Ming Lei <ming....@canonical.com> writes:
> 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.
>
> Signed-off-by: Ming Lei <ming....@canonical.com>
Reviewed-by: Jeff Moyer <jmo...@redhat.com>
> ---
> block/blk-merge.c | 29 ++++++++++++++++++++++-------
> 1 file changed, 22 insertions(+), 7 deletions(-)
>
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index c4e9c37..22293fd 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -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 @@ new_segment:
> 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);
--
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