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block: Merge bio before checking ->cached_rq

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It checks if plug->cached_rq is empty before merging bio. But the merge action
doesn't have relationship with plug->cached_rq, it trys to merge bio with
requests within plug->mq_list. Now it checks if ->cached_rq is empty before
merging bio. If it's empty, it will miss the merge chances. So move the merge
function before checking ->cached_rq.

Signed-off-by: Xiao Ni <xni@redhat.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230209031930.27354-1-xni@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Xiao Ni 2023-02-09 11:19:30 +08:00 committed by Jens Axboe
parent dcb5220143
commit 23f3e3272e
1 changed files with 4 additions and 3 deletions
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7
block/blk-mq.c
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@ -2879,15 +2879,16 @@ static inline struct request *blk_mq_get_cached_request(struct request_queue *q,
if (!plug)
return NULL;
rq = rq_list_peek(&plug->cached_rq);
if (!rq || rq->q != q)
return NULL;
if (blk_mq_attempt_bio_merge(q, *bio, nsegs)) {
*bio = NULL;
return NULL;
}
rq = rq_list_peek(&plug->cached_rq);
if (!rq || rq->q != q)
return NULL;
type = blk_mq_get_hctx_type((*bio)->bi_opf);
hctx_type = rq->mq_hctx->type;
if (type != hctx_type &&