Share the main merge / split / integrity preparation code between the
cached request vs newly allocated request cases, and add comments
explaining the cached request handling.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
block/blk-mq.c | 41 ++++++++++++++++++++++-------------------
1 file changed, 22 insertions(+), 19 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 66df323c2b9489..edb9ee463bd0f0 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2976,30 +2976,25 @@ void blk_mq_submit_bio(struct bio *bio)
struct blk_plug *plug = blk_mq_plug(bio);
const int is_sync = op_is_sync(bio->bi_opf);
struct blk_mq_hw_ctx *hctx;
- struct request *rq = NULL;
unsigned int nr_segs = 1;
+ struct request *rq;
blk_status_t ret;
bio = blk_queue_bounce(bio, q);
bio_set_ioprio(bio);
+ /*
+ * If the plug has a cached request for this queue, try use it.
+ *
+ * The cached request already holds a q_usage_counter reference and we
+ * don't have to acquire a new one if we use it.
+ */
rq = blk_mq_peek_cached_request(plug, q, bio->bi_opf);
- if (rq) {
- if (unlikely(bio_may_exceed_limits(bio, &q->limits))) {
- bio = __bio_split_to_limits(bio, &q->limits, &nr_segs);
- if (!bio)
- return;
- }
- if (!bio_integrity_prep(bio))
- return;
- if (blk_mq_attempt_bio_merge(q, bio, nr_segs))
+ if (!rq) {
+ if (unlikely(bio_queue_enter(bio)))
return;
- blk_mq_use_cached_rq(rq, plug, bio);
- goto done;
}
- if (unlikely(bio_queue_enter(bio)))
- return;
if (unlikely(bio_may_exceed_limits(bio, &q->limits))) {
bio = __bio_split_to_limits(bio, &q->limits, &nr_segs);
if (!bio)
@@ -3011,11 +3006,14 @@ void blk_mq_submit_bio(struct bio *bio)
if (blk_mq_attempt_bio_merge(q, bio, nr_segs))
goto queue_exit;
- rq = blk_mq_get_new_requests(q, plug, bio, nr_segs);
- if (unlikely(!rq))
- goto queue_exit;
+ if (!rq) {
+ rq = blk_mq_get_new_requests(q, plug, bio, nr_segs);
+ if (unlikely(!rq))
+ goto queue_exit;
+ } else {
+ blk_mq_use_cached_rq(rq, plug, bio);
+ }
-done:
trace_block_getrq(bio);
rq_qos_track(q, rq, bio);
@@ -3049,7 +3047,12 @@ void blk_mq_submit_bio(struct bio *bio)
return;
queue_exit:
- blk_queue_exit(q);
+ /*
+ * Don't drop the queue reference if we were trying to use a cached
+ * request and thus didn't acquire one.
+ */
+ if (!rq)
+ blk_queue_exit(q);
}
#ifdef CONFIG_BLK_MQ_STACKING
--
2.39.2
