[PATCH v4 03/10] scsi: core: Support failing requests while recovering

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

The current behavior for SCSI commands submitted while error recovery
is ongoing is to retry command submission after error recovery has
finished. See also the scsi_host_in_recovery() check in
scsi_host_queue_ready(). Add support for failing SCSI commands while
host recovery is in progress. This functionality will be used to fix a
deadlock in the UFS driver.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: John Garry <john.garry@huawei.com>
Cc: Mike Christie <michael.christie@oracle.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/scsi_lib.c  | 8 +++++---
 include/scsi/scsi_cmnd.h | 3 ++-
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index fa96d3cfdfa3..ec890865abae 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1341,9 +1341,6 @@ static inline int scsi_host_queue_ready(struct request_queue *q,
 				   struct scsi_device *sdev,
 				   struct scsi_cmnd *cmd)
 {
-	if (scsi_host_in_recovery(shost))
-		return 0;
-
 	if (atomic_read(&shost->host_blocked) > 0) {
 		if (scsi_host_busy(shost) > 0)
 			goto starved;
@@ -1732,6 +1729,11 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
 	ret = BLK_STS_RESOURCE;
 	if (!scsi_target_queue_ready(shost, sdev))
 		goto out_put_budget;
+	if (unlikely(scsi_host_in_recovery(shost))) {
+		if (cmd->flags & SCMD_FAIL_IF_RECOVERING)
+			ret = BLK_STS_OFFLINE;
+		goto out_dec_target_busy;
+	}
 	if (!scsi_host_queue_ready(q, shost, sdev, cmd))
 		goto out_dec_target_busy;
 
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 7d3622db38ed..c2cb5f69635c 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -52,8 +52,9 @@ struct scsi_pointer {
 #define SCMD_TAGGED		(1 << 0)
 #define SCMD_INITIALIZED	(1 << 1)
 #define SCMD_LAST		(1 << 2)
+#define SCMD_FAIL_IF_RECOVERING	(1 << 4)
 /* flags preserved across unprep / reprep */
-#define SCMD_PRESERVED_FLAGS	(SCMD_INITIALIZED)
+#define SCMD_PRESERVED_FLAGS	(SCMD_INITIALIZED | SCMD_FAIL_IF_RECOVERING)
 
 /* for scmd->state */
 #define SCMD_STATE_COMPLETE	0