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block: Check for gaps on front and back merges

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We are checking for gaps to previous bio_vec, which can
only detect back merges gaps. Moreover, at the point where
we check for a gap, we don't know if we will attempt a back
or a front merge. Thus, check for gap to prev in a back merge
attempt and check for a gap to next in a front merge attempt.

Signed-off-by: Jens Axboe <axboe@fb.com>
[sagig: Minor rename change]
Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
This commit is contained in:
Jens Axboe 2015-09-03 19:28:20 +03:00
parent 5fdb7e1b97
commit 5e7c4274a7
2 changed files with 26 additions and 13 deletions
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19
block/blk-merge.c
View File

@ -438,6 +438,8 @@ no_merge:
int ll_back_merge_fn(struct request_queue *q, struct request *req,
struct bio *bio)
{
if (req_gap_back_merge(req, bio))
return 0;
if (blk_rq_sectors(req) + bio_sectors(bio) >
blk_rq_get_max_sectors(req)) {
req->cmd_flags |= REQ_NOMERGE;
@ -456,6 +458,9 @@ int ll_back_merge_fn(struct request_queue *q, struct request *req,
int ll_front_merge_fn(struct request_queue *q, struct request *req,
struct bio *bio)
{
if (req_gap_front_merge(req, bio))
return 0;
if (blk_rq_sectors(req) + bio_sectors(bio) >
blk_rq_get_max_sectors(req)) {
req->cmd_flags |= REQ_NOMERGE;
@ -482,14 +487,6 @@ static bool req_no_special_merge(struct request *req)
return !q->mq_ops && req->special;
}
static int req_gap_to_prev(struct request *req, struct bio *next)
{
struct bio *prev = req->biotail;
return bvec_gap_to_prev(req->q, &prev->bi_io_vec[prev->bi_vcnt - 1],
next->bi_io_vec[0].bv_offset);
}
static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
struct request *next)
{
@ -504,7 +501,7 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
if (req_no_special_merge(req) || req_no_special_merge(next))
return 0;
if (req_gap_to_prev(req, next->bio))
if (req_gap_back_merge(req, next->bio))
return 0;
/*
@ -712,10 +709,6 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
!blk_write_same_mergeable(rq->bio, bio))
return false;
/* Only check gaps if the bio carries data */
if (bio_has_data(bio) && req_gap_to_prev(rq, bio))
return false;
return true;
}

20
include/linux/blkdev.h
View File

@ -1368,6 +1368,26 @@ static inline bool bvec_gap_to_prev(struct request_queue *q,
((bprv->bv_offset + bprv->bv_len) & queue_virt_boundary(q));
}
static inline bool bio_will_gap(struct request_queue *q, struct bio *prev,
struct bio *next)
{
if (!bio_has_data(prev))
return false;
return bvec_gap_to_prev(q, &prev->bi_io_vec[prev->bi_vcnt - 1],
next->bi_io_vec[0].bv_offset);
}
static inline bool req_gap_back_merge(struct request *req, struct bio *bio)
{
return bio_will_gap(req->q, req->biotail, bio);
}
static inline bool req_gap_front_merge(struct request *req, struct bio *bio)
{
return bio_will_gap(req->q, bio, req->bio);
}
struct work_struct;
int kblockd_schedule_work(struct work_struct *work);
int kblockd_schedule_delayed_work(struct delayed_work *dwork, unsigned long delay);