[PATCH] blk-mq: don't insert FUA request with data into scheduler queue

Ming Lei
2021-11-18T15:31:01Z

We never insert flush request into scheduler queue before.

Recently commit d92ca9d8348f ("blk-mq: don't handle non-flush requests in
blk_insert_flush") tries to handle FUA data request as normal request.
This way has caused warning[1] in mq-deadline dd_exit_sched() or io hang in
case of kyber since RQF_ELVPRIV isn't set for flush request, then
->finish_request won't be called.

Fix the issue by inserting FUA data request with blk_mq_request_bypass_insert()
when the device supports FUA, just like what we did before.

[1] https://lore.kernel.org/linux-block/CAHj4cs-_vkTW=dAzbZYGxpEWSpzpcmaNeY1R=vH311+9vMUSdg@mail.gmail.com/

Reported-by: Yi Zhang <yi.zhang@redhat.com>
Fixes: d92ca9d8348f ("blk-mq: don't handle non-flush requests in blk_insert_flush")
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
block/blk-flush.c | 12 ++++++------
block/blk-mq.c | 4 +++-
block/blk.h | 2 +-
3 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/block/blk-flush.c b/block/blk-flush.c
index 8e364bda5166..1fce6d16e6d3 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -379,7 +379,7 @@ static void mq_flush_data_end_io(struct request *rq, blk_status_t error)
* @rq is being submitted. Analyze what needs to be done and put it on the
* right queue.
*/
-bool blk_insert_flush(struct request *rq)
+void blk_insert_flush(struct request *rq)
{
struct request_queue *q = rq->q;
unsigned long fflags = q->queue_flags; /* may change, cache */
@@ -409,7 +409,7 @@ bool blk_insert_flush(struct request *rq)
*/
if (!policy) {
blk_mq_end_request(rq, 0);
- return true;
+ return;
}

BUG_ON(rq->bio != rq->biotail); /*assumes zero or single bio rq */
@@ -420,8 +420,10 @@ bool blk_insert_flush(struct request *rq)
* for normal execution.
*/
if ((policy & REQ_FSEQ_DATA) &&
- !(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH)))
- return false;
+ !(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH))) {
+ blk_mq_request_bypass_insert(rq, false, true);
+ return;
+ }

/*
* @rq should go through flush machinery. Mark it part of flush
@@ -437,8 +439,6 @@ bool blk_insert_flush(struct request *rq)
spin_lock_irq(&fq->mq_flush_lock);
blk_flush_complete_seq(rq, fq, REQ_FSEQ_ACTIONS & ~policy, 0);
spin_unlock_irq(&fq->mq_flush_lock);
-
- return true;
}

/**
diff --git a/block/blk-mq.c b/block/blk-mq.c
index c219271f9d6a..fa1a00d71b61 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2647,8 +2647,10 @@ void blk_mq_submit_bio(struct bio *bio)
return;
}

- if (op_is_flush(bio->bi_opf) && blk_insert_flush(rq))
+ if (op_is_flush(bio->bi_opf)) {
+ blk_insert_flush(rq);
return;
+ }

if (plug && (q->nr_hw_queues == 1 ||
blk_mq_is_shared_tags(rq->mq_hctx->flags) ||
diff --git a/block/blk.h b/block/blk.h
index 4a910742cce9..7c6f7635bff0 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -272,7 +272,7 @@ void __blk_account_io_done(struct request *req, u64 now);
*/
#define ELV_ON_HASH(rq) ((rq)->rq_flags & RQF_HASHED)

-bool blk_insert_flush(struct request *rq);
+void blk_insert_flush(struct request *rq);

int elevator_switch_mq(struct request_queue *q,
struct elevator_type *new_e);
--
2.31.1