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>

2 files changed, 15 insertions, 7 deletions

diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c
index 61365fc87786..283fd603624b 100644
--- a/drivers/scsi/hpsa.c
+++ b/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;
 }
diff --git a/drivers/scsi/hpsa.h b/drivers/scsi/hpsa.h
index 7aa7378f70dd..75210de71917 100644
--- a/drivers/scsi/hpsa.h
+++ b/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