[PATCH] libata: dec scmd->retries for qcs with zero err_mask

qcs might get retried because of unrelated failure.  e.g. NCQ command
failure causes the whole command set to be aborted.  Decrement
scmd->retries for such retrials to avoid unnecessarily failing
commands.  Note that scmd->retries will be incremented the first time.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/scsi/libata-scsi.c

@@ -831,11 +831,14 @@ void ata_eh_qc_complete(struct ata_queued_cmd *qc)
  *	should be retried.  To be used from EH.
  *
  *	SCSI midlayer limits the number of retries to scmd->allowed.
- *	This function might need to adjust scmd->retries for commands
- *	which get retried due to unrelated NCQ failures.
+ *	scmd->retries is decremented for commands which get retried
+ *	due to unrelated failures (qc->err_mask is zero).
  */
 void ata_eh_qc_retry(struct ata_queued_cmd *qc)
 {
+	struct scsi_cmnd *scmd = qc->scsicmd;
+	if (!qc->err_mask && scmd->retries)
+		scmd->retries--;
 	__ata_eh_qc_complete(qc);
 }