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block: Add a new helper to attempt to merge a bio 

There are lots of duplicated code when trying to merge a bio from
plug list and sw queue, we can introduce a new helper to attempt
to merge a bio, which can simplify the blk_bio_list_merge()
and blk_attempt_plug_merge().

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Baolin Wang 2020-08-28 10:52:56 +08:00 committed by Jens Axboe
parent bdc6a287bc
commit 7d7ca7c526
3 changed files with 71 additions and 60 deletions
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104
block/blk-merge.c
View File

@ -907,13 +907,14 @@ static void blk_account_io_merge_bio(struct request *req)
part_stat_unlock();
}
bool bio_attempt_back_merge(struct request *req, struct bio *bio,
unsigned int nr_segs)
enum bio_merge_status bio_attempt_back_merge(struct request *req,
struct bio *bio,
unsigned int nr_segs)
{
const int ff = bio->bi_opf & REQ_FAILFAST_MASK;
if (!ll_back_merge_fn(req, bio, nr_segs))
return false;
return BIO_MERGE_FAILED;
trace_block_bio_backmerge(req->q, req, bio);
rq_qos_merge(req->q, req, bio);
@ -928,16 +929,17 @@ bool bio_attempt_back_merge(struct request *req, struct bio *bio,
bio_crypt_free_ctx(bio);
blk_account_io_merge_bio(req);
return true;
return BIO_MERGE_OK;
}
bool bio_attempt_front_merge(struct request *req, struct bio *bio,
unsigned int nr_segs)
enum bio_merge_status bio_attempt_front_merge(struct request *req,
struct bio *bio,
unsigned int nr_segs)
{
const int ff = bio->bi_opf & REQ_FAILFAST_MASK;
if (!ll_front_merge_fn(req, bio, nr_segs))
return false;
return BIO_MERGE_FAILED;
trace_block_bio_frontmerge(req->q, req, bio);
rq_qos_merge(req->q, req, bio);
@ -954,11 +956,12 @@ bool bio_attempt_front_merge(struct request *req, struct bio *bio,
bio_crypt_do_front_merge(req, bio);
blk_account_io_merge_bio(req);
return true;
return BIO_MERGE_OK;
}
bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
struct bio *bio)
enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q,
struct request *req,
struct bio *bio)
{
unsigned short segments = blk_rq_nr_discard_segments(req);
@ -976,10 +979,39 @@ bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
req->nr_phys_segments = segments + 1;
blk_account_io_merge_bio(req);
return true;
return BIO_MERGE_OK;
no_merge:
req_set_nomerge(q, req);
return false;
return BIO_MERGE_FAILED;
}
static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q,
struct request *rq,
struct bio *bio,
unsigned int nr_segs,
bool sched_allow_merge)
{
if (!blk_rq_merge_ok(rq, bio))
return BIO_MERGE_NONE;
switch (blk_try_merge(rq, bio)) {
case ELEVATOR_BACK_MERGE:
if (!sched_allow_merge ||
(sched_allow_merge && blk_mq_sched_allow_merge(q, rq, bio)))
return bio_attempt_back_merge(rq, bio, nr_segs);
break;
case ELEVATOR_FRONT_MERGE:
if (!sched_allow_merge ||
(sched_allow_merge && blk_mq_sched_allow_merge(q, rq, bio)))
return bio_attempt_front_merge(rq, bio, nr_segs);
break;
case ELEVATOR_DISCARD_MERGE:
return bio_attempt_discard_merge(q, rq, bio);
default:
return BIO_MERGE_NONE;
}
return BIO_MERGE_FAILED;
}
/**
@ -1018,8 +1050,6 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
plug_list = &plug->mq_list;
list_for_each_entry_reverse(rq, plug_list, queuelist) {
bool merged = false;
if (rq->q == q && same_queue_rq) {
/*
* Only blk-mq multiple hardware queues case checks the
@ -1029,24 +1059,11 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
*same_queue_rq = rq;
}
if (rq->q != q || !blk_rq_merge_ok(rq, bio))
if (rq->q != q)
continue;
switch (blk_try_merge(rq, bio)) {
case ELEVATOR_BACK_MERGE:
merged = bio_attempt_back_merge(rq, bio, nr_segs);
break;
case ELEVATOR_FRONT_MERGE:
merged = bio_attempt_front_merge(rq, bio, nr_segs);
break;
case ELEVATOR_DISCARD_MERGE:
merged = bio_attempt_discard_merge(q, rq, bio);
break;
default:
break;
}
if (merged)
if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) ==
BIO_MERGE_OK)
return true;
}
@ -1064,33 +1081,18 @@ bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,
int checked = 8;
list_for_each_entry_reverse(rq, list, queuelist) {
bool merged = false;
if (!checked--)
break;
if (!blk_rq_merge_ok(rq, bio))
continue;
switch (blk_try_merge(rq, bio)) {
case ELEVATOR_BACK_MERGE:
if (blk_mq_sched_allow_merge(q, rq, bio))
merged = bio_attempt_back_merge(rq, bio,
nr_segs);
break;
case ELEVATOR_FRONT_MERGE:
if (blk_mq_sched_allow_merge(q, rq, bio))
merged = bio_attempt_front_merge(rq, bio,
nr_segs);
break;
case ELEVATOR_DISCARD_MERGE:
merged = bio_attempt_discard_merge(q, rq, bio);
break;
default:
switch (blk_attempt_bio_merge(q, rq, bio, nr_segs, true)) {
case BIO_MERGE_NONE:
continue;
case BIO_MERGE_OK:
return true;
case BIO_MERGE_FAILED:
return false;
}
return merged;
}
return false;

6
block/blk-mq-sched.c
View File

@ -368,7 +368,7 @@ bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
case ELEVATOR_BACK_MERGE:
if (!blk_mq_sched_allow_merge(q, rq, bio))
return false;
if (!bio_attempt_back_merge(rq, bio, nr_segs))
if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
return false;
*merged_request = attempt_back_merge(q, rq);
if (!*merged_request)
@ -377,14 +377,14 @@ bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
case ELEVATOR_FRONT_MERGE:
if (!blk_mq_sched_allow_merge(q, rq, bio))
return false;
if (!bio_attempt_front_merge(rq, bio, nr_segs))
if (bio_attempt_front_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
return false;
*merged_request = attempt_front_merge(q, rq);
if (!*merged_request)
elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
return true;
case ELEVATOR_DISCARD_MERGE:
return bio_attempt_discard_merge(q, rq, bio);
return bio_attempt_discard_merge(q, rq, bio) == BIO_MERGE_OK;
default:
return false;
}

21
block/blk.h
View File

@ -29,6 +29,12 @@ struct blk_flush_queue {
spinlock_t mq_flush_lock;
};
enum bio_merge_status {
BIO_MERGE_OK,
BIO_MERGE_NONE,
BIO_MERGE_FAILED,
};
extern struct kmem_cache *blk_requestq_cachep;
extern struct kobj_type blk_queue_ktype;
extern struct ida blk_queue_ida;
@ -169,12 +175,15 @@ static inline void blk_integrity_del(struct gendisk *disk)
unsigned long blk_rq_timeout(unsigned long timeout);
void blk_add_timer(struct request *req);
bool bio_attempt_front_merge(struct request *req, struct bio *bio,
unsigned int nr_segs);
bool bio_attempt_back_merge(struct request *req, struct bio *bio,
unsigned int nr_segs);
bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
struct bio *bio);
enum bio_merge_status bio_attempt_front_merge(struct request *req,
struct bio *bio,
unsigned int nr_segs);
enum bio_merge_status bio_attempt_back_merge(struct request *req,
struct bio *bio,
unsigned int nr_segs);
enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q,
struct request *req,
struct bio *bio);
bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
unsigned int nr_segs, struct request **same_queue_rq);
bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,