Once we mark the queue as needing a restart, re-check if we can
get a driver tag. This fixes a theoretical issue where the needed
IO completes _after_ blk_mq_get_driver_tag() fails, but before we
manage to set the restart bit.
Signed-off-by: Jens Axboe <axboe@xxxxxx>
---
block/blk-mq.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 223b9b080820..8041ad330289 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -928,7 +928,16 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list)
if (!blk_mq_get_driver_tag(rq, &hctx, false)) {
if (!queued && reorder_tags_to_front(list))
continue;
+
+ /*
+ * We failed getting a driver tag. Mark the queue(s)
+ * as needing a restart. Retry getting a tag again,
+ * in case the needed IO completed right before we
+ * marked the queue as needing a restart.
+ */
blk_mq_sched_mark_restart(hctx);
+ if (!blk_mq_get_driver_tag(rq, &hctx, false))
+ break;
break;
}
list_del_init(&rq->queuelist);
--
2.7.4
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