Limit overall SCSI EH runtime

This patchs adds an 'eh_deadline' attribute to the scsi host which limits the overall runtime of the SCSI EH. When a command is failed the start time of the EH is stored in 'last_reset'. If the overall runtime of the SCSI EH is longer than last_reset + eh_deadline, the EH is short-circuited and falls through to issue a host reset only.

Signed-off-by Hannes Reinecke <[email protected]>

---
 drivers/scsi/hosts.c      |   7 +++
 drivers/scsi/scsi_error.c | 142 +++++++++++++++++++++++++++++++++++++++++++---
 drivers/scsi/scsi_sysfs.c |  37 ++++++++++++
 include/scsi/scsi_host.h  |   2 +-
 4 files changed, 180 insertions(+), 8 deletions(-)

drivers/scsi/hosts.c +6 -0

index df0c3c7..c8d828f 100644
@@ -316,6 +316,12 @@ static void scsi_host_dev_release(struct device *dev)
 	kfree(shost);
 }
 
+static unsigned int shost_eh_deadline;
+
+module_param_named(eh_deadline, shost_eh_deadline, uint, S_IRUGO|S_IWUSR);
+MODULE_PARM_DESC(eh_deadline,
+		 "SCSI EH deadline in seconds (should be between 1 and 2^32-1)");
+
 static struct device_type scsi_host_type = {
 	.name =		"scsi_host",
 	.release =	scsi_host_dev_release,

drivers/scsi/hosts.c +0 -0

 	if (sht->supported_mode == MODE_UNKNOWN)
 		/* means we didn't set it ... default to INITIATOR */

drivers/scsi/scsi_error.c +41 -1

index 467cb3c..cf30475 100644
@@ -91,6 +91,31 @@ void scsi_schedule_eh(struct Scsi_Host *shost)
 }
 EXPORT_SYMBOL_GPL(scsi_schedule_eh);
 
+static int sdev_eh_deadline(struct Scsi_Host *shost,
+			   unsigned long eh_start)
+{
+	if (!shost->eh_deadline)
+		return 0;
+
+	if (shost->last_reset != 0 &&
+	    time_before(shost->last_reset, eh_start))
+		eh_start = shost->last_reset;
+
+	if (time_before(jiffies,
+			eh_start + shost->eh_deadline))
+		return 0;
+
+	return 1;
+}
+
+static int scsi_host_eh_deadline(struct Scsi_Host *shost)
+{
+	if (!shost->last_reset)
+		return 0;
+
+	return sdev_eh_deadline(shost, shost->last_reset);
+}
+
 /**
  * scsi_eh_abort_handler - Handle command aborts
  * @work:	sdev on which commands should be aborted.

@@ -102,13 +127,15 @@ scsi_eh_abort_handler(struct work_struct *work)
 		container_of(work, struct scsi_device, abort_work);
 	struct scsi_cmnd *scmd, *tmp;
 	LIST_HEAD(abort_list);
-	unsigned long flags;
+	unsigned long flags, eh_start;
 	int rtn;
 
 	spin_lock_irqsave(&sdev->list_lock, flags);
 	list_splice_init(&sdev->eh_abort_list, &abort_list);
 	spin_unlock_irqrestore(&sdev->list_lock, flags);
 
+	eh_start = jiffies;
+
 	list_for_each_entry_safe(scmd, tmp, &abort_list, eh_entry) {
 		list_del_init(&scmd->eh_entry);
 		if (sdev->sdev_state == SDEV_CANCEL) {

@@ -119,6 +146,13 @@ scsi_eh_abort_handler(struct work_struct *work)
 			scsi_finish_command(scmd);
 			continue;
 		}
+		if (sdev_eh_deadline(sdev->host, eh_start)) {
+			SCSI_LOG_ERROR_RECOVERY(3,
+				scmd_printk(KERN_INFO, scmd,
+					     "eh timeout, not aborting\n"));
+			list_move_tail(&scmd->eh_entry, &abort_list);
+			goto start_eh;
+		}
 		SCSI_LOG_ERROR_RECOVERY(3,
 			scmd_printk(KERN_INFO, scmd,
 				    "aborting command %p\n", scmd));

@@ -151,6 +185,12 @@ scsi_eh_abort_handler(struct work_struct *work)
 		return;
 
 start_eh:
+	spin_lock_irqsave(sdev->host->host_lock, flags);
+	if (sdev->host->eh_deadline &&
+	    (!sdev->host->last_reset ||
+	     time_before(eh_start, sdev->host->last_reset)))
+		sdev->host->last_reset = eh_start;
+	spin_unlock_irqrestore(sdev->host->host_lock, flags);
 	list_for_each_entry_safe(scmd, tmp, &abort_list, eh_entry) {
 		scmd->result |= DID_TIME_OUT << 16;
 		if (!scsi_eh_scmd_add(scmd, 0)) {

drivers/scsi/scsi_error.c +13 -0

 	ret = 1;
 	scmd->eh_eflags |= eh_flag;
 	list_add_tail(&scmd->eh_entry, &shost->eh_cmd_q);

@@ -1052,13 +1095,25 @@ int scsi_eh_get_sense(struct list_head *work_q,
 		      struct list_head *done_q)
 {
 	struct scsi_cmnd *scmd, *next;
+	struct Scsi_Host *shost;
 	int rtn;
+	unsigned long flags;
 
 	list_for_each_entry_safe(scmd, next, work_q, eh_entry) {
 		if ((scmd->eh_eflags & SCSI_EH_CANCEL_CMD) ||
 		    SCSI_SENSE_VALID(scmd))
 			continue;
 
+		shost = scmd->device->host;
+		spin_lock_irqsave(shost->host_lock, flags);
+		if (scsi_host_eh_deadline(shost)) {
+			spin_unlock_irqrestore(shost->host_lock, flags);
+			SCSI_LOG_ERROR_RECOVERY(3,
+				shost_printk(KERN_INFO, shost,
+					    "skip %s, eh timeout\n", __func__));
+			break;
+		}
+		spin_unlock_irqrestore(shost->host_lock, flags);
 		SCSI_LOG_ERROR_RECOVERY(2, scmd_printk(KERN_INFO, scmd,
 						  "%s: requesting sense\n",
 						  current->comm));

@@ -1143,11 +1198,22 @@ static int scsi_eh_test_devices(struct list_head *cmd_list,
 	struct scsi_cmnd *scmd, *next;
 	struct scsi_device *sdev;
 	int finish_cmds;
+	unsigned long flags;

drivers/scsi/scsi_error.c +5 -0

+				break;
+			}
+			spin_unlock_irqrestore(sdev->host->host_lock, flags);
+		}
+
 		finish_cmds = !scsi_device_online(scmd->device) ||
 			(try_stu && !scsi_eh_try_stu(scmd) &&
 			 !scsi_eh_tur(scmd)) ||

@@ -1183,14 +1249,26 @@ static int scsi_eh_abort_cmds(struct list_head *work_q,
 	struct scsi_cmnd *scmd, *next;
 	LIST_HEAD(check_list);
 	int rtn;

drivers/scsi/scsi_error.c +27 -1

+			SCSI_LOG_ERROR_RECOVERY(3,
+				shost_printk(KERN_INFO, shost,
+					    "skip %s, eh timeout\n", __func__));
+			return 1;
+		}
+		spin_unlock_irqrestore(shost->host_lock, flags);
 		SCSI_LOG_ERROR_RECOVERY(3, printk("%s: aborting cmd:"
 						  "0x%p\n", current->comm,
 						  scmd));
-		rtn = scsi_try_to_abort_cmd(scmd->device->host->hostt, scmd);
+		rtn = scsi_try_to_abort_cmd(shost->hostt, scmd);
 		if (rtn == SUCCESS || rtn == FAST_IO_FAIL) {
 			scmd->eh_eflags &= ~SCSI_EH_CANCEL_CMD;
 			if (rtn == FAST_IO_FAIL)

@@ -1248,8 +1326,18 @@ static int scsi_eh_stu(struct Scsi_Host *shost,
 {
 	struct scsi_cmnd *scmd, *stu_scmd, *next;
 	struct scsi_device *sdev;
+	unsigned long flags;
 
 	shost_for_each_device(sdev, shost) {
+		spin_lock_irqsave(shost->host_lock, flags);
+		if (scsi_host_eh_deadline(shost)) {
+			spin_unlock_irqrestore(shost->host_lock, flags);
+			SCSI_LOG_ERROR_RECOVERY(3,
+				shost_printk(KERN_INFO, shost,
+					    "skip %s, eh timeout\n", __func__));
+			break;
+		}
+		spin_unlock_irqrestore(shost->host_lock, flags);
 		stu_scmd = NULL;
 		list_for_each_entry(scmd, work_q, eh_entry)
 			if (scmd->device == sdev && SCSI_SENSE_VALID(scmd) &&

@@ -1302,9 +1390,19 @@ static int scsi_eh_bus_device_reset(struct Scsi_Host *shost,
 {
 	struct scsi_cmnd *scmd, *bdr_scmd, *next;
 	struct scsi_device *sdev;
+	unsigned long flags;
 	int rtn;
 
 	shost_for_each_device(sdev, shost) {
+		spin_lock_irqsave(shost->host_lock, flags);
+		if (scsi_host_eh_deadline(shost)) {
+			spin_unlock_irqrestore(shost->host_lock, flags);
+			SCSI_LOG_ERROR_RECOVERY(3,
+				shost_printk(KERN_INFO, shost,
+					    "skip %s, eh timeout\n", __func__));
+			break;
+		}
+		spin_unlock_irqrestore(shost->host_lock, flags);
 		bdr_scmd = NULL;
 		list_for_each_entry(scmd, work_q, eh_entry)
 			if (scmd->device == sdev) {

drivers/scsi/scsi_error.c +8 -0

+			list_splice_init(&tmp_list, work_q);
+			SCSI_LOG_ERROR_RECOVERY(3,
+				shost_printk(KERN_INFO, shost,
+					    "skip %s, eh timeout\n", __func__));
+			return list_empty(work_q);
+		}
+		spin_unlock_irqrestore(shost->host_lock, flags);
 
 		scmd = list_entry(tmp_list.next, struct scsi_cmnd, eh_entry);
 		id = scmd_id(scmd);

@@ -1408,6 +1519,7 @@ static int scsi_eh_bus_reset(struct Scsi_Host *shost,
 	LIST_HEAD(check_list);
 	unsigned int channel;
 	int rtn;
+	unsigned long flags;
 
 	/*
 	 * we really want to loop over the various channels, and do this on

drivers/scsi/scsi_error.c +10 -2

+			SCSI_LOG_ERROR_RECOVERY(3,
+				shost_printk(KERN_INFO, shost,
+					    "skip %s, eh timeout\n", __func__));
+			return list_empty(work_q);
+		}
+		spin_unlock_irqrestore(shost->host_lock, flags);
+
 		chan_scmd = NULL;
 		list_for_each_entry(scmd, work_q, eh_entry) {
 			if (channel == scmd_channel(scmd)) {

@@ -1822,8 +1944,9 @@ static void scsi_restart_operations(struct Scsi_Host *shost)
 	 * will be requests for character device operations, and also for
 	 * ioctls to queued block devices.
 	 */
-	SCSI_LOG_ERROR_RECOVERY(3, printk("%s: waking up host to restart\n",
-					  __func__));
+	SCSI_LOG_ERROR_RECOVERY(3,
+		printk("scsi_eh_%d waking up host to restart\n",
+		       shost->host_no));
 
 	spin_lock_irqsave(shost->host_lock, flags);
 	if (scsi_host_set_state(shost, SHOST_RUNNING))

drivers/scsi/scsi_error.c +6 -3

+		shost->last_reset = 0;
+	spin_unlock_irqrestore(shost->host_lock, flags);
 	scsi_eh_flush_done_q(&eh_done_q);
 }
 

@@ -1976,7 +2103,7 @@ int scsi_error_handler(void *data)
 		if ((shost->host_failed == 0 && shost->host_eh_scheduled == 0) ||
 		    shost->host_failed != shost->host_busy) {
 			SCSI_LOG_ERROR_RECOVERY(1,
-				printk("Error handler scsi_eh_%d sleeping\n",
+				printk("scsi_eh_%d: sleeping\n",
 					shost->host_no));
 			schedule();
 			continue;

@@ -1984,8 +2111,9 @@ int scsi_error_handler(void *data)
 
 		__set_current_state(TASK_RUNNING);
 		SCSI_LOG_ERROR_RECOVERY(1,
-			printk("Error handler scsi_eh_%d waking up\n",
-				shost->host_no));
+			printk("scsi_eh_%d: waking up %d/%d/%d\n",
+			       shost->host_no, shost->host_eh_scheduled,
+			       shost->host_failed, shost->host_busy));
 
 		/*
 		 * We have a host that is failing for some reason.  Figure out

drivers/scsi/scsi_sysfs.c +0 -0

index af64c1c..3c1742f 100644

drivers/scsi/scsi_sysfs.c +10 -0

+}
+
+static ssize_t
+store_shost_eh_deadline(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t count)
+{
+	struct Scsi_Host *shost = class_to_shost(dev);
+	int ret = -EINVAL;
+	int timeout;
+	unsigned long flags;

drivers/scsi/scsi_sysfs.c +10 -0

+			ret = count;
+		}
+		spin_unlock_irqrestore(shost->host_lock, flags);
+	}
+	return ret;
+}
+
+static DEVICE_ATTR(eh_deadline, S_IRUGO | S_IWUSR, show_shost_eh_deadline, store_shost_eh_deadline);
+
 shost_rd_attr(unique_id, "%u\n");
 shost_rd_attr(host_busy, "%hu\n");
 shost_rd_attr(cmd_per_lun, "%hd\n");

@@ -308,6 +344,7 @@ static struct attribute *scsi_sysfs_shost_attrs[] = {
 	&dev_attr_prot_capabilities.attr,
 	&dev_attr_prot_guard_type.attr,
 	&dev_attr_host_reset.attr,
+	&dev_attr_eh_deadline.attr,
 	NULL
 };
 

include/scsi/scsi_host.h +1 -1

index 7552435..ca87486 100644
@@ -598,7 +598,7 @@ struct Scsi_Host {
 	unsigned int host_eh_scheduled;    /* EH scheduled without command */
 
 	unsigned int host_no;  /* Used for IOCTL_GET_IDLUN, /proc/scsi et al. */
-	int resetting; /* if set, it means that last_reset is a valid value */
+	int eh_deadline; /* Deadline for EH runtime */
 	unsigned long last_reset;
 
 	/*

The eh_deadline changes allow for a significant improvement in multipath failover time. It works very well in our testing. I do have a few corrections, see below:

Quoted 32 lines · Hannes Reinecke

This patchs adds an 'eh_deadline' attribute to the scsi host which limits the overall runtime of the SCSI EH. When a command is failed the start time of the EH is stored in 'last_reset'. If the overall runtime of the SCSI EH is longer than last_reset + eh_deadline, the EH is short-circuited and falls through to issue a host reset only.

Signed-off-by Hannes Reinecke <[email protected]>

---
 drivers/scsi/hosts.c      |   7 +++
 drivers/scsi/scsi_error.c | 142 +++++++++++++++++++++++++++++++++++++++++++---
 drivers/scsi/scsi_sysfs.c |  37 ++++++++++++
 include/scsi/scsi_host.h  |   2 +-
 4 files changed, 180 insertions(+), 8 deletions(-)

drivers/scsi/hosts.c +6 -0

index df0c3c7..c8d828f 100644
@@ -316,6 +316,12 @@ static void scsi_host_dev_release(struct device *dev)
 	kfree(shost);
 }
 
+static unsigned int shost_eh_deadline;
+
+module_param_named(eh_deadline, shost_eh_deadline, uint, S_IRUGO|S_IWUSR);
+MODULE_PARM_DESC(eh_deadline,
+		 "SCSI EH deadline in seconds (should be between 1 and 2^32-1)");
+
 static struct device_type scsi_host_type = {
 	.name =		"scsi_host",
 	.release =	scsi_host_dev_release,

drivers/scsi/hosts.c struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize) · line 397

Quoted 5 lines

drivers/scsi/hosts.c +1 -0

@@ -388,6 +394,7 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 	shost->unchecked_isa_dma = sht->unchecked_isa_dma;
 	shost->use_clustering = sht->use_clustering;
 	shost->ordered_tag = sht->ordered_tag;
+	shost->eh_deadline = shost_eh_deadline;

This should be shost->eh_deadline = shost_eh_deadline * HZ; since the parameter is specified in seconds.

drivers/scsi/hosts.c int scsi_eh_scmd_add(struct scsi_cmnd *scmd, int eh_flag) · line 277

Quoted 7 lines

drivers/scsi/hosts.c +3 -0

@@ -232,6 +272,9 @@ int scsi_eh_scmd_add(struct scsi_cmnd *scmd, int eh_flag)
 		if (scsi_host_set_state(shost, SHOST_CANCEL_RECOVERY))
 			goto out_unlock;
 
+	if (sdev->eh_deadline && !shost->last_reset)
+		shost->last_reset = jiffies;
+

I think this is supposed to be if (shost->eh_deadline ...

Quoted 10 lines

drivers/scsi/hosts.c +1 -0

@@ -1143,11 +1198,22 @@ static int scsi_eh_test_devices(struct list_head *cmd_list,
 	struct scsi_cmnd *scmd, *next;
 	struct scsi_device *sdev;
 	int finish_cmds;
+	unsigned long flags;
 
 	while (!list_empty(cmd_list)) {
 		scmd = list_entry(cmd_list->next, struct scsi_cmnd, eh_entry);
 		sdev = scmd->device;
 

drivers/scsi/hosts.c static int scsi_eh_test_devices(struct list_head *cmd_list, · line 1211

Quoted 5 lines

drivers/scsi/hosts.c +5 -0

+		if (!try_stu) {
+			spin_lock_irqsave(sdev->host->host_lock, flags);
+			if (scsi_host_eh_deadline(sdev->host)) {
+				spin_unlock_irqrestore(sdev->host->host_lock,
+						       flags);

I think a list_splice_init(cmd_list, work_q); is needed here, otherwise scmds that are still on the cmd_list will be orphaned. There should also be a SCSI_LOG_ERROR_RECOVERY() as was done in other places.

Quoted 15 lines

drivers/scsi/hosts.c +7 -0

+				break;
+			}
+			spin_unlock_irqrestore(sdev->host->host_lock, flags);
+		}
+
 		finish_cmds = !scsi_device_online(scmd->device) ||
 			(try_stu && !scsi_eh_try_stu(scmd) &&
 			 !scsi_eh_tur(scmd)) ||

@@ -1183,14 +1249,26 @@ static int scsi_eh_abort_cmds(struct list_head *work_q,
 	struct scsi_cmnd *scmd, *next;
 	LIST_HEAD(check_list);
 	int rtn;
+	struct Scsi_Host *shost;
+	unsigned long flags;
 

drivers/scsi/hosts.c static int scsi_eh_abort_cmds(struct list_head *work_q, · line 1261

Quoted 7 lines

drivers/scsi/hosts.c +4 -0

 	list_for_each_entry_safe(scmd, next, work_q, eh_entry) {
 		if (!(scmd->eh_eflags & SCSI_EH_CANCEL_CMD))
 			continue;
+		shost = scmd->device->host;
+		spin_lock_irqsave(shost->host_lock, flags);
+		if (scsi_host_eh_deadline(shost)) {
+			spin_unlock_irqrestore(shost->host_lock, flags);

I think a list_splice_init(&check_list, work_q); is needed here, otherwise scmds that are on the check_list will be orphaned.

Quoted 5 lines

drivers/scsi/hosts.c +1 -0

@@ -1364,6 +1462,19 @@ static int scsi_eh_target_reset(struct Scsi_Host *shost,
 		struct scsi_cmnd *next, *scmd;
 		int rtn;
 		unsigned int id;
+		unsigned long flags;

drivers/scsi/hosts.c static int scsi_eh_target_reset(struct Scsi_Host *shost, · line 1470

Quoted 5 lines

drivers/scsi/hosts.c +5 -0

+
+		spin_lock_irqsave(shost->host_lock, flags);
+		if (scsi_host_eh_deadline(shost)) {
+			spin_unlock_irqrestore(shost->host_lock, flags);
+			/* push back on work queue for further processing */

I think a list_splice_init(&check_list, work_q); is needed here, otherwise scmds that are on the check_list will be orphaned.

Quoted 21 lines

drivers/scsi/hosts.c +8 -0

+			list_splice_init(&tmp_list, work_q);
+			SCSI_LOG_ERROR_RECOVERY(3,
+				shost_printk(KERN_INFO, shost,
+					    "skip %s, eh timeout\n", __func__));
+			return list_empty(work_q);
+		}
+		spin_unlock_irqrestore(shost->host_lock, flags);
 
 		scmd = list_entry(tmp_list.next, struct scsi_cmnd, eh_entry);
 		id = scmd_id(scmd);

@@ -1408,6 +1519,7 @@ static int scsi_eh_bus_reset(struct Scsi_Host *shost,
 	LIST_HEAD(check_list);
 	unsigned int channel;
 	int rtn;
+	unsigned long flags;
 
 	/*
 	 * we really want to loop over the various channels, and do this on

@@ -1417,6 +1529,16 @@ static int scsi_eh_bus_reset(struct Scsi_Host *shost,
 	 */
 

drivers/scsi/hosts.c static int scsi_eh_bus_reset(struct Scsi_Host *shost, · line 1534

Quoted 4 lines

drivers/scsi/hosts.c +3 -0

 	for (channel = 0; channel <= shost->max_channel; channel++) {
+		spin_lock_irqsave(shost->host_lock, flags);
+		if (scsi_host_eh_deadline(shost)) {
+			spin_unlock_irqrestore(shost->host_lock, flags);

I think a list_splice_init(&check_list, work_q); is needed here, otherwise scmds that are on the check_list will be orphaned.

Quoted 26 lines

drivers/scsi/hosts.c +10 -2

+			SCSI_LOG_ERROR_RECOVERY(3,
+				shost_printk(KERN_INFO, shost,
+					    "skip %s, eh timeout\n", __func__));
+			return list_empty(work_q);
+		}
+		spin_unlock_irqrestore(shost->host_lock, flags);
+
 		chan_scmd = NULL;
 		list_for_each_entry(scmd, work_q, eh_entry) {
 			if (channel == scmd_channel(scmd)) {

@@ -1822,8 +1944,9 @@ static void scsi_restart_operations(struct Scsi_Host *shost)
 	 * will be requests for character device operations, and also for
 	 * ioctls to queued block devices.
 	 */
-	SCSI_LOG_ERROR_RECOVERY(3, printk("%s: waking up host to restart\n",
-					  __func__));
+	SCSI_LOG_ERROR_RECOVERY(3,
+		printk("scsi_eh_%d waking up host to restart\n",
+		       shost->host_no));
 
 	spin_lock_irqsave(shost->host_lock, flags);
 	if (scsi_host_set_state(shost, SHOST_RUNNING))

@@ -1950,6 +2073,10 @@ static void scsi_unjam_host(struct Scsi_Host *shost)
 		if (!scsi_eh_abort_cmds(&eh_work_q, &eh_done_q))
 			scsi_eh_ready_devs(shost, &eh_work_q, &eh_done_q);
 

drivers/scsi/hosts.c static void scsi_unjam_host(struct Scsi_Host *shost) · line 2077

Quoted 2 lines

drivers/scsi/hosts.c +2 -0

+	spin_lock_irqsave(shost->host_lock, flags);
+	if (sdev->eh_deadline)

I think this is supposed to be if (shost->eh_deadline ...

Quoted 34 lines

drivers/scsi/hosts.c +6 -3

+		shost->last_reset = 0;
+	spin_unlock_irqrestore(shost->host_lock, flags);
 	scsi_eh_flush_done_q(&eh_done_q);
 }
 

@@ -1976,7 +2103,7 @@ int scsi_error_handler(void *data)
 		if ((shost->host_failed == 0 && shost->host_eh_scheduled == 0) ||
 		    shost->host_failed != shost->host_busy) {
 			SCSI_LOG_ERROR_RECOVERY(1,
-				printk("Error handler scsi_eh_%d sleeping\n",
+				printk("scsi_eh_%d: sleeping\n",
 					shost->host_no));
 			schedule();
 			continue;

@@ -1984,8 +2111,9 @@ int scsi_error_handler(void *data)
 
 		__set_current_state(TASK_RUNNING);
 		SCSI_LOG_ERROR_RECOVERY(1,
-			printk("Error handler scsi_eh_%d waking up\n",
-				shost->host_no));
+			printk("scsi_eh_%d: waking up %d/%d/%d\n",
+			       shost->host_no, shost->host_eh_scheduled,
+			       shost->host_failed, shost->host_busy));
 
 		/*
 		 * We have a host that is failing for some reason.  Figure out

drivers/scsi/scsi_sysfs.c +0 -0

index af64c1c..3c1742f 100644
@@ -281,6 +281,42 @@ exit_store_host_reset:
 
 static DEVICE_ATTR(host_reset, S_IWUSR, NULL, store_host_reset);
 

drivers/scsi/scsi_sysfs.c exit_store_host_reset: · line 290

Quoted 7 lines

drivers/scsi/scsi_sysfs.c +7 -0

+static ssize_t
+show_shost_eh_deadline(struct device *dev,
+		      struct device_attribute *attr, char *buf)
+{
+	struct Scsi_Host *shost = class_to_shost(dev);
+
+	return sprintf(buf, "%d\n", shost->eh_deadline);

I think that the attribute should be specified in seconds, so this should be shost->eh_deadline / HZ.

Quoted 15 lines

drivers/scsi/scsi_sysfs.c +15 -0

+}
+
+static ssize_t
+store_shost_eh_deadline(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t count)
+{
+	struct Scsi_Host *shost = class_to_shost(dev);
+	int ret = -EINVAL;
+	int timeout;
+	unsigned long flags;
+
+	if (shost->transportt->eh_strategy_handler)
+		return ret;
+
+	if (sscanf(buf, "%d\n", &timeout) == 1) {

drivers/scsi/scsi_sysfs.c exit_store_host_reset: · line 310

Quoted 5 lines

drivers/scsi/scsi_sysfs.c +5 -0

+		spin_lock_irqsave(shost->host_lock, flags);
+		if (scsi_host_in_recovery(shost))
+			ret = -EBUSY;
+		else {
+			shost->eh_deadline = timeout;

I think the deadline should be specified in seconds, so this should be shost->eh_deadline = timeout * HZ;

Quoted 27 lines

drivers/scsi/scsi_sysfs.c +10 -0

+			ret = count;
+		}
+		spin_unlock_irqrestore(shost->host_lock, flags);
+	}
+	return ret;
+}
+
+static DEVICE_ATTR(eh_deadline, S_IRUGO | S_IWUSR, show_shost_eh_deadline, store_shost_eh_deadline);
+
 shost_rd_attr(unique_id, "%u\n");
 shost_rd_attr(host_busy, "%hu\n");
 shost_rd_attr(cmd_per_lun, "%hd\n");

@@ -308,6 +344,7 @@ static struct attribute *scsi_sysfs_shost_attrs[] = {
 	&dev_attr_prot_capabilities.attr,
 	&dev_attr_prot_guard_type.attr,
 	&dev_attr_host_reset.attr,
+	&dev_attr_eh_deadline.attr,
 	NULL
 };
 

include/scsi/scsi_host.h +0 -0

index 7552435..ca87486 100644
@@ -598,7 +598,7 @@ struct Scsi_Host {
 	unsigned int host_eh_scheduled;    /* EH scheduled without command */
 

include/scsi/scsi_host.h struct Scsi_Host { · line 604

Quoted 6 lines

include/scsi/scsi_host.h +1 -1

 	unsigned int host_no;  /* Used for IOCTL_GET_IDLUN, /proc/scsi et al. */
-	int resetting; /* if set, it means that last_reset is a valid value */
+	int eh_deadline; /* Deadline for EH runtime */
 	unsigned long last_reset;
 
 	/*

Quoted 10 lines

drivers/scsi/scsi_error.c int scsi_eh_scmd_add(struct scsi_cmnd *scmd, int eh_flag) · line 277

Quoted 7 lines

drivers/scsi/scsi_error.c +3 -0

@@ -232,6 +272,9 @@ int scsi_eh_scmd_add(struct scsi_cmnd *scmd, int eh_flag)
 		if (scsi_host_set_state(shost, SHOST_CANCEL_RECOVERY))
 			goto out_unlock;
 
+	if (sdev->eh_deadline && !shost->last_reset)
+		shost->last_reset = jiffies;
+

I think this is supposed to be if (shost->eh_deadline ...

No. ->last_reset is set to the time the first command timeout/failure.

->last_reset + ->eh_deadline will give you the expiry time.

drivers/scsi/scsi_error.c +14 -0

+static int sdev_eh_deadline(struct Scsi_Host *shost,
+			   unsigned long eh_start)
+{
+	if (!shost->eh_deadline)
+		return 0;
+
+	if (shost->last_reset != 0 &&
+	    time_before(shost->last_reset, eh_start))
+		eh_start = shost->last_reset;
+
+	if (time_before(jiffies,
+			eh_start + shost->eh_deadline))
+		return 0;
+

Quoted 14 lines · Hannes Reinecke

drivers/scsi/scsi_error.c +14 -0

+static int sdev_eh_deadline(struct Scsi_Host *shost,
+               unsigned long eh_start)
+{
+    if (!shost->eh_deadline)
+        return 0;
+
+    if (shost->last_reset != 0 &&
+        time_before(shost->last_reset, eh_start))
+        eh_start = shost->last_reset;
+
+    if (time_before(jiffies,
+            eh_start + shost->eh_deadline))
+        return 0;
+

drivers/scsi/scsi_error.c void scsi_schedule_eh(struct Scsi_Host *shost) · line 117

Quoted 10 lines

drivers/scsi/scsi_error.c +10 -0

+    return 1;
+}
+
+static int scsi_host_eh_deadline(struct Scsi_Host *shost)
+{
+    if (!shost->last_reset)
+        return 0;
+
+    return sdev_eh_deadline(shost, shost->last_reset);
+}

Hello Hannes,

I would appreciate if you would choose other names for these two functions and also for shost->eh_deadline. To me a deadline is a time instant. As far as I can see the two functions above check whether a deadline has been passed, and shost->eh_deadline is a time interval. How about the following names: sdev_eh_past_deadline(), shost_eh_past_deadline() and shost->max_eh_jiffies ?

This patchset implements a new 'eh_deadline' attribute to the SCSI host. It will limit the overall SCSI EH runtime by a given timeout. If the timeout expires all intermediate steps will be skipped and host reset will be scheduled immediately.