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 <[email protected]> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
