[PATCH stable 4.19 1/1] scsi: core: Fix race between handling STS_RESOURCE and completion

[Yu Kuai]

From: Ming Lei <ming.lei@xxxxxxxxxx>

commit 673235f915318ced5d7ec4b2bfd8cb909e6a4a55 upstream.

When queuing I/O request to LLD, STS_RESOURCE may be returned because:

 - Host is in recovery or blocked

 - Target queue throttling or target is blocked

 - LLD rejection

In these scenarios BLK_STS_DEV_RESOURCE is returned to the block layer to
avoid an unnecessary re-run of the queue. However, all of the requests
queued to this SCSI device may complete immediately after reading
'sdev->device_busy' and BLK_STS_DEV_RESOURCE is returned to block layer. In
that case the current I/O won't get a chance to get queued since it is
invisible at that time for both scsi_run_queue_async() and blk-mq's
RESTART.

Fix the issue by not returning BLK_STS_DEV_RESOURCE in this situation.

Link: https://lore.kernel.org/r/20201202100419.525144-1-ming.lei@xxxxxxxxxx
Fixes: 86ff7c2a80cd ("blk-mq: introduce BLK_STS_DEV_RESOURCE")
Cc: Hannes Reinecke <hare@xxxxxxxx>
Cc: Sumit Saxena <sumit.saxena@xxxxxxxxxxxx>
Cc: Kashyap Desai <kashyap.desai@xxxxxxxxxxxx>
Cc: Bart Van Assche <bvanassche@xxxxxxx>
Cc: Ewan Milne <emilne@xxxxxxxxxx>
Cc: Long Li <longli@xxxxxxxxxxxxx>
Reported-by: John Garry <john.garry@xxxxxxxxxx>
Tested-by: "chenxiang (M)" <chenxiang66@xxxxxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
 drivers/scsi/scsi_lib.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 0191708c9dd4..ace4a7230bcf 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2157,8 +2157,7 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
 	case BLK_STS_OK:
 		break;
 	case BLK_STS_RESOURCE:
-		if (atomic_read(&sdev->device_busy) ||
-		    scsi_device_blocked(sdev))
+		if (scsi_device_blocked(sdev))
 			ret = BLK_STS_DEV_RESOURCE;
 		break;
 	default:
-- 
2.31.1