scsi: hpsa: check for tag collision

Correct rare multipath issue where a device is deleted with an
outstanding cmd which results in a tag collision.

The cmd eventually completes. If a collision is detected wait until
the command slot is cleared.
Reviewed-by: Justin Lindley <justin.lindley@microsemi.com>
Reviewed-by: David Carroll <david.carroll@microsemi.com>
Reviewed-by: Scott Teel <scott.teel@microsemi.com>
Signed-off-by: Don Brace <don.brace@microsemi.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/hpsa.c

@@ -5635,6 +5635,8 @@ static int hpsa_scsi_queue_command(struct Scsi_Host *sh, struct scsi_cmnd *cmd)
 		return 0;
 	}
 	c = cmd_tagged_alloc(h, cmd);
+	if (c == NULL)
+		return SCSI_MLQUEUE_DEVICE_BUSY;
 
 	/*
 	 * Call alternate submit routine for I/O accelerated commands.
@@ -6041,7 +6043,6 @@ static struct CommandList *cmd_tagged_alloc(struct ctlr_info *h,
 		BUG();
 	}
 
-	atomic_inc(&c->refcount);
 	if (unlikely(!hpsa_is_cmd_idle(c))) {
 		/*
 		 * We expect that the SCSI layer will hand us a unique tag
@@ -6049,14 +6050,20 @@ static struct CommandList *cmd_tagged_alloc(struct ctlr_info *h,
 		 * two requests...because if the selected command isn't idle
 		 * then someone is going to be very disappointed.
 		 */
-		dev_err(&h->pdev->dev,
-			"tag collision (tag=%d) in cmd_tagged_alloc().\n",
-			idx);
-		if (c->scsi_cmd != NULL)
-			scsi_print_command(c->scsi_cmd);
-		scsi_print_command(scmd);
+		if (idx != h->last_collision_tag) { /* Print once per tag */
+			dev_warn(&h->pdev->dev,
+				"%s: tag collision (tag=%d)\n", __func__, idx);
+			if (c->scsi_cmd != NULL)
+				scsi_print_command(c->scsi_cmd);
+			if (scmd)
+				scsi_print_command(scmd);
+			h->last_collision_tag = idx;
+		}
+		return NULL;
 	}
 
+	atomic_inc(&c->refcount);
+
 	hpsa_cmd_partial_init(h, idx, c);
 	return c;
 }

drivers/scsi/hpsa.h

@@ -174,6 +174,7 @@ struct ctlr_info {
 	struct CfgTable __iomem *cfgtable;
 	int	interrupts_enabled;
 	int 	max_commands;
+	int	last_collision_tag; /* tags are global */
 	atomic_t commands_outstanding;
 #	define PERF_MODE_INT	0
 #	define DOORBELL_INT	1