[PATCH 1/2] scsi: core: Retry passthrough commands if SCMD_RETRY_PASST_ON_UA is set

[Bart Van Assche <bvanassche@acm.org>]

The SCSI core does not retry passthrough commands even if the SCSI device
reports a retryable unit attention condition. Support retrying in this case
by introducing the SCMD_RETRY_PASST_ON_UA flag.

Cc: Damien Le Moal <dlemoal@kernel.org>
Cc: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/scsi_error.c | 5 ++++-
 include/scsi/scsi_cmnd.h  | 5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 612489afe8d2..38e3ea85e381 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -1855,7 +1855,10 @@ bool scsi_noretry_cmd(struct scsi_cmnd *scmd)
 	 * assume caller has checked sense and determined
 	 * the check condition was retryable.
 	 */
-	if (req->cmd_flags & REQ_FAILFAST_DEV || blk_rq_is_passthrough(req))
+	if (req->cmd_flags & REQ_FAILFAST_DEV)
+		return true;
+	if (blk_rq_is_passthrough(req) &&
+	    !(scmd->flags & SCMD_RETRY_PASST_ON_UA))
 		return true;
 
 	return false;
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 45c40d200154..43c584fbeaca 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -58,8 +58,11 @@ struct scsi_pointer {
  */
 #define SCMD_FORCE_EH_SUCCESS	(1 << 3)
 #define SCMD_FAIL_IF_RECOVERING	(1 << 4)
+/* If set, retry a passthrough command in case of a unit attention. */
+#define SCMD_RETRY_PASST_ON_UA	(1 << 5)
 /* flags preserved across unprep / reprep */
-#define SCMD_PRESERVED_FLAGS	(SCMD_INITIALIZED | SCMD_FAIL_IF_RECOVERING)
+#define SCMD_PRESERVED_FLAGS	\
+	(SCMD_INITIALIZED | SCMD_FAIL_IF_RECOVERING | SCMD_RETRY_PASST_ON_UA)
 
 /* for scmd->state */
 #define SCMD_STATE_COMPLETE	0