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Stop scsi eh when fast_io_fail_tmo fires

PATCH In review Christof Schmitt 2 participants 4 messages Mar 24, 2010 – Mar 25, 2010

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#0 lore raw

cover Stop scsi eh when fast_io_fail_tmo fires

As a follow-up for the draft mentioned in
http://marc.info/?l=linux-scsi&m=126926716605409&w=2

The patches allow the scsi eh to exit early when the fast_io_fail_tmo fires. This fixes the problem that the scsi eh will block until the dev_loss_tmo fires, thus potentially blocking the scsi host for a very long time.

Comments?

--
Christof Schmitt

#1 lore raw

PATCH 1/2 scsi: Allow FC LLD to fast-fail scsi eh

From: Christof Schmitt <[email protected]>

If the scsi eh is running and then a FC LLD calls fc_remote_port_delete, the SCSI commands sent from the eh will fail. To prevent this, a FC LLD can call fc_block_scsi_eh from the eh callback, blocking the eh thread until the dev_loss_tmo fires or the remote port is available again.

If (e.g. for a multipathing setup) the dev_loss_tmo is set to a very large value, thus preventing the scsi device removal , the scsi eh can block for a long time. For multipathing, the fast_io_fail_tmo is then set to a low value to detect path problems sooner.

This patch introduces a new return code FAST_IO_FAIL. The function fc_block_scsi_eh now returns FAST_IO_FAIL when the fast_io_fail_tmo fires. This indicates that the LLD terminated all pending I/O requests and there are no more pending SCSI commands for the scsi eh to wait for. This return code can be passed back to the scsi eh to stop the escalation and finish the recovery process for this device.

---
 drivers/scsi/scsi_error.c        |   15 ++++++++++-----
 drivers/scsi/scsi_transport_fc.c |   20 +++++++++++++++-----
 include/scsi/scsi.h              |    1 +
 include/scsi/scsi_transport_fc.h |    2 +-
 4 files changed, 27 insertions(+), 11 deletions(-)
drivers/scsi/scsi_error.c +10 -5
@@ -956,9 +956,10 @@ static int scsi_eh_abort_cmds(struct lis
 						  "0x%p\n", current->comm,
 						  scmd));
 		rtn = scsi_try_to_abort_cmd(scmd);
-		if (rtn == SUCCESS) {
+		if (rtn == SUCCESS || rtn == FAST_IO_FAIL) {
 			scmd->eh_eflags &= ~SCSI_EH_CANCEL_CMD;
 			if (!scsi_device_online(scmd->device) ||
+			    rtn == FAST_IO_FAIL ||
 			    !scsi_eh_tur(scmd)) {
 				scsi_eh_finish_cmd(scmd, done_q);
 			}
@@ -1085,8 +1086,9 @@ static int scsi_eh_bus_device_reset(stru
 						  " 0x%p\n", current->comm,
 						  sdev));
 		rtn = scsi_try_bus_device_reset(bdr_scmd);
-		if (rtn == SUCCESS) {
+		if (rtn == SUCCESS || rtn == FAST_IO_FAIL) {
 			if (!scsi_device_online(sdev) ||
+			    rtn == FAST_IO_FAIL ||
 			    !scsi_eh_tur(bdr_scmd)) {
 				list_for_each_entry_safe(scmd, next,
 							 work_q, eh_entry) {
@@ -1149,10 +1151,11 @@ static int scsi_eh_target_reset(struct S
 						  "to target %d\n",
 						  current->comm, id));
 		rtn = scsi_try_target_reset(tgtr_scmd);
-		if (rtn == SUCCESS) {
+		if (rtn == SUCCESS || rtn == FAST_IO_FAIL) {
 			list_for_each_entry_safe(scmd, next, work_q, eh_entry) {
 				if (id == scmd_id(scmd))
 					if (!scsi_device_online(scmd->device) ||
+					    rtn == FAST_IO_FAIL ||
 					    !scsi_eh_tur(tgtr_scmd))
 						scsi_eh_finish_cmd(scmd,
 								   done_q);
@@ -1208,10 +1211,11 @@ static int scsi_eh_bus_reset(struct Scsi
 						  " %d\n", current->comm,
 						  channel));
 		rtn = scsi_try_bus_reset(chan_scmd);
-		if (rtn == SUCCESS) {
+		if (rtn == SUCCESS || rtn == FAST_IO_FAIL) {
 			list_for_each_entry_safe(scmd, next, work_q, eh_entry) {
 				if (channel == scmd_channel(scmd))
 					if (!scsi_device_online(scmd->device) ||
+					    rtn == FAST_IO_FAIL ||
 					    !scsi_eh_tur(scmd))
 						scsi_eh_finish_cmd(scmd,
 								   done_q);
@@ -1245,9 +1249,10 @@ static int scsi_eh_host_reset(struct lis
 						  , current->comm));
 
 		rtn = scsi_try_host_reset(scmd);
-		if (rtn == SUCCESS) {
+		if (rtn == SUCCESS || rtn == FAST_IO_FAIL) {
 			list_for_each_entry_safe(scmd, next, work_q, eh_entry) {
 				if (!scsi_device_online(scmd->device) ||
+				    rtn == FAST_IO_FAIL ||
 				    (!scsi_eh_try_stu(scmd) && !scsi_eh_tur(scmd)) ||
 				    !scsi_eh_tur(scmd))
 					scsi_eh_finish_cmd(scmd, done_q);
drivers/scsi/scsi_transport_fc.c +15 -5
@@ -3190,23 +3190,33 @@ fc_scsi_scan_rport(struct work_struct *w
  *
  * This routine can be called from a FC LLD scsi_eh callback. It
  * blocks the scsi_eh thread until the fc_rport leaves the
- * FC_PORTSTATE_BLOCKED. This is necessary to avoid the scsi_eh
- * failing recovery actions for blocked rports which would lead to
- * offlined SCSI devices.
+ * FC_PORTSTATE_BLOCKED, or the fast_io_fail_tmo fires. This is
+ * necessary to avoid the scsi_eh failing recovery actions for blocked
+ * rports which would lead to offlined SCSI devices.
+ *
+ * Returns: 0 if the fc_rport left the state FC_PORTSTATE_BLOCKED.
+ *	    FAST_IO_FAIL if the fast_io_fail_tmo fired, this should be
+ *	    passed back to scsi_eh.
  */
-void fc_block_scsi_eh(struct scsi_cmnd *cmnd)
+int fc_block_scsi_eh(struct scsi_cmnd *cmnd)
 {
 	struct Scsi_Host *shost = cmnd->device->host;
 	struct fc_rport *rport = starget_to_rport(scsi_target(cmnd->device));
 	unsigned long flags;
 
 	spin_lock_irqsave(shost->host_lock, flags);
-	while (rport->port_state == FC_PORTSTATE_BLOCKED) {
+	while (rport->port_state == FC_PORTSTATE_BLOCKED &&
+	       !(rport->flags & FC_RPORT_FAST_FAIL_TIMEDOUT)) {
 		spin_unlock_irqrestore(shost->host_lock, flags);
 		msleep(1000);
 		spin_lock_irqsave(shost->host_lock, flags);
 	}
 	spin_unlock_irqrestore(shost->host_lock, flags);
+
+	if (rport->flags & FC_RPORT_FAST_FAIL_TIMEDOUT)
+		return FAST_IO_FAIL;
+
+	return 0;
 }
 EXPORT_SYMBOL(fc_block_scsi_eh);
 
include/scsi/scsi.h +1 -0
@@ -423,6 +423,7 @@ static inline int scsi_is_wlun(unsigned 
 #define ADD_TO_MLQUEUE  0x2006
 #define TIMEOUT_ERROR   0x2007
 #define SCSI_RETURN_NOT_HANDLED   0x2008
+#define FAST_IO_FAIL	0x2009
 
 /*
  * Midlevel queue return values.
include/scsi/scsi_transport_fc.h +1 -1
@@ -807,6 +807,6 @@ void fc_host_post_vendor_event(struct Sc
 struct fc_vport *fc_vport_create(struct Scsi_Host *shost, int channel,
 		struct fc_vport_identifiers *);
 int fc_vport_terminate(struct fc_vport *vport);
-void fc_block_scsi_eh(struct scsi_cmnd *cmnd);
+int fc_block_scsi_eh(struct scsi_cmnd *cmnd);
 
 #endif /* SCSI_TRANSPORT_FC_H */
#2 lore raw

Re: [patch 1/2] scsi: Allow FC LLD to fast-fail scsi eh

Quoted 13 lines · Christof Schmitt

From: Christof Schmitt<[email protected]>

If the scsi eh is running and then a FC LLD calls fc_remote_port_delete, the SCSI commands sent from the eh will fail. To prevent this, a FC LLD can call fc_block_scsi_eh from the eh callback, blocking the eh thread until the dev_loss_tmo fires or the remote port is available again.

If (e.g. for a multipathing setup) the dev_loss_tmo is set to a very large value, thus preventing the scsi device removal , the scsi eh can block for a long time. For multipathing, the fast_io_fail_tmo is then set to a low value to detect path problems sooner.

Quoted 7 lines

This patch introduces a new return code FAST_IO_FAIL. The function fc_block_scsi_eh now returns FAST_IO_FAIL when the fast_io_fail_tmo fires. This indicates that the LLD terminated all pending I/O requests and there are no more pending SCSI commands for the scsi eh to wait for. This return code can be passed back to the scsi eh to stop the escalation and finish the recovery process for this device.

Patch seems ok to me. It fixes the bug I was trying to fix with my other patch but I think your patch is nicer with the new error code to use.

#3 lore raw

PATCH 2/2 zfcp: Pass return code from fc_block_scsi_eh to scsi eh

In reply to Christof Schmitt

From: Christof Schmitt <[email protected]>

The return code FAST_IO_FAIL from fc_block_scsi_eh indicates that the pending I/O requests have been terminated as a result of the fast_io_fail_tmo. Pass this return code back to the scsi eh to stop the scsi eh in this case.

---
 drivers/s390/scsi/zfcp_scsi.c |   18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)
drivers/s390/scsi/zfcp_scsi.c +13 -5
@@ -174,7 +174,7 @@ static int zfcp_scsi_eh_abort_handler(st
 	struct zfcp_fsf_req *old_req, *abrt_req;
 	unsigned long flags;
 	unsigned long old_reqid = (unsigned long) scpnt->host_scribble;
-	int retval = SUCCESS;
+	int retval = SUCCESS, ret;
 	int retry = 3;
 	char *dbf_tag;
 
@@ -199,7 +199,9 @@ static int zfcp_scsi_eh_abort_handler(st
 			break;
 
 		zfcp_erp_wait(adapter);
-		fc_block_scsi_eh(scpnt);
+		ret = fc_block_scsi_eh(scpnt);
+		if (ret)
+			return ret;
 		if (!(atomic_read(&adapter->status) &
 		      ZFCP_STATUS_COMMON_RUNNING)) {
 			zfcp_dbf_scsi_abort("nres", adapter->dbf, scpnt, NULL,
@@ -230,7 +232,7 @@ static int zfcp_task_mgmt_function(struc
 	struct zfcp_unit *unit = scpnt->device->hostdata;
 	struct zfcp_adapter *adapter = unit->port->adapter;
 	struct zfcp_fsf_req *fsf_req = NULL;
-	int retval = SUCCESS;
+	int retval = SUCCESS, ret;
 	int retry = 3;
 
 	while (retry--) {
@@ -239,7 +241,10 @@ static int zfcp_task_mgmt_function(struc
 			break;
 
 		zfcp_erp_wait(adapter);
-		fc_block_scsi_eh(scpnt);
+		ret = fc_block_scsi_eh(scpnt);
+		if (ret)
+			return ret;
+
 		if (!(atomic_read(&adapter->status) &
 		      ZFCP_STATUS_COMMON_RUNNING)) {
 			zfcp_dbf_scsi_devreset("nres", tm_flags, unit, scpnt);
@@ -275,10 +280,13 @@ static int zfcp_scsi_eh_host_reset_handl
 {
 	struct zfcp_unit *unit = scpnt->device->hostdata;
 	struct zfcp_adapter *adapter = unit->port->adapter;
+	int ret;
 
 	zfcp_erp_adapter_reopen(adapter, 0, "schrh_1", scpnt);
 	zfcp_erp_wait(adapter);
-	fc_block_scsi_eh(scpnt);
+	ret = fc_block_scsi_eh(scpnt);
+	if (ret)
+		return ret;
 
 	return SUCCESS;
 }