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block: setup bi_phys_segments after splitting 

The number of bio->bi_phys_segments is always obtained
during bio splitting, so it is natural to setup it
just after bio splitting, then we can avoid to compute
nr_segment again during merge.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Ming Lei 2015-10-20 23:13:52 +08:00 committed by Jens Axboe
parent 0809e3ac62
commit bdced438ac
1 changed files with 22 additions and 7 deletions
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29
block/blk-merge.c
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@ -11,13 +11,16 @@
static struct bio *blk_bio_discard_split(struct request_queue *q,
struct bio *bio,
struct bio_set *bs)
struct bio_set *bs,
unsigned *nsegs)
{
unsigned int max_discard_sectors, granularity;
int alignment;
sector_t tmp;
unsigned split_sectors;
*nsegs = 1;
/* Zero-sector (unknown) and one-sector granularities are the same. */
granularity = max(q->limits.discard_granularity >> 9, 1U);
@ -51,8 +54,11 @@ static struct bio *blk_bio_discard_split(struct request_queue *q,
static struct bio *blk_bio_write_same_split(struct request_queue *q,
struct bio *bio,
struct bio_set *bs)
struct bio_set *bs,
unsigned *nsegs)
{
*nsegs = 1;
if (!q->limits.max_write_same_sectors)
return NULL;
@ -64,7 +70,8 @@ static struct bio *blk_bio_write_same_split(struct request_queue *q,
static struct bio *blk_bio_segment_split(struct request_queue *q,
struct bio *bio,
struct bio_set *bs)
struct bio_set *bs,
unsigned *segs)
{
struct bio_vec bv, bvprv, *bvprvp = NULL;
struct bvec_iter iter;
@ -106,22 +113,30 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
sectors += bv.bv_len >> 9;
}
*segs = nsegs;
return NULL;
split:
*segs = nsegs;
return bio_split(bio, sectors, GFP_NOIO, bs);
}
void blk_queue_split(struct request_queue *q, struct bio **bio,
struct bio_set *bs)
{
struct bio *split;
struct bio *split, *res;
unsigned nsegs;
if ((*bio)->bi_rw & REQ_DISCARD)
split = blk_bio_discard_split(q, *bio, bs);
split = blk_bio_discard_split(q, *bio, bs, &nsegs);
else if ((*bio)->bi_rw & REQ_WRITE_SAME)
split = blk_bio_write_same_split(q, *bio, bs);
split = blk_bio_write_same_split(q, *bio, bs, &nsegs);
else
split = blk_bio_segment_split(q, *bio, q->bio_split);
split = blk_bio_segment_split(q, *bio, q->bio_split, &nsegs);
/* physical segments can be figured out during splitting */
res = split ? split : *bio;
res->bi_phys_segments = nsegs;
bio_set_flag(res, BIO_SEG_VALID);
if (split) {
bio_chain(split, *bio);