diff mbox series

[v2,5/9] scsi: Do not wait for a request in scsi_eh_lock_door()

Message ID 20201116030459.13963-6-bvanassche@acm.org (mailing list archive)
State Superseded
Headers show
Series Rework runtime suspend and SCSI domain validation | expand

Commit Message

Bart Van Assche Nov. 16, 2020, 3:04 a.m. UTC 
scsi_eh_lock_door() is the only function in the SCSI error handler that
calls blk_get_request(). It is not guaranteed that a request is available
when scsi_eh_lock_door() is called. Hence pass the BLK_MQ_REQ_NOWAIT flag
to blk_get_request(). This patch has a second purpose, namely preventing
that scsi_eh_lock_door() deadlocks if sdev->request_queue is frozen and if
a SCSI command is submitted to a SCSI device through a second request
queue that has not been frozen. A later patch will namely modify the SPI
DV code such that sdev->requeust_queue is frozen during domain validation.

Cc: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Can Guo <cang@codeaurora.org>
Cc: Stanley Chu <stanley.chu@mediatek.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/scsi_error.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Comments

Christoph Hellwig Nov. 16, 2020, 5:18 p.m. UTC | #1 
On Sun, Nov 15, 2020 at 07:04:55PM -0800, Bart Van Assche wrote:
> scsi_eh_lock_door() is the only function in the SCSI error handler that
> calls blk_get_request(). It is not guaranteed that a request is available
> when scsi_eh_lock_door() is called. Hence pass the BLK_MQ_REQ_NOWAIT flag
> to blk_get_request(). This patch has a second purpose, namely preventing
> that scsi_eh_lock_door() deadlocks if sdev->request_queue is frozen and if
> a SCSI command is submitted to a SCSI device through a second request
> queue that has not been frozen. A later patch will namely modify the SPI
> DV code such that sdev->requeust_queue is frozen during domain validation.

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>
diff mbox series

Patch

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index d94449188270..6de6e1bf3dcb 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -1993,7 +1993,12 @@  static void scsi_eh_lock_door(struct scsi_device *sdev)
 	struct request *req;
 	struct scsi_request *rq;
 
-	req = blk_get_request(sdev->request_queue, REQ_OP_SCSI_IN, 0);
+	/*
+	 * It is not guaranteed that a request is available nor that
+	 * sdev->request_queue is unfrozen. Hence the BLK_MQ_REQ_NOWAIT below.
+	 */
+	req = blk_get_request(sdev->request_queue, REQ_OP_SCSI_IN,
+			      BLK_MQ_REQ_NOWAIT);
 	if (IS_ERR(req))
 		return;
 	rq = scsi_req(req);