* [PATCH] blk-mq: fix two misuses on RQF_USE_SCHED
@ 2023-06-24 13:01 Ming Lei
2023-06-25 8:31 ` Guangwu Zhang
2023-06-25 14:01 ` Jens Axboe
0 siblings, 2 replies; 3+ messages in thread
From: Ming Lei @ 2023-06-24 13:01 UTC (permalink / raw
To: Jens Axboe; +Cc: linux-block, Ming Lei, Guangwu Zhang, Christoph Hellwig
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@redhat.com>
Closes: https://lore.kernel.org/linux-block/CAGS2=YrBjpLPOKa-gzcKuuOG60AGth5794PNCDwatdnnscB9ug@mail.gmail.com/
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] blk-mq: fix two misuses on RQF_USE_SCHED
2023-06-24 13:01 [PATCH] blk-mq: fix two misuses on RQF_USE_SCHED Ming Lei
@ 2023-06-25 8:31 ` Guangwu Zhang
2023-06-25 14:01 ` Jens Axboe
1 sibling, 0 replies; 3+ messages in thread
From: Guangwu Zhang @ 2023-06-25 8:31 UTC (permalink / raw
To: Ming Lei; +Cc: Jens Axboe, linux-block, Christoph Hellwig
Hi, Ming
Could not hit the error after apply your patch. good job!
Ming Lei <ming.lei@redhat.com> 于2023年6月24日周六 21:01写道：
>
> 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@redhat.com>
> Closes: https://lore.kernel.org/linux-block/CAGS2=YrBjpLPOKa-gzcKuuOG60AGth5794PNCDwatdnnscB9ug@mail.gmail.com/
> Cc: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
> 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
>
--
Guangwu Zhang
Thanks
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] blk-mq: fix two misuses on RQF_USE_SCHED
2023-06-24 13:01 [PATCH] blk-mq: fix two misuses on RQF_USE_SCHED Ming Lei
2023-06-25 8:31 ` Guangwu Zhang
@ 2023-06-25 14:01 ` Jens Axboe
1 sibling, 0 replies; 3+ messages in thread
From: Jens Axboe @ 2023-06-25 14:01 UTC (permalink / raw
To: Ming Lei; +Cc: linux-block, Guangwu Zhang, Christoph Hellwig
On Sat, 24 Jun 2023 21:01:05 +0800, Ming Lei wrote:
> 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().
>
> [...]
Applied, thanks!
[1/1] blk-mq: fix two misuses on RQF_USE_SCHED
commit: c6b7a3a26e809c9d2a51ae303764c1d2994f31cf
Best regards,
--
Jens Axboe
^ permalink raw reply [flat|nested] 3+ messages in thread
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2023-06-24 13:01 [PATCH] blk-mq: fix two misuses on RQF_USE_SCHED Ming Lei
2023-06-25 8:31 ` Guangwu Zhang
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