From c6b7a3a26e809c9d2a51ae303764c1d2994f31cf Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Sat, 24 Jun 2023 21:01:05 +0800 Subject: [PATCH] blk-mq: fix two misuses on RQF_USE_SCHED Request allocated from sched tags can't be issued via ->queue_rqs() directly, since driver tag isn't allocated yet. This is the 1st misuse of RQF_USE_SCHED for figuring out plug->has_elevator. Request allocated from sched tags can't be ended by blk_mq_end_request_batch() too, fix the 2nd RQF_USE_SCHED misuse in blk_mq_add_to_batch(). Without this patch, NVMe uring cmd passthrough IO workload can run into hang easily with real io scheduler. Fixes: dd6216bb16e8 ("blk-mq: make sure elevator callbacks aren't called for passthrough request") Reported-by: Guangwu Zhang Closes: https://lore.kernel.org/linux-block/CAGS2=YrBjpLPOKa-gzcKuuOG60AGth5794PNCDwatdnnscB9ug@mail.gmail.com/ Cc: Christoph Hellwig Signed-off-by: Ming Lei Link: https://lore.kernel.org/r/20230624130105.1443879-1-ming.lei@redhat.com Signed-off-by: Jens Axboe --- block/blk-mq.c | 6 +++++- include/linux/blk-mq.h | 6 +++++- 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 720b506..32e50bc 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1280,7 +1280,11 @@ static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq) if (!plug->multiple_queues && last && last->q != rq->q) plug->multiple_queues = true; - if (!plug->has_elevator && (rq->rq_flags & RQF_USE_SCHED)) + /* + * Any request allocated from sched tags can't be issued to + * ->queue_rqs() directly + */ + if (!plug->has_elevator && (rq->rq_flags & RQF_SCHED_TAGS)) plug->has_elevator = true; rq->rq_next = NULL; rq_list_add(&plug->mq_list, rq); diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index f401067..aaed687 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -852,7 +852,11 @@ static inline bool blk_mq_add_to_batch(struct request *req, struct io_comp_batch *iob, int ioerror, void (*complete)(struct io_comp_batch *)) { - if (!iob || (req->rq_flags & RQF_USE_SCHED) || ioerror || + /* + * blk_mq_end_request_batch() can't end request allocated from + * sched tags + */ + if (!iob || (req->rq_flags & RQF_SCHED_TAGS) || ioerror || (req->end_io && !blk_rq_is_passthrough(req))) return false; -- 2.7.4