New EH command timeout handler

index e8bee9f..67c0014 100644
@@ -941,12 +941,6 @@ retry:
 
 	scsi_eh_restore_cmnd(scmd, &ses);
 
-	if (scmd->request->cmd_type != REQ_TYPE_BLOCK_PC) {
-		struct scsi_driver *sdrv = scsi_cmd_to_driver(scmd);
-		if (sdrv->eh_action)
-			rtn = sdrv->eh_action(scmd, cmnd, cmnd_size, rtn);
-	}
-
 	return rtn;
 }
 

@@ -964,6 +958,16 @@ static int scsi_request_sense(struct scsi_cmnd *scmd)
 	return scsi_send_eh_cmnd(scmd, NULL, 0, scmd->device->eh_timeout, ~0);
 }
 
+static int scsi_eh_action(struct scsi_cmnd *scmd, int rtn)
+{
+	if (scmd->request->cmd_type != REQ_TYPE_BLOCK_PC) {
+		struct scsi_driver *sdrv = scsi_cmd_to_driver(scmd);
+		if (sdrv->eh_action)
+			rtn = sdrv->eh_action(scmd, rtn);
+	}
+	return rtn;
+}
+
 /**
  * scsi_eh_finish_cmd - Handle a cmd that eh is finished with.
  * @scmd:	Original SCSI cmd that eh has finished.

@@ -1142,7 +1146,9 @@ static int scsi_eh_test_devices(struct list_head *cmd_list,
 
 		list_for_each_entry_safe(scmd, next, cmd_list, eh_entry)
 			if (scmd->device == sdev) {
-				if (finish_cmds)
+				if (finish_cmds &&
+				    (try_stu ||
+				     scsi_eh_action(scmd, SUCCESS) == SUCCESS))
 					scsi_eh_finish_cmd(scmd, done_q);
 				else
 					list_move_tail(&scmd->eh_entry, work_q);

@@ -1283,7 +1289,8 @@ static int scsi_eh_stu(struct Scsi_Host *shost,
 			    !scsi_eh_tur(stu_scmd)) {
 				list_for_each_entry_safe(scmd, next,
 							  work_q, eh_entry) {
-					if (scmd->device == sdev)
+					if (scmd->device == sdev &&
+					    scsi_eh_action(scmd, SUCCESS) == SUCCESS)
 						scsi_eh_finish_cmd(scmd, done_q);
 				}
 			}

@@ -1350,7 +1357,8 @@ static int scsi_eh_bus_device_reset(struct Scsi_Host *shost,
 			    !scsi_eh_tur(bdr_scmd)) {
 				list_for_each_entry_safe(scmd, next,
 							 work_q, eh_entry) {
-					if (scmd->device == sdev)
+					if (scmd->device == sdev &&
+					    scsi_eh_action(scmd, rtn) != FAILED)
 						scsi_eh_finish_cmd(scmd,
 								   done_q);
 				}

index fd874b8..1929838 100644
@@ -110,7 +110,7 @@ static int sd_suspend_runtime(struct device *);
 static int sd_resume(struct device *);
 static void sd_rescan(struct device *);
 static int sd_done(struct scsi_cmnd *);
-static int sd_eh_action(struct scsi_cmnd *, unsigned char *, int, int);
+static int sd_eh_action(struct scsi_cmnd *, int);
 static void sd_read_capacity(struct scsi_disk *sdkp, unsigned char *buffer);
 static void scsi_disk_release(struct device *cdev);
 static void sd_print_sense_hdr(struct scsi_disk *, struct scsi_sense_hdr *);

@@ -1551,23 +1551,23 @@ static const struct block_device_operations sd_fops = {
 /**
  *	sd_eh_action - error handling callback
  *	@scmd:		sd-issued command that has failed
- *	@eh_cmnd:	The command that was sent during error handling
- *	@eh_cmnd_len:	Length of eh_cmnd in bytes
  *	@eh_disp:	The recovery disposition suggested by the midlayer
  *
- *	This function is called by the SCSI midlayer upon completion of
- *	an error handling command (TEST UNIT READY, START STOP UNIT,
- *	etc.) The command sent to the device by the error handler is
- *	stored in eh_cmnd. The result of sending the eh command is
- *	passed in eh_disp.
+ *	This function is called by the SCSI midlayer upon completion of an
+ *	error test command (currently TEST UNIT READY). The result of sending
+ *	the eh command is passed in eh_disp.  We're looking for devices that
+ *	fail medium access commands but are OK with non access commands like
+ *	test unit ready (so wrongly see the device as having a successful
+ *	recovery)
  **/
-static int sd_eh_action(struct scsi_cmnd *scmd, unsigned char *eh_cmnd,
-			int eh_cmnd_len, int eh_disp)
+static int sd_eh_action(struct scsi_cmnd *scmd, int eh_disp)
 {
 	struct scsi_disk *sdkp = scsi_disk(scmd->request->rq_disk);
 
 	if (!scsi_device_online(scmd->device) ||
-	    !scsi_medium_access_command(scmd))
+	    !scsi_medium_access_command(scmd) ||
+	    host_byte(scmd->result) != DID_TIME_OUT ||
+	    eh_disp != SUCCESS)
 		return eh_disp;
 
 	/*

@@ -1577,9 +1577,7 @@ static int sd_eh_action(struct scsi_cmnd *scmd, unsigned char *eh_cmnd,
 	 * process of recovering or has it suffered an internal failure
 	 * that prevents access to the storage medium.
 	 */
-	if (host_byte(scmd->result) == DID_TIME_OUT && eh_disp == SUCCESS &&
-	    eh_cmnd_len && eh_cmnd[0] == TEST_UNIT_READY)
-		sdkp->medium_access_timed_out++;
+	sdkp->medium_access_timed_out++;
 
 	/*
 	 * If the device keeps failing read/write commands but TEST UNIT

index d443aa0..20fdfc2 100644
@@ -16,7 +16,7 @@ struct scsi_driver {
 
 	void (*rescan)(struct device *);
 	int (*done)(struct scsi_cmnd *);
-	int (*eh_action)(struct scsi_cmnd *, unsigned char *, int, int);
+	int (*eh_action)(struct scsi_cmnd *, int);
 };
 #define to_scsi_driver(drv) \
 	container_of((drv), struct scsi_driver, gendrv)

index f334859..3b619819 100644
@@ -169,6 +169,7 @@ void scsi_remove_host(struct Scsi_Host *shost)
 	spin_unlock_irqrestore(shost->host_lock, flags);
 
 	scsi_autopm_get_host(shost);
+	flush_workqueue(shost->tmf_work_q);
 	scsi_forget_host(shost);
 	mutex_unlock(&shost->scan_mutex);
 	scsi_proc_host_rm(shost);

@@ -294,6 +295,8 @@ static void scsi_host_dev_release(struct device *dev)
 
 	scsi_proc_hostdir_rm(shost->hostt);
 
+	if (shost->tmf_work_q)
+		destroy_workqueue(shost->tmf_work_q);
 	if (shost->ehandler)
 		kthread_stop(shost->ehandler);
 	if (shost->work_q)

@@ -360,7 +363,6 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 	INIT_LIST_HEAD(&shost->eh_cmd_q);
 	INIT_LIST_HEAD(&shost->starved_list);
 	init_waitqueue_head(&shost->host_wait);
-
 	mutex_init(&shost->scan_mutex);
 
 	/*

@@ -443,9 +445,19 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 		goto fail_kfree;
 	}
 
+	shost->tmf_work_q = alloc_workqueue("scsi_tmf_%d",
+					    WQ_UNBOUND | WQ_MEM_RECLAIM,
+					   1, shost->host_no);
+	if (!shost->tmf_work_q) {
+		printk(KERN_WARNING "scsi%d: failed to create tmf workq\n",
+		       shost->host_no);
+		goto fail_kthread;
+	}
 	scsi_proc_hostdir_add(shost->hostt);
 	return shost;
 
+ fail_kthread:
+	kthread_stop(shost->ehandler);
  fail_kfree:
 	kfree(shost);
 	return NULL;

index fe0bcb1..2b04a57 100644
@@ -297,6 +297,7 @@ struct scsi_cmnd *scsi_get_command(struct scsi_device *dev, gfp_t gfp_mask)
 
 		cmd->device = dev;
 		INIT_LIST_HEAD(&cmd->list);
+		INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler);
 		spin_lock_irqsave(&dev->list_lock, flags);
 		list_add_tail(&cmd->list, &dev->cmd_list);
 		spin_unlock_irqrestore(&dev->list_lock, flags);

@@ -353,6 +354,8 @@ void scsi_put_command(struct scsi_cmnd *cmd)
 	list_del_init(&cmd->list);
 	spin_unlock_irqrestore(&cmd->device->list_lock, flags);
 
+	cancel_delayed_work(&cmd->abort_work);
+
 	__scsi_put_command(cmd->device->host, cmd, &sdev->sdev_gendev);
 }
 EXPORT_SYMBOL(scsi_put_command);

202 lines not on this page · raw message

index 8f9a0ca..f079a59 100644
@@ -19,6 +19,7 @@ struct scsi_nl_hdr;
  * Scsi Error Handler Flags
  */
 #define SCSI_EH_CANCEL_CMD	0x0001	/* Cancel this cmd */
+#define SCSI_EH_ABORT_SCHEDULED	0x0002	/* Abort has been scheduled */
 
 #define SCSI_SENSE_VALID(scmd) \
 	(((scmd)->sense_buffer[0] & 0x70) == 0x70)

@@ -66,6 +67,7 @@ extern int __init scsi_init_devinfo(void);
 extern void scsi_exit_devinfo(void);
 
 /* scsi_error.c */
+extern void scmd_eh_abort_handler(struct work_struct *work);
 extern enum blk_eh_timer_return scsi_times_out(struct request *req);
 extern int scsi_error_handler(void *host);
 extern int scsi_decide_disposition(struct scsi_cmnd *cmd);

index de5f5d8..91558a1 100644
@@ -55,6 +55,7 @@ struct scsi_cmnd {
 	struct scsi_device *device;
 	struct list_head list;  /* scsi_cmnd participates in queue lists */
 	struct list_head eh_entry; /* entry for the host eh_cmd_q */
+	struct delayed_work abort_work;
 	int eh_eflags;		/* Used by error handlr */
 
 	/*

index 5460849..4d671ac 100644
@@ -476,6 +476,11 @@ struct scsi_host_template {
 	unsigned ordered_tag:1;
 
 	/*
+	 * True if asynchronous aborts are not supported
+	 */
+	unsigned no_async_abort:1;
+
+	/*
 	 * Countdown for host blocking with no commands outstanding.
 	 */
 	unsigned int max_host_blocked;

@@ -684,6 +689,11 @@ struct Scsi_Host {
 	struct workqueue_struct *work_q;
 
 	/*
+	 * Task management function work queue
+	 */
+	struct workqueue_struct *tmf_work_q;
+
+	/*
 	 * Host has rejected a command because it was busy.
 	 */
 	unsigned int host_blocked;

index cab3c9b..1d27625 100644
@@ -94,8 +94,15 @@ static int scsi_host_eh_past_deadline(struct Scsi_Host *shost)
 	if (!shost->last_reset || !shost->eh_deadline)
 		return 0;
 
-	if (time_before(jiffies,
-			shost->last_reset + shost->eh_deadline))
+	/*
+	 * 32bit accesses are guaranteed to be atomic
+	 * (on all supported architectures), so instead
+	 * of using a spinlock we can as well double check
+	 * if eh_deadline has been unset during the
+	 * time_before call.
+	 */
+	if (time_before(jiffies, shost->last_reset + shost->eh_deadline) &&
+	    shost->eh_deadline != 0)
 		return 0;
 
 	return 1;

@@ -111,18 +118,14 @@ scmd_eh_abort_handler(struct work_struct *work)
 	struct scsi_cmnd *scmd =
 		container_of(work, struct scsi_cmnd, abort_work.work);
 	struct scsi_device *sdev = scmd->device;
-	unsigned long flags;
 	int rtn;
 
-	spin_lock_irqsave(sdev->host->host_lock, flags);
 	if (scsi_host_eh_past_deadline(sdev->host)) {
-		spin_unlock_irqrestore(sdev->host->host_lock, flags);
 		SCSI_LOG_ERROR_RECOVERY(3,
 			scmd_printk(KERN_INFO, scmd,
 				    "scmd %p eh timeout, not aborting\n",
 				    scmd));
 	} else {
-		spin_unlock_irqrestore(sdev->host->host_lock, flags);
 		SCSI_LOG_ERROR_RECOVERY(3,
 			scmd_printk(KERN_INFO, scmd,
 				    "aborting command %p\n", scmd));

@@ -1132,7 +1135,6 @@ int scsi_eh_get_sense(struct list_head *work_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) ||

@@ -1140,16 +1142,13 @@ int scsi_eh_get_sense(struct list_head *work_q,
 			continue;
 
 		shost = scmd->device->host;
-		spin_lock_irqsave(shost->host_lock, flags);
 		if (scsi_host_eh_past_deadline(shost)) {
-			spin_unlock_irqrestore(shost->host_lock, flags);
 			SCSI_LOG_ERROR_RECOVERY(3,
 				shost_printk(KERN_INFO, shost,
 					    "skip %s, past eh deadline\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));

@@ -1235,26 +1234,21 @@ 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;
 
 		if (!try_stu) {
-			spin_lock_irqsave(sdev->host->host_lock, flags);
 			if (scsi_host_eh_past_deadline(sdev->host)) {
 				/* Push items back onto work_q */
 				list_splice_init(cmd_list, work_q);
-				spin_unlock_irqrestore(sdev->host->host_lock,
-						       flags);
 				SCSI_LOG_ERROR_RECOVERY(3,
 					shost_printk(KERN_INFO, sdev->host,
 						     "skip %s, past eh deadline",
 						     __func__));
 				break;
 			}
-			spin_unlock_irqrestore(sdev->host->host_lock, flags);
 		}
 
 		finish_cmds = !scsi_device_online(scmd->device) ||

@@ -1295,15 +1289,12 @@ static int scsi_eh_abort_cmds(struct list_head *work_q,
 	LIST_HEAD(check_list);
 	int rtn;
 	struct Scsi_Host *shost;
-	unsigned long flags;
 
 	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_past_deadline(shost)) {
-			spin_unlock_irqrestore(shost->host_lock, flags);
 			list_splice_init(&check_list, work_q);
 			SCSI_LOG_ERROR_RECOVERY(3,
 				shost_printk(KERN_INFO, shost,

@@ -1311,7 +1302,6 @@ static int scsi_eh_abort_cmds(struct list_head *work_q,
 					     __func__));
 			return list_empty(work_q);
 		}
-		spin_unlock_irqrestore(shost->host_lock, flags);
 		SCSI_LOG_ERROR_RECOVERY(3, printk("%s: aborting cmd:"
 						  "0x%p\n", current->comm,
 						  scmd));

@@ -1375,19 +1365,15 @@ 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_past_deadline(shost)) {
-			spin_unlock_irqrestore(shost->host_lock, flags);
 			SCSI_LOG_ERROR_RECOVERY(3,
 				shost_printk(KERN_INFO, shost,
 					    "skip %s, past eh deadline\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) &&

@@ -1441,20 +1427,16 @@ 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_past_deadline(shost)) {
-			spin_unlock_irqrestore(shost->host_lock, flags);
 			SCSI_LOG_ERROR_RECOVERY(3,
 				shost_printk(KERN_INFO, shost,
 					    "skip %s, past eh deadline\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) {

@@ -1515,11 +1497,8 @@ static int scsi_eh_target_reset(struct Scsi_Host *shost,
 		struct scsi_cmnd *next, *scmd;
 		int rtn;
 		unsigned int id;
-		unsigned long flags;
 
-		spin_lock_irqsave(shost->host_lock, flags);
 		if (scsi_host_eh_past_deadline(shost)) {
-			spin_unlock_irqrestore(shost->host_lock, flags);
 			/* push back on work queue for further processing */
 			list_splice_init(&check_list, work_q);
 			list_splice_init(&tmp_list, work_q);

@@ -1529,7 +1508,6 @@ static int scsi_eh_target_reset(struct Scsi_Host *shost,
 					     __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);

@@ -1574,7 +1552,6 @@ 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

@@ -1584,9 +1561,7 @@ static int scsi_eh_bus_reset(struct Scsi_Host *shost,
 	 */
 
 	for (channel = 0; channel <= shost->max_channel; channel++) {
-		spin_lock_irqsave(shost->host_lock, flags);
 		if (scsi_host_eh_past_deadline(shost)) {
-			spin_unlock_irqrestore(shost->host_lock, flags);
 			list_splice_init(&check_list, work_q);
 			SCSI_LOG_ERROR_RECOVERY(3,
 				shost_printk(KERN_INFO, shost,

@@ -1594,7 +1569,6 @@ static int scsi_eh_bus_reset(struct Scsi_Host *shost,
 					     __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) {

index 3b619819..6966def 100644
@@ -319,11 +319,11 @@ static void scsi_host_dev_release(struct device *dev)
 	kfree(shost);
 }
 
-static unsigned int shost_eh_deadline;
+static int shost_eh_deadline = -1;
 
-module_param_named(eh_deadline, shost_eh_deadline, uint, S_IRUGO|S_IWUSR);
+module_param_named(eh_deadline, shost_eh_deadline, int, S_IRUGO|S_IWUSR);
 MODULE_PARM_DESC(eh_deadline,
-		 "SCSI EH timeout in seconds (should be between 1 and 2^32-1)");
+		 "SCSI EH timeout in seconds (should be between 0 and 2^31-1)");
 
 static struct device_type scsi_host_type = {
 	.name =		"scsi_host",

@@ -396,7 +396,15 @@ 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 * HZ;
+	if (shost_eh_deadline == -1)
+		shost->eh_deadline = -1;
+	else if ((ulong) shost_eh_deadline * HZ > INT_MAX) {
+		shost_printk(KERN_WARNING, shost,
+			     "eh_deadline %u too large, setting to %u\n",
+			     shost_eh_deadline, INT_MAX / HZ);
+		shost->eh_deadline = INT_MAX;
+	} else
+		shost->eh_deadline = shost_eh_deadline * HZ;
 
 	if (sht->supported_mode == MODE_UNKNOWN)
 		/* means we didn't set it ... default to INITIATOR */

index 1d27625..04c2ce8 100644
@@ -91,18 +91,18 @@ EXPORT_SYMBOL_GPL(scsi_schedule_eh);
 
 static int scsi_host_eh_past_deadline(struct Scsi_Host *shost)
 {
-	if (!shost->last_reset || !shost->eh_deadline)
+	if (!shost->last_reset || shost->eh_deadline == -1)
 		return 0;
 
 	/*
 	 * 32bit accesses are guaranteed to be atomic
 	 * (on all supported architectures), so instead
 	 * of using a spinlock we can as well double check
-	 * if eh_deadline has been unset during the
+	 * if eh_deadline has been set to 'off' during the
 	 * time_before call.
 	 */
 	if (time_before(jiffies, shost->last_reset + shost->eh_deadline) &&
-	    shost->eh_deadline != 0)
+	    shost->eh_deadline > -1)
 		return 0;
 
 	return 1;

@@ -132,26 +132,34 @@ scmd_eh_abort_handler(struct work_struct *work)
 		rtn = scsi_try_to_abort_cmd(sdev->host->hostt, scmd);
 		if (rtn == SUCCESS) {
 			scmd->result |= DID_TIME_OUT << 16;
-			if (!scsi_noretry_cmd(scmd) &&
+			if (scsi_host_eh_past_deadline(sdev->host)) {
+				SCSI_LOG_ERROR_RECOVERY(3,
+					scmd_printk(KERN_INFO, scmd,
+						    "scmd %p eh timeout, "
+						    "not retrying aborted "
+						    "command\n", scmd));
+			} else if (!scsi_noretry_cmd(scmd) &&
 			    (++scmd->retries <= scmd->allowed)) {
 				SCSI_LOG_ERROR_RECOVERY(3,
 					scmd_printk(KERN_WARNING, scmd,
 						    "scmd %p retry "
 						    "aborted command\n", scmd));
 				scsi_queue_insert(scmd, SCSI_MLQUEUE_EH_RETRY);
+				return;
 			} else {
 				SCSI_LOG_ERROR_RECOVERY(3,
 					scmd_printk(KERN_WARNING, scmd,
 						    "scmd %p finish "
 						    "aborted command\n", scmd));
 				scsi_finish_command(scmd);
+				return;
 			}
-			return;
+		} else {
+			SCSI_LOG_ERROR_RECOVERY(3,
+				scmd_printk(KERN_INFO, scmd,
+					    "scmd %p abort failed, rtn %d\n",
+					    scmd, rtn));
 		}
-		SCSI_LOG_ERROR_RECOVERY(3,
-			scmd_printk(KERN_INFO, scmd,
-				    "scmd %p abort failed, rtn %d\n",
-				    scmd, rtn));
 	}
 
 	if (!scsi_eh_scmd_add(scmd, 0)) {

@@ -202,7 +210,7 @@ scsi_abort_command(struct scsi_cmnd *scmd)
 		return FAILED;
 	}
 
-	if (shost->eh_deadline && !shost->last_reset)
+	if (shost->eh_deadline != -1 && !shost->last_reset)
 		shost->last_reset = jiffies;
 	spin_unlock_irqrestore(shost->host_lock, flags);
 

@@ -236,7 +244,7 @@ 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 (shost->eh_deadline && !shost->last_reset)
+	if (shost->eh_deadline != -1 && !shost->last_reset)
 		shost->last_reset = jiffies;
 
 	ret = 1;

@@ -270,7 +278,7 @@ enum blk_eh_timer_return scsi_times_out(struct request *req)
 	trace_scsi_dispatch_cmd_timeout(scmd);
 	scsi_log_completion(scmd, TIMEOUT_ERROR);
 
-	if (host->eh_deadline && !host->last_reset)
+	if (host->eh_deadline != -1 && !host->last_reset)
 		host->last_reset = jiffies;
 
 	if (host->transportt->eh_timed_out)

@@ -2106,7 +2114,7 @@ static void scsi_unjam_host(struct Scsi_Host *shost)
 			scsi_eh_ready_devs(shost, &eh_work_q, &eh_done_q);
 
 	spin_lock_irqsave(shost->host_lock, flags);
-	if (shost->eh_deadline)
+	if (shost->eh_deadline != -1)
 		shost->last_reset = 0;
 	spin_unlock_irqrestore(shost->host_lock, flags);
 	scsi_eh_flush_done_q(&eh_done_q);

index 8ff62c2..9117d0b 100644
@@ -287,7 +287,9 @@ show_shost_eh_deadline(struct device *dev,
 {
 	struct Scsi_Host *shost = class_to_shost(dev);
 
-	return sprintf(buf, "%d\n", shost->eh_deadline / HZ);
+	if (shost->eh_deadline == -1)
+		return snprintf(buf, strlen("off") + 2, "off\n");
+	return sprintf(buf, "%u\n", shost->eh_deadline / HZ);
 }
 
 static ssize_t

@@ -296,22 +298,34 @@ store_shost_eh_deadline(struct device *dev, struct device_attribute *attr,
 {
 	struct Scsi_Host *shost = class_to_shost(dev);
 	int ret = -EINVAL;
-	int deadline;
-	unsigned long flags;
+	unsigned long deadline, flags;
 
 	if (shost->transportt && shost->transportt->eh_strategy_handler)
 		return ret;
 
-	if (sscanf(buf, "%d\n", &deadline) == 1) {
-		spin_lock_irqsave(shost->host_lock, flags);
-		if (scsi_host_in_recovery(shost))
-			ret = -EBUSY;
-		else {
+	if (!strncmp(buf, "off", strlen("off")))
+		deadline = -1;
+	else {
+		ret = kstrtoul(buf, 10, &deadline);
+		if (ret)
+			return ret;
+		if (deadline * HZ > UINT_MAX)
+			return -EINVAL;
+	}
+
+	spin_lock_irqsave(shost->host_lock, flags);
+	if (scsi_host_in_recovery(shost))
+		ret = -EBUSY;
+	else {
+		if (deadline == -1)
+			shost->eh_deadline = -1;
+		else
 			shost->eh_deadline = deadline * HZ;
-			ret = count;
-		}
-		spin_unlock_irqrestore(shost->host_lock, flags);
+
+		ret = count;
 	}
+	spin_unlock_irqrestore(shost->host_lock, flags);
+
 	return ret;
 }
 

index 2b04a57..d8afec8 100644
@@ -745,15 +745,13 @@ int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
 }
 
 /**
- * scsi_done - Enqueue the finished SCSI command into the done queue.
+ * scsi_done - Invoke completion on finished SCSI command.
  * @cmd: The SCSI Command for which a low-level device driver (LLDD) gives
  * ownership back to SCSI Core -- i.e. the LLDD has finished with it.
  *
  * Description: This function is the mid-level's (SCSI Core) interrupt routine,
  * which regains ownership of the SCSI command (de facto) from a LLDD, and
- * enqueues the command to the done queue for further processing.
- *
- * This is the producer of the done queue who enqueues at the tail.
+ * calls blk_complete_request() for further processing.
  *
  * This function is interrupt context safe.
  */