[PATCH v=2] ata: libata-scsi: fix requeue of deferred ATA PASS-THROUGH commands

[Igor Pylypiv]

Commit 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation")
introduced ata_scsi_requeue_deferred_qc() to handle commands deferred
during resets or NCQ failures. This deferral logic completed commands
with DID_SOFT_ERROR to trigger a retry in the SCSI mid-layer.

However, DID_SOFT_ERROR is subject to scsi_cmd_retry_allowed() checks.
ATA PASS-THROUGH commands sent via SG_IO ioctl have scmd->allowed set
to zero. This causes the mid-layer to fail the command immediately
instead of retrying, even though the command was never actually issued
to the hardware.

Switch to DID_REQUEUE to ensure these commands are inserted back into
the request queue regardless of retry limits.

Fixes: 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation")
Reviewed-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
Signed-off-by: Igor Pylypiv <ipylypiv@xxxxxxxxxx>
---

Changes from v1:
- Dropped the usage of set_host_byte() because it is logically a separate
  change from what this commit is fixing. set_host_byte() does not clear
  the status byte and the ML byte.

 drivers/ata/libata-scsi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 3b65df914ebb..cd607911d724 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -1692,7 +1692,7 @@ void ata_scsi_requeue_deferred_qc(struct ata_port *ap)
 	/*
 	 * If we have a deferred qc when a reset occurs or NCQ commands fail,
 	 * do not try to be smart about what to do with this deferred command
-	 * and simply retry it by completing it with DID_SOFT_ERROR.
+	 * and simply requeue it by completing it with DID_REQUEUE.
 	 */
 	if (!qc)
 		return;
@@ -1701,7 +1701,7 @@ void ata_scsi_requeue_deferred_qc(struct ata_port *ap)
 	ap->deferred_qc = NULL;
 	cancel_work(&ap->deferred_qc_work);
 	ata_qc_free(qc);
-	scmd->result = (DID_SOFT_ERROR << 16);
+	scmd->result = (DID_REQUEUE << 16);
 	scsi_done(scmd);
 }
 
-- 
2.53.0.1213.gd9a14994de-goog