[PATCH v2 4/5] scsi: Add scsi_restart_hctx()

Bart Van Assche
2017-04-03T23:22:27Z

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 <bart.vanassche@sandisk.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
---
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..0e240aebc150 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_hctx(struct request_queue *q,
+ struct blk_mq_hw_ctx *hctx)
+{
+ struct blk_mq_tags *tags = hctx->tags;
+ struct blk_mq_tag_set *set = q->tag_set;
+ int i;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(q, &set->tag_list, tag_set_list)
+ queue_for_each_hw_ctx(q, hctx, i)
+ if (hctx->tags == tags)
+ blk_mq_sched_restart_hctx(hctx);
+ rcu_read_unlock();
+}
+
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_hctx = scsi_restart_hctx,
.complete = scsi_softirq_done,
.timeout = scsi_timeout,
.init_request = scsi_init_request,
--
2.12.0