@@ -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);
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@fb.com> --- block/blk-mq.c | 9 +++++++++ 1 file changed, 9 insertions(+)