blk_mq_submit_bio has two different plug cases, one that uses full
plugging and a limited plugging one.
The limited plugging case is only used for a corner case that does
not matter in real life:
- no ->commit_rqs (so not NVMe)
- no shared tags (so not SCSI)
- not rotational (so no old disk or floppy driver)
- must have multiple queues (so no eMMC)
Remove the limited merging case and all the related junk to simplify
blk_mq_submit_bio and the functions called from it.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
block/blk-merge.c | 9 +------
block/blk-mq.c | 68 +++++++++--------------------------------------
block/blk.h | 2 +-
3 files changed, 15 insertions(+), 64 deletions(-)
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 893c1a60b701f..ba761c3f482ba 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -1067,7 +1067,6 @@ static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q,
* @q: request_queue new bio is being queued at
* @bio: new bio being queued
* @nr_segs: number of segments in @bio
- * @same_queue_rq: output value, will be true if there's an existing request
* from the passed in @q already in the plug list
*
* Determine whether @bio being queued on @q can be merged with the previous
@@ -1084,7 +1083,7 @@ static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q,
* Caller must ensure !blk_queue_nomerges(q) beforehand.
*/
bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
- unsigned int nr_segs, bool *same_queue_rq)
+ unsigned int nr_segs)
{
struct blk_plug *plug;
struct request *rq;
@@ -1096,12 +1095,6 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
/* check the previously added entry for a quick merge attempt */
rq = rq_list_peek(&plug->mq_list);
if (rq->q == q) {
- /*
- * Only blk-mq multiple hardware queues case checks the rq in
- * the same queue, there should be only one such rq in a queue
- */
- *same_queue_rq = true;
-
if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) ==
BIO_MERGE_OK)
return true;
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 1feb9ab65f28a..f05c458d983b4 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2689,11 +2689,10 @@ static inline unsigned short blk_plug_max_rq_count(struct blk_plug *plug)
}
static bool blk_mq_attempt_bio_merge(struct request_queue *q,
- struct bio *bio, unsigned int nr_segs,
- bool *same_queue_rq)
+ struct bio *bio, unsigned int nr_segs)
{
if (!blk_queue_nomerges(q) && bio_mergeable(bio)) {
- if (blk_attempt_plug_merge(q, bio, nr_segs, same_queue_rq))
+ if (blk_attempt_plug_merge(q, bio, nr_segs))
return true;
if (blk_mq_sched_bio_merge(q, bio, nr_segs))
return true;
@@ -2704,8 +2703,7 @@ static bool blk_mq_attempt_bio_merge(struct request_queue *q,
static struct request *blk_mq_get_new_requests(struct request_queue *q,
struct blk_plug *plug,
struct bio *bio,
- unsigned int nsegs,
- bool *same_queue_rq)
+ unsigned int nsegs)
{
struct blk_mq_alloc_data data = {
.q = q,
@@ -2714,7 +2712,7 @@ static struct request *blk_mq_get_new_requests(struct request_queue *q,
};
struct request *rq;
- if (blk_mq_attempt_bio_merge(q, bio, nsegs, same_queue_rq))
+ if (blk_mq_attempt_bio_merge(q, bio, nsegs))
return NULL;
rq_qos_throttle(q, bio);
@@ -2751,8 +2749,7 @@ static inline bool blk_mq_can_use_cached_rq(struct request *rq,
static inline struct request *blk_mq_get_request(struct request_queue *q,
struct blk_plug *plug,
struct bio *bio,
- unsigned int nsegs,
- bool *same_queue_rq)
+ unsigned int nsegs)
{
struct request *rq;
bool checked = false;
@@ -2763,8 +2760,7 @@ static inline struct request *blk_mq_get_request(struct request_queue *q,
if (rq && rq->q == q) {
if (unlikely(!submit_bio_checks(bio)))
return NULL;
- if (blk_mq_attempt_bio_merge(q, bio, nsegs,
- same_queue_rq))
+ if (blk_mq_attempt_bio_merge(q, bio, nsegs))
return NULL;
checked = true;
if (!blk_mq_can_use_cached_rq(rq, bio))
@@ -2782,7 +2778,7 @@ static inline struct request *blk_mq_get_request(struct request_queue *q,
return NULL;
if (!checked && !submit_bio_checks(bio))
return NULL;
- rq = blk_mq_get_new_requests(q, plug, bio, nsegs, same_queue_rq);
+ rq = blk_mq_get_new_requests(q, plug, bio, nsegs);
if (!rq)
blk_queue_exit(q);
return rq;
@@ -2807,7 +2803,6 @@ void blk_mq_submit_bio(struct bio *bio)
const int is_sync = op_is_sync(bio->bi_opf);
struct request *rq;
struct blk_plug *plug;
- bool same_queue_rq = false;
unsigned int nr_segs = 1;
blk_status_t ret;
@@ -2822,7 +2817,7 @@ void blk_mq_submit_bio(struct bio *bio)
return;
plug = blk_mq_plug(q, bio);
- rq = blk_mq_get_request(q, plug, bio, nr_segs, &same_queue_rq);
+ rq = blk_mq_get_request(q, plug, bio, nr_segs);
if (unlikely(!rq))
return;
@@ -2843,16 +2838,7 @@ void blk_mq_submit_bio(struct bio *bio)
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) ||
- q->mq_ops->commit_rqs || !blk_queue_nonrot(q))) {
- /*
- * Use plugging if we have a ->commit_rqs() hook as well, as
- * we know the driver uses bd->last in a smart fashion.
- *
- * Use normal plugging if this disk is slow HDD, as sequential
- * IO may benefit a lot from plug merging.
- */
+ if (plug) {
unsigned int request_count = plug->rq_count;
struct request *last = NULL;
@@ -2870,40 +2856,12 @@ void blk_mq_submit_bio(struct bio *bio)
}
blk_add_rq_to_plug(plug, rq);
- } else if (rq->rq_flags & RQF_ELV) {
- /* Insert the request at the IO scheduler queue */
+ } else if ((rq->rq_flags & RQF_ELV) ||
+ (rq->mq_hctx->dispatch_busy &&
+ (q->nr_hw_queues == 1 || !is_sync))) {
blk_mq_sched_insert_request(rq, false, true, true);
- } else if (plug && !blk_queue_nomerges(q)) {
- struct request *next_rq = NULL;
-
- /*
- * We do limited plugging. If the bio can be merged, do that.
- * Otherwise the existing request in the plug list will be
- * issued. So the plug list will have one request at most
- * The plug list might get flushed before this. If that happens,
- * the plug list is empty, and same_queue_rq is invalid.
- */
- if (same_queue_rq) {
- next_rq = rq_list_pop(&plug->mq_list);
- plug->rq_count--;
- }
- blk_add_rq_to_plug(plug, rq);
- trace_block_plug(q);
-
- if (next_rq) {
- trace_block_unplug(q, 1, true);
- blk_mq_try_issue_directly(next_rq->mq_hctx, next_rq);
- }
- } else if ((q->nr_hw_queues > 1 && is_sync) ||
- !rq->mq_hctx->dispatch_busy) {
- /*
- * There is no scheduler and we can try to send directly
- * to the hardware.
- */
- blk_mq_try_issue_directly(rq->mq_hctx, rq);
} else {
- /* Default case. */
- blk_mq_sched_insert_request(rq, false, true, true);
+ blk_mq_try_issue_directly(rq->mq_hctx, rq);
}
}
diff --git a/block/blk.h b/block/blk.h
index 296e3010f8d65..cfac3bdeb77d9 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -253,7 +253,7 @@ void blk_add_timer(struct request *req);
const char *blk_status_to_str(blk_status_t status);
bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
- unsigned int nr_segs, bool *same_queue_rq);
+ unsigned int nr_segs);
bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,
struct bio *bio, unsigned int nr_segs);
--
2.30.2
