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

Bart Van Assche
2020-11-16T03:05:31Z

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(-)

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);