This patch avoids that if multiple SCSI devices are associated with
a SCSI host that a queue can get stuck if scsi_queue_rq() returns
"busy".

Signed-off-by: Bart Van Assche <[email protected]>
Cc: Martin K. Petersen <[email protected]>
Cc: James Bottomley <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Hannes Reinecke <[email protected]>
---
 drivers/scsi/scsi_lib.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index c1519660824b..1d804e33971a 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -555,6 +555,21 @@ void scsi_run_host_queues(struct Scsi_Host *shost)
                scsi_run_queue(sdev->request_queue);
 }
 
+static void scsi_restart_queues(struct request_queue *q)
+{
+       struct scsi_device *sdev = q->queuedata;
+       struct Scsi_Host *shost = sdev->host;
+       unsigned long flags;
+
+       spin_lock_irqsave(shost->host_lock, flags);
+       __shost_for_each_device(sdev, shost) {
+               q = sdev->request_queue;
+               if (q->mq_ops && !blk_queue_dying(q))
+                       blk_mq_run_hw_queues(q, true);
+       }
+       spin_unlock_irqrestore(shost->host_lock, flags);
+}
+
 static void scsi_uninit_cmd(struct scsi_cmnd *cmd)
 {
        if (!blk_rq_is_passthrough(cmd->request)) {
@@ -2156,6 +2171,7 @@ struct request_queue *scsi_alloc_queue(struct scsi_device 
*sdev)
 
 static const struct blk_mq_ops scsi_mq_ops = {
        .queue_rq       = scsi_queue_rq,
+       .restart_queues = scsi_restart_queues,
        .complete       = scsi_softirq_done,
        .timeout        = scsi_timeout,
        .init_request   = scsi_init_request,
-- 
2.12.0

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