmnd = srp_claim_req(target, req, NULL, NULL);
+		req = &ch->req_ring[rsp->tag];
+		scmnd = srp_claim_req(ch, req, NULL, NULL);
 		if (!scmnd) {
 			shost_printk(KERN_ERR, target->scsi_host,
 				     "Null scmnd for RSP w/tag %016llx\n",
 				     (unsigned long long) rsp->tag);
 
-			spin_lock_irqsave(&target->lock, flags);
-			target->req_lim += be32_to_cpu(rsp->req_lim_delta);
-			spin_unlock_irqrestore(&target->lock, flags);
+			spin_lock_irqsave(&ch->lock, flags);
+			ch->req_lim += be32_to_cpu(rsp->req_lim_delta);
+			spin_unlock_irqrestore(&ch->lock, flags);
 
 			return;
 		}
@@ -1655,7 +1679,7 @@ static void srp_process_rsp(struct srp_target_port *target, struct srp_rsp *rsp)
 		else if (unlikely(rsp->flags & SRP_RSP_FLAG_DOOVER))
 			scsi_set_resid(scmnd, -be32_to_cpu(rsp->data_out_res_cnt));
 
-		srp_free_req(target, req, scmnd,
+		srp_free_req(ch, req, scmnd,
 			     be32_to_cpu(rsp->req_lim_delta));
 
 		scmnd->host_scribble = NULL;
@@ -1663,18 +1687,19 @@ static void srp_process_rsp(struct srp_target_port *target, struct srp_rsp *rsp)
 	}
 }
 
-static int srp_response_common(struct srp_target_port *target, s32 req_delta,
+static int srp_response_common(struct srp_rdma_ch *ch, s32 req_delta,
 			       void *rsp, int len)
 {
+	struct srp_target_port *target = ch->target;
 	struct ib_device *dev = target->srp_host->srp_dev->dev;
 	unsigned long flags;
 	struct srp_iu *iu;
 	int err;
 
-	spin_lock_irqsave(&target->lock, flags);
-	target->req_lim += req_delta;
-	iu = __srp_get_tx_iu(target, SRP_IU_RSP);
-	spin_unlock_irqrestore(&target->lock, flags);
+	spin_lock_irqsave(&ch->lock, flags);
+	ch->req_lim += req_delta;
+	iu = __srp_get_tx_iu(ch, SRP_IU_RSP);
+	spin_unlock_irqrestore(&ch->lock, flags);
 
 	if (!iu) {
 		shost_printk(KERN_ERR, target->scsi_host, PFX
@@ -1686,17 +1711,17 @@ static int srp_response_common(struct srp_target_port *target, s32 req_delta,
 	memcpy(iu->buf, rsp, len);
 	ib_dma_sync_single_for_device(dev, iu->dma, len, DMA_TO_DEVICE);
 
-	err = srp_post_send(target, iu, len);
+	err = srp_post_send(ch, iu, len);
 	if (err) {
 		shost_printk(KERN_ERR, target->scsi_host, PFX
 			     "unable to post response: %d\n", err);
-		srp_put_tx_iu(target, iu, SRP_IU_RSP);
+		srp_put_tx_iu(ch, iu, SRP_IU_RSP);
 	}
 
 	return err;
 }
 
-static void srp_process_cred_req(struct srp_target_port *target,
+static void srp_process_cred_req(struct srp_rdma_ch *ch,
 				 struct srp_cred_req *req)
 {
 	struct srp_cred_rsp rsp = {
@@ -1705,14 +1730,15 @@ static void srp_process_cred_req(struct srp_target_port *target,
 	};
 	s32 delta = be32_to_cpu(req->req_lim_delta);
 
-	if (srp_response_common(target, delta, &rsp, sizeof rsp))
-		shost_printk(KERN_ERR, target->scsi_host, PFX
+	if (srp_response_common(ch, delta, &rsp, sizeof(rsp)))
+		shost_printk(KERN_ERR, ch->target->scsi_host, PFX
 			     "problems processing SRP_CRED_REQ\n");
 }
 
-static void srp_process_aer_req(struct srp_target_port *target,
+static void srp_process_aer_req(struct srp_rdma_ch *ch,
 				struct srp_aer_req *req)
 {
+	struct srp_target_port *target = ch->target;
 	struct srp_aer_rsp rsp = {
 		.opcode = SRP_AER_RSP,
 		.tag = req->tag,
@@ -1722,19 +1748,20 @@ static void srp_process_aer_req(struct srp_target_port *target,
 	shost_printk(KERN_ERR, target->scsi_host, PFX
 		     "ignoring AER for LUN %llu\n", be64_to_cpu(req->lun));
 
-	if (srp_response_common(target, delta, &rsp, sizeof rsp))
+	if (srp_response_common(ch, delta, &rsp, sizeof(rsp)))
 		shost_printk(KERN_ERR, target->scsi_host, PFX
 			     "problems processing SRP_AER_REQ\n");
 }
 
-static void srp_handle_recv(struct srp_target_port *target, struct ib_wc *wc)
+static void srp_handle_recv(struct srp_rdma_ch *ch, struct ib_wc *wc)
 {
+	struct srp_target_port *target = ch->target;
 	struct ib_device *dev = target->srp_host->srp_dev->dev;
 	struct srp_iu *iu = (struct srp_iu *) (uintptr_t) wc->wr_id;
 	int res;
 	u8 opcode;
 
-	ib_dma_sync_single_for_cpu(dev, iu->dma, target->max_ti_iu_len,
+	ib_dma_sync_single_for_cpu(dev, iu->dma, ch->max_ti_iu_len,
 				   DMA_FROM_DEVICE);
 
 	opcode = *(u8 *) iu->buf;
@@ -1748,15 +1775,15 @@ static void srp_handle_recv(struct srp_target_port *target, struct ib_wc *wc)
 
 	switch (opcode) {
 	case SRP_RSP:
-		srp_process_rsp(target, iu->buf);
+		srp_process_rsp(ch, iu->buf);
 		break;
 
 	case SRP_CRED_REQ:
-		srp_process_cred_req(target, iu->buf);
+		srp_process_cred_req(ch, iu->buf);
 		break;
 
 	case SRP_AER_REQ:
-		srp_process_aer_req(target, iu->buf);
+		srp_process_aer_req(ch, iu->buf);
 		break;
 
 	case SRP_T_LOGOUT:
@@ -1771,10 +1798,10 @@ static void srp_handle_recv(struct srp_target_port *target, struct ib_wc *wc)
 		break;
 	}
 
-	ib_dma_sync_single_for_device(dev, iu->dma, target->max_ti_iu_len,
+	ib_dma_sync_single_for_device(dev, iu->dma, ch->max_ti_iu_len,
 				      DMA_FROM_DEVICE);
 
-	res = srp_post_recv(target, iu);
+	res = srp_post_recv(ch, iu);
 	if (res != 0)
 		shost_printk(KERN_ERR, target->scsi_host,
 			     PFX "Recv failed with error code %d\n", res);
@@ -1819,33 +1846,35 @@ static void srp_handle_qp_err(u64 wr_id, enum ib_wc_status wc_status,
 	target->qp_in_error = true;
 }
 
-static void srp_recv_completion(struct ib_cq *cq, void *target_ptr)
+static void srp_recv_completion(struct ib_cq *cq, void *ch_ptr)
 {
-	struct srp_target_port *target = target_ptr;
+	struct srp_rdma_ch *ch = ch_ptr;
 	struct ib_wc wc;
 
 	ib_req_notify_cq(cq, IB_CQ_NEXT_COMP);
 	while (ib_poll_cq(cq, 1, &wc) > 0) {
 		if (likely(wc.status == IB_WC_SUCCESS)) {
-			srp_handle_recv(target, &wc);
+			srp_handle_recv(ch, &wc);
 		} else {
-			srp_handle_qp_err(wc.wr_id, wc.status, false, target);
+			srp_handle_qp_err(wc.wr_id, wc.status, false,
+					  ch->target);
 		}
 	}
 }
 
-static void srp_send_completion(struct ib_cq *cq, void *target_ptr)
+static void srp_send_completion(struct ib_cq *cq, void *ch_ptr)
 {
-	struct srp_target_port *target = target_ptr;
+	struct srp_rdma_ch *ch = ch_ptr;
 	struct ib_wc wc;
 	struct srp_iu *iu;
 
 	while (ib_poll_cq(cq, 1, &wc) > 0) {
 		if (likely(wc.status == IB_WC_SUCCESS)) {
 			iu = (struct srp_iu *) (uintptr_t) wc.wr_id;
-			list_add(&iu->list, &target->free_tx);
+			list_add(&iu->list, &ch->free_tx);
 		} else {
-			srp_handle_qp_err(wc.wr_id, wc.status, true, target);
+			srp_handle_qp_err(wc.wr_id, wc.status, true,
+					  ch->target);
 		}
 	}
 }
@@ -1854,6 +1883,7 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
 {
 	struct srp_target_port *target = host_to_target(shost);
 	struct srp_rport *rport = target->rport;
+	struct srp_rdma_ch *ch;
 	struct srp_request *req;
 	struct srp_iu *iu;
 	struct srp_cmd *cmd;
@@ -1875,14 +1905,16 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
 	if (unlikely(scmnd->result))
 		goto err;
 
-	spin_lock_irqsave(&target->lock, flags);
-	iu = __srp_get_tx_iu(target, SRP_IU_CMD);
+	ch = &target->ch;
+
+	spin_lock_irqsave(&ch->lock, flags);
+	iu = __srp_get_tx_iu(ch, SRP_IU_CMD);
 	if (!iu)
 		goto err_unlock;
 
-	req = list_first_entry(&target->free_reqs, struct srp_request, list);
+	req = list_first_entry(&ch->free_reqs, struct srp_request, list);
 	list_del(&req->list);
-	spin_unlock_irqrestore(&target->lock, flags);
+	spin_unlock_irqrestore(&ch->lock, flags);
 
 	dev = target->srp_host->srp_dev->dev;
 	ib_dma_sync_single_for_cpu(dev, iu->dma, target->max_iu_len,
@@ -1901,7 +1933,7 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
 	req->scmnd    = scmnd;
 	req->cmd      = iu;
 
-	len = srp_map_data(scmnd, target, req);
+	len = srp_map_data(scmnd, ch, req);
 	if (len < 0) {
 		shost_printk(KERN_ERR, target->scsi_host,
 			     PFX "Failed to map data (%d)\n", len);
@@ -1919,7 +1951,7 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
 	ib_dma_sync_single_for_device(dev, iu->dma, target->max_iu_len,
 				      DMA_TO_DEVICE);
 
-	if (srp_post_send(target, iu, len)) {
+	if (srp_post_send(ch, iu, len)) {
 		shost_printk(KERN_ERR, target->scsi_host, PFX "Send failed\n");
 		goto err_unmap;
 	}
@@ -1933,10 +1965,10 @@ unlock_rport:
 	return ret;
 
 err_unmap:
-	srp_unmap_data(scmnd, target, req);
+	srp_unmap_data(scmnd, ch, req);
 
 err_iu:
-	srp_put_tx_iu(target, iu, SRP_IU_CMD);
+	srp_put_tx_iu(ch, iu, SRP_IU_CMD);
 
 	/*
 	 * Avoid that the loops that iterate over the request ring can
@@ -1944,11 +1976,11 @@ err_iu:
 	 */
 	req->scmnd = NULL;
 
-	spin_lock_irqsave(&target->lock, flags);
-	list_add(&req->list, &target->free_reqs);
+	spin_lock_irqsave(&ch->lock, flags);
+	list_add(&req->list, &ch->free_reqs);
 
 err_unlock:
-	spin_unlock_irqrestore(&target->lock, flags);
+	spin_unlock_irqrestore(&ch->lock, flags);
 
 err:
 	if (scmnd->result) {
@@ -1963,53 +1995,54 @@ err:
 
 /*
  * Note: the resources allocated in this function are freed in
- * srp_free_target_ib().
+ * srp_free_ch_ib().
  */
-static int srp_alloc_iu_bufs(struct srp_target_port *target)
+static int srp_alloc_iu_bufs(struct srp_rdma_ch *ch)
 {
+	struct srp_target_port *target = ch->target;
 	int i;
 
-	target->rx_ring = kzalloc(target->queue_size * sizeof(*target->rx_ring),
-				  GFP_KERNEL);
-	if (!target->rx_ring)
+	ch->rx_ring = kcalloc(target->queue_size, sizeof(*ch->rx_ring),
+			      GFP_KERNEL);
+	if (!ch->rx_ring)
 		goto err_no_ring;
-	target->tx_ring = kzalloc(target->queue_size * sizeof(*target->tx_ring),
-				  GFP_KERNEL);
-	if (!target->tx_ring)
+	ch->tx_ring = kcalloc(target->queue_size, sizeof(*ch->tx_ring),
+			      GFP_KERNEL);
+	if (!ch->tx_ring)
 		goto err_no_ring;
 
 	for (i = 0; i < target->queue_size; ++i) {
-		target->rx_ring[i] = srp_alloc_iu(target->srp_host,
-						  target->max_ti_iu_len,
-						  GFP_KERNEL, DMA_FROM_DEVICE);
-		if (!target->rx_ring[i])
+		ch->rx_ring[i] = srp_alloc_iu(target->srp_host,
+					      ch->max_ti_iu_len,
+					      GFP_KERNEL, DMA_FROM_DEVICE);
+		if (!ch->rx_ring[i])
 			goto err;
 	}
 
 	for (i = 0; i < target->queue_size; ++i) {
-		target->tx_ring[i] = srp_alloc_iu(target->srp_host,
-						  target->max_iu_len,
-						  GFP_KERNEL, DMA_TO_DEVICE);
-		if (!target->tx_ring[i])
+		ch->tx_ring[i] = srp_alloc_iu(target->srp_host,
+					      target->max_iu_len,
+					      GFP_KERNEL, DMA_TO_DEVICE);
+		if (!ch->tx_ring[i])
 			goto err;
 
-		list_add(&target->tx_ring[i]->list, &target->free_tx);
+		list_add(&ch->tx_ring[i]->list, &ch->free_tx);
 	}
 
 	return 0;
 
 err:
 	for (i = 0; i < target->queue_size; ++i) {
-		srp_free_iu(target->srp_host, target->rx_ring[i]);
-		srp_free_iu(target->srp_host, target->tx_ring[i]);
+		srp_free_iu(target->srp_host, ch->rx_ring[i]);
+		srp_free_iu(target->srp_host, ch->tx_ring[i]);
 	}
 
 
 err_no_ring:
-	kfree(target->tx_ring);
-	target->tx_ring = NULL;
-	kfree(target->rx_ring);
-	target->rx_ring = NULL;
+	kfree(ch->tx_ring);
+	ch->tx_ring = NULL;
+	kfree(ch->rx_ring);
+	ch->rx_ring = NULL;
 
 	return -ENOMEM;
 }
@@ -2043,23 +2076,24 @@ static uint32_t srp_compute_rq_tmo(struct ib_qp_attr *qp_attr, int attr_mask)
 
 static void srp_cm_rep_handler(struct ib_cm_id *cm_id,
 			       struct srp_login_rsp *lrsp,
-			       struct srp_target_port *target)
+			       struct srp_rdma_ch *ch)
 {
+	struct srp_target_port *target = ch->target;
 	struct ib_qp_attr *qp_attr = NULL;
 	int attr_mask = 0;
 	int ret;
 	int i;
 
 	if (lrsp->opcode == SRP_LOGIN_RSP) {
-		target->max_ti_iu_len = be32_to_cpu(lrsp->max_ti_iu_len);
-		target->req_lim       = be32_to_cpu(lrsp->req_lim_delta);
+		ch->max_ti_iu_len = be32_to_cpu(lrsp->max_ti_iu_len);
+		ch->req_lim       = be32_to_cpu(lrsp->req_lim_delta);
 
 		/*
 		 * Reserve credits for task management so we don't
 		 * bounce requests back to the SCSI mid-layer.
 		 */
 		target->scsi_host->can_queue
-			= min(target->req_lim - SRP_TSK_MGMT_SQ_SIZE,
+			= min(ch->req_lim - SRP_TSK_MGMT_SQ_SIZE,
 			      target->scsi_host->can_queue);
 		target->scsi_host->cmd_per_lun
 			= min_t(int, target->scsi_host->can_queue,
@@ -2071,8 +2105,8 @@ static void srp_cm_rep_handler(struct ib_cm_id *cm_id,
 		goto error;
 	}
 
-	if (!target->rx_ring) {
-		ret = srp_alloc_iu_bufs(target);
+	if (!ch->rx_ring) {
+		ret = srp_alloc_iu_bufs(ch);
 		if (ret)
 			goto error;
 	}
@@ -2087,13 +2121,14 @@ static void srp_cm_rep_handler(struct ib_cm_id *cm_id,
 	if (ret)
 		goto error_free;
 
-	ret = ib_modify_qp(target->qp, qp_attr, attr_mask);
+	ret = ib_modify_qp(ch->qp, qp_attr, attr_mask);
 	if (ret)
 		goto error_free;
 
 	for (i = 0; i < target->queue_size; i++) {
-		struct srp_iu *iu = target->rx_ring[i];
-		ret = srp_post_recv(target, iu);
+		struct srp_iu *iu = ch->rx_ring[i];
+
+		ret = srp_post_recv(ch, iu);
 		if (ret)
 			goto error_free;
 	}
@@ -2105,7 +2140,7 @@ static void srp_cm_rep_handler(struct ib_cm_id *cm_id,
 
 	target->rq_tmo_jiffies = srp_compute_rq_tmo(qp_attr, attr_mask);
 
-	ret = ib_modify_qp(target->qp, qp_attr, attr_mask);
+	ret = ib_modify_qp(ch->qp, qp_attr, attr_mask);
 	if (ret)
 		goto error_free;
 
@@ -2115,13 +2150,14 @@ error_free:
 	kfree(qp_attr);
 
 error:
-	target->status = ret;
+	ch->status = ret;
 }
 
 static void srp_cm_rej_handler(struct ib_cm_id *cm_id,
 			       struct ib_cm_event *event,
-			       struct srp_target_port *target)
+			       struct srp_rdma_ch *ch)
 {
+	struct srp_target_port *target = ch->target;
 	struct Scsi_Host *shost = target->scsi_host;
 	struct ib_class_port_info *cpi;
 	int opcode;
@@ -2129,12 +2165,12 @@ static void srp_cm_rej_handler(struct ib_cm_id *cm_id,
 	switch (event->param.rej_rcvd.reason) {
 	case IB_CM_REJ_PORT_CM_REDIRECT:
 		cpi = event->param.rej_rcvd.ari;
-		target->path.dlid = cpi->redirect_lid;
-		target->path.pkey = cpi->redirect_pkey;
+		ch->path.dlid = cpi->redirect_lid;
+		ch->path.pkey = cpi->redirect_pkey;
 		cm_id->remote_cm_qpn = be32_to_cpu(cpi->redirect_qp) & 0x00ffffff;
-		memcpy(target->path.dgid.raw, cpi->redirect_gid, 16);
+		memcpy(ch->path.dgid.raw, cpi->redirect_gid, 16);
 
-		target->status = target->path.dlid ?
+		ch->status = ch->path.dlid ?
 			SRP_DLID_REDIRECT : SRP_PORT_REDIRECT;
 		break;
 
@@ -2145,26 +2181,26 @@ static void srp_cm_rej_handler(struct ib_cm_id *cm_id,
 			 * reject reason code 25 when they mean 24
 			 * (port redirect).
 			 */
-			memcpy(target->path.dgid.raw,
+			memcpy(ch->path.dgid.raw,
 			       event->param.rej_rcvd.ari, 16);
 
 			shost_printk(KERN_DEBUG, shost,
 				     PFX "Topspin/Cisco redirect to target port GID %016llx%016llx\n",
-				     (unsigned long long) be64_to_cpu(target->path.dgid.global.subnet_prefix),
-				     (unsigned long long) be64_to_cpu(target->path.dgid.global.interface_id));
+				     be64_to_cpu(ch->path.dgid.global.subnet_prefix),
+				     be64_to_cpu(ch->path.dgid.global.interface_id));
 
-			target->status = SRP_PORT_REDIRECT;
+			ch->status = SRP_PORT_REDIRECT;
 		} else {
 			shost_printk(KERN_WARNING, shost,
 				     "  REJ reason: IB_CM_REJ_PORT_REDIRECT\n");
-			target->status = -ECONNRESET;
+			ch->status = -ECONNRESET;
 		}
 		break;
 
 	case IB_CM_REJ_DUPLICATE_LOCAL_COMM_ID:
 		shost_printk(KERN_WARNING, shost,
 			    "  REJ reason: IB_CM_REJ_DUPLICATE_LOCAL_COMM_ID\n");
-		target->status = -ECONNRESET;
+		ch->status = -ECONNRESET;
 		break;
 
 	case IB_CM_REJ_CONSUMER_DEFINED:
@@ -2185,24 +2221,25 @@ static void srp_cm_rej_handler(struct ib_cm_id *cm_id,
 			shost_printk(KERN_WARNING, shost,
 				     "  REJ reason: IB_CM_REJ_CONSUMER_DEFINED,"
 				     " opcode 0x%02x\n", opcode);
-		target->status = -ECONNRESET;
+		ch->status = -ECONNRESET;
 		break;
 
 	case IB_CM_REJ_STALE_CONN:
 		shost_printk(KERN_WARNING, shost, "  REJ reason: stale connection\n");
-		target->status = SRP_STALE_CONN;
+		ch->status = SRP_STALE_CONN;
 		break;
 
 	default:
 		shost_printk(KERN_WARNING, shost, "  REJ reason 0x%x\n",
 			     event->param.rej_rcvd.reason);
-		target->status = -ECONNRESET;
+		ch->status = -ECONNRESET;
 	}
 }
 
 static int srp_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event)
 {
-	struct srp_target_port *target = cm_id->context;
+	struct srp_rdma_ch *ch = cm_id->context;
+	struct srp_target_port *target = ch->target;
 	int comp = 0;
 
 	switch (event->event) {
@@ -2210,19 +2247,19 @@ static int srp_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event)
 		shost_printk(KERN_DEBUG, target->scsi_host,
 			     PFX "Sending CM REQ failed\n");
 		comp = 1;
-		target->status = -ECONNRESET;
+		ch->status = -ECONNRESET;
 		break;
 
 	case IB_CM_REP_RECEIVED:
 		comp = 1;
-		srp_cm_rep_handler(cm_id, event->private_data, target);
+		srp_cm_rep_handler(cm_id, event->private_data, ch);
 		break;
 
 	case IB_CM_REJ_RECEIVED:
 		shost_printk(KERN_DEBUG, target->scsi_host, PFX "REJ received\n");
 		comp = 1;
 
-		srp_cm_rej_handler(cm_id, event, target);
+		srp_cm_rej_handler(cm_id, event, ch);
 		break;
 
 	case IB_CM_DREQ_RECEIVED:
@@ -2240,7 +2277,7 @@ static int srp_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event)
 			     PFX "connection closed\n");
 		comp = 1;
 
-		target->status = 0;
+		ch->status = 0;
 		break;
 
 	case IB_CM_MRA_RECEIVED:
@@ -2255,7 +2292,7 @@ static int srp_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event)
 	}
 
 	if (comp)
-		complete(&target->done);
+		complete(&ch->done);
 
 	return 0;
 }
@@ -2311,9 +2348,10 @@ srp_change_queue_depth(struct scsi_device *sdev, int qdepth, int reason)
 	return sdev->queue_depth;
 }
 
-static int srp_send_tsk_mgmt(struct srp_target_port *target,
-			     u64 req_tag, unsigned int lun, u8 func)
+static int srp_send_tsk_mgmt(struct srp_rdma_ch *ch, u64 req_tag,
+			     unsigned int lun, u8 func)
 {
+	struct srp_target_port *target = ch->target;
 	struct srp_rport *rport = target->rport;
 	struct ib_device *dev = target->srp_host->srp_dev->dev;
 	struct srp_iu *iu;
@@ -2322,16 +2360,16 @@ static int srp_send_tsk_mgmt(struct srp_target_port *target,
 	if (!target->connected || target->qp_in_error)
 		return -1;
 
-	init_completion(&target->tsk_mgmt_done);
+	init_completion(&ch->tsk_mgmt_done);
 
 	/*
-	 * Lock the rport mutex to avoid that srp_create_target_ib() is
+	 * Lock the rport mutex to avoid that srp_create_ch_ib() is
 	 * invoked while a task management function is being sent.
 	 */
 	mutex_lock(&rport->mutex);
-	spin_lock_irq(&target->lock);
-	iu = __srp_get_tx_iu(target, SRP_IU_TSK_MGMT);
-	spin_unlock_irq(&target->lock);
+	spin_lock_irq(&ch->lock);
+	iu = __srp_get_tx_iu(ch, SRP_IU_TSK_MGMT);
+	spin_unlock_irq(&ch->lock);
 
 	if (!iu) {
 		mutex_unlock(&rport->mutex);
@@ -2352,15 +2390,15 @@ static int srp_send_tsk_mgmt(struct srp_target_port *target,
 
 	ib_dma_sync_single_for_device(dev, iu->dma, sizeof *tsk_mgmt,
 				      DMA_TO_DEVICE);
-	if (srp_post_send(target, iu, sizeof *tsk_mgmt)) {
-		srp_put_tx_iu(target, iu, SRP_IU_TSK_MGMT);
+	if (srp_post_send(ch, iu, sizeof(*tsk_mgmt))) {
+		srp_put_tx_iu(ch, iu, SRP_IU_TSK_MGMT);
 		mutex_unlock(&rport->mutex);
 
 		return -1;
 	}
 	mutex_unlock(&rport->mutex);
 
-	if (!wait_for_completion_timeout(&target->tsk_mgmt_done,
+	if (!wait_for_completion_timeout(&ch->tsk_mgmt_done,
 					 msecs_to_jiffies(SRP_ABORT_TIMEOUT_MS)))
 		return -1;
 
@@ -2371,20 +2409,22 @@ static int srp_abort(struct scsi_cmnd *scmnd)
 {
 	struct srp_target_port *target = host_to_target(scmnd->device->host);
 	struct srp_request *req = (struct srp_request *) scmnd->host_scribble;
+	struct srp_rdma_ch *ch;
 	int ret;
 
 	shost_printk(KERN_ERR, target->scsi_host, "SRP abort called\n");
 
-	if (!req || !srp_claim_req(target, req, NULL, scmnd))
+	ch = &target->ch;
+	if (!req || !srp_claim_req(ch, req, NULL, scmnd))
 		return SUCCESS;
-	if (srp_send_tsk_mgmt(target, req->index, scmnd->device->lun,
+	if (srp_send_tsk_mgmt(ch, req->index, scmnd->device->lun,
 			      SRP_TSK_ABORT_TASK) == 0)
 		ret = SUCCESS;
 	else if (target->rport->state == SRP_RPORT_LOST)
 		ret = FAST_IO_FAIL;
 	else
 		ret = FAILED;
-	srp_free_req(target, req, scmnd, 0);
+	srp_free_req(ch, req, scmnd, 0);
 	scmnd->result = DID_ABORT << 16;
 	scmnd->scsi_done(scmnd);
 
@@ -2394,19 +2434,21 @@ static int srp_abort(struct scsi_cmnd *scmnd)
 static int srp_reset_device(struct scsi_cmnd *scmnd)
 {
 	struct srp_target_port *target = host_to_target(scmnd->device->host);
+	struct srp_rdma_ch *ch = &target->ch;
 	int i;
 
 	shost_printk(KERN_ERR, target->scsi_host, "SRP reset_device called\n");
 
-	if (srp_send_tsk_mgmt(target, SRP_TAG_NO_REQ, scmnd->device->lun,
+	if (srp_send_tsk_mgmt(ch, SRP_TAG_NO_REQ, scmnd->device->lun,
 			      SRP_TSK_LUN_RESET))
 		return FAILED;
-	if (target->tsk_mgmt_status)
+	if (ch->tsk_mgmt_status)
 		return FAILED;
 
 	for (i = 0; i < target->req_ring_size; ++i) {
-		struct srp_request *req = &target->req_ring[i];
-		srp_finish_req(target, req, scmnd->device, DID_RESET << 16);
+		struct srp_request *req = &ch->req_ring[i];
+
+		srp_finish_req(ch, req, scmnd->device, DID_RESET << 16);
 	}
 
 	return SUCCESS;
@@ -2483,8 +2525,9 @@ static ssize_t show_dgid(struct device *dev, struct device_attribute *attr,
 			 char *buf)
 {
 	struct srp_target_port *target = host_to_target(class_to_shost(dev));
+	struct srp_rdma_ch *ch = &target->ch;
 
-	return sprintf(buf, "%pI6\n", target->path.dgid.raw);
+	return sprintf(buf, "%pI6\n", ch->path.dgid.raw);
 }
 
 static ssize_t show_orig_dgid(struct device *dev,
@@ -2500,7 +2543,7 @@ static ssize_t show_req_lim(struct device *dev,
 {
 	struct srp_target_port *target = host_to_target(class_to_shost(dev));
 
-	return sprintf(buf, "%d\n", target->req_lim);
+	return sprintf(buf, "%d\n", target->ch.req_lim);
 }
 
 static ssize_t show_zero_req_lim(struct device *dev,
@@ -2992,6 +3035,7 @@ static ssize_t srp_create_target(struct device *dev,
 		container_of(dev, struct srp_host, dev);
 	struct Scsi_Host *target_host;
 	struct srp_target_port *target;
+	struct srp_rdma_ch *ch;
 	struct srp_device *srp_dev = host->srp_dev;
 	struct ib_device *ibdev = srp_dev->dev;
 	int ret;
@@ -3060,8 +3104,12 @@ static ssize_t srp_create_target(struct device *dev,
 	INIT_WORK(&target->tl_err_work, srp_tl_err_work);
 	INIT_WORK(&target->remove_work, srp_remove_work);
 	spin_lock_init(&target->lock);
-	INIT_LIST_HEAD(&target->free_tx);
-	ret = srp_alloc_req_data(target);
+	ch = &target->ch;
+	ch->target = target;
+	ch->comp_vector = target->comp_vector;
+	spin_lock_init(&ch->lock);
+	INIT_LIST_HEAD(&ch->free_tx);
+	ret = srp_alloc_req_data(ch);
 	if (ret)
 		goto err_free_mem;
 
@@ -3069,15 +3117,15 @@ static ssize_t srp_create_target(struct device *dev,
 	if (ret)
 		goto err_free_mem;
 
-	ret = srp_create_target_ib(target);
+	ret = srp_create_ch_ib(ch);
 	if (ret)
 		goto err_free_mem;
 
-	ret = srp_new_cm_id(target);
+	ret = srp_new_cm_id(ch);
 	if (ret)
 		goto err_free_ib;
 
-	ret = srp_connect_target(target);
+	ret = srp_connect_ch(ch);
 	if (ret) {
 		shost_printk(KERN_ERR, target->scsi_host,
 			     PFX "Connection failed\n");
@@ -3111,10 +3159,10 @@ err_disconnect:
 	srp_disconnect_target(target);
 
 err_free_ib:
-	srp_free_target_ib(target);
+	srp_free_ch_ib(target, ch);
 
 err_free_mem:
-	srp_free_req_data(target);
+	srp_free_req_data(target, ch);
 
 err:
 	scsi_host_put(target_host);
drivers/infiniband/ulp/srp/ib_srp.h +42 -22

105 lines not on this page · raw message

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1.8.4.5

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#56 lore raw

PATCH v2 10/12 IB/srp: Use block layer tags

In reply to Bart Van Assche

Since the block layer already contains functionality to assign a tag to each request, use that functionality instead of reimplementing that functionality in the SRP initiator driver.

Cc Sagi Grimberg <[email protected]>
Cc Sebastian Parschauer <[email protected]>
---
 drivers/infiniband/ulp/srp/ib_srp.c | 30 +++++++++++++++++++++++++-----
 drivers/infiniband/ulp/srp/ib_srp.h |  1 -
 2 files changed, 25 insertions(+), 6 deletions(-)
drivers/infiniband/ulp/srp/ib_srp.c +25 -5
index cc0bf83b..224ef25 100644
@@ -853,7 +853,6 @@ static int srp_alloc_req_data(struct srp_rdma_ch *ch)
 			goto out;
 
 		req->indirect_dma_addr = dma_addr;
-		req->index = i;
 		list_add_tail(&req->list, &ch->free_reqs);
 	}
 	ret = 0;
@@ -1648,8 +1647,11 @@ static void srp_process_rsp(struct srp_rdma_ch *ch, struct srp_rsp *rsp)
 			ch->tsk_mgmt_status = rsp->data[3];
 		complete(&ch->tsk_mgmt_done);
 	} else {
-		req = &ch->req_ring[rsp->tag];
-		scmnd = srp_claim_req(ch, req, NULL, NULL);
+		scmnd = scsi_host_find_tag(target->scsi_host, rsp->tag);
+		if (scmnd) {
+			req = (void *)scmnd->host_scribble;
+			scmnd = srp_claim_req(ch, req, NULL, scmnd);
+		}
 		if (!scmnd) {
 			shost_printk(KERN_ERR, target->scsi_host,
 				     "Null scmnd for RSP w/tag %016llx\n",
@@ -1889,6 +1891,7 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
 	struct srp_cmd *cmd;
 	struct ib_device *dev;
 	unsigned long flags;
+	u32 tag;
 	int len, ret;
 	const bool in_scsi_eh = !in_interrupt() && current == shost->ehandler;
 
@@ -1905,6 +1908,7 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
 	if (unlikely(scmnd->result))
 		goto err;
 
+	tag = blk_mq_unique_tag(scmnd->request);
 	ch = &target->ch;
 
 	spin_lock_irqsave(&ch->lock, flags);
@@ -1927,7 +1931,7 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
 
 	cmd->opcode = SRP_CMD;
 	cmd->lun    = cpu_to_be64((u64) scmnd->device->lun << 48);
-	cmd->tag    = req->index;
+	cmd->tag    = tag;
 	memcpy(cmd->cdb, scmnd->cmnd, scmnd->cmd_len);
 
 	req->scmnd    = scmnd;
@@ -2409,6 +2413,7 @@ static int srp_abort(struct scsi_cmnd *scmnd)
 {
 	struct srp_target_port *target = host_to_target(scmnd->device->host);
 	struct srp_request *req = (struct srp_request *) scmnd->host_scribble;
+	u32 tag;
 	struct srp_rdma_ch *ch;
 	int ret;
 
@@ -2417,7 +2422,8 @@ static int srp_abort(struct scsi_cmnd *scmnd)
 	ch = &target->ch;
 	if (!req || !srp_claim_req(ch, req, NULL, scmnd))
 		return SUCCESS;
-	if (srp_send_tsk_mgmt(ch, req->index, scmnd->device->lun,
+	tag = blk_mq_unique_tag(scmnd->request);
+	if (srp_send_tsk_mgmt(ch, tag, scmnd->device->lun,
 			      SRP_TSK_ABORT_TASK) == 0)
 		ret = SUCCESS;
 	else if (target->rport->state == SRP_RPORT_LOST)
@@ -2463,6 +2469,15 @@ static int srp_reset_host(struct scsi_cmnd *scmnd)
 	return srp_reconnect_rport(target->rport) == 0 ? SUCCESS : FAILED;
 }
 
+static int srp_slave_alloc(struct scsi_device *sdev)
+{
+	sdev->tagged_supported = 1;
+
+	scsi_activate_tcq(sdev, sdev->queue_depth);
+
+	return 0;
+}
+
 static int srp_slave_configure(struct scsi_device *sdev)
 {
 	struct Scsi_Host *shost = sdev->host;
@@ -2641,6 +2656,7 @@ static struct scsi_host_template srp_template = {
 	.module				= THIS_MODULE,
 	.name				= "InfiniBand SRP initiator",
 	.proc_name			= DRV_NAME,
+	.slave_alloc			= srp_slave_alloc,
 	.slave_configure		= srp_slave_configure,
 	.info				= srp_target_info,
 	.queuecommand			= srp_queuecommand,
@@ -3076,6 +3092,10 @@ static ssize_t srp_create_target(struct device *dev,
 	if (ret)
 		goto err;
 
+	ret = scsi_init_shared_tag_map(target_host, target_host->can_queue);
+	if (ret)
+		goto err;
+
 	target->req_ring_size = target->queue_size - SRP_TSK_MGMT_SQ_SIZE;
 
 	if (!srp_conn_unique(target->srp_host, target)) {
drivers/infiniband/ulp/srp/ib_srp.h +0 -1
index 74530d9..75e8f36 100644
@@ -127,7 +127,6 @@ struct srp_request {
 	struct srp_direct_buf  *indirect_desc;
 	dma_addr_t		indirect_dma_addr;
 	short			nmdesc;
-	short			index;
 };
 
 /**
Signature · 1 line
1.8.4.5
#26 lore raw

PATCH v2 11/12 IB/srp: Eliminate free_reqs list

In reply to a message not in the archive

The free_reqs list is no longer needed now that we are using tags assigned by the block layer. Hence remove it.

Cc Sagi Grimberg <sagig-VPRAkNaXOzVWk0Htik3J/[email protected]>
Cc Sebastian Parschauer <[email protected]>
---
 drivers/infiniband/ulp/srp/ib_srp.c | 24 +++++++++---------------
 drivers/infiniband/ulp/srp/ib_srp.h |  1 -
 2 files changed, 9 insertions(+), 16 deletions(-)
drivers/infiniband/ulp/srp/ib_srp.c +9 -15
index 224ef25..eccaf65 100644
@@ -821,8 +821,6 @@ static int srp_alloc_req_data(struct srp_rdma_ch *ch)
 	dma_addr_t dma_addr;
 	int i, ret = -ENOMEM;
 
-	INIT_LIST_HEAD(&ch->free_reqs);
-
 	ch->req_ring = kcalloc(target->req_ring_size, sizeof(*ch->req_ring),
 			       GFP_KERNEL);
 	if (!ch->req_ring)
@@ -853,7 +851,6 @@ static int srp_alloc_req_data(struct srp_rdma_ch *ch)
 			goto out;
 
 		req->indirect_dma_addr = dma_addr;
-		list_add_tail(&req->list, &ch->free_reqs);
 	}
 	ret = 0;
 
@@ -1075,7 +1072,6 @@ static void srp_free_req(struct srp_rdma_ch *ch, struct srp_request *req,
 
 	spin_lock_irqsave(&ch->lock, flags);
 	ch->req_lim += req_lim_delta;
-	list_add_tail(&req->list, &ch->free_reqs);
 	spin_unlock_irqrestore(&ch->lock, flags);
 }
 
@@ -1892,6 +1888,7 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
 	struct ib_device *dev;
 	unsigned long flags;
 	u32 tag;
+	u16 idx;
 	int len, ret;
 	const bool in_scsi_eh = !in_interrupt() && current == shost->ehandler;
 
@@ -1910,16 +1907,19 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
 
 	tag = blk_mq_unique_tag(scmnd->request);
 	ch = &target->ch;
+	idx = blk_mq_unique_tag_to_tag(tag);
+	WARN_ONCE(idx >= target->req_ring_size, "%s: tag %#x: idx %d >= %d\n",
+		  dev_name(&shost->shost_gendev), tag, idx,
+		  target->req_ring_size);
 
 	spin_lock_irqsave(&ch->lock, flags);
 	iu = __srp_get_tx_iu(ch, SRP_IU_CMD);
-	if (!iu)
-		goto err_unlock;
-
-	req = list_first_entry(&ch->free_reqs, struct srp_request, list);
-	list_del(&req->list);
 	spin_unlock_irqrestore(&ch->lock, flags);
 
+	if (!iu)
+		goto err;
+
+	req = &ch->req_ring[idx];
 	dev = target->srp_host->srp_dev->dev;
 	ib_dma_sync_single_for_cpu(dev, iu->dma, target->max_iu_len,
 				   DMA_TO_DEVICE);
@@ -1980,12 +1980,6 @@ err_iu:
 	 */
 	req->scmnd = NULL;
 
-	spin_lock_irqsave(&ch->lock, flags);
-	list_add(&req->list, &ch->free_reqs);
-
-err_unlock:
-	spin_unlock_irqrestore(&ch->lock, flags);
-
 err:
 	if (scmnd->result) {
 		scmnd->scsi_done(scmnd);
drivers/infiniband/ulp/srp/ib_srp.h +0 -1
index 75e8f36..bb185d4 100644
@@ -136,7 +136,6 @@ struct srp_request {
 struct srp_rdma_ch {
 	/* These are RW in the hot path, and commonly used together */
 	struct list_head	free_tx;
-	struct list_head	free_reqs;
 	spinlock_t		lock;
 	s32			req_lim;
 
Signature · 6 lines
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maintainer
#76 lore raw

PATCH v2 12/12 IB/srp: Add multichannel support

In reply to Bart Van Assche

Improve performance by using multiple RDMA/RC channels per SCSI host for communication with an SRP target. About the implementation:
- Introduce a loop over all channels in the code that uses target->ch.
- Set the SRP_MULTICHAN_MULTI flag during login for the creation of the second and subsequent channels.
- RDMA completion vectors are chosen such that RDMA completion interrupts are handled by the CPU socket that submitted the I/O request. As one can see in this patch it has been assumed if a system contains n CPU sockets and m RDMA completion vectors have been assigned to an RDMA HCA that IRQ affinity has been configured such that completion vectors [i*m/n..(i+1)*m/n) are bound to CPU socket i with 0 <= i < n.
- Modify srp_free_ch_ib() and srp_free_req_data() such that it becomes safe to invoke these functions after the corresponding allocation function failed.
- Add a ch_count sysfs attribute per target port.

Cc Sagi Grimberg <[email protected]>
Cc Sebastian Parschauer <[email protected]>
---
 Documentation/ABI/stable/sysfs-driver-ib_srp |  25 ++-
 drivers/infiniband/ulp/srp/ib_srp.c          | 291 ++++++++++++++++++++-------
 drivers/infiniband/ulp/srp/ib_srp.h          |   3 +-
 3 files changed, 238 insertions(+), 81 deletions(-)
Documentation/ABI/stable/sysfs-driver-ib_srp +19 -6
index b9688de..d5a459e 100644
@@ -55,12 +55,12 @@ Description:	Interface for making ib_srp connect to a new target.
 		  only safe with partial memory descriptor list support enabled
 		  (allow_ext_sg=1).
 		* comp_vector, a number in the range 0..n-1 specifying the
-		  MSI-X completion vector. Some HCA's allocate multiple (n)
-		  MSI-X vectors per HCA port. If the IRQ affinity masks of
-		  these interrupts have been configured such that each MSI-X
-		  interrupt is handled by a different CPU then the comp_vector
-		  parameter can be used to spread the SRP completion workload
-		  over multiple CPU's.
+		  MSI-X completion vector of the first RDMA channel. Some
+		  HCA's allocate multiple (n) MSI-X vectors per HCA port. If
+		  the IRQ affinity masks of these interrupts have been
+		  configured such that each MSI-X interrupt is handled by a
+		  different CPU then the comp_vector parameter can be used to
+		  spread the SRP completion workload over multiple CPU's.
 		* tl_retry_count, a number in the range 2..7 specifying the
 		  IB RC retry count.
 		* queue_size, the maximum number of commands that the
@@ -88,6 +88,13 @@ Description:	Whether ib_srp is allowed to include a partial memory
 		descriptor list in an SRP_CMD when communicating with an SRP
 		target.
 
+What:		/sys/class/scsi_host/host<n>/ch_count
+Date:		November 1, 2014
+KernelVersion:	3.18
+Contact:	[email protected]
+Description:	Number of RDMA channels used for communication with the SRP
+		target.
+
 What:		/sys/class/scsi_host/host<n>/cmd_sg_entries
 Date:		May 19, 2011
 KernelVersion:	2.6.39
@@ -95,6 +102,12 @@ Contact:	[email protected]
 Description:	Maximum number of data buffer descriptors that may be sent to
 		the target in a single SRP_CMD request.
 
+What:		/sys/class/scsi_host/host<n>/comp_vector
+Date:		September 2, 2013
+KernelVersion:	3.11
+Contact:	[email protected]
+Description:	Completion vector used for the first RDMA channel.
+
 What:		/sys/class/scsi_host/host<n>/dgid
 Date:		June 17, 2006
 KernelVersion:	2.6.17
drivers/infiniband/ulp/srp/ib_srp.c +217 -74

501 lines not on this page · raw message

drivers/infiniband/ulp/srp/ib_srp.h +2 -1
index bb185d4..5b7dada 100644
@@ -180,8 +180,9 @@ struct srp_target_port {
 	/* read and written in the hot path */
 	spinlock_t		lock;
 
-	struct srp_rdma_ch	ch;
 	/* read only in the hot path */
+	struct srp_rdma_ch	*ch;
+	u32			ch_count;
 	u32			lkey;
 	u32			rkey;
 	enum srp_target_state	state;
Signature · 1 line
1.8.4.5
maintainer
#3 lore raw

Re: [PATCH v2 01/12] blk-mq: Use all available hardware queues

In reply to Bart Van Assche
Quoted 41 lines · Bart Van Assche

Suppose that a system has two CPU sockets, three cores per socket, that it does not support hyperthreading and that four hardware queues are provided by a block driver. With the current algorithm this will lead to the following assignment of CPU cores to hardware queues:

HWQ 0: 0 1
HWQ 1: 2 3
HWQ 2: 4 5
HWQ 3: (none)

This patch changes the queue assignment into:

HWQ 0: 0 1
HWQ 1: 2
HWQ 2: 3 4
HWQ 3: 5

In other words, this patch has the following three effects:
- All four hardware queues are used instead of only three.
- CPU cores are spread more evenly over hardware queues. For the above example the range of the number of CPU cores associated with a single HWQ is reduced from [0..2] to [1..2].
- If the number of HWQ's is a multiple of the number of CPU sockets it is now guaranteed that all CPU cores associated with a single HWQ reside on the same CPU socket.

---
 block/blk-mq-cpumap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
block/blk-mq-cpumap.c +0 -0
index 1065d7c..8e56455 100644

block/blk-mq-cpumap.c line 23

Quoted 8 lines
block/blk-mq-cpumap.c +1 -1
@@ -17,7 +17,7 @@
 static int cpu_to_queue_index(unsigned int nr_cpus, unsigned int nr_queues,
 			      const int cpu)
 {
-	return cpu / ((nr_cpus + nr_queues - 1) / nr_queues);
+	return cpu * nr_queues / nr_cpus;
 }
 
 static int get_first_sibling(unsigned int cpu)

Lets do this separate, as explained last time, it needs to be evaluated on its own and doesn't really belong in this series of patches.

Signature · 1 line
Jens Axboe
maintainer
#115 lore raw

PATCH 1/1 blk-mq: Use all available hardware queues

In reply to Bart Van Assche

Suppose that a system has two CPU sockets, three cores per socket, that it does not support hyperthreading and that four hardware queues are provided by a block driver. With the current algorithm this will lead to the following assignment of CPU cores to hardware queues:

HWQ 0: 0 1
HWQ 1: 2 3
HWQ 2: 4 5
HWQ 3: (none)

This patch changes the queue assignment into:

HWQ 0: 0 1
HWQ 1: 2
HWQ 2: 3 4
HWQ 3: 5

In other words, this patch has the following three effects:
- All four hardware queues are used instead of only three.
- CPU cores are spread more evenly over hardware queues. For the above example the range of the number of CPU cores associated with a single HWQ is reduced from [0..2] to [1..2].
- If the number of HWQ's is a multiple of the number of CPU sockets it is now guaranteed that all CPU cores associated with a single HWQ reside on the same CPU socket.

---
 block/blk-mq-cpumap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
block/blk-mq-cpumap.c +1 -1
index 1065d7c..8e56455 100644
@@ -17,7 +17,7 @@
 static int cpu_to_queue_index(unsigned int nr_cpus, unsigned int nr_queues,
 			      const int cpu)
 {
-	return cpu / ((nr_cpus + nr_queues - 1) / nr_queues);
+	return cpu * nr_queues / nr_cpus;
 }
  static int get_first_sibling(unsigned int cpu)
Signature · 1 line
1.8.4.5
#5 lore raw

Re: [PATCH v2 01/12] blk-mq: Use all available hardware queues

In reply to a message not in the archive
Quoted 2 lines · Jens Axboe

Lets do this separate, as explained last time, it needs to be evaluated on its own and doesn't really belong in this series of patches.

Hello Jens,

A few minutes ago I have resent this patch to you with the LKML in CC. I hope that Christoph agrees with leaving out this patch from this series without me having to resend this series. BTW, Sagi promised me off-list to review the other patches in this series.

Bart.

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#34 lore raw

Re: [PATCH v2 02/12] blk-mq: Add blk_mq_unique_tag()

In reply to Bart Van Assche

include/linux/blk-mq.h struct request *blk_mq_alloc_request(struct request_queue *q, int rw, · line 180

Quoted 4 lines
include/linux/blk-mq.h +4 -0
+static inline u32 blk_mq_build_unique_tag(int hwq, int tag)
+{
+	return (hwq << BLK_MQ_UNIQUE_TAG_BITS) | (tag & BLK_MQ_UNIQUE_TAG_MASK);
+}

Is there any value in having this as a separate helper?

#7 lore raw

Re: [PATCH v2 01/12] blk-mq: Use all available hardware queues

In reply to a message not in the archive
Quoted 10 lines · Bart Van Assche
Quoted 2 lines · Jens Axboe

Lets do this separate, as explained last time, it needs to be evaluated on its own and doesn't really belong in this series of patches.

Hello Jens,

A few minutes ago I have resent this patch to you with the LKML in CC. I hope that Christoph agrees with leaving out this patch from this series without me having to resend this series. BTW, Sagi promised me off-list to review the other patches in this series.

Ignoring patches is one of the easier tasks, np. Do you want me to merge all the srp updates? They normally go through the IB tree, but I can pick them up this time so that we don't need to synchronize the two trees.

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maintainer
#35 lore raw

Re: [PATCH v2 02/12] blk-mq: Add blk_mq_unique_tag()

In reply to Christoph Hellwig
Quoted 6 lines · Christoph Hellwig

include/linux/blk-mq.h struct request *blk_mq_alloc_request(struct request_queue *q, int rw, · line 180

Quoted 4 lines
include/linux/blk-mq.h +4 -0
+static inline u32 blk_mq_build_unique_tag(int hwq, int tag)
+{
+	return (hwq << BLK_MQ_UNIQUE_TAG_BITS) | (tag & BLK_MQ_UNIQUE_TAG_MASK);
+}

Is there any value in having this as a separate helper?

Hello Christoph,

With the approach for block layer tag management proposed in this patch series SCSI LLDs no longer need to call this function. This means that the blk_mq_build_unique_tag() function can be eliminated by inlining it into blk_mq_unique_tag(). Would you like me to rework this patch accordingly ?

Bart.

#9 lore raw

Re: [PATCH v2 01/12] blk-mq: Use all available hardware queues

In reply to a message not in the archive
Quoted 12 lines · Christoph Hellwig
Quoted 10 lines · Bart Van Assche
Quoted 2 lines · Jens Axboe

Lets do this separate, as explained last time, it needs to be evaluated on its own and doesn't really belong in this series of patches.

Hello Jens,

A few minutes ago I have resent this patch to you with the LKML in CC. I hope that Christoph agrees with leaving out this patch from this series without me having to resend this series. BTW, Sagi promised me off-list to review the other patches in this series.

Quoted 4 lines

Ignoring patches is one of the easier tasks, np. Do you want me to merge all the srp updates? They normally go through the IB tree, but I can pick them up this time so that we don't need to synchronize the two trees.

Hello Christoph,

Since patch 1/12 already has been sent separately to Jens patches 2/12..12/12 remain. The SRP initiator changes in this series depend on the blk-mq and scsi-mq features added in patches 2/12..4/12. I think we should avoid splitting these patches over multiple kernel trees to avoid having to deal with dependencies between kernel trees.

Bart.
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#37 lore raw

Re: [PATCH v2 02/12] blk-mq: Add blk_mq_unique_tag()

In reply to a message not in the archive
Quoted 4 lines · Bart Van Assche

With the approach for block layer tag management proposed in this patch series SCSI LLDs no longer need to call this function. This means that the blk_mq_build_unique_tag() function can be eliminated by inlining it into blk_mq_unique_tag(). Would you like me to rework this patch accordingly ?

Yes, please.

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#58 lore raw

Re: [PATCH v2 10/12] IB/srp: Use block layer tags

In reply to a message not in the archive

drivers/infiniband/ulp/srp/ib_srp.c static int srp_alloc_req_data(struct srp_rdma_ch *ch) · line 857

Quoted 11 lines
drivers/infiniband/ulp/srp/ib_srp.c +0 -1
index cc0bf83b..224ef25 100644
@@ -853,7 +853,6 @@ static int srp_alloc_req_data(struct srp_rdma_ch *ch)
 			goto out;
 
 		req->indirect_dma_addr = dma_addr;
-		req->index = i;
 		list_add_tail(&req->list, &ch->free_reqs);
 	}

Seems like a nice optimization for the future would be to preallocate the srp requests with the block ones and the scsi command.

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#28 lore raw

Re: [PATCH v2 11/12] IB/srp: Eliminate free_reqs list

In reply to a message not in the archive
Quoted 2 lines · Bart Van Assche

The free_reqs list is no longer needed now that we are using tags assigned by the block layer. Hence remove it.

Is there any good reason not to fold this into the previous patch?

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#77 lore raw

EH action after scsi_remove_host, was: Re: [PATCH v2 12/12] IB/srp: Add multichannel support

In reply to Bart Van Assche

drivers/infiniband/ulp/srp/ib_srp.c static void srp_free_ch_ib(struct srp_target_port *target, · line 579

Quoted 7 lines · Bart Van Assche
drivers/infiniband/ulp/srp/ib_srp.c +7 -0
+	/*
+	 * Avoid that the SCSI error handler tries to use this channel after
+	 * it has been freed. The SCSI error handler can namely continue
+	 * trying to perform recovery actions after scsi_remove_host()
+	 * returned.
+	 */
+	ch->target = NULL;

Do you have a reproducer for that? I think we should fix the root cause.

#80 lore raw
In reply to Bart Van Assche

drivers/infiniband/ulp/srp/ib_srp.c static void srp_process_rsp(struct srp_rdma_ch *ch, struct srp_rsp *rsp) · line 1710

Quoted 5 lines
drivers/infiniband/ulp/srp/ib_srp.c +3 -0
 	} else {
+		if (blk_mq_unique_tag_to_hwq(rsp->tag) != ch - target->ch)
+			pr_err("Channel idx mismatch: tag %#llx <> ch %#lx\n",
+			       rsp->tag, ch - target->ch);
 		scmnd = scsi_host_find_tag(target->scsi_host, rsp->tag);

Shouldn't we do this validity check inside scsi_host_find_tag, so that all callers get it? That means adding an argument to it, but there are very few callers at the moment.

#11 lore raw

Re: [PATCH v2 01/12] blk-mq: Use all available hardware queues

In reply to a message not in the archive
Quoted 5 lines · Bart Van Assche

Since patch 1/12 already has been sent separately to Jens patches 2/12..12/12 remain. The SRP initiator changes in this series depend on the blk-mq and scsi-mq features added in patches 2/12..4/12. I think we should avoid splitting these patches over multiple kernel trees to avoid having to deal with dependencies between kernel trees.

I'd like to pull it in and Roland already did indicate that he's fine with it.

Sagi, can I get a review from you for the remaining SRP patches?

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#13 lore raw

Re: [PATCH v2 01/12] blk-mq: Use all available hardware queues

In reply to a message not in the archive
Quoted 8 lines
Quoted 7 lines · Bart Van Assche

Since patch 1/12 already has been sent separately to Jens patches 2/12..12/12 remain. The SRP initiator changes in this series depend on the blk-mq and scsi-mq features added in patches 2/12..4/12. I think we should avoid splitting these patches over multiple kernel trees to avoid having to deal with dependencies between kernel trees.

Quoted 4 lines

I'd like to pull it in and Roland already did indicate that he's fine with it.

Sagi, can I get a review from you for the remaining SRP patches?

As I promised Bart, it's on my todo list. Unfortunately this week I was violently pulled to another project... It's a holiday here in Israel, so I'm planning to review the set by mid next week.

Sagi.
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Reviewed-by
#16 lore raw

Re: [PATCH v2 03/12] scsi-mq: Add support for multiple hardware queues

In reply to a message not in the archive
Quoted 34 lines · Bart Van Assche

Allow a SCSI LLD to declare how many hardware queues it supports by setting Scsi_Host.nr_hw_queues before calling scsi_add_host().

Note: it is assumed that each hardware queue has a queue depth of shost->can_queue. In other words, the total queue depth per host is (number of hardware queues) * (shost->can_queue).

Cc Christoph Hellwig <[email protected]>
Cc Sagi Grimberg <sagig-VPRAkNaXOzVWk0Htik3J/[email protected]>
---
  drivers/scsi/scsi_lib.c  | 2 +-
  include/scsi/scsi_host.h | 4 ++++
  2 files changed, 5 insertions(+), 1 deletion(-)
drivers/scsi/scsi_lib.c +1 -1
index db8c449..f829c42 100644
@@ -2072,7 +2072,7 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
 
  	memset(&shost->tag_set, 0, sizeof(shost->tag_set));
  	shost->tag_set.ops = &scsi_mq_ops;
-	shost->tag_set.nr_hw_queues = 1;
+	shost->tag_set.nr_hw_queues = shost->nr_hw_queues ? : 1;
  	shost->tag_set.queue_depth = shost->can_queue;
  	shost->tag_set.cmd_size = cmd_size;
  	shost->tag_set.numa_node = NUMA_NO_NODE;
include/scsi/scsi_host.h +0 -0
index cafb260..d38cab9 100644

include/scsi/scsi_host.h struct Scsi_Host { · line 647

Quoted 10 lines
include/scsi/scsi_host.h +4 -0
@@ -638,6 +638,10 @@ struct Scsi_Host {
  	short unsigned int sg_prot_tablesize;
  	unsigned int max_sectors;
  	unsigned long dma_boundary;
+	/*
+	 * In scsi-mq mode, the number of hardware queues supported by the LLD.
+	 */
+	unsigned nr_hw_queues;
  	/*
  	 * Used to assign serial numbers to the cmds.
  	 * Protected by the host lock.

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#42 lore raw

Re: [PATCH v2 04/12] scsi_tcq.h: Add support for multiple hardware queues

In reply to Bart Van Assche
Quoted 41 lines · Bart Van Assche

Modify scsi_find_tag() and scsi_host_find_tag() such that these fuctions can translate a tag generated by blk_mq_unique_tag().

Cc Christoph Hellwig <[email protected]>
Cc Sagi Grimberg <[email protected]>
---
  include/scsi/scsi_tcq.h | 19 +++++++++++--------
  1 file changed, 11 insertions(+), 8 deletions(-)
include/scsi/scsi_tcq.h +7 -4
index e645835..ea1ca9c 100644
@@ -111,18 +111,21 @@ static inline int scsi_populate_tag_msg(struct scsi_cmnd *cmd, char *msg)
  }
 
  static inline struct scsi_cmnd *scsi_mq_find_tag(struct Scsi_Host *shost,
-		unsigned int hw_ctx, int tag)
+						 int unique_tag)
  {
-	struct request *req;
+	u16 hwq = blk_mq_unique_tag_to_hwq(unique_tag);
+	struct request *req = NULL;
 
-	req = blk_mq_tag_to_rq(shost->tag_set.tags[hw_ctx], tag);
+	if (hwq < shost->tag_set.nr_hw_queues)
+		req = blk_mq_tag_to_rq(shost->tag_set.tags[hwq],
+				       blk_mq_unique_tag_to_tag(unique_tag));
  	return req ? (struct scsi_cmnd *)req->special : NULL;
  }
 
  /**
   * scsi_find_tag - find a tagged command by device
   * @SDpnt:	pointer to the ScSI device
- * @tag:	the tag number
+ * @tag:	tag generated by blk_mq_unique_tag()
   *
   * Notes:
   *	Only works with tags allocated by the generic blk layer.

include/scsi/scsi_tcq.h static inline struct scsi_cmnd *scsi_find_tag(struct scsi_device *sdev, int tag) · line 141

Quoted 8 lines
include/scsi/scsi_tcq.h +2 -2
@@ -133,9 +136,9 @@ static inline struct scsi_cmnd *scsi_find_tag(struct scsi_device *sdev, int tag)
 
          if (tag != SCSI_NO_TAG) {
  		if (shost_use_blk_mq(sdev->host))
-			return scsi_mq_find_tag(sdev->host, 0, tag);
+			return scsi_mq_find_tag(sdev->host, tag);
 
-        	req = blk_queue_find_tag(sdev->request_queue, tag);
+		req = blk_queue_find_tag(sdev->request_queue, tag);

Why is this line different?

Quoted 22 lines
include/scsi/scsi_tcq.h +2 -2
  	        return req ? (struct scsi_cmnd *)req->special : NULL;
  	}
 
@@ -174,7 +177,7 @@ static inline int scsi_init_shared_tag_map(struct Scsi_Host *shost, int depth)
  /**
   * scsi_host_find_tag - find the tagged command by host
   * @shost:	pointer to scsi_host
- * @tag:	tag of the scsi_cmnd
+ * @tag:	tag generated by blk_mq_unique_tag()
   *
   * Notes:
   *	Only works with tags allocated by the generic blk layer.
@@ -186,7 +189,7 @@ static inline struct scsi_cmnd *scsi_host_find_tag(struct Scsi_Host *shost,
 
  	if (tag != SCSI_NO_TAG) {
  		if (shost_use_blk_mq(shost))
-			return scsi_mq_find_tag(shost, 0, tag);
+			return scsi_mq_find_tag(shost, tag);
  		req = blk_map_queue_find_tag(shost->bqt, tag);
  		return req ? (struct scsi_cmnd *)req->special : NULL;
  	}
Reviewed-by
#38 lore raw

Re: [PATCH v2 02/12] blk-mq: Add blk_mq_unique_tag()

In reply to Christoph Hellwig
Quoted 8 lines · Christoph Hellwig
Quoted 4 lines · Bart Van Assche

With the approach for block layer tag management proposed in this patch series SCSI LLDs no longer need to call this function. This means that the blk_mq_build_unique_tag() function can be eliminated by inlining it into blk_mq_unique_tag(). Would you like me to rework this patch accordingly ?

Yes, please.

With this bit you can add:

#50 lore raw

Re: [PATCH v2 07/12] IB/srp: Avoid that I/O hangs due to a cable pull during LUN scanning

In reply to Bart Van Assche
Quoted 41 lines · Bart Van Assche

If a cable is pulled during LUN scanning it can happen that the SRP rport and the SCSI host have been created but no LUNs have been added to the SCSI host. Since multipathd only sends SCSI commands to a SCSI target if one or more SCSI devices are present and since there is no keepalive mechanism for IB queue pairs this means that after a LUN scan failed and after a reconnect has succeeded no data will be sent over the QP and hence that a subsequent cable pull will not be detected. Avoid this by not creating an rport or SCSI host if a cable is pulled during a SCSI LUN scan.

Note: so far the above behavior has only been observed with the kernel module parameter ch_count set to a value >= 2.

Cc Sagi Grimberg <[email protected]>
Cc Sebastian Parschauer <[email protected]>
---
  drivers/infiniband/ulp/srp/ib_srp.c | 60 +++++++++++++++++++++++++++++++------
  drivers/infiniband/ulp/srp/ib_srp.h |  1 +
  2 files changed, 52 insertions(+), 9 deletions(-)
drivers/infiniband/ulp/srp/ib_srp.c +5 -0
index 9608e7a..a662c29 100644
@@ -1111,6 +1111,10 @@ static int srp_rport_reconnect(struct srp_rport *rport)
  	int i, ret;
 
  	srp_disconnect_target(target);
+
+	if (target->state == SRP_TARGET_SCANNING)
+		return -ENODEV;
+
  	/*
  	 * Now get a new local CM ID so that we avoid confusing the target in
  	 * case things are really fouled up. Doing so also ensures that all CM
@@ -2607,11 +2611,23 @@ static struct scsi_host_template srp_template = {
  	.shost_attrs			= srp_host_attrs
  };
 
+static int srp_sdev_count(struct Scsi_Host *host)

drivers/infiniband/ulp/srp/ib_srp.c static struct scsi_host_template srp_template = { · line 2624

Quoted 10 lines
drivers/infiniband/ulp/srp/ib_srp.c +10 -0
+{
+	struct scsi_device *sdev;
+	int c = 0;
+
+	shost_for_each_device(sdev, host)
+		c++;
+
+	return c;
+}
+

Is this really an SRP specific routine?
Can you move it to a more natural location?

Quoted 14 lines
drivers/infiniband/ulp/srp/ib_srp.c +1 -1
  static int srp_add_target(struct srp_host *host, struct srp_target_port *target)
  {
  	struct srp_rport_identifiers ids;
  	struct srp_rport *rport;
 
+	target->state = SRP_TARGET_SCANNING;
  	sprintf(target->target_name, "SRP.T10:%016llX",
  		 (unsigned long long) be64_to_cpu(target->id_ext));
 
@@ -2634,11 +2650,26 @@ static int srp_add_target(struct srp_host *host, struct srp_target_port *target)
  	list_add_tail(&target->list, &host->target_list);
  	spin_unlock(&host->target_lock);
 
-	target->state = SRP_TARGET_LIVE;

drivers/infiniband/ulp/srp/ib_srp.c static int srp_add_target(struct srp_host *host, struct srp_target_port *target) · line 2661

Quoted 10 lines
drivers/infiniband/ulp/srp/ib_srp.c +6 -1
-
  	scsi_scan_target(&target->scsi_host->shost_gendev,
  			 0, target->scsi_id, SCAN_WILD_CARD, 0);
 
+	if (!target->connected || target->qp_in_error) {
+		shost_printk(KERN_INFO, target->scsi_host,
+			     PFX "SCSI scan failed - removing SCSI host\n");
+		srp_queue_remove_work(target);
+		goto out;
+	}

So my impression is that by conditioning target->qp_in_error you are relying on the fact that SRP eh was invoked here (RC error), what if scsi eh was invoked prior to that? did you test this path?

Quoted 71 lines
drivers/infiniband/ulp/srp/ib_srp.c +29 -7
+
+	pr_debug(PFX "%s: SCSI scan succeeded - detected %d LUNs\n",
+		 dev_name(&target->scsi_host->shost_gendev),
+		 srp_sdev_count(target->scsi_host));
+
+	spin_lock_irq(&target->lock);
+	if (target->state == SRP_TARGET_SCANNING)
+		target->state = SRP_TARGET_LIVE;
+	spin_unlock_irq(&target->lock);
+
+out:
  	return 0;
  }
 
@@ -2982,6 +3013,12 @@ static ssize_t srp_create_target(struct device *dev,
  	target->tl_retry_count	= 7;
  	target->queue_size	= SRP_DEFAULT_QUEUE_SIZE;
 
+	/*
+	 * Avoid that the SCSI host can be removed by srp_remove_target()
+	 * before this function returns.
+	 */
+	scsi_host_get(target->scsi_host);
+
  	mutex_lock(&host->add_target_mutex);
 
  	ret = srp_parse_options(buf, target);
@@ -3044,18 +3081,23 @@ static ssize_t srp_create_target(struct device *dev,
  	if (ret)
  		goto err_disconnect;
 
-	shost_printk(KERN_DEBUG, target->scsi_host, PFX
-		     "new target: id_ext %016llx ioc_guid %016llx pkey %04x service_id %016llx sgid %pI6 dgid %pI6\n",
-		     be64_to_cpu(target->id_ext),
-		     be64_to_cpu(target->ioc_guid),
-		     be16_to_cpu(target->path.pkey),
-		     be64_to_cpu(target->service_id),
-		     target->path.sgid.raw, target->path.dgid.raw);
+	if (target->state != SRP_TARGET_REMOVED) {
+		shost_printk(KERN_DEBUG, target->scsi_host, PFX
+			     "new target: id_ext %016llx ioc_guid %016llx pkey %04x service_id %016llx sgid %pI6 dgid %pI6\n",
+			     be64_to_cpu(target->id_ext),
+			     be64_to_cpu(target->ioc_guid),
+			     be16_to_cpu(target->path.pkey),
+			     be64_to_cpu(target->service_id),
+			     target->path.sgid.raw, target->orig_dgid);
+	}
 
  	ret = count;
 
  out:
  	mutex_unlock(&host->add_target_mutex);
+
+	scsi_host_put(target->scsi_host);
+
  	return ret;
 
  err_disconnect:
drivers/infiniband/ulp/srp/ib_srp.h +1 -0
index e46ecb1..00c7c48 100644
@@ -73,6 +73,7 @@ enum {
  };
 
  enum srp_target_state {
+	SRP_TARGET_SCANNING,
  	SRP_TARGET_LIVE,
  	SRP_TARGET_REMOVED,
  };
Reviewed-by on v2 8/12
#55 lore raw

Re: [PATCH v2 08/12] IB/srp: Introduce two new srp_target_port member variables

In reply to Bart Van Assche
Quoted 164 lines · Bart Van Assche

Introduce the srp_target_port member variables 'sgid' and 'pkey'. Change the type of 'orig_dgid' from __be16[8] into union ib_gid. This patch does not change any functionality but makes the "Separate target and channel variables" patch easier to verify.

Cc Sagi Grimberg <[email protected]>
Cc Sebastian Parschauer <[email protected]>
---
  drivers/infiniband/ulp/srp/ib_srp.c | 39 ++++++++++++++++++++++---------------
  drivers/infiniband/ulp/srp/ib_srp.h |  4 +++-
  2 files changed, 26 insertions(+), 17 deletions(-)
drivers/infiniband/ulp/srp/ib_srp.c +23 -16
index a662c29..5685062 100644
@@ -262,7 +262,7 @@ static int srp_init_qp(struct srp_target_port *target,
 
  	ret = ib_find_pkey(target->srp_host->srp_dev->dev,
  			   target->srp_host->port,
-			   be16_to_cpu(target->path.pkey),
+			   be16_to_cpu(target->pkey),
  			   &attr->pkey_index);
  	if (ret)
  		goto out;
@@ -295,6 +295,10 @@ static int srp_new_cm_id(struct srp_target_port *target)
  	if (target->cm_id)
  		ib_destroy_cm_id(target->cm_id);
  	target->cm_id = new_cm_id;
+	target->path.sgid = target->sgid;
+	target->path.dgid = target->orig_dgid;
+	target->path.pkey = target->pkey;
+	target->path.service_id = target->service_id;
 
  	return 0;
  }
@@ -689,7 +693,7 @@ static int srp_send_req(struct srp_target_port *target)
  	 */
  	if (target->io_class == SRP_REV10_IB_IO_CLASS) {
  		memcpy(req->priv.initiator_port_id,
-		       &target->path.sgid.global.interface_id, 8);
+		       &target->sgid.global.interface_id, 8);
  		memcpy(req->priv.initiator_port_id + 8,
  		       &target->initiator_ext, 8);
  		memcpy(req->priv.target_port_id,     &target->ioc_guid, 8);
@@ -698,7 +702,7 @@ static int srp_send_req(struct srp_target_port *target)
  		memcpy(req->priv.initiator_port_id,
  		       &target->initiator_ext, 8);
  		memcpy(req->priv.initiator_port_id + 8,
-		       &target->path.sgid.global.interface_id, 8);
+		       &target->sgid.global.interface_id, 8);
  		memcpy(req->priv.target_port_id,     &target->id_ext, 8);
  		memcpy(req->priv.target_port_id + 8, &target->ioc_guid, 8);
  	}
@@ -2175,8 +2179,8 @@ static void srp_cm_rej_handler(struct ib_cm_id *cm_id,
  			else
  				shost_printk(KERN_WARNING, shost, PFX
  					     "SRP LOGIN from %pI6 to %pI6 REJECTED, reason 0x%08x\n",
-					     target->path.sgid.raw,
-					     target->orig_dgid, reason);
+					     target->sgid.raw,
+					     target->orig_dgid.raw, reason);
  		} else
  			shost_printk(KERN_WARNING, shost,
  				     "  REJ reason: IB_CM_REJ_CONSUMER_DEFINED,"
@@ -2464,7 +2468,7 @@ static ssize_t show_pkey(struct device *dev, struct device_attribute *attr,
  {
  	struct srp_target_port *target = host_to_target(class_to_shost(dev));
 
-	return sprintf(buf, "0x%04x\n", be16_to_cpu(target->path.pkey));
+	return sprintf(buf, "0x%04x\n", be16_to_cpu(target->pkey));
  }
 
  static ssize_t show_sgid(struct device *dev, struct device_attribute *attr,
@@ -2472,7 +2476,7 @@ static ssize_t show_sgid(struct device *dev, struct device_attribute *attr,
  {
  	struct srp_target_port *target = host_to_target(class_to_shost(dev));
 
-	return sprintf(buf, "%pI6\n", target->path.sgid.raw);
+	return sprintf(buf, "%pI6\n", target->sgid.raw);
  }
 
  static ssize_t show_dgid(struct device *dev, struct device_attribute *attr,
@@ -2488,7 +2492,7 @@ static ssize_t show_orig_dgid(struct device *dev,
  {
  	struct srp_target_port *target = host_to_target(class_to_shost(dev));
 
-	return sprintf(buf, "%pI6\n", target->orig_dgid);
+	return sprintf(buf, "%pI6\n", target->orig_dgid.raw);
  }
 
  static ssize_t show_req_lim(struct device *dev,
@@ -2826,11 +2830,15 @@ static int srp_parse_options(const char *buf, struct srp_target_port *target)
  			}
 
  			for (i = 0; i < 16; ++i) {
-				strlcpy(dgid, p + i * 2, 3);
-				target->path.dgid.raw[i] = simple_strtoul(dgid, NULL, 16);
+				strlcpy(dgid, p + i * 2, sizeof(dgid));
+				if (sscanf(dgid, "%hhx",
+					   &target->orig_dgid.raw[i]) < 1) {
+					ret = -EINVAL;
+					kfree(p);
+					goto out;
+				}
  			}
  			kfree(p);
-			memcpy(target->orig_dgid, target->path.dgid.raw, 16);
  			break;
 
  		case SRP_OPT_PKEY:
@@ -2838,7 +2846,7 @@ static int srp_parse_options(const char *buf, struct srp_target_port *target)
  				pr_warn("bad P_Key parameter '%s'\n", p);
  				goto out;
  			}
-			target->path.pkey = cpu_to_be16(token);
+			target->pkey = cpu_to_be16(token);
  			break;
 
  		case SRP_OPT_SERVICE_ID:
@@ -2848,7 +2856,6 @@ static int srp_parse_options(const char *buf, struct srp_target_port *target)
  				goto out;
  			}
  			target->service_id = cpu_to_be64(simple_strtoull(p, NULL, 16));
-			target->path.service_id = target->service_id;
  			kfree(p);
  			break;
 
@@ -3058,7 +3065,7 @@ static ssize_t srp_create_target(struct device *dev,
  	if (ret)
  		goto err_free_mem;
 
-	ret = ib_query_gid(ibdev, host->port, 0, &target->path.sgid);
+	ret = ib_query_gid(ibdev, host->port, 0, &target->sgid);
  	if (ret)
  		goto err_free_mem;
 
@@ -3086,9 +3093,9 @@ static ssize_t srp_create_target(struct device *dev,
  			     "new target: id_ext %016llx ioc_guid %016llx pkey %04x service_id %016llx sgid %pI6 dgid %pI6\n",
  			     be64_to_cpu(target->id_ext),
  			     be64_to_cpu(target->ioc_guid),
-			     be16_to_cpu(target->path.pkey),
+			     be16_to_cpu(target->pkey),
  			     be64_to_cpu(target->service_id),
-			     target->path.sgid.raw, target->orig_dgid);
+			     target->sgid.raw, target->orig_dgid.raw);
  	}
 
  	ret = count;
drivers/infiniband/ulp/srp/ib_srp.h +1 -0
index 00c7c48..8635ab6 100644
@@ -157,6 +157,7 @@ struct srp_target_port {
  	 * command processing. Try to keep them packed into cachelines.
  	 */
 
+	union ib_gid		sgid;
  	__be64			id_ext;
  	__be64			ioc_guid;
  	__be64			service_id;

drivers/infiniband/ulp/srp/ib_srp.h struct srp_target_port { · line 182

Quoted 10 lines
drivers/infiniband/ulp/srp/ib_srp.h +2 -1
@@ -173,8 +174,9 @@ struct srp_target_port {
  	int			comp_vector;
  	int			tl_retry_count;
 
+	union ib_gid		orig_dgid;
+	__be16			pkey;
  	struct ib_sa_path_rec	path;
-	__be16			orig_dgid[8];
  	struct ib_sa_query     *path_query;
  	int			path_query_id;
 

Yeh looks good.

Acked-by on v2 9/12
#25 lore raw

Re: [PATCH v2 09/12] IB/srp: Separate target and channel variables

In reply to Bart Van Assche
Quoted 6 lines · Bart Van Assche

Changes in this patch:
- Move channel variables into a new structure (struct srp_rdma_ch).
- Add an srp_target_port pointer, 'lock' and 'comp_vector' members in struct srp_rdma_ch.
- Add code to initialize these three new member variables.
- Many boring "target->" into "ch->" changes.

Quoted 8 lines

- The cm_id and completion handler context pointers are now of type srp_rdma_ch * instead of srp_target_port *.
- Three kzalloc(a * b, f) calls have been changed into kcalloc(a, b, f) to avoid that this patch would trigger a checkpatch warning.
- Two casts from u64 into unsigned long long have been left out because these are superfluous. Since considerable time u64 is defined as unsigned long long for all architectures supported by the Linux kernel.

This patch is pretty exhausting...
Didn't find anything wrong but I didn't carefully review every bit of it.

You can add:

Quoted 1,792 lines
Cc Sagi Grimberg <[email protected]>
Cc Sebastian Parschauer <[email protected]>
---
  drivers/infiniband/ulp/srp/ib_srp.c | 674 +++++++++++++++++++-----------------
  drivers/infiniband/ulp/srp/ib_srp.h |  64 ++--
  2 files changed, 403 insertions(+), 335 deletions(-)
drivers/infiniband/ulp/srp/ib_srp.c +361 -313
index 5685062..cc0bf83b 100644
@@ -125,8 +125,8 @@ MODULE_PARM_DESC(dev_loss_tmo,
 
  static void srp_add_one(struct ib_device *device);
  static void srp_remove_one(struct ib_device *device);
-static void srp_recv_completion(struct ib_cq *cq, void *target_ptr);
-static void srp_send_completion(struct ib_cq *cq, void *target_ptr);
+static void srp_recv_completion(struct ib_cq *cq, void *ch_ptr);
+static void srp_send_completion(struct ib_cq *cq, void *ch_ptr);
  static int srp_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event);
 
  static struct scsi_transport_template *ib_srp_transport_template;
@@ -283,22 +283,23 @@ out:
  	return ret;
  }
 
-static int srp_new_cm_id(struct srp_target_port *target)
+static int srp_new_cm_id(struct srp_rdma_ch *ch)
  {
+	struct srp_target_port *target = ch->target;
  	struct ib_cm_id *new_cm_id;
 
  	new_cm_id = ib_create_cm_id(target->srp_host->srp_dev->dev,
-				    srp_cm_handler, target);
+				    srp_cm_handler, ch);
  	if (IS_ERR(new_cm_id))
  		return PTR_ERR(new_cm_id);
 
-	if (target->cm_id)
-		ib_destroy_cm_id(target->cm_id);
-	target->cm_id = new_cm_id;
-	target->path.sgid = target->sgid;
-	target->path.dgid = target->orig_dgid;
-	target->path.pkey = target->pkey;
-	target->path.service_id = target->service_id;
+	if (ch->cm_id)
+		ib_destroy_cm_id(ch->cm_id);
+	ch->cm_id = new_cm_id;
+	ch->path.sgid = target->sgid;
+	ch->path.dgid = target->orig_dgid;
+	ch->path.pkey = target->pkey;
+	ch->path.service_id = target->service_id;
 
  	return 0;
  }
@@ -447,8 +448,9 @@ static struct srp_fr_pool *srp_alloc_fr_pool(struct srp_target_port *target)
  				  dev->max_pages_per_mr);
  }
 
-static int srp_create_target_ib(struct srp_target_port *target)
+static int srp_create_ch_ib(struct srp_rdma_ch *ch)
  {
+	struct srp_target_port *target = ch->target;
  	struct srp_device *dev = target->srp_host->srp_dev;
  	struct ib_qp_init_attr *init_attr;
  	struct ib_cq *recv_cq, *send_cq;
@@ -462,15 +464,15 @@ static int srp_create_target_ib(struct srp_target_port *target)
  	if (!init_attr)
  		return -ENOMEM;
 
-	recv_cq = ib_create_cq(dev->dev, srp_recv_completion, NULL, target,
-			       target->queue_size, target->comp_vector);
+	recv_cq = ib_create_cq(dev->dev, srp_recv_completion, NULL, ch,
+			       target->queue_size, ch->comp_vector);
  	if (IS_ERR(recv_cq)) {
  		ret = PTR_ERR(recv_cq);
  		goto err;
  	}
 
-	send_cq = ib_create_cq(dev->dev, srp_send_completion, NULL, target,
-			       m * target->queue_size, target->comp_vector);
+	send_cq = ib_create_cq(dev->dev, srp_send_completion, NULL, ch,
+			       m * target->queue_size, ch->comp_vector);
  	if (IS_ERR(send_cq)) {
  		ret = PTR_ERR(send_cq);
  		goto err_recv_cq;
@@ -506,9 +508,9 @@ static int srp_create_target_ib(struct srp_target_port *target)
  				     "FR pool allocation failed (%d)\n", ret);
  			goto err_qp;
  		}
-		if (target->fr_pool)
-			srp_destroy_fr_pool(target->fr_pool);
-		target->fr_pool = fr_pool;
+		if (ch->fr_pool)
+			srp_destroy_fr_pool(ch->fr_pool);
+		ch->fr_pool = fr_pool;
  	} else if (!dev->use_fast_reg && dev->has_fmr) {
  		fmr_pool = srp_alloc_fmr_pool(target);
  		if (IS_ERR(fmr_pool)) {
@@ -517,21 +519,21 @@ static int srp_create_target_ib(struct srp_target_port *target)
  				     "FMR pool allocation failed (%d)\n", ret);
  			goto err_qp;
  		}
-		if (target->fmr_pool)
-			ib_destroy_fmr_pool(target->fmr_pool);
-		target->fmr_pool = fmr_pool;
+		if (ch->fmr_pool)
+			ib_destroy_fmr_pool(ch->fmr_pool);
+		ch->fmr_pool = fmr_pool;
  	}
 
-	if (target->qp)
-		ib_destroy_qp(target->qp);
-	if (target->recv_cq)
-		ib_destroy_cq(target->recv_cq);
-	if (target->send_cq)
-		ib_destroy_cq(target->send_cq);
+	if (ch->qp)
+		ib_destroy_qp(ch->qp);
+	if (ch->recv_cq)
+		ib_destroy_cq(ch->recv_cq);
+	if (ch->send_cq)
+		ib_destroy_cq(ch->send_cq);
 
-	target->qp = qp;
-	target->recv_cq = recv_cq;
-	target->send_cq = send_cq;
+	ch->qp = qp;
+	ch->recv_cq = recv_cq;
+	ch->send_cq = send_cq;
 
  	kfree(init_attr);
  	return 0;
@@ -552,98 +554,102 @@ err:
 
  /*
   * Note: this function may be called without srp_alloc_iu_bufs() having been
- * invoked. Hence the target->[rt]x_ring checks.
+ * invoked. Hence the ch->[rt]x_ring checks.
   */
-static void srp_free_target_ib(struct srp_target_port *target)
+static void srp_free_ch_ib(struct srp_target_port *target,
+			   struct srp_rdma_ch *ch)
  {
  	struct srp_device *dev = target->srp_host->srp_dev;
  	int i;
 
-	if (target->cm_id) {
-		ib_destroy_cm_id(target->cm_id);
-		target->cm_id = NULL;
+	if (ch->cm_id) {
+		ib_destroy_cm_id(ch->cm_id);
+		ch->cm_id = NULL;
  	}
 
  	if (dev->use_fast_reg) {
-		if (target->fr_pool)
-			srp_destroy_fr_pool(target->fr_pool);
+		if (ch->fr_pool)
+			srp_destroy_fr_pool(ch->fr_pool);
  	} else {
-		if (target->fmr_pool)
-			ib_destroy_fmr_pool(target->fmr_pool);
+		if (ch->fmr_pool)
+			ib_destroy_fmr_pool(ch->fmr_pool);
  	}
-	ib_destroy_qp(target->qp);
-	ib_destroy_cq(target->send_cq);
-	ib_destroy_cq(target->recv_cq);
+	ib_destroy_qp(ch->qp);
+	ib_destroy_cq(ch->send_cq);
+	ib_destroy_cq(ch->recv_cq);
 
-	target->qp = NULL;
-	target->send_cq = target->recv_cq = NULL;
+	ch->qp = NULL;
+	ch->send_cq = ch->recv_cq = NULL;
 
-	if (target->rx_ring) {
+	if (ch->rx_ring) {
  		for (i = 0; i < target->queue_size; ++i)
-			srp_free_iu(target->srp_host, target->rx_ring[i]);
-		kfree(target->rx_ring);
-		target->rx_ring = NULL;
+			srp_free_iu(target->srp_host, ch->rx_ring[i]);
+		kfree(ch->rx_ring);
+		ch->rx_ring = NULL;
  	}
-	if (target->tx_ring) {
+	if (ch->tx_ring) {
  		for (i = 0; i < target->queue_size; ++i)
-			srp_free_iu(target->srp_host, target->tx_ring[i]);
-		kfree(target->tx_ring);
-		target->tx_ring = NULL;
+			srp_free_iu(target->srp_host, ch->tx_ring[i]);
+		kfree(ch->tx_ring);
+		ch->tx_ring = NULL;
  	}
  }
 
  static void srp_path_rec_completion(int status,
  				    struct ib_sa_path_rec *pathrec,
-				    void *target_ptr)
+				    void *ch_ptr)
  {
-	struct srp_target_port *target = target_ptr;
+	struct srp_rdma_ch *ch = ch_ptr;
+	struct srp_target_port *target = ch->target;
 
-	target->status = status;
+	ch->status = status;
  	if (status)
  		shost_printk(KERN_ERR, target->scsi_host,
  			     PFX "Got failed path rec status %d\n", status);
  	else
-		target->path = *pathrec;
-	complete(&target->done);
+		ch->path = *pathrec;
+	complete(&ch->done);
  }
 
-static int srp_lookup_path(struct srp_target_port *target)
+static int srp_lookup_path(struct srp_rdma_ch *ch)
  {
+	struct srp_target_port *target = ch->target;
  	int ret;
 
-	target->path.numb_path = 1;
-
-	init_completion(&target->done);
-
-	target->path_query_id = ib_sa_path_rec_get(&srp_sa_client,
-						   target->srp_host->srp_dev->dev,
-						   target->srp_host->port,
-						   &target->path,
-						   IB_SA_PATH_REC_SERVICE_ID	|
-						   IB_SA_PATH_REC_DGID		|
-						   IB_SA_PATH_REC_SGID		|
-						   IB_SA_PATH_REC_NUMB_PATH	|
-						   IB_SA_PATH_REC_PKEY,
-						   SRP_PATH_REC_TIMEOUT_MS,
-						   GFP_KERNEL,
-						   srp_path_rec_completion,
-						   target, &target->path_query);
-	if (target->path_query_id < 0)
-		return target->path_query_id;
-
-	ret = wait_for_completion_interruptible(&target->done);
+	ch->path.numb_path = 1;
+
+	init_completion(&ch->done);
+
+	ch->path_query_id = ib_sa_path_rec_get(&srp_sa_client,
+					       target->srp_host->srp_dev->dev,
+					       target->srp_host->port,
+					       &ch->path,
+					       IB_SA_PATH_REC_SERVICE_ID |
+					       IB_SA_PATH_REC_DGID	 |
+					       IB_SA_PATH_REC_SGID	 |
+					       IB_SA_PATH_REC_NUMB_PATH	 |
+					       IB_SA_PATH_REC_PKEY,
+					       SRP_PATH_REC_TIMEOUT_MS,
+					       GFP_KERNEL,
+					       srp_path_rec_completion,
+					       ch, &ch->path_query);
+	if (ch->path_query_id < 0)
+		return ch->path_query_id;
+
+	ret = wait_for_completion_interruptible(&ch->done);
  	if (ret < 0)
  		return ret;
 
-	if (target->status < 0)
+	if (ch->status < 0)
  		shost_printk(KERN_WARNING, target->scsi_host,
  			     PFX "Path record query failed\n");
 
-	return target->status;
+	return ch->status;
  }
 
-static int srp_send_req(struct srp_target_port *target)
+static int srp_send_req(struct srp_rdma_ch *ch)
  {
+	struct srp_target_port *target = ch->target;
  	struct {
  		struct ib_cm_req_param param;
  		struct srp_login_req   priv;
@@ -654,11 +660,11 @@ static int srp_send_req(struct srp_target_port *target)
  	if (!req)
  		return -ENOMEM;
 
-	req->param.primary_path 	      = &target->path;
+	req->param.primary_path		      = &ch->path;
  	req->param.alternate_path 	      = NULL;
  	req->param.service_id 		      = target->service_id;
-	req->param.qp_num 		      = target->qp->qp_num;
-	req->param.qp_type 		      = target->qp->qp_type;
+	req->param.qp_num		      = ch->qp->qp_num;
+	req->param.qp_type		      = ch->qp->qp_type;
  	req->param.private_data 	      = &req->priv;
  	req->param.private_data_len 	      = sizeof req->priv;
  	req->param.flow_control 	      = 1;
@@ -722,7 +728,7 @@ static int srp_send_req(struct srp_target_port *target)
  		       &target->srp_host->srp_dev->dev->node_guid, 8);
  	}
 
-	status = ib_send_cm_req(target->cm_id, &req->param);
+	status = ib_send_cm_req(ch->cm_id, &req->param);
 
  	kfree(req);
 
@@ -763,28 +769,31 @@ static bool srp_change_conn_state(struct srp_target_port *target,
 
  static void srp_disconnect_target(struct srp_target_port *target)
  {
+	struct srp_rdma_ch *ch = &target->ch;
+
  	if (srp_change_conn_state(target, false)) {
  		/* XXX should send SRP_I_LOGOUT request */
 
-		if (ib_send_cm_dreq(target->cm_id, NULL, 0)) {
+		if (ib_send_cm_dreq(ch->cm_id, NULL, 0)) {
  			shost_printk(KERN_DEBUG, target->scsi_host,
  				     PFX "Sending CM DREQ failed\n");
  		}
  	}
  }
 
-static void srp_free_req_data(struct srp_target_port *target)
+static void srp_free_req_data(struct srp_target_port *target,
+			      struct srp_rdma_ch *ch)
  {
  	struct srp_device *dev = target->srp_host->srp_dev;
  	struct ib_device *ibdev = dev->dev;
  	struct srp_request *req;
  	int i;
 
-	if (!target->req_ring)
+	if (!ch->req_ring)
  		return;
 
  	for (i = 0; i < target->req_ring_size; ++i) {
-		req = &target->req_ring[i];
+		req = &ch->req_ring[i];
  		if (dev->use_fast_reg)
  			kfree(req->fr_list);
  		else
@@ -798,12 +807,13 @@ static void srp_free_req_data(struct srp_target_port *target)
  		kfree(req->indirect_desc);
  	}
 
-	kfree(target->req_ring);
-	target->req_ring = NULL;
+	kfree(ch->req_ring);
+	ch->req_ring = NULL;
  }
 
-static int srp_alloc_req_data(struct srp_target_port *target)
+static int srp_alloc_req_data(struct srp_rdma_ch *ch)
  {
+	struct srp_target_port *target = ch->target;
  	struct srp_device *srp_dev = target->srp_host->srp_dev;
  	struct ib_device *ibdev = srp_dev->dev;
  	struct srp_request *req;
@@ -811,15 +821,15 @@ static int srp_alloc_req_data(struct srp_target_port *target)
  	dma_addr_t dma_addr;
  	int i, ret = -ENOMEM;
 
-	INIT_LIST_HEAD(&target->free_reqs);
+	INIT_LIST_HEAD(&ch->free_reqs);
 
-	target->req_ring = kzalloc(target->req_ring_size *
-				   sizeof(*target->req_ring), GFP_KERNEL);
-	if (!target->req_ring)
+	ch->req_ring = kcalloc(target->req_ring_size, sizeof(*ch->req_ring),
+			       GFP_KERNEL);
+	if (!ch->req_ring)
  		goto out;
 
  	for (i = 0; i < target->req_ring_size; ++i) {
-		req = &target->req_ring[i];
+		req = &ch->req_ring[i];
  		mr_list = kmalloc(target->cmd_sg_cnt * sizeof(void *),
  				  GFP_KERNEL);
  		if (!mr_list)
@@ -844,7 +854,7 @@ static int srp_alloc_req_data(struct srp_target_port *target)
 
  		req->indirect_dma_addr = dma_addr;
  		req->index = i;
-		list_add_tail(&req->list, &target->free_reqs);
+		list_add_tail(&req->list, &ch->free_reqs);
  	}
  	ret = 0;
 
@@ -869,6 +879,8 @@ static void srp_del_scsi_host_attr(struct Scsi_Host *shost)
 
  static void srp_remove_target(struct srp_target_port *target)
  {
+	struct srp_rdma_ch *ch = &target->ch;
+
  	WARN_ON_ONCE(target->state != SRP_TARGET_REMOVED);
 
  	srp_del_scsi_host_attr(target->scsi_host);
@@ -877,10 +889,10 @@ static void srp_remove_target(struct srp_target_port *target)
  	scsi_remove_host(target->scsi_host);
  	srp_stop_rport_timers(target->rport);
  	srp_disconnect_target(target);
-	srp_free_target_ib(target);
+	srp_free_ch_ib(target, ch);
  	cancel_work_sync(&target->tl_err_work);
  	srp_rport_put(target->rport);
-	srp_free_req_data(target);
+	srp_free_req_data(target, ch);
 
  	spin_lock(&target->srp_host->target_lock);
  	list_del(&target->list);
@@ -906,24 +918,25 @@ static void srp_rport_delete(struct srp_rport *rport)
  	srp_queue_remove_work(target);
  }
 
-static int srp_connect_target(struct srp_target_port *target)
+static int srp_connect_ch(struct srp_rdma_ch *ch)
  {
+	struct srp_target_port *target = ch->target;
  	int ret;
 
  	WARN_ON_ONCE(target->connected);
 
  	target->qp_in_error = false;
 
-	ret = srp_lookup_path(target);
+	ret = srp_lookup_path(ch);
  	if (ret)
  		return ret;
 
  	while (1) {
-		init_completion(&target->done);
-		ret = srp_send_req(target);
+		init_completion(&ch->done);
+		ret = srp_send_req(ch);
  		if (ret)
  			return ret;
-		ret = wait_for_completion_interruptible(&target->done);
+		ret = wait_for_completion_interruptible(&ch->done);
  		if (ret < 0)
  			return ret;
 
@@ -933,13 +946,13 @@ static int srp_connect_target(struct srp_target_port *target)
  		 * back, or SRP_DLID_REDIRECT if we get a lid/qp
  		 * redirect REJ back.
  		 */
-		switch (target->status) {
+		switch (ch->status) {
  		case 0:
  			srp_change_conn_state(target, true);
  			return 0;
 
  		case SRP_PORT_REDIRECT:
-			ret = srp_lookup_path(target);
+			ret = srp_lookup_path(ch);
  			if (ret)
  				return ret;
  			break;
@@ -950,16 +963,16 @@ static int srp_connect_target(struct srp_target_port *target)
  		case SRP_STALE_CONN:
  			shost_printk(KERN_ERR, target->scsi_host, PFX
  				     "giving up on stale connection\n");
-			target->status = -ECONNRESET;
-			return target->status;
+			ch->status = -ECONNRESET;
+			return ch->status;
 
  		default:
-			return target->status;
+			return ch->status;
  		}
  	}
  }
 
-static int srp_inv_rkey(struct srp_target_port *target, u32 rkey)
+static int srp_inv_rkey(struct srp_rdma_ch *ch, u32 rkey)
  {
  	struct ib_send_wr *bad_wr;
  	struct ib_send_wr wr = {
@@ -971,13 +984,14 @@ static int srp_inv_rkey(struct srp_target_port *target, u32 rkey)
  		.ex.invalidate_rkey = rkey,
  	};
 
-	return ib_post_send(target->qp, &wr, &bad_wr);
+	return ib_post_send(ch->qp, &wr, &bad_wr);
  }
 
  static void srp_unmap_data(struct scsi_cmnd *scmnd,
-			   struct srp_target_port *target,
+			   struct srp_rdma_ch *ch,
  			   struct srp_request *req)
  {
+	struct srp_target_port *target = ch->target;
  	struct srp_device *dev = target->srp_host->srp_dev;
  	struct ib_device *ibdev = dev->dev;
  	int i, res;
@@ -991,7 +1005,7 @@ static void srp_unmap_data(struct scsi_cmnd *scmnd,
  		struct srp_fr_desc **pfr;
 
  		for (i = req->nmdesc, pfr = req->fr_list; i > 0; i--, pfr++) {
-			res = srp_inv_rkey(target, (*pfr)->mr->rkey);
+			res = srp_inv_rkey(ch, (*pfr)->mr->rkey);
  			if (res < 0) {
  				shost_printk(KERN_ERR, target->scsi_host, PFX
  				  "Queueing INV WR for rkey %#x failed (%d)\n",
@@ -1001,7 +1015,7 @@ static void srp_unmap_data(struct scsi_cmnd *scmnd,
  			}
  		}
  		if (req->nmdesc)
-			srp_fr_pool_put(target->fr_pool, req->fr_list,
+			srp_fr_pool_put(ch->fr_pool, req->fr_list,
  					req->nmdesc);
  	} else {
  		struct ib_pool_fmr **pfmr;
@@ -1016,7 +1030,7 @@ static void srp_unmap_data(struct scsi_cmnd *scmnd,
 
  /**
   * srp_claim_req - Take ownership of the scmnd associated with a request.
- * @target: SRP target port.
+ * @ch: SRP RDMA channel.
   * @req: SRP request.
   * @sdev: If not NULL, only take ownership for this SCSI device.
   * @scmnd: If NULL, take ownership of @req->scmnd. If not NULL, only take
@@ -1025,14 +1039,14 @@ static void srp_unmap_data(struct scsi_cmnd *scmnd,
   * Return value:
   * Either NULL or a pointer to the SCSI command the caller became owner of.
   */
-static struct scsi_cmnd *srp_claim_req(struct srp_target_port *target,
+static struct scsi_cmnd *srp_claim_req(struct srp_rdma_ch *ch,
  				       struct srp_request *req,
  				       struct scsi_device *sdev,
  				       struct scsi_cmnd *scmnd)
  {
  	unsigned long flags;
 
-	spin_lock_irqsave(&target->lock, flags);
+	spin_lock_irqsave(&ch->lock, flags);
  	if (req->scmnd &&
  	    (!sdev || req->scmnd->device == sdev) &&
  	    (!scmnd || req->scmnd == scmnd)) {
@@ -1041,40 +1055,38 @@ static struct scsi_cmnd *srp_claim_req(struct srp_target_port *target,
  	} else {
  		scmnd = NULL;
  	}
-	spin_unlock_irqrestore(&target->lock, flags);
+	spin_unlock_irqrestore(&ch->lock, flags);
 
  	return scmnd;
  }
 
  /**
   * srp_free_req() - Unmap data and add request to the free request list.
- * @target: SRP target port.
+ * @ch:     SRP RDMA channel.
   * @req:    Request to be freed.
   * @scmnd:  SCSI command associated with @req.
   * @req_lim_delta: Amount to be added to @target->req_lim.
   */
-static void srp_free_req(struct srp_target_port *target,
-			 struct srp_request *req, struct scsi_cmnd *scmnd,
-			 s32 req_lim_delta)
+static void srp_free_req(struct srp_rdma_ch *ch, struct srp_request *req,
+			 struct scsi_cmnd *scmnd, s32 req_lim_delta)
  {
  	unsigned long flags;
 
-	srp_unmap_data(scmnd, target, req);
+	srp_unmap_data(scmnd, ch, req);
 
-	spin_lock_irqsave(&target->lock, flags);
-	target->req_lim += req_lim_delta;
-	list_add_tail(&req->list, &target->free_reqs);
-	spin_unlock_irqrestore(&target->lock, flags);
+	spin_lock_irqsave(&ch->lock, flags);
+	ch->req_lim += req_lim_delta;
+	list_add_tail(&req->list, &ch->free_reqs);
+	spin_unlock_irqrestore(&ch->lock, flags);
  }
 
-static void srp_finish_req(struct srp_target_port *target,
-			   struct srp_request *req, struct scsi_device *sdev,
-			   int result)
+static void srp_finish_req(struct srp_rdma_ch *ch, struct srp_request *req,
+			   struct scsi_device *sdev, int result)
  {
-	struct scsi_cmnd *scmnd = srp_claim_req(target, req, sdev, NULL);
+	struct scsi_cmnd *scmnd = srp_claim_req(ch, req, sdev, NULL);
 
  	if (scmnd) {
-		srp_free_req(target, req, scmnd, 0);
+		srp_free_req(ch, req, scmnd, 0);
  		scmnd->result = result;
  		scmnd->scsi_done(scmnd);
  	}
@@ -1083,6 +1095,7 @@ static void srp_finish_req(struct srp_target_port *target,
  static void srp_terminate_io(struct srp_rport *rport)
  {
  	struct srp_target_port *target = rport->lld_data;
+	struct srp_rdma_ch *ch = &target->ch;
  	struct Scsi_Host *shost = target->scsi_host;
  	struct scsi_device *sdev;
  	int i;
@@ -1095,8 +1108,9 @@ static void srp_terminate_io(struct srp_rport *rport)
  		WARN_ON_ONCE(sdev->request_queue->request_fn_active);
 
  	for (i = 0; i < target->req_ring_size; ++i) {
-		struct srp_request *req = &target->req_ring[i];
-		srp_finish_req(target, req, NULL, DID_TRANSPORT_FAILFAST << 16);
+		struct srp_request *req = &ch->req_ring[i];
+
+		srp_finish_req(ch, req, NULL, DID_TRANSPORT_FAILFAST << 16);
  	}
  }
 
@@ -1112,6 +1126,7 @@ static void srp_terminate_io(struct srp_rport *rport)
  static int srp_rport_reconnect(struct srp_rport *rport)
  {
  	struct srp_target_port *target = rport->lld_data;
+	struct srp_rdma_ch *ch = &target->ch;
  	int i, ret;
 
  	srp_disconnect_target(target);
@@ -1124,11 +1139,12 @@ static int srp_rport_reconnect(struct srp_rport *rport)
  	 * case things are really fouled up. Doing so also ensures that all CM
  	 * callbacks will have finished before a new QP is allocated.
  	 */
-	ret = srp_new_cm_id(target);
+	ret = srp_new_cm_id(ch);
 
  	for (i = 0; i < target->req_ring_size; ++i) {
-		struct srp_request *req = &target->req_ring[i];
-		srp_finish_req(target, req, NULL, DID_RESET << 16);
+		struct srp_request *req = &ch->req_ring[i];
+
+		srp_finish_req(ch, req, NULL, DID_RESET << 16);
  	}
 
  	/*
@@ -1136,14 +1152,14 @@ static int srp_rport_reconnect(struct srp_rport *rport)
  	 * QP. This guarantees that all callback functions for the old QP have
  	 * finished before any send requests are posted on the new QP.
  	 */
-	ret += srp_create_target_ib(target);
+	ret += srp_create_ch_ib(ch);
 
-	INIT_LIST_HEAD(&target->free_tx);
+	INIT_LIST_HEAD(&ch->free_tx);
  	for (i = 0; i < target->queue_size; ++i)
-		list_add(&target->tx_ring[i]->list, &target->free_tx);
+		list_add(&ch->tx_ring[i]->list, &ch->free_tx);
 
  	if (ret == 0)
-		ret = srp_connect_target(target);
+		ret = srp_connect_ch(ch);
 
  	if (ret == 0)
  		shost_printk(KERN_INFO, target->scsi_host,
@@ -1167,12 +1183,12 @@ static void srp_map_desc(struct srp_map_state *state, dma_addr_t dma_addr,
  }
 
  static int srp_map_finish_fmr(struct srp_map_state *state,
-			      struct srp_target_port *target)
+			      struct srp_rdma_ch *ch)
  {
  	struct ib_pool_fmr *fmr;
  	u64 io_addr = 0;
 
-	fmr = ib_fmr_pool_map_phys(target->fmr_pool, state->pages,
+	fmr = ib_fmr_pool_map_phys(ch->fmr_pool, state->pages,
  				   state->npages, io_addr);
  	if (IS_ERR(fmr))
  		return PTR_ERR(fmr);
@@ -1186,15 +1202,16 @@ static int srp_map_finish_fmr(struct srp_map_state *state,
  }
 
  static int srp_map_finish_fr(struct srp_map_state *state,
-			     struct srp_target_port *target)
+			     struct srp_rdma_ch *ch)
  {
+	struct srp_target_port *target = ch->target;
  	struct srp_device *dev = target->srp_host->srp_dev;
  	struct ib_send_wr *bad_wr;
  	struct ib_send_wr wr;
  	struct srp_fr_desc *desc;
  	u32 rkey;
 
-	desc = srp_fr_pool_get(target->fr_pool);
+	desc = srp_fr_pool_get(ch->fr_pool);
  	if (!desc)
  		return -ENOMEM;
 
@@ -1223,12 +1240,13 @@ static int srp_map_finish_fr(struct srp_map_state *state,
  	srp_map_desc(state, state->base_dma_addr, state->dma_len,
  		     desc->mr->rkey);
 
-	return ib_post_send(target->qp, &wr, &bad_wr);
+	return ib_post_send(ch->qp, &wr, &bad_wr);
  }
 
  static int srp_finish_mapping(struct srp_map_state *state,
-			      struct srp_target_port *target)
+			      struct srp_rdma_ch *ch)
  {
+	struct srp_target_port *target = ch->target;
  	int ret = 0;
 
  	if (state->npages == 0)
@@ -1239,8 +1257,8 @@ static int srp_finish_mapping(struct srp_map_state *state,
  			     target->rkey);
  	else
  		ret = target->srp_host->srp_dev->use_fast_reg ?
-			srp_map_finish_fr(state, target) :
-			srp_map_finish_fmr(state, target);
+			srp_map_finish_fr(state, ch) :
+			srp_map_finish_fmr(state, ch);
 
  	if (ret == 0) {
  		state->npages = 0;
@@ -1260,10 +1278,11 @@ static void srp_map_update_start(struct srp_map_state *state,
  }
 
  static int srp_map_sg_entry(struct srp_map_state *state,
-			    struct srp_target_port *target,
+			    struct srp_rdma_ch *ch,
  			    struct scatterlist *sg, int sg_index,
  			    bool use_mr)
  {
+	struct srp_target_port *target = ch->target;
  	struct srp_device *dev = target->srp_host->srp_dev;
  	struct ib_device *ibdev = dev->dev;
  	dma_addr_t dma_addr = ib_sg_dma_address(ibdev, sg);
@@ -1292,7 +1311,7 @@ static int srp_map_sg_entry(struct srp_map_state *state,
  	 */
  	if ((!dev->use_fast_reg && dma_addr & ~dev->mr_page_mask) ||
  	    dma_len > dev->mr_max_size) {
-		ret = srp_finish_mapping(state, target);
+		ret = srp_finish_mapping(state, ch);
  		if (ret)
  			return ret;
 
@@ -1313,7 +1332,7 @@ static int srp_map_sg_entry(struct srp_map_state *state,
  	while (dma_len) {
  		unsigned offset = dma_addr & ~dev->mr_page_mask;
  		if (state->npages == dev->max_pages_per_mr || offset != 0) {
-			ret = srp_finish_mapping(state, target);
+			ret = srp_finish_mapping(state, ch);
  			if (ret)
  				return ret;
 
@@ -1337,17 +1356,18 @@ static int srp_map_sg_entry(struct srp_map_state *state,
  	 */
  	ret = 0;
  	if (len != dev->mr_page_size) {
-		ret = srp_finish_mapping(state, target);
+		ret = srp_finish_mapping(state, ch);
  		if (!ret)
  			srp_map_update_start(state, NULL, 0, 0);
  	}
  	return ret;
  }
 
-static int srp_map_sg(struct srp_map_state *state,
-		      struct srp_target_port *target, struct srp_request *req,
-		      struct scatterlist *scat, int count)
+static int srp_map_sg(struct srp_map_state *state, struct srp_rdma_ch *ch,
+		      struct srp_request *req, struct scatterlist *scat,
+		      int count)
  {
+	struct srp_target_port *target = ch->target;
  	struct srp_device *dev = target->srp_host->srp_dev;
  	struct ib_device *ibdev = dev->dev;
  	struct scatterlist *sg;
@@ -1358,14 +1378,14 @@ static int srp_map_sg(struct srp_map_state *state,
  	state->pages	= req->map_page;
  	if (dev->use_fast_reg) {
  		state->next_fr = req->fr_list;
-		use_mr = !!target->fr_pool;
+		use_mr = !!ch->fr_pool;
  	} else {
  		state->next_fmr = req->fmr_list;
-		use_mr = !!target->fmr_pool;
+		use_mr = !!ch->fmr_pool;
  	}
 
  	for_each_sg(scat, sg, count, i) {
-		if (srp_map_sg_entry(state, target, sg, i, use_mr)) {
+		if (srp_map_sg_entry(state, ch, sg, i, use_mr)) {
  			/*
  			 * Memory registration failed, so backtrack to the
  			 * first unmapped entry and continue on without using
@@ -1387,7 +1407,7 @@ backtrack:
  		}
  	}
 
-	if (use_mr && srp_finish_mapping(state, target))
+	if (use_mr && srp_finish_mapping(state, ch))
  		goto backtrack;
 
  	req->nmdesc = state->nmdesc;
@@ -1395,9 +1415,10 @@ backtrack:
  	return 0;
  }
 
-static int srp_map_data(struct scsi_cmnd *scmnd, struct srp_target_port *target,
+static int srp_map_data(struct scsi_cmnd *scmnd, struct srp_rdma_ch *ch,
  			struct srp_request *req)
  {
+	struct srp_target_port *target = ch->target;
  	struct scatterlist *scat;
  	struct srp_cmd *cmd = req->cmd->buf;
  	int len, nents, count;
@@ -1459,7 +1480,7 @@ static int srp_map_data(struct scsi_cmnd *scmnd, struct srp_target_port *target,
  				   target->indirect_size, DMA_TO_DEVICE);
 
  	memset(&state, 0, sizeof(state));
-	srp_map_sg(&state, target, req, scat, count);
+	srp_map_sg(&state, ch, req, scat, count);
 
  	/* We've mapped the request, now pull as much of the indirect
  	 * descriptor table as we can into the command buffer. If this
@@ -1520,20 +1541,20 @@ map_complete:
  /*
   * Return an IU and possible credit to the free pool
   */
-static void srp_put_tx_iu(struct srp_target_port *target, struct srp_iu *iu,
+static void srp_put_tx_iu(struct srp_rdma_ch *ch, struct srp_iu *iu,
  			  enum srp_iu_type iu_type)
  {
  	unsigned long flags;
 
-	spin_lock_irqsave(&target->lock, flags);
-	list_add(&iu->list, &target->free_tx);
+	spin_lock_irqsave(&ch->lock, flags);
+	list_add(&iu->list, &ch->free_tx);
  	if (iu_type != SRP_IU_RSP)
-		++target->req_lim;
-	spin_unlock_irqrestore(&target->lock, flags);
+		++ch->req_lim;
+	spin_unlock_irqrestore(&ch->lock, flags);
  }
 
  /*
- * Must be called with target->lock held to protect req_lim and free_tx.
+ * Must be called with ch->lock held to protect req_lim and free_tx.
   * If IU is not sent, it must be returned using srp_put_tx_iu().
   *
   * Note:
@@ -1545,35 +1566,36 @@ static void srp_put_tx_iu(struct srp_target_port *target, struct srp_iu *iu,
   * - SRP_IU_RSP: 1, since a conforming SRP target never sends more than
   *   one unanswered SRP request to an initiator.
   */
-static struct srp_iu *__srp_get_tx_iu(struct srp_target_port *target,
+static struct srp_iu *__srp_get_tx_iu(struct srp_rdma_ch *ch,
  				      enum srp_iu_type iu_type)
  {
+	struct srp_target_port *target = ch->target;
  	s32 rsv = (iu_type == SRP_IU_TSK_MGMT) ? 0 : SRP_TSK_MGMT_SQ_SIZE;
  	struct srp_iu *iu;
 
-	srp_send_completion(target->send_cq, target);
+	srp_send_completion(ch->send_cq, ch);
 
-	if (list_empty(&target->free_tx))
+	if (list_empty(&ch->free_tx))
  		return NULL;
 
  	/* Initiator responses to target requests do not consume credits */
  	if (iu_type != SRP_IU_RSP) {
-		if (target->req_lim <= rsv) {
+		if (ch->req_lim <= rsv) {
  			++target->zero_req_lim;
  			return NULL;
  		}
 
-		--target->req_lim;
+		--ch->req_lim;
  	}
 
-	iu = list_first_entry(&target->free_tx, struct srp_iu, list);
+	iu = list_first_entry(&ch->free_tx, struct srp_iu, list);
  	list_del(&iu->list);
  	return iu;
  }
 
-static int srp_post_send(struct srp_target_port *target,
-			 struct srp_iu *iu, int len)
+static int srp_post_send(struct srp_rdma_ch *ch, struct srp_iu *iu, int len)
  {
+	struct srp_target_port *target = ch->target;
  	struct ib_sge list;
  	struct ib_send_wr wr, *bad_wr;
 
@@ -1588,11 +1610,12 @@ static int srp_post_send(struct srp_target_port *target,
  	wr.opcode     = IB_WR_SEND;
  	wr.send_flags = IB_SEND_SIGNALED;
 
-	return ib_post_send(target->qp, &wr, &bad_wr);
+	return ib_post_send(ch->qp, &wr, &bad_wr);
  }
 
-static int srp_post_recv(struct srp_target_port *target, struct srp_iu *iu)
+static int srp_post_recv(struct srp_rdma_ch *ch, struct srp_iu *iu)
  {
+	struct srp_target_port *target = ch->target;
  	struct ib_recv_wr wr, *bad_wr;
  	struct ib_sge list;
 
@@ -1605,35 +1628,36 @@ static int srp_post_recv(struct srp_target_port *target, struct srp_iu *iu)
  	wr.sg_list  = &list;
  	wr.num_sge  = 1;
 
-	return ib_post_recv(target->qp, &wr, &bad_wr);
+	return ib_post_recv(ch->qp, &wr, &bad_wr);
  }
 
-static void srp_process_rsp(struct srp_target_port *target, struct srp_rsp *rsp)
+static void srp_process_rsp(struct srp_rdma_ch *ch, struct srp_rsp *rsp)
  {
+	struct srp_target_port *target = ch->target;
  	struct srp_request *req;
  	struct scsi_cmnd *scmnd;
  	unsigned long flags;
 
  	if (unlikely(rsp->tag & SRP_TAG_TSK_MGMT)) {
-		spin_lock_irqsave(&target->lock, flags);
-		target->req_lim += be32_to_cpu(rsp->req_lim_delta);
-		spin_unlock_irqrestore(&target->lock, flags);
+		spin_lock_irqsave(&ch->lock, flags);
+		ch->req_lim += be32_to_cpu(rsp->req_lim_delta);
+		spin_unlock_irqrestore(&ch->lock, flags);
 
-		target->tsk_mgmt_status = -1;
+		ch->tsk_mgmt_status = -1;
  		if (be32_to_cpu(rsp->resp_data_len) >= 4)
-			target->tsk_mgmt_status = rsp->data[3];
-		complete(&target->tsk_mgmt_done);
+			ch->tsk_mgmt_status = rsp->data[3];
+		complete(&ch->tsk_mgmt_done);
  	} else {
-		req = &target->req_ring[rsp->tag];
-		scmnd = srp_claim_req(target, req, NULL, NULL);
+		req = &ch->req_ring[rsp->tag];
+		scmnd = srp_claim_req(ch, req, NULL, NULL);
  		if (!scmnd) {
  			shost_printk(KERN_ERR, target->scsi_host,
  				     "Null scmnd for RSP w/tag %016llx\n",
  				     (unsigned long long) rsp->tag);
 
-			spin_lock_irqsave(&target->lock, flags);
-			target->req_lim += be32_to_cpu(rsp->req_lim_delta);
-			spin_unlock_irqrestore(&target->lock, flags);
+			spin_lock_irqsave(&ch->lock, flags);
+			ch->req_lim += be32_to_cpu(rsp->req_lim_delta);
+			spin_unlock_irqrestore(&ch->lock, flags);
 
  			return;
  		}
@@ -1655,7 +1679,7 @@ static void srp_process_rsp(struct srp_target_port *target, struct srp_rsp *rsp)
  		else if (unlikely(rsp->flags & SRP_RSP_FLAG_DOOVER))
  			scsi_set_resid(scmnd, -be32_to_cpu(rsp->data_out_res_cnt));
 
-		srp_free_req(target, req, scmnd,
+		srp_free_req(ch, req, scmnd,
  			     be32_to_cpu(rsp->req_lim_delta));
 
  		scmnd->host_scribble = NULL;
@@ -1663,18 +1687,19 @@ static void srp_process_rsp(struct srp_target_port *target, struct srp_rsp *rsp)
  	}
  }
 
-static int srp_response_common(struct srp_target_port *target, s32 req_delta,
+static int srp_response_common(struct srp_rdma_ch *ch, s32 req_delta,
  			       void *rsp, int len)
  {
+	struct srp_target_port *target = ch->target;
  	struct ib_device *dev = target->srp_host->srp_dev->dev;
  	unsigned long flags;
  	struct srp_iu *iu;
  	int err;
 
-	spin_lock_irqsave(&target->lock, flags);
-	target->req_lim += req_delta;
-	iu = __srp_get_tx_iu(target, SRP_IU_RSP);
-	spin_unlock_irqrestore(&target->lock, flags);
+	spin_lock_irqsave(&ch->lock, flags);
+	ch->req_lim += req_delta;
+	iu = __srp_get_tx_iu(ch, SRP_IU_RSP);
+	spin_unlock_irqrestore(&ch->lock, flags);
 
  	if (!iu) {
  		shost_printk(KERN_ERR, target->scsi_host, PFX
@@ -1686,17 +1711,17 @@ static int srp_response_common(struct srp_target_port *target, s32 req_delta,
  	memcpy(iu->buf, rsp, len);
  	ib_dma_sync_single_for_device(dev, iu->dma, len, DMA_TO_DEVICE);
 
-	err = srp_post_send(target, iu, len);
+	err = srp_post_send(ch, iu, len);
  	if (err) {
  		shost_printk(KERN_ERR, target->scsi_host, PFX
  			     "unable to post response: %d\n", err);
-		srp_put_tx_iu(target, iu, SRP_IU_RSP);
+		srp_put_tx_iu(ch, iu, SRP_IU_RSP);
  	}
 
  	return err;
  }
 
-static void srp_process_cred_req(struct srp_target_port *target,
+static void srp_process_cred_req(struct srp_rdma_ch *ch,
  				 struct srp_cred_req *req)
  {
  	struct srp_cred_rsp rsp = {
@@ -1705,14 +1730,15 @@ static void srp_process_cred_req(struct srp_target_port *target,
  	};
  	s32 delta = be32_to_cpu(req->req_lim_delta);
 
-	if (srp_response_common(target, delta, &rsp, sizeof rsp))
-		shost_printk(KERN_ERR, target->scsi_host, PFX
+	if (srp_response_common(ch, delta, &rsp, sizeof(rsp)))
+		shost_printk(KERN_ERR, ch->target->scsi_host, PFX
  			     "problems processing SRP_CRED_REQ\n");
  }
 
-static void srp_process_aer_req(struct srp_target_port *target,
+static void srp_process_aer_req(struct srp_rdma_ch *ch,
  				struct srp_aer_req *req)
  {
+	struct srp_target_port *target = ch->target;
  	struct srp_aer_rsp rsp = {
  		.opcode = SRP_AER_RSP,
  		.tag = req->tag,
@@ -1722,19 +1748,20 @@ static void srp_process_aer_req(struct srp_target_port *target,
  	shost_printk(KERN_ERR, target->scsi_host, PFX
  		     "ignoring AER for LUN %llu\n", be64_to_cpu(req->lun));
 
-	if (srp_response_common(target, delta, &rsp, sizeof rsp))
+	if (srp_response_common(ch, delta, &rsp, sizeof(rsp)))
  		shost_printk(KERN_ERR, target->scsi_host, PFX
  			     "problems processing SRP_AER_REQ\n");
  }
 
-static void srp_handle_recv(struct srp_target_port *target, struct ib_wc *wc)
+static void srp_handle_recv(struct srp_rdma_ch *ch, struct ib_wc *wc)
  {
+	struct srp_target_port *target = ch->target;
  	struct ib_device *dev = target->srp_host->srp_dev->dev;
  	struct srp_iu *iu = (struct srp_iu *) (uintptr_t) wc->wr_id;
  	int res;
  	u8 opcode;
 
-	ib_dma_sync_single_for_cpu(dev, iu->dma, target->max_ti_iu_len,
+	ib_dma_sync_single_for_cpu(dev, iu->dma, ch->max_ti_iu_len,
  				   DMA_FROM_DEVICE);
 
  	opcode = *(u8 *) iu->buf;
@@ -1748,15 +1775,15 @@ static void srp_handle_recv(struct srp_target_port *target, struct ib_wc *wc)
 
  	switch (opcode) {
  	case SRP_RSP:
-		srp_process_rsp(target, iu->buf);
+		srp_process_rsp(ch, iu->buf);
  		break;
 
  	case SRP_CRED_REQ:
-		srp_process_cred_req(target, iu->buf);
+		srp_process_cred_req(ch, iu->buf);
  		break;
 
  	case SRP_AER_REQ:
-		srp_process_aer_req(target, iu->buf);
+		srp_process_aer_req(ch, iu->buf);
  		break;
 
  	case SRP_T_LOGOUT:
@@ -1771,10 +1798,10 @@ static void srp_handle_recv(struct srp_target_port *target, struct ib_wc *wc)
  		break;
  	}
 
-	ib_dma_sync_single_for_device(dev, iu->dma, target->max_ti_iu_len,
+	ib_dma_sync_single_for_device(dev, iu->dma, ch->max_ti_iu_len,
  				      DMA_FROM_DEVICE);
 
-	res = srp_post_recv(target, iu);
+	res = srp_post_recv(ch, iu);
  	if (res != 0)
  		shost_printk(KERN_ERR, target->scsi_host,
  			     PFX "Recv failed with error code %d\n", res);
@@ -1819,33 +1846,35 @@ static void srp_handle_qp_err(u64 wr_id, enum ib_wc_status wc_status,
  	target->qp_in_error = true;
  }
 
-static void srp_recv_completion(struct ib_cq *cq, void *target_ptr)
+static void srp_recv_completion(struct ib_cq *cq, void *ch_ptr)
  {
-	struct srp_target_port *target = target_ptr;
+	struct srp_rdma_ch *ch = ch_ptr;
  	struct ib_wc wc;
 
  	ib_req_notify_cq(cq, IB_CQ_NEXT_COMP);
  	while (ib_poll_cq(cq, 1, &wc) > 0) {
  		if (likely(wc.status == IB_WC_SUCCESS)) {
-			srp_handle_recv(target, &wc);
+			srp_handle_recv(ch, &wc);
  		} else {
-			srp_handle_qp_err(wc.wr_id, wc.status, false, target);
+			srp_handle_qp_err(wc.wr_id, wc.status, false,
+					  ch->target);
  		}
  	}
  }
 
-static void srp_send_completion(struct ib_cq *cq, void *target_ptr)
+static void srp_send_completion(struct ib_cq *cq, void *ch_ptr)
  {
-	struct srp_target_port *target = target_ptr;
+	struct srp_rdma_ch *ch = ch_ptr;
  	struct ib_wc wc;
  	struct srp_iu *iu;
 
  	while (ib_poll_cq(cq, 1, &wc) > 0) {
  		if (likely(wc.status == IB_WC_SUCCESS)) {
  			iu = (struct srp_iu *) (uintptr_t) wc.wr_id;
-			list_add(&iu->list, &target->free_tx);
+			list_add(&iu->list, &ch->free_tx);
  		} else {
-			srp_handle_qp_err(wc.wr_id, wc.status, true, target);
+			srp_handle_qp_err(wc.wr_id, wc.status, true,
+					  ch->target);
  		}
  	}
  }
@@ -1854,6 +1883,7 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
  {
  	struct srp_target_port *target = host_to_target(shost);
  	struct srp_rport *rport = target->rport;
+	struct srp_rdma_ch *ch;
  	struct srp_request *req;
  	struct srp_iu *iu;
  	struct srp_cmd *cmd;
@@ -1875,14 +1905,16 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
  	if (unlikely(scmnd->result))
  		goto err;
 
-	spin_lock_irqsave(&target->lock, flags);
-	iu = __srp_get_tx_iu(target, SRP_IU_CMD);
+	ch = &target->ch;
+
+	spin_lock_irqsave(&ch->lock, flags);
+	iu = __srp_get_tx_iu(ch, SRP_IU_CMD);
  	if (!iu)
  		goto err_unlock;
 
-	req = list_first_entry(&target->free_reqs, struct srp_request, list);
+	req = list_first_entry(&ch->free_reqs, struct srp_request, list);
  	list_del(&req->list);
-	spin_unlock_irqrestore(&target->lock, flags);
+	spin_unlock_irqrestore(&ch->lock, flags);
 
  	dev = target->srp_host->srp_dev->dev;
  	ib_dma_sync_single_for_cpu(dev, iu->dma, target->max_iu_len,
@@ -1901,7 +1933,7 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
  	req->scmnd    = scmnd;
  	req->cmd      = iu;
 
-	len = srp_map_data(scmnd, target, req);
+	len = srp_map_data(scmnd, ch, req);
  	if (len < 0) {
  		shost_printk(KERN_ERR, target->scsi_host,
  			     PFX "Failed to map data (%d)\n", len);
@@ -1919,7 +1951,7 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
  	ib_dma_sync_single_for_device(dev, iu->dma, target->max_iu_len,
  				      DMA_TO_DEVICE);
 
-	if (srp_post_send(target, iu, len)) {
+	if (srp_post_send(ch, iu, len)) {
  		shost_printk(KERN_ERR, target->scsi_host, PFX "Send failed\n");
  		goto err_unmap;
  	}
@@ -1933,10 +1965,10 @@ unlock_rport:
  	return ret;
 
  err_unmap:
-	srp_unmap_data(scmnd, target, req);
+	srp_unmap_data(scmnd, ch, req);
 
  err_iu:
-	srp_put_tx_iu(target, iu, SRP_IU_CMD);
+	srp_put_tx_iu(ch, iu, SRP_IU_CMD);
 
  	/*
  	 * Avoid that the loops that iterate over the request ring can
@@ -1944,11 +1976,11 @@ err_iu:
  	 */
  	req->scmnd = NULL;
 
-	spin_lock_irqsave(&target->lock, flags);
-	list_add(&req->list, &target->free_reqs);
+	spin_lock_irqsave(&ch->lock, flags);
+	list_add(&req->list, &ch->free_reqs);
 
  err_unlock:
-	spin_unlock_irqrestore(&target->lock, flags);
+	spin_unlock_irqrestore(&ch->lock, flags);
 
  err:
  	if (scmnd->result) {
@@ -1963,53 +1995,54 @@ err:
 
  /*
   * Note: the resources allocated in this function are freed in
- * srp_free_target_ib().
+ * srp_free_ch_ib().
   */
-static int srp_alloc_iu_bufs(struct srp_target_port *target)
+static int srp_alloc_iu_bufs(struct srp_rdma_ch *ch)
  {
+	struct srp_target_port *target = ch->target;
  	int i;
 
-	target->rx_ring = kzalloc(target->queue_size * sizeof(*target->rx_ring),
-				  GFP_KERNEL);
-	if (!target->rx_ring)
+	ch->rx_ring = kcalloc(target->queue_size, sizeof(*ch->rx_ring),
+			      GFP_KERNEL);
+	if (!ch->rx_ring)
  		goto err_no_ring;
-	target->tx_ring = kzalloc(target->queue_size * sizeof(*target->tx_ring),
-				  GFP_KERNEL);
-	if (!target->tx_ring)
+	ch->tx_ring = kcalloc(target->queue_size, sizeof(*ch->tx_ring),
+			      GFP_KERNEL);
+	if (!ch->tx_ring)
  		goto err_no_ring;
 
  	for (i = 0; i < target->queue_size; ++i) {
-		target->rx_ring[i] = srp_alloc_iu(target->srp_host,
-						  target->max_ti_iu_len,
-						  GFP_KERNEL, DMA_FROM_DEVICE);
-		if (!target->rx_ring[i])
+		ch->rx_ring[i] = srp_alloc_iu(target->srp_host,
+					      ch->max_ti_iu_len,
+					      GFP_KERNEL, DMA_FROM_DEVICE);
+		if (!ch->rx_ring[i])
  			goto err;
  	}
 
  	for (i = 0; i < target->queue_size; ++i) {
-		target->tx_ring[i] = srp_alloc_iu(target->srp_host,
-						  target->max_iu_len,
-						  GFP_KERNEL, DMA_TO_DEVICE);
-		if (!target->tx_ring[i])
+		ch->tx_ring[i] = srp_alloc_iu(target->srp_host,
+					      target->max_iu_len,
+					      GFP_KERNEL, DMA_TO_DEVICE);
+		if (!ch->tx_ring[i])
  			goto err;
 
-		list_add(&target->tx_ring[i]->list, &target->free_tx);
+		list_add(&ch->tx_ring[i]->list, &ch->free_tx);
  	}
 
  	return 0;
 
  err:
  	for (i = 0; i < target->queue_size; ++i) {
-		srp_free_iu(target->srp_host, target->rx_ring[i]);
-		srp_free_iu(target->srp_host, target->tx_ring[i]);
+		srp_free_iu(target->srp_host, ch->rx_ring[i]);
+		srp_free_iu(target->srp_host, ch->tx_ring[i]);
  	}
 
 
  err_no_ring:
-	kfree(target->tx_ring);
-	target->tx_ring = NULL;
-	kfree(target->rx_ring);
-	target->rx_ring = NULL;
+	kfree(ch->tx_ring);
+	ch->tx_ring = NULL;
+	kfree(ch->rx_ring);
+	ch->rx_ring = NULL;
 
  	return -ENOMEM;
  }
@@ -2043,23 +2076,24 @@ static uint32_t srp_compute_rq_tmo(struct ib_qp_attr *qp_attr, int attr_mask)
 
  static void srp_cm_rep_handler(struct ib_cm_id *cm_id,
  			       struct srp_login_rsp *lrsp,
-			       struct srp_target_port *target)
+			       struct srp_rdma_ch *ch)
  {
+	struct srp_target_port *target = ch->target;
  	struct ib_qp_attr *qp_attr = NULL;
  	int attr_mask = 0;
  	int ret;
  	int i;
 
  	if (lrsp->opcode == SRP_LOGIN_RSP) {
-		target->max_ti_iu_len = be32_to_cpu(lrsp->max_ti_iu_len);
-		target->req_lim       = be32_to_cpu(lrsp->req_lim_delta);
+		ch->max_ti_iu_len = be32_to_cpu(lrsp->max_ti_iu_len);
+		ch->req_lim       = be32_to_cpu(lrsp->req_lim_delta);
 
  		/*
  		 * Reserve credits for task management so we don't
  		 * bounce requests back to the SCSI mid-layer.
  		 */
  		target->scsi_host->can_queue
-			= min(target->req_lim - SRP_TSK_MGMT_SQ_SIZE,
+			= min(ch->req_lim - SRP_TSK_MGMT_SQ_SIZE,
  			      target->scsi_host->can_queue);
  		target->scsi_host->cmd_per_lun
  			= min_t(int, target->scsi_host->can_queue,
@@ -2071,8 +2105,8 @@ static void srp_cm_rep_handler(struct ib_cm_id *cm_id,
  		goto error;
  	}
 
-	if (!target->rx_ring) {
-		ret = srp_alloc_iu_bufs(target);
+	if (!ch->rx_ring) {
+		ret = srp_alloc_iu_bufs(ch);
  		if (ret)
  			goto error;
  	}
@@ -2087,13 +2121,14 @@ static void srp_cm_rep_handler(struct ib_cm_id *cm_id,
  	if (ret)
  		goto error_free;
 
-	ret = ib_modify_qp(target->qp, qp_attr, attr_mask);
+	ret = ib_modify_qp(ch->qp, qp_attr, attr_mask);
  	if (ret)
  		goto error_free;
 
  	for (i = 0; i < target->queue_size; i++) {
-		struct srp_iu *iu = target->rx_ring[i];
-		ret = srp_post_recv(target, iu);
+		struct srp_iu *iu = ch->rx_ring[i];
+
+		ret = srp_post_recv(ch, iu);
  		if (ret)
  			goto error_free;
  	}
@@ -2105,7 +2140,7 @@ static void srp_cm_rep_handler(struct ib_cm_id *cm_id,
 
  	target->rq_tmo_jiffies = srp_compute_rq_tmo(qp_attr, attr_mask);
 
-	ret = ib_modify_qp(target->qp, qp_attr, attr_mask);
+	ret = ib_modify_qp(ch->qp, qp_attr, attr_mask);
  	if (ret)
  		goto error_free;
 
@@ -2115,13 +2150,14 @@ error_free:
  	kfree(qp_attr);
 
  error:
-	target->status = ret;
+	ch->status = ret;
  }
 
  static void srp_cm_rej_handler(struct ib_cm_id *cm_id,
  			       struct ib_cm_event *event,
-			       struct srp_target_port *target)
+			       struct srp_rdma_ch *ch)
  {
+	struct srp_target_port *target = ch->target;
  	struct Scsi_Host *shost = target->scsi_host;
  	struct ib_class_port_info *cpi;
  	int opcode;
@@ -2129,12 +2165,12 @@ static void srp_cm_rej_handler(struct ib_cm_id *cm_id,
  	switch (event->param.rej_rcvd.reason) {
  	case IB_CM_REJ_PORT_CM_REDIRECT:
  		cpi = event->param.rej_rcvd.ari;
-		target->path.dlid = cpi->redirect_lid;
-		target->path.pkey = cpi->redirect_pkey;
+		ch->path.dlid = cpi->redirect_lid;
+		ch->path.pkey = cpi->redirect_pkey;
  		cm_id->remote_cm_qpn = be32_to_cpu(cpi->redirect_qp) & 0x00ffffff;
-		memcpy(target->path.dgid.raw, cpi->redirect_gid, 16);
+		memcpy(ch->path.dgid.raw, cpi->redirect_gid, 16);
 
-		target->status = target->path.dlid ?
+		ch->status = ch->path.dlid ?
  			SRP_DLID_REDIRECT : SRP_PORT_REDIRECT;
  		break;
 
@@ -2145,26 +2181,26 @@ static void srp_cm_rej_handler(struct ib_cm_id *cm_id,
  			 * reject reason code 25 when they mean 24
  			 * (port redirect).
  			 */
-			memcpy(target->path.dgid.raw,
+			memcpy(ch->path.dgid.raw,
  			       event->param.rej_rcvd.ari, 16);
 
  			shost_printk(KERN_DEBUG, shost,
  				     PFX "Topspin/Cisco redirect to target port GID %016llx%016llx\n",
-				     (unsigned long long) be64_to_cpu(target->path.dgid.global.subnet_prefix),
-				     (unsigned long long) be64_to_cpu(target->path.dgid.global.interface_id));
+				     be64_to_cpu(ch->path.dgid.global.subnet_prefix),
+				     be64_to_cpu(ch->path.dgid.global.interface_id));
 
-			target->status = SRP_PORT_REDIRECT;
+			ch->status = SRP_PORT_REDIRECT;
  		} else {
  			shost_printk(KERN_WARNING, shost,
  				     "  REJ reason: IB_CM_REJ_PORT_REDIRECT\n");
-			target->status = -ECONNRESET;
+			ch->status = -ECONNRESET;
  		}
  		break;
 
  	case IB_CM_REJ_DUPLICATE_LOCAL_COMM_ID:
  		shost_printk(KERN_WARNING, shost,
  			    "  REJ reason: IB_CM_REJ_DUPLICATE_LOCAL_COMM_ID\n");
-		target->status = -ECONNRESET;
+		ch->status = -ECONNRESET;
  		break;
 
  	case IB_CM_REJ_CONSUMER_DEFINED:
@@ -2185,24 +2221,25 @@ static void srp_cm_rej_handler(struct ib_cm_id *cm_id,
  			shost_printk(KERN_WARNING, shost,
  				     "  REJ reason: IB_CM_REJ_CONSUMER_DEFINED,"
  				     " opcode 0x%02x\n", opcode);
-		target->status = -ECONNRESET;
+		ch->status = -ECONNRESET;
  		break;
 
  	case IB_CM_REJ_STALE_CONN:
  		shost_printk(KERN_WARNING, shost, "  REJ reason: stale connection\n");
-		target->status = SRP_STALE_CONN;
+		ch->status = SRP_STALE_CONN;
  		break;
 
  	default:
  		shost_printk(KERN_WARNING, shost, "  REJ reason 0x%x\n",
  			     event->param.rej_rcvd.reason);
-		target->status = -ECONNRESET;
+		ch->status = -ECONNRESET;
  	}
  }
 
  static int srp_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event)
  {
-	struct srp_target_port *target = cm_id->context;
+	struct srp_rdma_ch *ch = cm_id->context;
+	struct srp_target_port *target = ch->target;
  	int comp = 0;
 
  	switch (event->event) {
@@ -2210,19 +2247,19 @@ static int srp_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event)
  		shost_printk(KERN_DEBUG, target->scsi_host,
  			     PFX "Sending CM REQ failed\n");
  		comp = 1;
-		target->status = -ECONNRESET;
+		ch->status = -ECONNRESET;
  		break;
 
  	case IB_CM_REP_RECEIVED:
  		comp = 1;
-		srp_cm_rep_handler(cm_id, event->private_data, target);
+		srp_cm_rep_handler(cm_id, event->private_data, ch);
  		break;
 
  	case IB_CM_REJ_RECEIVED:
  		shost_printk(KERN_DEBUG, target->scsi_host, PFX "REJ received\n");
  		comp = 1;
 
-		srp_cm_rej_handler(cm_id, event, target);
+		srp_cm_rej_handler(cm_id, event, ch);
  		break;
 
  	case IB_CM_DREQ_RECEIVED:
@@ -2240,7 +2277,7 @@ static int srp_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event)
  			     PFX "connection closed\n");
  		comp = 1;
 
-		target->status = 0;
+		ch->status = 0;
  		break;
 
  	case IB_CM_MRA_RECEIVED:
@@ -2255,7 +2292,7 @@ static int srp_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event)
  	}
 
  	if (comp)
-		complete(&target->done);
+		complete(&ch->done);
 
  	return 0;
  }
@@ -2311,9 +2348,10 @@ srp_change_queue_depth(struct scsi_device *sdev, int qdepth, int reason)
  	return sdev->queue_depth;
  }
 
-static int srp_send_tsk_mgmt(struct srp_target_port *target,
-			     u64 req_tag, unsigned int lun, u8 func)
+static int srp_send_tsk_mgmt(struct srp_rdma_ch *ch, u64 req_tag,
+			     unsigned int lun, u8 func)
  {
+	struct srp_target_port *target = ch->target;
  	struct srp_rport *rport = target->rport;
  	struct ib_device *dev = target->srp_host->srp_dev->dev;
  	struct srp_iu *iu;
@@ -2322,16 +2360,16 @@ static int srp_send_tsk_mgmt(struct srp_target_port *target,
  	if (!target->connected || target->qp_in_error)
  		return -1;
 
-	init_completion(&target->tsk_mgmt_done);
+	init_completion(&ch->tsk_mgmt_done);
 
  	/*
-	 * Lock the rport mutex to avoid that srp_create_target_ib() is
+	 * Lock the rport mutex to avoid that srp_create_ch_ib() is
  	 * invoked while a task management function is being sent.
  	 */
  	mutex_lock(&rport->mutex);
-	spin_lock_irq(&target->lock);
-	iu = __srp_get_tx_iu(target, SRP_IU_TSK_MGMT);
-	spin_unlock_irq(&target->lock);
+	spin_lock_irq(&ch->lock);
+	iu = __srp_get_tx_iu(ch, SRP_IU_TSK_MGMT);
+	spin_unlock_irq(&ch->lock);
 
  	if (!iu) {
  		mutex_unlock(&rport->mutex);
@@ -2352,15 +2390,15 @@ static int srp_send_tsk_mgmt(struct srp_target_port *target,
 
  	ib_dma_sync_single_for_device(dev, iu->dma, sizeof *tsk_mgmt,
  				      DMA_TO_DEVICE);
-	if (srp_post_send(target, iu, sizeof *tsk_mgmt)) {
-		srp_put_tx_iu(target, iu, SRP_IU_TSK_MGMT);
+	if (srp_post_send(ch, iu, sizeof(*tsk_mgmt))) {
+		srp_put_tx_iu(ch, iu, SRP_IU_TSK_MGMT);
  		mutex_unlock(&rport->mutex);
 
  		return -1;
  	}
  	mutex_unlock(&rport->mutex);
 
-	if (!wait_for_completion_timeout(&target->tsk_mgmt_done,
+	if (!wait_for_completion_timeout(&ch->tsk_mgmt_done,
  					 msecs_to_jiffies(SRP_ABORT_TIMEOUT_MS)))
  		return -1;
 
@@ -2371,20 +2409,22 @@ static int srp_abort(struct scsi_cmnd *scmnd)
  {
  	struct srp_target_port *target = host_to_target(scmnd->device->host);
  	struct srp_request *req = (struct srp_request *) scmnd->host_scribble;
+	struct srp_rdma_ch *ch;
  	int ret;
 
  	shost_printk(KERN_ERR, target->scsi_host, "SRP abort called\n");
 
-	if (!req || !srp_claim_req(target, req, NULL, scmnd))
+	ch = &target->ch;
+	if (!req || !srp_claim_req(ch, req, NULL, scmnd))
  		return SUCCESS;
-	if (srp_send_tsk_mgmt(target, req->index, scmnd->device->lun,
+	if (srp_send_tsk_mgmt(ch, req->index, scmnd->device->lun,
  			      SRP_TSK_ABORT_TASK) == 0)
  		ret = SUCCESS;
  	else if (target->rport->state == SRP_RPORT_LOST)
  		ret = FAST_IO_FAIL;
  	else
  		ret = FAILED;
-	srp_free_req(target, req, scmnd, 0);
+	srp_free_req(ch, req, scmnd, 0);
  	scmnd->result = DID_ABORT << 16;
  	scmnd->scsi_done(scmnd);
 
@@ -2394,19 +2434,21 @@ static int srp_abort(struct scsi_cmnd *scmnd)
  static int srp_reset_device(struct scsi_cmnd *scmnd)
  {
  	struct srp_target_port *target = host_to_target(scmnd->device->host);
+	struct srp_rdma_ch *ch = &target->ch;
  	int i;
 
  	shost_printk(KERN_ERR, target->scsi_host, "SRP reset_device called\n");
 
-	if (srp_send_tsk_mgmt(target, SRP_TAG_NO_REQ, scmnd->device->lun,
+	if (srp_send_tsk_mgmt(ch, SRP_TAG_NO_REQ, scmnd->device->lun,
  			      SRP_TSK_LUN_RESET))
  		return FAILED;
-	if (target->tsk_mgmt_status)
+	if (ch->tsk_mgmt_status)
  		return FAILED;
 
  	for (i = 0; i < target->req_ring_size; ++i) {
-		struct srp_request *req = &target->req_ring[i];
-		srp_finish_req(target, req, scmnd->device, DID_RESET << 16);
+		struct srp_request *req = &ch->req_ring[i];
+
+		srp_finish_req(ch, req, scmnd->device, DID_RESET << 16);
  	}
 
  	return SUCCESS;
@@ -2483,8 +2525,9 @@ static ssize_t show_dgid(struct device *dev, struct device_attribute *attr,
  			 char *buf)
  {
  	struct srp_target_port *target = host_to_target(class_to_shost(dev));
+	struct srp_rdma_ch *ch = &target->ch;
 
-	return sprintf(buf, "%pI6\n", target->path.dgid.raw);
+	return sprintf(buf, "%pI6\n", ch->path.dgid.raw);
  }
 
  static ssize_t show_orig_dgid(struct device *dev,
@@ -2500,7 +2543,7 @@ static ssize_t show_req_lim(struct device *dev,
  {
  	struct srp_target_port *target = host_to_target(class_to_shost(dev));
 
-	return sprintf(buf, "%d\n", target->req_lim);
+	return sprintf(buf, "%d\n", target->ch.req_lim);
  }
 
  static ssize_t show_zero_req_lim(struct device *dev,
@@ -2992,6 +3035,7 @@ static ssize_t srp_create_target(struct device *dev,
  		container_of(dev, struct srp_host, dev);
  	struct Scsi_Host *target_host;
  	struct srp_target_port *target;
+	struct srp_rdma_ch *ch;
  	struct srp_device *srp_dev = host->srp_dev;
  	struct ib_device *ibdev = srp_dev->dev;
  	int ret;
@@ -3060,8 +3104,12 @@ static ssize_t srp_create_target(struct device *dev,
  	INIT_WORK(&target->tl_err_work, srp_tl_err_work);
  	INIT_WORK(&target->remove_work, srp_remove_work);
  	spin_lock_init(&target->lock);
-	INIT_LIST_HEAD(&target->free_tx);
-	ret = srp_alloc_req_data(target);
+	ch = &target->ch;
+	ch->target = target;
+	ch->comp_vector = target->comp_vector;
+	spin_lock_init(&ch->lock);
+	INIT_LIST_HEAD(&ch->free_tx);
+	ret = srp_alloc_req_data(ch);
  	if (ret)
  		goto err_free_mem;
 
@@ -3069,15 +3117,15 @@ static ssize_t srp_create_target(struct device *dev,
  	if (ret)
  		goto err_free_mem;
 
-	ret = srp_create_target_ib(target);
+	ret = srp_create_ch_ib(ch);
  	if (ret)
  		goto err_free_mem;
 
-	ret = srp_new_cm_id(target);
+	ret = srp_new_cm_id(ch);
  	if (ret)
  		goto err_free_ib;
 
-	ret = srp_connect_target(target);
+	ret = srp_connect_ch(ch);
  	if (ret) {
  		shost_printk(KERN_ERR, target->scsi_host,
  			     PFX "Connection failed\n");
@@ -3111,10 +3159,10 @@ err_disconnect:
  	srp_disconnect_target(target);
 
  err_free_ib:
-	srp_free_target_ib(target);
+	srp_free_ch_ib(target, ch);
 
  err_free_mem:
-	srp_free_req_data(target);
+	srp_free_req_data(target, ch);
 
  err:
  	scsi_host_put(target_host);
drivers/infiniband/ulp/srp/ib_srp.h +42 -22
index 8635ab6..74530d9 100644
@@ -130,7 +130,11 @@ struct srp_request {
  	short			index;
  };
 
-struct srp_target_port {
+/**
+ * struct srp_rdma_ch
+ * @comp_vector: Completion vector used by this RDMA channel.
+ */
+struct srp_rdma_ch {
  	/* These are RW in the hot path, and commonly used together */
  	struct list_head	free_tx;
  	struct list_head	free_reqs;
@@ -138,13 +142,48 @@ struct srp_target_port {
  	s32			req_lim;
 
  	/* These are read-only in the hot path */
-	struct ib_cq	       *send_cq ____cacheline_aligned_in_smp;
+	struct srp_target_port *target ____cacheline_aligned_in_smp;
+	struct ib_cq	       *send_cq;
  	struct ib_cq	       *recv_cq;
  	struct ib_qp	       *qp;
  	union {
  		struct ib_fmr_pool     *fmr_pool;
  		struct srp_fr_pool     *fr_pool;
  	};
+
+	/* Everything above this point is used in the hot path of
+	 * command processing. Try to keep them packed into cachelines.
+	 */
+
+	struct completion	done;
+	int			status;
+
+	struct ib_sa_path_rec	path;
+	struct ib_sa_query     *path_query;
+	int			path_query_id;
+
+	struct ib_cm_id	       *cm_id;
+	struct srp_iu	      **tx_ring;
+	struct srp_iu	      **rx_ring;
+	struct srp_request     *req_ring;
+	int			max_ti_iu_len;
+	int			comp_vector;
+
+	struct completion	tsk_mgmt_done;
+	u8			tsk_mgmt_status;
+};
+
+/**
+ * struct srp_target_port
+ * @comp_vector: Completion vector used by the first RDMA channel created for
+ *   this target port.
+ */
+struct srp_target_port {
+	/* read and written in the hot path */
+	spinlock_t		lock;
+
+	struct srp_rdma_ch	ch;
+	/* read only in the hot path */
  	u32			lkey;
  	u32			rkey;
  	enum srp_target_state	state;
@@ -153,10 +192,7 @@ struct srp_target_port {
  	unsigned int		indirect_size;
  	bool			allow_ext_sg;
 
-	/* Everything above this point is used in the hot path of
-	 * command processing. Try to keep them packed into cachelines.
-	 */
-
+	/* other member variables */
  	union ib_gid		sgid;
  	__be64			id_ext;
  	__be64			ioc_guid;
@@ -176,33 +212,17 @@ struct srp_target_port {
 
  	union ib_gid		orig_dgid;
  	__be16			pkey;
-	struct ib_sa_path_rec	path;
-	struct ib_sa_query     *path_query;
-	int			path_query_id;
 
  	u32			rq_tmo_jiffies;
  	bool			connected;
 
-	struct ib_cm_id	       *cm_id;
-
-	int			max_ti_iu_len;
-
  	int			zero_req_lim;
 
-	struct srp_iu	       **tx_ring;
-	struct srp_iu	       **rx_ring;
-	struct srp_request	*req_ring;
-
  	struct work_struct	tl_err_work;
  	struct work_struct	remove_work;
 
  	struct list_head	list;
-	struct completion	done;
-	int			status;
  	bool			qp_in_error;
-
-	struct completion	tsk_mgmt_done;
-	u8			tsk_mgmt_status;
  };
 
  struct srp_iu {
#30 lore raw

Re: [PATCH v2 11/12] IB/srp: Eliminate free_reqs list

In reply to a message not in the archive
Quoted 6 lines · Christoph Hellwig
Quoted 2 lines · Bart Van Assche

The free_reqs list is no longer needed now that we are using tags assigned by the block layer. Hence remove it.

Is there any good reason not to fold this into the previous patch?

Agree.

Sagi.
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#85 lore raw
In reply to a message not in the archive
Quoted 38 lines · Bart Van Assche

Improve performance by using multiple RDMA/RC channels per SCSI host for communication with an SRP target. About the implementation:
- Introduce a loop over all channels in the code that uses target->ch.
- Set the SRP_MULTICHAN_MULTI flag during login for the creation of the second and subsequent channels.
- RDMA completion vectors are chosen such that RDMA completion interrupts are handled by the CPU socket that submitted the I/O request. As one can see in this patch it has been assumed if a system contains n CPU sockets and m RDMA completion vectors have been assigned to an RDMA HCA that IRQ affinity has been configured such that completion vectors [i*m/n..(i+1)*m/n) are bound to CPU socket i with 0 <= i < n.
- Modify srp_free_ch_ib() and srp_free_req_data() such that it becomes safe to invoke these functions after the corresponding allocation function failed.
- Add a ch_count sysfs attribute per target port.

Cc Sagi Grimberg <sagig-VPRAkNaXOzVWk0Htik3J/[email protected]>
Cc Sebastian Parschauer <[email protected]>
---
  Documentation/ABI/stable/sysfs-driver-ib_srp |  25 ++-
  drivers/infiniband/ulp/srp/ib_srp.c          | 291 ++++++++++++++++++++-------
  drivers/infiniband/ulp/srp/ib_srp.h          |   3 +-
  3 files changed, 238 insertions(+), 81 deletions(-)
Documentation/ABI/stable/sysfs-driver-ib_srp +0 -2
index b9688de..d5a459e 100644
@@ -55,12 +55,12 @@ Description:	Interface for making ib_srp connect to a new target.
  		  only safe with partial memory descriptor list support enabled
  		  (allow_ext_sg=1).
  		* comp_vector, a number in the range 0..n-1 specifying the
-		  MSI-X completion vector. Some HCA's allocate multiple (n)
-		  MSI-X vectors per HCA port. If the IRQ affinity masks of

Documentation/ABI/stable/sysfs-driver-ib_srp Description: Interface for making ib_srp connect to a new target. · line 63

Quoted 10 lines
Documentation/ABI/stable/sysfs-driver-ib_srp +6 -4
-		  these interrupts have been configured such that each MSI-X
-		  interrupt is handled by a different CPU then the comp_vector
-		  parameter can be used to spread the SRP completion workload
-		  over multiple CPU's.
+		  MSI-X completion vector of the first RDMA channel. Some
+		  HCA's allocate multiple (n) MSI-X vectors per HCA port. If
+		  the IRQ affinity masks of these interrupts have been
+		  configured such that each MSI-X interrupt is handled by a
+		  different CPU then the comp_vector parameter can be used to
+		  spread the SRP completion workload over multiple CPU's.

This is fairly not trivial for the user...

Aren't we requesting a bit too much awareness here?
Can't we just "make it work"? The user hands out ch_count - why can't you do some least-used logic here?

Maybe we can even go with per-cpu QPs and discard comp_vector argument? this would probably bring the best performance, wouldn't it? (fallback to least-used logic in case HW support less vectors)

Quoted 35 lines
Documentation/ABI/stable/sysfs-driver-ib_srp +13 -0
  		* tl_retry_count, a number in the range 2..7 specifying the
  		  IB RC retry count.
  		* queue_size, the maximum number of commands that the
@@ -88,6 +88,13 @@ Description:	Whether ib_srp is allowed to include a partial memory
  		descriptor list in an SRP_CMD when communicating with an SRP
  		target.
 
+What:		/sys/class/scsi_host/host<n>/ch_count
+Date:		November 1, 2014
+KernelVersion:	3.18
+Contact:	[email protected]
+Description:	Number of RDMA channels used for communication with the SRP
+		target.
+
  What:		/sys/class/scsi_host/host<n>/cmd_sg_entries
  Date:		May 19, 2011
  KernelVersion:	2.6.39
@@ -95,6 +102,12 @@ Contact:	[email protected]
  Description:	Maximum number of data buffer descriptors that may be sent to
  		the target in a single SRP_CMD request.
 
+What:		/sys/class/scsi_host/host<n>/comp_vector
+Date:		September 2, 2013
+KernelVersion:	3.11
+Contact:	[email protected]
+Description:	Completion vector used for the first RDMA channel.
+
  What:		/sys/class/scsi_host/host<n>/dgid
  Date:		June 17, 2006
  KernelVersion:	2.6.17
drivers/infiniband/ulp/srp/ib_srp.c +0 -0
index eccaf65..80699a9 100644

drivers/infiniband/ulp/srp/ib_srp.c MODULE_PARM_DESC(dev_loss_tmo, · line 130

Quoted 8 lines
drivers/infiniband/ulp/srp/ib_srp.c +5 -0
@@ -123,6 +123,11 @@ MODULE_PARM_DESC(dev_loss_tmo,
  		 " if fast_io_fail_tmo has not been set. \"off\" means that"
  		 " this functionality is disabled.");
 
+static unsigned ch_count;
+module_param(ch_count, uint, 0444);
+MODULE_PARM_DESC(ch_count,
+		 "Number of RDMA channels to use for communication with an SRP target. Using more than one channel improves performance if the HCA supports multiple completion vectors. The default value is the minimum of four times the number of online CPU sockets and the number of completion vectors supported by the HCA.");
+

Why? how did you get to this magic equation?

drivers/infiniband/ulp/srp/ib_srp.c MODULE_PARM_DESC(dev_loss_tmo, · line 131

Quoted 1 line
drivers/infiniband/ulp/srp/ib_srp.c +0 -0
  static void srp_add_one(struct ib_device *device);

...
So it's pretty late for today, this is where I got so far... Will continue later this week.

Sagi.
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#60 lore raw

Re: [PATCH v2 10/12] IB/srp: Use block layer tags

In reply to a message not in the archive
Quoted 7 lines · Christoph Hellwig
Quoted 7 lines
drivers/infiniband/ulp/srp/ib_srp.c +0 -0
index cc0bf83b..224ef25 100644
@@ -853,7 +853,6 @@ static int srp_alloc_req_data(struct srp_rdma_ch *ch)
  			goto out;
 
Quoted 7 lines

drivers/infiniband/ulp/srp/ib_srp.c static int srp_alloc_req_data(struct srp_rdma_ch *ch) · line 857

Quoted 4 lines
drivers/infiniband/ulp/srp/ib_srp.c +0 -1
  		req->indirect_dma_addr = dma_addr;
-		req->index = i;
  		list_add_tail(&req->list, &ch->free_reqs);
  	}

Seems like a nice optimization for the future would be to preallocate the srp requests with the block ones and the scsi command.

Agreed. The reason why that optimization has not been included in this patch series is because it would require more work than the optimization in patch 10/12. The free_reqs list is namely not only used when a SCSI command is submitted by the SCSI core but also when submitting a task management command or when replying to a request submitted by the target system. In other words, the free_reqs list would have to be modified such that it is only used for the latter two purposes.

Bart.

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#31 lore raw

Re: [PATCH v2 11/12] IB/srp: Eliminate free_reqs list

In reply to a message not in the archive
Quoted 5 lines · Christoph Hellwig
Quoted 2 lines · Bart Van Assche

The free_reqs list is no longer needed now that we are using tags assigned by the block layer. Hence remove it.

Is there any good reason not to fold this into the previous patch?

The only reason why patches 10/12 and 11/12 are separate patches is to reduce the size of individual patches and hence to make it easier to review these patches. If everyone agrees I'm fine with folding patch 11/12 into patch 10/12.

Bart.

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#82 lore raw
In reply to a message not in the archive
Quoted 9 lines · Christoph Hellwig

drivers/infiniband/ulp/srp/ib_srp.c static void srp_process_rsp(struct srp_rdma_ch *ch, struct srp_rsp *rsp) · line 1710

Quoted 5 lines
  	} else {
drivers/infiniband/ulp/srp/ib_srp.c +3 -0
+		if (blk_mq_unique_tag_to_hwq(rsp->tag) != ch - target->ch)
+			pr_err("Channel idx mismatch: tag %#llx <> ch %#lx\n",
+			       rsp->tag, ch - target->ch);
  		scmnd = scsi_host_find_tag(target->scsi_host, rsp->tag);

Shouldn't we do this validity check inside scsi_host_find_tag, so that all callers get it? That means adding an argument to it, but there are very few callers at the moment.

Hello Christoph,

That pr_err() statement was convenient while debugging the multiqueue code in the SRP initiator driver but can be left out. Would you agree with leaving the above three lines of debug code out instead of adding an additional argument to scsi_host_find_tag() ?

Bart.
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#44 lore raw

Re: [PATCH v2 04/12] scsi_tcq.h: Add support for multiple hardware queues

In reply to a message not in the archive
Quoted 5 lines · Sagi Grimberg

include/scsi/scsi_tcq.h static inline struct scsi_cmnd *scsi_find_tag(struct scsi_device *sdev, int tag) · line 141

Quoted 2 lines · Bart Van Assche
include/scsi/scsi_tcq.h +1 -1
-            req = blk_queue_find_tag(sdev->request_queue, tag);
+        req = blk_queue_find_tag(sdev->request_queue, tag);

Why is this line different?

This is because the indentation has been modified from "8x<space><tab>" into "<tab><tab>". I can leave out that change if you want.

Bart.
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#52 lore raw

Re: [PATCH v2 07/12] IB/srp: Avoid that I/O hangs due to a cable pull during LUN scanning

In reply to a message not in the archive
Quoted 15 lines · Sagi Grimberg

drivers/infiniband/ulp/srp/ib_srp.c static struct scsi_host_template srp_template = { · line 2624

Quoted 11 lines · Bart Van Assche
drivers/infiniband/ulp/srp/ib_srp.c +11 -0
+static int srp_sdev_count(struct Scsi_Host *host)
+{
+    struct scsi_device *sdev;
+    int c = 0;
+
+    shost_for_each_device(sdev, host)
+        c++;
+
+    return c;
+}
+

Is this really an SRP specific routine?
Can you move it to a more natural location?

How about renaming this function into shost_sdev_count() and moving its declaration to <scsi/scsi_device.h> and its implementation to drivers/scsi/scsi_lib.c ?

Quoted 20 lines
Quoted 20 lines

static int srp_add_target(struct srp_host *host, struct
srp_target_port *target)

  {
      struct srp_rport_identifiers ids;
      struct srp_rport *rport;
drivers/infiniband/ulp/srp/ib_srp.c +1 -2
+    target->state = SRP_TARGET_SCANNING;
      sprintf(target->target_name, "SRP.T10:%016llX",
           (unsigned long long) be64_to_cpu(target->id_ext));
@@ -2634,11 +2650,26 @@ static int srp_add_target(struct srp_host
 *host, struct srp_target_port *target)
      list_add_tail(&target->list, &host->target_list);
      spin_unlock(&host->target_lock);
 
-    target->state = SRP_TARGET_LIVE;
-
      scsi_scan_target(&target->scsi_host->shost_gendev,
               0, target->scsi_id, SCAN_WILD_CARD, 0);
 
Quoted 10 lines

drivers/infiniband/ulp/srp/ib_srp.c static int srp_add_target(struct srp_host *host, struct srp_target_port *target) · line 2661

Quoted 6 lines
drivers/infiniband/ulp/srp/ib_srp.c +6 -0
+    if (!target->connected || target->qp_in_error) {
+        shost_printk(KERN_INFO, target->scsi_host,
+                 PFX "SCSI scan failed - removing SCSI host\n");
+        srp_queue_remove_work(target);
+        goto out;
+    }

So my impression is that by conditioning target->qp_in_error you are relying on the fact that SRP eh was invoked here (RC error), what if scsi eh was invoked prior to that? did you test this path?

This code path has been tested. It's not that hard to trigger this code path - setting the channel count (ch_count) parameter to a high value and running a loop at the target side that disables IB ports after a random delay between 0s and (2*srp_daemon_scan_interval) is sufficient. After not too many iterations this code will be hit because the higher the channel count the longer it takes to log in.

The SCSI EH is only activated after a SCSI command has failed. No SCSI commands are sent to a target system before the scsi_scan_target() call. This means that the SCSI EH can only get activated while scsi_scan_target() is in progress or after that function has finished.

Bart.
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maintainer
#86 lore raw
In reply to Sagi Grimberg
Quoted 17 lines · Sagi Grimberg

Documentation/ABI/stable/sysfs-driver-ib_srp Description: Interface for making ib_srp connect to a new target. · line 63

Quoted 13 lines · Bart Van Assche

* comp_vector, a number in the range 0..n-1 specifying the

Documentation/ABI/stable/sysfs-driver-ib_srp +6 -6
-          MSI-X completion vector. Some HCA's allocate multiple (n)
-          MSI-X vectors per HCA port. If the IRQ affinity masks of
-          these interrupts have been configured such that each MSI-X
-          interrupt is handled by a different CPU then the comp_vector
-          parameter can be used to spread the SRP completion workload
-          over multiple CPU's.
+          MSI-X completion vector of the first RDMA channel. Some
+          HCA's allocate multiple (n) MSI-X vectors per HCA port. If
+          the IRQ affinity masks of these interrupts have been
+          configured such that each MSI-X interrupt is handled by a
+          different CPU then the comp_vector parameter can be used to
+          spread the SRP completion workload over multiple CPU's.

This is fairly not trivial for the user...

Quoted 7 lines

Aren't we requesting a bit too much awareness here?
Can't we just "make it work"? The user hands out ch_count - why can't you do some least-used logic here?

Maybe we can even go with per-cpu QPs and discard comp_vector argument? this would probably bring the best performance, wouldn't it? (fallback to least-used logic in case HW support less vectors)

Hello Sagi,

The only reason the comp_vector parameter is still supported is because of backwards compatibility. What I expect is that users will set the ch_count parameter but not the comp_vector parameter.

Using one QP per CPU thread does not necessarily result in the best performance. In the tests I ran performance was about 4% better when using one QP for each pair of CPU threads (with hyperthreading enabled).

Quoted 10 lines
Quoted 8 lines
drivers/infiniband/ulp/srp/ib_srp.c +4 -0
+static unsigned ch_count;
+module_param(ch_count, uint, 0444);
+MODULE_PARM_DESC(ch_count,
+         "Number of RDMA channels to use for communication with an

SRP target. Using more than one channel improves performance if the HCA supports multiple completion vectors. The default value is the minimum of four times the number of online CPU sockets and the number of completion vectors supported by the HCA.");

Why? how did you get to this magic equation?

On the systems I have access to measurements have shown that this choice for the ch_count parameter results in a significant performance improvement without consuming too many system resources. The performance difference when using more than four channels was small. This means that the exact value of this parameter is not that important. What matters to me is that users can benefit from improved performance even if the ch_count kernel module parameter has been left to its default value.

Bart.

maintainer
#78 lore raw

Re: EH action after scsi_remove_host, was: Re: [PATCH v2 12/12] IB/srp: Add multichannel support

In reply to Christoph Hellwig
Quoted 11 lines · Christoph Hellwig

drivers/infiniband/ulp/srp/ib_srp.c static void srp_free_ch_ib(struct srp_target_port *target, · line 579

Quoted 7 lines · Bart Van Assche
drivers/infiniband/ulp/srp/ib_srp.c +7 -0
+	/*
+	 * Avoid that the SCSI error handler tries to use this channel after
+	 * it has been freed. The SCSI error handler can namely continue
+	 * trying to perform recovery actions after scsi_remove_host()
+	 * returned.
+	 */
+	ch->target = NULL;

Do you have a reproducer for that? I think we should fix the root cause.

Hello Christoph,

The above assignment statement has been reported to fix a kernel oops that could be triggered by cable pulling. Regarding fixing the root cause: some time ago I had posted a patch series that makes scsi_remove_host() wait until all error handler callback functions have finished and also that prevents that any new error handler function calls are initiated after scsi_remove_host() has finished (http://thread.gmane.org/gmane.linux.scsi/82572/focus=87985). Should I repost that patch series ?

Bart.

#32 lore raw

Re: [PATCH v2 11/12] IB/srp: Eliminate free_reqs list

In reply to Bart Van Assche
Quoted 4 lines · Bart Van Assche

The only reason why patches 10/12 and 11/12 are separate patches is to reduce the size of individual patches and hence to make it easier to review these patches. If everyone agrees I'm fine with folding patch 11/12 into patch 10/12.

I would prefer to merge the two patches.

#83 lore raw
In reply to Bart Van Assche
Quoted 4 lines · Bart Van Assche

That pr_err() statement was convenient while debugging the multiqueue code in the SRP initiator driver but can be left out. Would you agree with leaving the above three lines of debug code out instead of adding an additional argument to scsi_host_find_tag() ?

Feel free to remove the check.

#46 lore raw

Re: [PATCH v2 04/12] scsi_tcq.h: Add support for multiple hardware queues

In reply to a message not in the archive
Quoted 9 lines · Bart Van Assche
Quoted 5 lines · Sagi Grimberg

include/scsi/scsi_tcq.h static inline struct scsi_cmnd *scsi_find_tag(struct scsi_device *sdev, int tag) · line 141

Quoted 2 lines · Bart Van Assche
include/scsi/scsi_tcq.h +1 -1
-            req = blk_queue_find_tag(sdev->request_queue, tag);
+        req = blk_queue_find_tag(sdev->request_queue, tag);

Why is this line different?

This is because the indentation has been modified from "8x<space><tab>" into "<tab><tab>". I can leave out that change if you want.

Please keep it.

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#53 lore raw

Re: [PATCH v2 07/12] IB/srp: Avoid that I/O hangs due to a cable pull during LUN scanning

In reply to Bart Van Assche
Quoted 3 lines · Bart Van Assche

How about renaming this function into shost_sdev_count() and moving its declaration to <scsi/scsi_device.h> and its implementation to drivers/scsi/scsi_lib.c ?

I'd prefer to defer this until we have an actual need for it elsewhere.

#79 lore raw

Re: EH action after scsi_remove_host, was: Re: [PATCH v2 12/12] IB/srp: Add multichannel support

In reply to Bart Van Assche
Quoted 8 lines · Bart Van Assche

The above assignment statement has been reported to fix a kernel oops that could be triggered by cable pulling. Regarding fixing the root cause: some time ago I had posted a patch series that makes scsi_remove_host() wait until all error handler callback functions have finished and also that prevents that any new error handler function calls are initiated after scsi_remove_host() has finished
(http://thread.gmane.org/gmane.linux.scsi/82572/focus=87985). Should I repost that patch series ?

Please keep the workaround in srp for now, and then resend the series, including a new patch to remove the workaround in srp.

#47 lore raw

Re: [PATCH v2 04/12] scsi_tcq.h: Add support for multiple hardware queues

In reply to Christoph Hellwig
Quoted 6 lines · Christoph Hellwig
Quoted 5 lines · Bart Van Assche
Quoted 4 lines · Sagi Grimberg
Quoted 2 lines · Bart Van Assche
include/scsi/scsi_tcq.h +1 -1
-            req = blk_queue_find_tag(sdev->request_queue, tag);
+        req = blk_queue_find_tag(sdev->request_queue, tag);
Quoted 7 lines
Quoted 4 lines
Quoted 1 line

Why is this line different?

This is because the indentation has been modified from "8x<space><tab>" into "<tab><tab>". I can leave out that change if you want.

Please keep it.

I don't have a big objection on this, but the problem with leaving this stuff is that it tends to screw up git blame...

#88 lore raw
In reply to a message not in the archive
Quoted 26 lines · Bart Van Assche
Quoted 17 lines · Sagi Grimberg

Documentation/ABI/stable/sysfs-driver-ib_srp Description: Interface for making ib_srp connect to a new target. · line 63

Quoted 13 lines · Bart Van Assche

* comp_vector, a number in the range 0..n-1 specifying the

Documentation/ABI/stable/sysfs-driver-ib_srp +6 -6
-          MSI-X completion vector. Some HCA's allocate multiple (n)
-          MSI-X vectors per HCA port. If the IRQ affinity masks of
-          these interrupts have been configured such that each MSI-X
-          interrupt is handled by a different CPU then the comp_vector
-          parameter can be used to spread the SRP completion workload
-          over multiple CPU's.
+          MSI-X completion vector of the first RDMA channel. Some
+          HCA's allocate multiple (n) MSI-X vectors per HCA port. If
+          the IRQ affinity masks of these interrupts have been
+          configured such that each MSI-X interrupt is handled by a
+          different CPU then the comp_vector parameter can be used to
+          spread the SRP completion workload over multiple CPU's.

This is fairly not trivial for the user...

Quoted 7 lines

Aren't we requesting a bit too much awareness here?
Can't we just "make it work"? The user hands out ch_count - why can't you do some least-used logic here?

Maybe we can even go with per-cpu QPs and discard comp_vector argument? this would probably bring the best performance, wouldn't it? (fallback to least-used logic in case HW support less vectors)

Quoted 5 lines

Hello Sagi,

The only reason the comp_vector parameter is still supported is because of backwards compatibility. What I expect is that users will set the ch_count parameter but not the comp_vector parameter.

Agreed...

Quoted 4 lines

Using one QP per CPU thread does not necessarily result in the best performance. In the tests I ran performance was about 4% better when using one QP for each pair of CPU threads (with hyperthreading enabled).

I usually don't like using defaults based on empirical experiments on specific workloads. IMO, going either full blown MQ (per-cpu), or go SQ for default.

But that is just my opinion...
you call it.

Quoted 12 lines
Quoted 11 lines
Quoted 9 lines
drivers/infiniband/ulp/srp/ib_srp.c +4 -0
+static unsigned ch_count;
+module_param(ch_count, uint, 0444);
+MODULE_PARM_DESC(ch_count,
+         "Number of RDMA channels to use for communication with an

SRP target. Using more than one channel improves performance if the HCA supports multiple completion vectors. The default value is the minimum of four times the number of online CPU sockets and the number of completion vectors supported by the HCA.");

Why? how did you get to this magic equation?

Quoted 7 lines

On the systems I have access to measurements have shown that this choice for the ch_count parameter results in a significant performance improvement without consuming too many system resources. The performance difference when using more than four channels was small. This means that the exact value of this parameter is not that important. What matters to me is that users can benefit from improved performance even if the ch_count kernel module parameter has been left to its default value.

I do like the idea of giving users high performance out-of-the-box. But as I wrote below, I less like the idea of basing your choice on experiments.

Sagi.

Quoted 2 lines

Bart.

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#112 lore raw
In reply to a message not in the archive
Quoted 22 lines · Bart Van Assche

Improve performance by using multiple RDMA/RC channels per SCSI host for communication with an SRP target. About the implementation:
- Introduce a loop over all channels in the code that uses target->ch.
- Set the SRP_MULTICHAN_MULTI flag during login for the creation of the second and subsequent channels.
- RDMA completion vectors are chosen such that RDMA completion interrupts are handled by the CPU socket that submitted the I/O request. As one can see in this patch it has been assumed if a system contains n CPU sockets and m RDMA completion vectors have been assigned to an RDMA HCA that IRQ affinity has been configured such that completion vectors [i*m/n..(i+1)*m/n) are bound to CPU socket i with 0 <= i < n.
- Modify srp_free_ch_ib() and srp_free_req_data() such that it becomes safe to invoke these functions after the corresponding allocation function failed.
- Add a ch_count sysfs attribute per target port.

Cc Sagi Grimberg <sagig-VPRAkNaXOzVWk0Htik3J/[email protected]>
Cc Sebastian Parschauer <[email protected]>

<SNIP>

drivers/infiniband/ulp/srp/ib_srp.c static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd) · line 1970

Quoted 4 lines
  			spin_lock_irqsave(&ch->lock, flags);
  			ch->req_lim += be32_to_cpu(rsp->req_lim_delta);
drivers/infiniband/ulp/srp/ib_srp.c +0 -0
@@ -1906,7 +1970,7 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
  		goto err;

Bart,

Any chance you can share some perf output on this code? I'm interested of knowing the contention on target->lock that is still taken on the IO path across channels.

Can we think on how to avoid it?

Also would like to understand the where did the bottleneck transition.

Sagi.
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#61 lore raw

RE: [PATCH v2 10/12] IB/srp: Use block layer tags

In reply to a message not in the archive

PiAtLS0tLU9yaWdpbmFsIE1lc3NhZ2UtLS0tLQ0KPiBGcm9tOiBCYXJ0IFZhbiBBc3NjaGUgW21h aWx0bzpidmFuYXNzY2hlQGFjbS5vcmddDQo+IFNlbnQ6IFR1ZXNkYXksIDA3IE9jdG9iZXIsIDIw MTQgODowNyBBTQ0KLi4uDQo+IEBAIC0xOTI3LDcgKzE5MzEsNyBAQCBzdGF0aWMgaW50IHNycF9x dWV1ZWNvbW1hbmQoc3RydWN0IFNjc2lfSG9zdA0KPiAqc2hvc3QsIHN0cnVjdCBzY3NpX2NtbmQg KnNjbW5kKQ0KPiANCj4gIAljbWQtPm9wY29kZSA9IFNSUF9DTUQ7DQo+ICAJY21kLT5sdW4gICAg PSBjcHVfdG9fYmU2NCgodTY0KSBzY21uZC0+ZGV2aWNlLT5sdW4gPDwgNDgpOw0KPiAtCWNtZC0+ dGFnICAgID0gcmVxLT5pbmRleDsNCj4gKwljbWQtPnRhZyAgICA9IHRhZzsNCj4gIAltZW1jcHko Y21kLT5jZGIsIHNjbW5kLT5jbW5kLCBzY21uZC0+Y21kX2xlbik7DQo+IA0KPiAgCXJlcS0+c2Nt bmQgICAgPSBzY21uZDsNCi4uLg0KPiANCj4gK3N0YXRpYyBpbnQgc3JwX3NsYXZlX2FsbG9jKHN0 cnVjdCBzY3NpX2RldmljZSAqc2RldikNCj4gK3sNCj4gKwlzZGV2LT50YWdnZWRfc3VwcG9ydGVk ID0gMTsNCj4gKw0KPiArCXNjc2lfYWN0aXZhdGVfdGNxKHNkZXYsIHNkZXYtPnF1ZXVlX2RlcHRo KTsNCj4gKw0KPiArCXJldHVybiAwOw0KPiArfQ0KPiArDQoNCkhhdmUgeW91IHRlc3RlZCB0aGlz IHdpdGggc2NzaV9tb2QudXNlX2Jsa19tcT1uPw0KDQpUcnlpbmcgc2ltaWxhciBjaGFuZ2VzIGlu IGhwc2EsIHdlIHN0aWxsIHJlY2VpdmUgc29tZSBJTlFVSVJZIGNvbW1hbmRzIA0Kc3VibWl0dGVk IHRocm91Z2ggcXVldWVjb21tYW5kIHdpdGggdGFnIC0xLiAgVGhleSBhcmUgZm9yIGRldmljZXMg Zm9yDQp3aGljaCBzbGF2ZV9hbGxvYyBoYXMgbm90IHlldCBiZWVuIHJ1biwgaW1wbHlpbmcgdGhp cyB3b3JrIG5lZWRzIHRvIA0KYmUgZG9uZSBldmVuIGVhcmxpZXIuICBNYXliZSB0aGUgbWlkbGF5 ZXIgaXMgbWlzc2luZyBhIHNsYXZlX2FsbG9jDQpjYWxsIHNvbWV3aGVyZT8NCg0KLS0tDQpSb2Ig RWxsaW90dCAgICBIUCBTZXJ2ZXIgU3RvcmFnZQ0KDQoNCg0K
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#63 lore raw

Re: [PATCH v2 10/12] IB/srp: Use block layer tags

In reply to a message not in the archive
Quoted 28 lines · Robert (Server Storage)
Quoted 3 lines

-----Original Message-----
From: Bart Van Assche [mailto:[email protected]]
Sent: Tuesday, 07 October, 2014 8:07 AM

...

Quoted 10 lines
drivers/infiniband/ulp/srp/ib_srp.c +1 -1
@@ -1927,7 +1931,7 @@ static int srp_queuecommand(struct Scsi_Host
 *shost, struct scsi_cmnd *scmnd)
 
  	cmd->opcode = SRP_CMD;
  	cmd->lun    = cpu_to_be64((u64) scmnd->device->lun << 48);
-	cmd->tag    = req->index;
+	cmd->tag    = tag;
  	memcpy(cmd->cdb, scmnd->cmnd, scmnd->cmd_len);
 
  	req->scmnd    = scmnd;

...

drivers/infiniband/ulp/srp/ib_srp.c static int srp_reset_host(struct scsi_cmnd *scmnd) · line 2480

Quoted 10 lines
drivers/infiniband/ulp/srp/ib_srp.c +9 -0
+static int srp_slave_alloc(struct scsi_device *sdev)
+{
+	sdev->tagged_supported = 1;
+
+	scsi_activate_tcq(sdev, sdev->queue_depth);
+
+	return 0;
+}
+

Have you tested this with scsi_mod.use_blk_mq=n?

Quoted 5 lines

Trying similar changes in hpsa, we still receive some INQUIRY commands submitted through queuecommand with tag -1. They are for devices for which slave_alloc has not yet been run, implying this work needs to be done even earlier. Maybe the midlayer is missing a slave_alloc call somewhere?

Hello Rob,

All my tests with use_blk_mq=n were run with a WARN_ON_ONCE(req->tag < 0) statement present in srp_queuecommand(). I haven't seen any kernel warning being triggered during the tests I ran.

I also had a look at scsi_alloc_sdev() in drivers/scsi/scsi_scan.c. The number of statements between queue allocation and the slave_alloc() call is limited. The only scenario I can think of which could cause queuecommand() to be invoked before slave_alloc() is a LUN scan initiated from user space via sysfs due to scsi_sysfs_device_initialize() being invoked before slave_alloc(). Does that make sense to you ?

Bart.
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#69 lore raw

Re: [PATCH v2 10/12] IB/srp: Use block layer tags

In reply to Elliott, Robert (Server Storage)
Quoted 7 lines · Robert (Server Storage)

Have you tested this with scsi_mod.use_blk_mq=n?

Trying similar changes in hpsa, we still receive some INQUIRY commands submitted through queuecommand with tag -1. They are for devices for which slave_alloc has not yet been run, implying this work needs to be done even earlier. Maybe the midlayer is missing a slave_alloc call somewhere?

Did that version of hpsa really enable tagging in slave_alloc or just in slave_configure? The latter would cause INQUIRY to be sent untagged.

#64 lore raw

Re: [PATCH v2 10/12] IB/srp: Use block layer tags

In reply to Bart Van Assche
Quoted 1 line · Bart Van Assche

All my tests with use_blk_mq=n were run with a WARN_ON_ONCE(req->tag < 0) statement present in srp_queuecommand(). I haven't seen any kernel warning being triggered during the tests I ran.

Bart, what's the data type of "req->tag", here? (E.g., if it "unsigned", it will never be less than zero, right?)

Thanks,

Webb

#70 lore raw

RE: [PATCH v2 10/12] IB/srp: Use block layer tags

In reply to Christoph Hellwig
Quoted 21 lines

-----Original Message-----
From: Christoph Hellwig [mailto:[email protected]]
Sent: Thursday, October 23, 2014 3:48 AM
To: Elliott, Robert (Server Storage)
Cc: Bart Van Assche; Jens Axboe; Sagi Grimberg; Sebastian Parschauer; Ming Lei; [email protected]; linux-rdma; Scales, Webb; Don Brace (PMC)
Subject: Re: [PATCH v2 10/12] IB/srp: Use block layer tags

Quoted 7 lines · Robert (Server Storage)

Have you tested this with scsi_mod.use_blk_mq=n?

Trying similar changes in hpsa, we still receive some INQUIRY commands submitted through queuecommand with tag -1. They are for devices for which slave_alloc has not yet been run, implying this work needs to be done even earlier. Maybe the midlayer is missing a slave_alloc call somewhere?

Quoted 3 lines

Did that version of hpsa really enable tagging in slave_alloc or just in slave_configure? The latter would cause INQUIRY to be sent untagged.

Yes, it is slave_alloc, not slave_configure.

However, it was looking at scmd->tag, which is always 0xff (at least in those early discovery commands). scmd->request->tag looks like it is the field that has the correct values.

Also, I noticed that scmd->tag is just an 8 bit field, so it could never represent a large number of tags.

Just to confirm: After calling scsi_init_shared_tag_map() in non-mq mode, will scmd->request->tag be based on controller-wide tag allocation (never using the same value at the same time for the request queues of multiple devices in that controller)?

#66 lore raw

Re: [PATCH v2 10/12] IB/srp: Use block layer tags

In reply to a message not in the archive
Quoted 7 lines · Webb Scales
Quoted 3 lines · Bart Van Assche

All my tests with use_blk_mq=n were run with a WARN_ON_ONCE(req->tag <
0) statement present in srp_queuecommand(). I haven't seen any kernel warning being triggered during the tests I ran.

Bart, what's the data type of "req->tag", here? (E.g., if it "unsigned", it will never be less than zero, right?)

Hello Webb,

This is what I found in "struct request" in <linux/blkdev.h>:

struct request {
	[ ... ]
	int tag;
	[ ... ]
};

Bart.

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#71 lore raw

Re: [PATCH v2 10/12] IB/srp: Use block layer tags

In reply to Elliott, Robert (Server Storage)
Quoted 6 lines · Robert (Server Storage)

However, it was looking at scmd->tag, which is always 0xff (at least in those early discovery commands). scmd->request->tag looks like it is the field that has the correct values.

Also, I noticed that scmd->tag is just an 8 bit field, so it could never represent a large number of tags.

Yes, we need to get rid of scmd->tag. Hannes had a patchset to get started on it, and I hope either he or someone else will have time to get back to it ASAP.

Quoted 5 lines

Just to confirm: After calling scsi_init_shared_tag_map() in non-mq mode, will scmd->request->tag be based on controller-wide tag allocation (never using the same value at the same time for the request queues of multiple devices in that controller)?

Yes.

#68 lore raw

Re: [PATCH v2 10/12] IB/srp: Use block layer tags

In reply to a message not in the archive
Quoted 13 lines · Bart Van Assche
Quoted 7 lines · Webb Scales
Quoted 3 lines · Bart Van Assche

All my tests with use_blk_mq=n were run with a WARN_ON_ONCE(req->tag <
0) statement present in srp_queuecommand(). I haven't seen any kernel warning being triggered during the tests I ran.

Bart, what's the data type of "req->tag", here? (E.g., if it "unsigned", it will never be less than zero, right?)

Hello Webb,

This is what I found in "struct request" in <linux/blkdev.h>:

Quoted 7 lines
struct request {
    [ ... ]
    int tag;
    [ ... ]
};

Bart.

Good: I just wanted to make sure that you weren't referencing the "tag" field in the "scsi_cmnd" struct (which _is_ unsigned).

Webb
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Reviewed-by
#40 lore raw

Re: [PATCH v2 02/12] blk-mq: Add blk_mq_unique_tag()

In reply to a message not in the archive
Quoted 1 line
Quoted 1 line
Quoted 1 line
Quoted 1 line
Quoted 1 line

"Bart" == Bart Van Assche <[email protected]> writes:

Bart> The queuecommand() callback functions in SCSI low-level drivers Bart> need to know which hardware context has been selected by the block Bart> layer. Since this information is not available in the request Bart> structure, and since passing the hctx pointer directly to the Bart> queuecommand callback function would require modification of all Bart> SCSI LLDs, add a function to the block layer that allows to query Bart> the hardware context index.

I agree with consolidating the two functions. Otherwise OK.

Signature · 5 lines
Martin K. Petersen	Oracle Linux Engineering
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Reviewed-by
#17 lore raw

Re: [PATCH v2 03/12] scsi-mq: Add support for multiple hardware queues

In reply to a message not in the archive
Quoted 1 line
Quoted 1 line
Quoted 1 line
Quoted 1 line
Quoted 1 line

"Bart" == Bart Van Assche <[email protected]> writes:

Bart> Allow a SCSI LLD to declare how many hardware queues it supports Bart> by setting Scsi_Host.nr_hw_queues before calling scsi_add_host().

Bart> Note: it is assumed that each hardware queue has a queue depth of Bart> shost-> can_queue. In other words, the total queue depth per host Bart> is (number of hardware queues) * (shost->can_queue).

I suggest you emphasize that assumption in the header file.

Also: What about the host template?

Signature · 5 lines
Martin K. Petersen	Oracle Linux Engineering
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Reviewed-by on v2 4/12
#48 lore raw

Re: [PATCH v2 04/12] scsi_tcq.h: Add support for multiple hardware queues

In reply to Bart Van Assche
Quoted 1 line
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"Bart" == Bart Van Assche <[email protected]> writes:

Bart> Modify scsi_find_tag() and scsi_host_find_tag() such that these Bart> fuctions can translate a tag generated by blk_mq_unique_tag().

Looks good to me.

Signature · 1 line
Martin K. Petersen	Oracle Linux Engineering
#90 lore raw
In reply to a message not in the archive
Quoted 27 lines · Sagi Grimberg
Quoted 26 lines · Bart Van Assche
Quoted 24 lines · Sagi Grimberg

Review

Quoted 13 lines · Bart Van Assche

* comp_vector, a number in the range 0..n-1 specifying the

(quoted diff) +6 -6
-          MSI-X completion vector. Some HCA's allocate multiple (n)
-          MSI-X vectors per HCA port. If the IRQ affinity masks of
-          these interrupts have been configured such that each MSI-X
-          interrupt is handled by a different CPU then the comp_vector
-          parameter can be used to spread the SRP completion workload
-          over multiple CPU's.
+          MSI-X completion vector of the first RDMA channel. Some
+          HCA's allocate multiple (n) MSI-X vectors per HCA port. If
+          the IRQ affinity masks of these interrupts have been
+          configured such that each MSI-X interrupt is handled by a
+          different CPU then the comp_vector parameter can be used to
+          spread the SRP completion workload over multiple CPU's.

This is fairly not trivial for the user...

Aren't we requesting a bit too much awareness here?
Can't we just "make it work"? The user hands out ch_count - why can't you do some least-used logic here?

Maybe we can even go with per-cpu QPs and discard comp_vector argument? this would probably bring the best performance, wouldn't it? (fallback to least-used logic in case HW support less vectors)

Quoted 6 lines
Quoted 5 lines

Hello Sagi,

The only reason the comp_vector parameter is still supported is because of backwards compatibility. What I expect is that users will set the ch_count parameter but not the comp_vector parameter.

Hey Bart,

Another wander I have with this. Say you have 8 cores on a single numa node. First connection will attach to vectors 0-3 (ch_count=4) and so are all the connections. Don't we want to spread that a little?

If we are not going per-cpu, why aren't we trying to spread vectors around to try and reduce the interference?

Sagi.
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#92 lore raw
In reply to a message not in the archive
Quoted 33 lines · Sagi Grimberg
Quoted 24 lines · Sagi Grimberg
Quoted 23 lines · Bart Van Assche
Quoted 22 lines · Sagi Grimberg
Quoted 6 lines · Bart Van Assche

* comp_vector, a number in the range 0..n-1 specifying the

(quoted diff) +0 -4
-          MSI-X completion vector. Some HCA's allocate multiple (n)
-          MSI-X vectors per HCA port. If the IRQ affinity masks of
-          these interrupts have been configured such that each MSI-X
-          interrupt is handled by a different CPU then the

comp_vector

Review

Quoted 8 lines
(quoted diff) +6 -2
-          parameter can be used to spread the SRP completion workload
-          over multiple CPU's.
+          MSI-X completion vector of the first RDMA channel. Some
+          HCA's allocate multiple (n) MSI-X vectors per HCA port. If
+          the IRQ affinity masks of these interrupts have been
+          configured such that each MSI-X interrupt is handled by a
+          different CPU then the comp_vector parameter can be used to
+          spread the SRP completion workload over multiple CPU's.

This is fairly not trivial for the user...

Aren't we requesting a bit too much awareness here?
Can't we just "make it work"? The user hands out ch_count - why can't you do some least-used logic here?

Quoted 7 lines
Quoted 7 lines
Quoted 3 lines

Maybe we can even go with per-cpu QPs and discard comp_vector argument? this would probably bring the best performance, wouldn't it? (fallback to least-used logic in case HW support less vectors)

The only reason the comp_vector parameter is still supported is because of backwards compatibility. What I expect is that users will set the ch_count parameter but not the comp_vector parameter.

Quoted 6 lines

Another wander I have with this. Say you have 8 cores on a single numa node. First connection will attach to vectors 0-3 (ch_count=4) and so are all the connections. Don't we want to spread that a little?

If we are not going per-cpu, why aren't we trying to spread vectors around to try and reduce the interference?

Hello Sagi,

Sorry but your question is not entirely clear to me. Are you referring to spreading the workload over CPU's or over completion vectors ? If a user wants to spread the completion workload maximally by using all completion vectors that can be achieved by setting ch_count to a value that is equal to or larger than the number of completion vectors.

As mentioned in the commit message, spreading the completion workload over CPU's is not entirely under control of the SRP initiator driver. It is assumed that a user assigns IRQ affinity such that the interrupts associated with different completion vectors are processed by different CPU threads. If there are more RDMA channels than completion vectors, the SRP initiator driver associates RDMA channels with completion vectors such that the workload is spread evenly over the completion vectors.

Bart.
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maintainer
#18 lore raw

Re: [PATCH v2 03/12] scsi-mq: Add support for multiple hardware queues

In reply to Martin K. Petersen
Quoted 9 lines · Martin K. Petersen
Quoted 1 line
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"Bart" == Bart Van Assche <[email protected]> writes:

Bart> Allow a SCSI LLD to declare how many hardware queues it supports Bart> by setting Scsi_Host.nr_hw_queues before calling scsi_add_host().

Bart> Note: it is assumed that each hardware queue has a queue depth of Bart> shost-> can_queue. In other words, the total queue depth per host Bart> is (number of hardware queues) * (shost->can_queue).

Quoted 5 lines

I suggest you emphasize that assumption in the header file.

Also: What about the host template?

Hello Martin,

Thanks for reviewing the blk-core and SCSI-core patches in this series. Regarding nr_hw_queues and the SCSI host template: setting that parameter in the host template is supported. I will mention this in the patch description. I will also clarify the queue size assumptions in scsi_host.h.

Bart.

maintainer
#19 lore raw

Re: [PATCH v2 03/12] scsi-mq: Add support for multiple hardware queues

Quoted 2 lines · Bart Van Assche

Regarding nr_hw_queues and the SCSI host template: setting that parameter in the host template is supported.

(replying to my own e-mail)

Let me correct this: setting nr_hw_queues in the host template is not yet supported. If anyone would consider this useful, such functionality would be easy to add.

Bart.

maintainer
#113 lore raw
In reply to Sagi Grimberg
Quoted 9 lines · Sagi Grimberg

Review static int srp_queuecommand(struct Scsi_Host · line 1971

Quoted 5 lines · Bart Van Assche
              spin_lock_irqsave(&ch->lock, flags);
              ch->req_lim += be32_to_cpu(rsp->req_lim_delta);
(quoted diff) +0 -0
@@ -1906,7 +1970,7 @@ static int srp_queuecommand(struct Scsi_Host
 *shost, struct scsi_cmnd *scmnd)
          goto err;

Bart,

Quoted 7 lines

Any chance you can share some perf output on this code? I'm interested of knowing the contention on target->lock that is still taken on the IO path across channels.

Can we think on how to avoid it?

Also would like to understand the where did the bottleneck transition.

Hello Sagi,

Are you referring to target->lock ? That lock isn't taken anywhere in the hot path. More in general, I haven't seen any lock contention in the perf output that was caused by the block layer, SCSI core, SRP initiator or HCA (mlx4) drivers. The code that showed up highest in the perf output was the direct I/O code, the code that is triggered by fio to submit I/O requests.

Bart.

#21 lore raw

Re: [PATCH v2 03/12] scsi-mq: Add support for multiple hardware queues

In reply to a message not in the archive
Quoted 1 line
Quoted 1 line
Quoted 1 line
Quoted 1 line
Quoted 1 line

"Bart" == Bart Van Assche <[email protected]> writes:

Bart> Let me correct this: setting nr_hw_queues in the host template is Bart> not yet supported. If anyone would consider this useful, such Bart> functionality would be easy to add.

It seemed like an obvious thing a device driver would want to describe in its host template. That's why I asked.

We can add it if somebody wants it but it's a bit of a chicken and egg problem. Anyway. Minor issue.

Signature · 5 lines
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#93 lore raw
In reply to Bart Van Assche
Quoted 41 lines · Bart Van Assche
Quoted 40 lines · Sagi Grimberg
Quoted 26 lines · Sagi Grimberg
Quoted 25 lines · Bart Van Assche
Quoted 24 lines · Sagi Grimberg
Quoted 14 lines · Bart Van Assche

* comp_vector, a number in the range 0..n-1 specifying the

(quoted diff) +0 -4
-          MSI-X completion vector. Some HCA's allocate multiple (n)
-          MSI-X vectors per HCA port. If the IRQ affinity masks of
-          these interrupts have been configured such that each MSI-X
-          interrupt is handled by a different CPU then the

comp_vector
- parameter can be used to spread the SRP completion
workload

(quoted diff) +5 -1
-          over multiple CPU's.
+          MSI-X completion vector of the first RDMA channel. Some
+          HCA's allocate multiple (n) MSI-X vectors per HCA port. If
+          the IRQ affinity masks of these interrupts have been
+          configured such that each MSI-X interrupt is handled by a
+          different CPU then the comp_vector parameter can be
Quoted 2 lines

used to
+ spread the SRP completion workload over multiple CPU's.

This is fairly not trivial for the user...

Aren't we requesting a bit too much awareness here?
Can't we just "make it work"? The user hands out ch_count - why can't you do some least-used logic here?

Quoted 8 lines
Quoted 8 lines
Quoted 4 lines

Maybe we can even go with per-cpu QPs and discard comp_vector argument?
this would probably bring the best performance, wouldn't it? (fallback to least-used logic in case HW support less vectors)

The only reason the comp_vector parameter is still supported is because of backwards compatibility. What I expect is that users will set the ch_count parameter but not the comp_vector parameter.

Another wander I have with this. Say you have 8 cores on a single numa node. First connection will attach to vectors 0-3 (ch_count=4) and so are all the connections. Don't we want to spread that a little?

Quoted 7 lines
Quoted 2 lines

If we are not going per-cpu, why aren't we trying to spread vectors around to try and reduce the interference?

Hello Sagi,

Sorry but your question is not entirely clear to me. Are you referring to spreading the workload over CPU's or over completion vectors ?

I'm talking about completion vectors, but I assume both as I consider spreading interrupt vectors across CPU cores a common practice.

Quoted 5 lines

If a
user wants to spread the completion workload maximally by using all completion vectors that can be achieved by setting ch_count to a value that is equal to or larger than the number of completion vectors.

I'm talking about the default.
My impression here that in the default settings, on a 1 NUMA node with 8 cores, 2 different srp connections (using 4 channels each) will be associated with comp vectors 0-3. while it could potentially use vectors 4-7 and reduce possible mutual interference. right? (you said yourself that the user is not expected to use comp_vector and it is only for backward compatibility).

Now given that each connection uses less than per-cpu channels, don't you think this logic will be helpful?

Quoted 2 lines

As mentioned in the commit message, spreading the completion workload over CPU's is not entirely under control of the SRP initiator driver.

I was referring to comp vectors - but I consider 1x1 mapping a common usage when it comes to RDMA (and not only btw).

Feel free to correct me if I misunderstand the implementation.

Sagi.

#114 lore raw
In reply to Bart Van Assche
Quoted 14 lines · Bart Van Assche
Quoted 13 lines · Sagi Grimberg

Review static int srp_queuecommand(struct Scsi_Host · line 1971

Quoted 5 lines · Bart Van Assche
              spin_lock_irqsave(&ch->lock, flags);
              ch->req_lim += be32_to_cpu(rsp->req_lim_delta);
(quoted diff) +0 -0
@@ -1906,7 +1970,7 @@ static int srp_queuecommand(struct Scsi_Host
 *shost, struct scsi_cmnd *scmnd)
          goto err;

Bart,

Any chance you can share some perf output on this code? I'm interested of knowing the contention on target->lock that is still taken on the IO path across channels.

Quoted 8 lines
Quoted 3 lines

Can we think on how to avoid it?

Also would like to understand the where did the bottleneck transition.

Hello Sagi,

Are you referring to target->lock ? That lock isn't taken anywhere in the hot path.

Right, my recollection was that we used to acquire the target-lock in srp_chkready(). I see that's not the case anymore.

Quoted 5 lines

More in general, I haven't seen any lock contention in the perf output that was caused by the block layer, SCSI core, SRP initiator or HCA (mlx4) drivers. The code that showed up highest in the perf output was the direct I/O code, the code that is triggered by fio to submit I/O requests.

Interesting, you don't see more contention on SQ/RQ/CQ locks? I find that surprising.

Sagi.

maintainer
#94 lore raw
In reply to Sagi Grimberg
Quoted 4 lines · Sagi Grimberg

My impression here that in the default settings, on a 1 NUMA node with 8 cores, 2 different srp connections (using 4 channels each) will be associated with comp vectors 0-3. while it could potentially use vectors 4-7 and reduce possible mutual interference. right?

Hello Sagi,

That's correct. For this example if use of all completion vectors is desired additional configuration is required, e.g. by setting ch_count to 8 in /etc/modprobe.d/ib_srp.conf. By the way, I'm not sure it is possible to avoid manual configuration and tuning entirely. As an example, with a six core CPU at the initiator side and with hyperthreading enabled (12 CPU threads in total) I see higher IOPS results with ch_count=6 compared to ch_count=8 or ch_count=12. I have not tried to determine why but maybe this is because ch_count values that are below the number of CPU threads cause some interrupt coalescing.

Bart.

#96 lore raw
In reply to a message not in the archive
Quoted 11 lines · Bart Van Assche
Quoted 4 lines · Sagi Grimberg

My impression here that in the default settings, on a 1 NUMA node with 8 cores, 2 different srp connections (using 4 channels each) will be associated with comp vectors 0-3. while it could potentially use vectors 4-7 and reduce possible mutual interference. right?

Hello Sagi,

That's correct. For this example if use of all completion vectors is desired additional configuration is required, e.g. by setting ch_count to 8 in /etc/modprobe.d/ib_srp.conf.

That is why I think that the user is still expected to be aware of the configuration in order to get max performance. I would like to see best performance to "just work". For example, I don't see any sort of sw queue count to configure, it "just works".

Now I also agree with this may mean more (or sometimes way more) resources, but I suggest that if we go with default of 4 per numa node we should take care of such situations.

I'm not strict about this wrt to this patch set. But I think we should consider this bit.

Quoted 8 lines

By the way, I'm not sure it is
possible to avoid manual configuration and tuning entirely. As an example, with a six core CPU at the initiator side and with hyperthreading enabled (12 CPU threads in total) I see higher IOPS results with ch_count=6 compared to ch_count=8 or ch_count=12. I have
not tried to determine why but maybe this is because ch_count values that are below the number of CPU threads cause some interrupt coalescing.

I'm not aware of any implicit interrupt coalescing effect... --
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#98 lore raw
In reply to a message not in the archive
Quoted 1 line · Sagi Grimberg

I'm not aware of any implicit interrupt coalescing effect...

In case it was not clear what I was referring to: if multiple completion queue handling routines run on the same CPU then the average number of work completions processed by each completion handling routine increases due to the increased time between generation of an interrupt and the start of the completion handler routine. As you know this helps overall system throughput.

Bart.

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#100 lore raw
In reply to a message not in the archive
Quoted 10 lines · Bart Van Assche
Quoted 1 line · Sagi Grimberg

I'm not aware of any implicit interrupt coalescing effect...

In case it was not clear what I was referring to: if multiple completion queue handling routines run on the same CPU then the average number of work completions processed by each completion handling routine increases due to the increased time between generation of an interrupt and the start of the completion handler routine. As you know this helps overall system throughput.

Now I realize that we can hit serious problems here since we never solved the issue of srp polling routine that might poll forever within an interrupt (or at least until a hard lockup). Its interesting that you weren't able to hit that with a high workload. Did you try running this code on a virtual function (I witnessed this issue in iser on a VM).

Moreover, the fairness issue is even more likely to be encountered in multichannel. Did you try to hit that? I really think this patchset *needs* to deal with the 2 issues I mentioned as the probability of
hitting them increases with a faster IO stack.

I remember this was discussed lately with consideration for using blk-iopoll or not. But I think that for now the initial approach of bailing out of the once we hit a budget is fine for now.

Sagi.
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maintainer
#101 lore raw
Quoted 6 lines · Sagi Grimberg

Now I realize that we can hit serious problems here since we never solved the issue of srp polling routine that might poll forever within an interrupt (or at least until a hard lockup). Its interesting that you weren't able to hit that with a high workload. Did you try running this code on a virtual function (I witnessed this issue in iser on a VM).

Quoted 8 lines

Moreover, the fairness issue is even more likely to be encountered in multichannel. Did you try to hit that? I really think this patchset *needs* to deal with the 2 issues I mentioned as the probability of hitting them increases with a faster IO stack.

I remember this was discussed lately with consideration for using blk-iopoll or not. But I think that for now the initial approach of bailing out of the once we hit a budget is fine for now.

Hello Sagi,

As you mentioned so far this fairness issue has only caused trouble with iSER in a virtual machine guest. I have not yet seen anyone reporting a QP servicing fairness problem for the SRP initiator. Although analyzing and if needed limiting the maximum number of iterations in the SRP polling routine is on my to-do list, addressing that issue is outside of the scope of this patch series.

Regarding the impact of this patch series on QP handling fairness: the time spent in the SRP RDMA completion handler depends on the number of completions processed at once. This number depends on:
(a) The number of CPU cores in the initiator system that submit I/O and
that are associated with a single RDMA channel.
(b) The target system processing speed per RDMA channel.

This patch series reduces (a) by a factor ch_count. (b) is either unaffected (linear scaling) or slightly reduced (less than linear scaling). My conclusion is that if this patch series has an impact on QP handling fairness that it will improve fairness since the number of completions processed at once either remains unchanged or that it is reduced.

Bart.

#73 lore raw

Re: [PATCH v2 10/12] IB/srp: Use block layer tags

In reply to a message not in the archive
Quoted 5 lines · Christoph Hellwig
Quoted 4 lines · Robert (Server Storage)

However, it was looking at scmd->tag, which is always 0xff (at least in those early discovery commands). scmd->request->tag looks like it is the field that has the correct values.

Quoted 7 lines
Quoted 2 lines

Also, I noticed that scmd->tag is just an 8 bit field, so it could never represent a large number of tags.

Yes, we need to get rid of scmd->tag. Hannes had a patchset to get started on it, and I hope either he or someone else will have time to get back to it ASAP.

I'm planning on doing so; just waiting for the NCR5380 cleanup to get in.

Cheers,

Hannes

Signature · 8 lines
Dr. Hannes Reinecke		      zSeries & Storage
[email protected]			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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#103 lore raw
In reply to a message not in the archive
Quoted 16 lines · Bart Van Assche
Quoted 6 lines · Sagi Grimberg

Now I realize that we can hit serious problems here since we never solved the issue of srp polling routine that might poll forever within an interrupt (or at least until a hard lockup). Its interesting that you weren't able to hit that with a high workload. Did you try running this code on a virtual function (I witnessed this issue in iser on a VM).

Quoted 8 lines

Moreover, the fairness issue is even more likely to be encountered in multichannel. Did you try to hit that? I really think this patchset *needs* to deal with the 2 issues I mentioned as the probability of hitting them increases with a faster IO stack.

I remember this was discussed lately with consideration for using blk-iopoll or not. But I think that for now the initial approach of bailing out of the once we hit a budget is fine for now.

Quoted 5 lines

Hello Sagi,

As you mentioned so far this fairness issue has only caused trouble with iSER in a virtual machine guest. I have not yet seen anyone reporting a QP servicing fairness problem for the SRP initiator.

IMHO, this is not iSER specific issue, it is easily indicated from the code that a specific workload SRP will poll recv completion queue forever in an interrupt context.

I encountered this issue on a virtual guest in a high workload (80+
sessions with heavy traffic on all) because qemu smp_affinity setting
was broken (might still be, didn't check that for a while). This caused all completion vectors to fire interrupts to core 0 causing a high events contention on a single event queue (causing lockup situations
and starvation of other CQs). Using more completion queues will enhance
this situation.

I think running multichannel code when all MSIX vectors affinity are directed to a single CPU can invoke what I'm talking about.

Quoted 4 lines

Although analyzing
and if needed limiting the maximum number of iterations in the SRP polling routine is on my to-do list, addressing that issue is outside of the scope of this patch series.

Although both of us did not yet hear of such complaints from SRP users, I disagree because this might make the problems worse. But if you want to take it later I guess that's fine too.

Quoted 9 lines

Regarding the impact of this patch series on QP handling fairness: the time spent in the SRP RDMA completion handler depends on the number of completions processed at once. This number depends on:
(a) The number of CPU cores in the initiator system that submit I/O and that are associated with a single RDMA channel.
(b) The target system processing speed per RDMA channel.

This patch series reduces (a) by a factor ch_count.

This is under the assumption that IRQ affinity is spread across several CPUS and that's fine, but we should *not* hit a hard lockup in case it is not (and I suspect we can).

Quoted 7 lines

(b) is either
unaffected (linear scaling) or slightly reduced (less than linear scaling). My conclusion is that if this patch series has an impact on QP handling fairness that it will improve fairness since the number of completions processed at once either remains unchanged or that it is reduced.

I think in the single CPU completion queue processing, this can enhance the problem as well.

Sagi.
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#104 lore raw
Quoted 10 lines

-----Original Message-----
From: Sagi Grimberg [mailto:[email protected]]
Sent: Sunday, November 02, 2014 7:03 AM
To: Bart Van Assche; Christoph Hellwig
Cc: Jens Axboe; Sagi Grimberg; Sebastian Parschauer; Elliott, Robert (Server Storage); Ming Lei; [email protected]; linux-rdma
Subject: Re: [PATCH v2 12/12] IB/srp: Add multichannel support

...

Quoted 12 lines

IMHO, this is not iSER specific issue, it is easily indicated from the code that a specific workload SRP will poll recv completion queue forever in an interrupt context.

I encountered this issue on a virtual guest in a high workload (80+ sessions with heavy traffic on all) because qemu smp_affinity setting was broken (might still be, didn't check that for a while). This caused all completion vectors to fire interrupts to core 0 causing a high events contention on a single event queue (causing lockup situations and starvation of other CQs). Using more completion queues will enhance this situation.

Quoted 2 lines

I think running multichannel code when all MSIX vectors affinity are directed to a single CPU can invoke what I'm talking about.

That's not an SRP specific problem either. If you ask just one CPU to service interrupts and block layer completions for submissions from lots of other CPUs, it's bound to become overloaded.

Setting rq_affinity=2 helps quite a bit for the block layer completion work. This patch proposed making that the default for blk-mq:

	https://lkml.org/lkml/2014/9/9/931

For SRP interrupt processing, irqbalance recently changed its default to ignore the affinity_hint; you now need to pass an option to honor the hint, or provide a policy script to do so for selected irqs. For multi-million IOPS workloads, irqbalance takes far too long to reroute them based on activity; you're likely to overload a CPU with 100% hardirq processing, creating self-detected stalls for the submitting processes on that CPU and other problems. Sending interrupts back to the submitting CPU provides self-throttling.

#74 lore raw

RE: [PATCH v2 10/12] IB/srp: Use block layer tags

In reply to Christoph Hellwig
Quoted 6 lines

-----Original Message-----
From: [email protected] [mailto:linux-scsi- [email protected]] On Behalf Of Christoph Hellwig
Sent: Friday, October 24, 2014 12:15 PM
To: Elliott, Robert (Server Storage)
Cc: Bart Van Assche; Jens Axboe; Sagi Grimberg; Sebastian Parschauer;

Ming

Quoted 1 line

Lei; [email protected]; linux-rdma; Scales, Webb; Don Brace

(PMC)

Quoted 3 lines

Subject: Re: [PATCH v2 10/12] IB/srp: Use block layer tags

On Fri, Oct 24, 2014 at 04:43:15AM +0000, Elliott, Robert (Server

Storage)

Quoted 9 lines
Quoted 6 lines · wrote:

However, it was looking at scmd->tag, which is always 0xff (at least in those early discovery commands). scmd->request->tag looks like it is the field that has the correct values.

Also, I noticed that scmd->tag is just an 8 bit field, so it could never represent a large number of tags.

Yes, we need to get rid of scmd->tag. Hannes had a patchset to get

started

Quoted 1 line

on it, and I hope either he or someone else will have time to get back

to it

Quoted 8 lines

ASAP.

Quoted 4 lines

Just to confirm: After calling scsi_init_shared_tag_map() in non-mq mode, will scmd->request->tag be based on controller-wide tag allocation (never using the same value at the same time for the request queues of multiple devices in that controller)?

Yes.

Hi Everyone, I am doing similar code changes for megaraid_sas driver. I found this thread more suitable to get help from you...

I also noticed that after using scsi_init_shared_tag_map() in driver, tags are coming controller wide.
And that is a good for megaraid_sas driver to get-rid-off internal command pool list and start using block layer tags.

As explained by Robert,
I also used below setting in slave_alloc(), so that first Inquiry command received by driver also has valid Tag in (Non-MQ mode).

	sdev->tagged_supported = 1

Without above setting Inquiry command comes with 0xFF. If I see below code in scsi_scan.c, it looks like tagged_supported value should be popped by after actual value reported from Inquiry command.

        if ((sdev->scsi_level >= SCSI_2) && (inq_result[7] & 2) &&
            !(*bflags & BLIST_NOTQ))
                sdev->tagged_supported = 1;

Does it means what driver set in slave_alloc is OK to get Inquiry commands with valid Tag ?
What will happen if Target really does not support Tagged command queue and driver overwrite it in slave_alloc ?

Thanks, Kashyap

Quoted 2 lines

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Quoted 2 lines

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#75 lore raw

Re: [PATCH v2 10/12] IB/srp: Use block layer tags

Quoted 7 lines · Kashyap Desai

I also used below setting in slave_alloc(), so that first Inquiry command received by driver also has valid Tag in (Non-MQ mode).

	sdev->tagged_supported = 1

Without above setting Inquiry command comes with 0xFF. If I see below code in scsi_scan.c, it looks like tagged_supported value should be popped by after actual value reported from Inquiry command.

Quoted 8 lines
        if ((sdev->scsi_level >= SCSI_2) && (inq_result[7] & 2) &&
            !(*bflags & BLIST_NOTQ))
                sdev->tagged_supported = 1;

Does it means what driver set in slave_alloc is OK to get Inquiry commands with valid Tag ?
What will happen if Target really does not support Tagged command queue and driver overwrite it in slave_alloc ?

I think the right thing here is to better differenciate between assigning a software tag, and a SCSI tagged command. That is, we should assign a request->tag value for every command if we enable host wide tags, independent of issuing an actual tagged command.

I'll send a series of patches for this ASAP.

maintainer
#105 lore raw
In reply to Elliott, Robert (Server Storage)
Quoted 32 lines · Robert (Server Storage)
Quoted 8 lines

-----Original Message-----
From: Sagi Grimberg [mailto:[email protected]]
Sent: Sunday, November 02, 2014 7:03 AM
To: Bart Van Assche; Christoph Hellwig
Cc: Jens Axboe; Sagi Grimberg; Sebastian Parschauer; Elliott, Robert (Server Storage); Ming Lei; [email protected]; linux-rdma
Subject: Re: [PATCH v2 12/12] IB/srp: Add multichannel support

...

Quoted 12 lines

IMHO, this is not iSER specific issue, it is easily indicated from the code that a specific workload SRP will poll recv completion queue forever in an interrupt context.

I encountered this issue on a virtual guest in a high workload (80+ sessions with heavy traffic on all) because qemu smp_affinity setting was broken (might still be, didn't check that for a while). This caused all completion vectors to fire interrupts to core 0 causing a high events contention on a single event queue (causing lockup situations and starvation of other CQs). Using more completion queues will enhance this situation.

Quoted 2 lines

I think running multichannel code when all MSIX vectors affinity are directed to a single CPU can invoke what I'm talking about.

That's not an SRP specific problem either. If you ask just one CPU to service interrupts and block layer completions for submissions from lots of other CPUs, it's bound to become overloaded.

Setting rq_affinity=2 helps quite a bit for the block layer completion work. This patch proposed making that the default for blk-mq:

	https://lkml.org/lkml/2014/9/9/931
Quoted 8 lines

For SRP interrupt processing, irqbalance recently changed its default to ignore the affinity_hint; you now need to pass an option to honor the hint, or provide a policy script to do so for selected irqs. For multi-million IOPS workloads, irqbalance takes far too long to reroute them based on activity; you're likely to overload a CPU with 100% hardirq processing, creating self-detected stalls for the submitting processes on that CPU and other problems. Sending interrupts back to the submitting CPU provides self-throttling.

Hello Sagi,

To me it seems like with Rob's reply all questions about this patch series have been answered. But I think Christoph is still waiting for a Reviewed-by tag from you for patch 12/12.

Bart.

Reviewed-by
#107 lore raw
In reply to a message not in the archive
Quoted 42 lines · Bart Van Assche
Quoted 32 lines · Robert (Server Storage)
Quoted 8 lines

-----Original Message-----
From: Sagi Grimberg [mailto:[email protected]]
Sent: Sunday, November 02, 2014 7:03 AM
To: Bart Van Assche; Christoph Hellwig
Cc: Jens Axboe; Sagi Grimberg; Sebastian Parschauer; Elliott, Robert (Server Storage); Ming Lei; [email protected]; linux-rdma
Subject: Re: [PATCH v2 12/12] IB/srp: Add multichannel support

...

Quoted 12 lines

IMHO, this is not iSER specific issue, it is easily indicated from the code that a specific workload SRP will poll recv completion queue forever in an interrupt context.

I encountered this issue on a virtual guest in a high workload (80+ sessions with heavy traffic on all) because qemu smp_affinity setting was broken (might still be, didn't check that for a while). This caused all completion vectors to fire interrupts to core 0 causing a high events contention on a single event queue (causing lockup situations and starvation of other CQs). Using more completion queues will enhance this situation.

Quoted 2 lines

I think running multichannel code when all MSIX vectors affinity are directed to a single CPU can invoke what I'm talking about.

That's not an SRP specific problem either. If you ask just one CPU to service interrupts and block layer completions for submissions from lots of other CPUs, it's bound to become overloaded.

Setting rq_affinity=2 helps quite a bit for the block layer completion work. This patch proposed making that the default for blk-mq:

    https://lkml.org/lkml/2014/9/9/931
Quoted 8 lines

For SRP interrupt processing, irqbalance recently changed its default to ignore the affinity_hint; you now need to pass an option to honor the hint, or provide a policy script to do so for selected irqs. For multi-million IOPS workloads, irqbalance takes far too long to reroute them based on activity; you're likely to overload a CPU with 100% hardirq processing, creating self-detected stalls for the submitting processes on that CPU and other problems. Sending interrupts back to the submitting CPU provides self-throttling.

Quoted 6 lines

Hello Sagi,

To me it seems like with Rob's reply all questions about this patch series have been answered. But I think Christoph is still waiting for a Reviewed-by tag from you for patch 12/12.

Hey Bart & Rob,

I'm sorry but I didn't get to reply to the Rob's email yesterday.

I think that Rob and I are not talking about the same issue. In case only a single core is servicing interrupts it is indeed expected that it will spend 100% in hard-irq, that's acceptable since it is pounded with completions all the time.

However, I'm referring to a condition where SRP will spend infinite time servicing a single interrupt (while loop on ib_poll_cq that never drains) which will lead to a hard lockup.

This *can* happen, and I do believe that with an optimized IO path it is even more likely to.

Anyway, since I am sure you ran sufficient testing on this code (and didn't see the issue) and I don't want to my concerns to block this code from 3.18, and I didn't find other gating issues, you can add:

Sagi.
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#109 lore raw
In reply to a message not in the archive
Quoted 10 lines

-----Original Message-----
From: Sagi Grimberg [mailto:[email protected]]
Sent: Tuesday, November 04, 2014 6:15 AM
To: Bart Van Assche; Elliott, Robert (Server Storage); Christoph Hellwig
Cc: Jens Axboe; Sagi Grimberg; Sebastian Parschauer; Ming Lei; linux- [email protected]; linux-rdma
Subject: Re: [PATCH v2 12/12] IB/srp: Add multichannel support

...

Quoted 11 lines

I think that Rob and I are not talking about the same issue. In case only a single core is servicing interrupts it is indeed expected that it will spend 100% in hard-irq, that's acceptable since it is pounded with completions all the time.

However, I'm referring to a condition where SRP will spend infinite time servicing a single interrupt (while loop on ib_poll_cq that never drains) which will lead to a hard lockup.

This *can* happen, and I do believe that with an optimized IO path it is even more likely to.

If the IB completions/interrupts are only for IOs submitted on this CPU, then the CQ will eventually drain, because this CPU is not submitting anything new while stuck in the loop.

This can become bursty, though - submit a lot of IOs, then be busy completing all of them and not submitting more, resulting in the queue depth bouncing from 0 to high to 0 to high. I've seen that with both hpsa and mpt3sas drivers. The fio options iodepth_batch, iodepth_batch_complete, and iodepth_low can amplify and reduce that effect (using libaio).

I haven't found a good way for the LLD ISRs and the block layer completion code to decide to yield the CPU based on how much time they are taking - that would almost qualify as a realtime kernel feature. If you compile with CONFIG_IRQ_TIME_ACCOUNTING, the kernel does keep track of that information; perhaps that could be exported so modules can use it?

---
Rob Elliott, HP Server Storage

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#111 lore raw
In reply to a message not in the archive
Quoted 20 lines · Robert (Server Storage)
Quoted 10 lines

-----Original Message-----
From: Sagi Grimberg [mailto:[email protected]]
Sent: Tuesday, November 04, 2014 6:15 AM
To: Bart Van Assche; Elliott, Robert (Server Storage); Christoph Hellwig
Cc: Jens Axboe; Sagi Grimberg; Sebastian Parschauer; Ming Lei; linux- [email protected]; linux-rdma
Subject: Re: [PATCH v2 12/12] IB/srp: Add multichannel support

...

Quoted 9 lines

I think that Rob and I are not talking about the same issue. In case only a single core is servicing interrupts it is indeed expected that it will spend 100% in hard-irq, that's acceptable since it is pounded with completions all the time.

However, I'm referring to a condition where SRP will spend infinite time servicing a single interrupt (while loop on ib_poll_cq that never drains) which will lead to a hard lockup.

Quoted 6 lines
Quoted 2 lines

This *can* happen, and I do believe that with an optimized IO path it is even more likely to.

If the IB completions/interrupts are only for IOs submitted on this CPU, then the CQ will eventually drain, because this CPU is not submitting anything new while stuck in the loop.

They're not (or not necessarily). I'm talking about the case where the IO completions are submitted from another CPU. This creates a cycle where the submitter is generating completions on CPU X and the completer is evacuating room for more submissions on CPU Y. This process can never end while the completer is in hard-irq context.

Quoted 8 lines

This can become bursty, though - submit a lot of IOs, then be busy completing all of them and not submitting more, resulting in the queue depth bouncing from 0 to high to 0 to high. I've seen that with both hpsa and mpt3sas drivers. The fio options iodepth_batch, iodepth_batch_complete, and iodepth_low can amplify and reduce that effect (using libaio).

blk-iopoll (or some other form of budgeting completions) should take care of that.

Sagi.
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