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blk-mq: don't grab ->q_usage_counter in blk_mq_sched_bio_merge

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blk_mq_sched_bio_merge is only called from blk-mq.c:blk_attempt_bio_merge(),
which is called when queue usage counter is grabbed already:

1) blk_mq_get_new_requests()

2) blk_mq_get_request()
- cached request in current plug owns one queue usage counter

So don't grab ->q_usage_counter in blk_mq_sched_bio_merge(), and more
importantly this nest way causes hang in blk_mq_freeze_queue_wait().

Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211111085134.345235-2-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2021-11-11 16:51:33 +08:00 committed by Jens Axboe
parent 438cd74223
commit 10f7335e36
1 changed files with 0 additions and 4 deletions
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4
block/blk-mq-sched.c
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@ -370,9 +370,6 @@ bool blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
bool ret = false;
enum hctx_type type;
if (bio_queue_enter(bio))
return false;
if (e && e->type->ops.bio_merge) {
ret = e->type->ops.bio_merge(q, bio, nr_segs);
goto out_put;
@ -397,7 +394,6 @@ bool blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
spin_unlock(&ctx->lock);
out_put:
blk_queue_exit(q);
return ret;
}