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 <guazhang@xxxxxxxxxx>
Closes: https://lore.kernel.org/linux-block/CAGS2=YrBjpLPOKa-gzcKuuOG60AGth5794PNCDwatdnnscB9ug@xxxxxxxxxxxxxx/
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
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 1628873d7587..0aba08a9ded6 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1302,7 +1302,11 @@ 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 fa265e85d753..12103d5654f5 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;
--
2.40.1
