Single-page bvec can often be seen in small BS workloads, so introduce bvec_nth_page() for avoiding to call nth_page() unnecessarily, which looks not cheap.
Signed-off-by: Ming Lei <[email protected]> --- block/blk-merge.c | 2 +- include/linux/bvec.h | 11 ++++++++--- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/block/blk-merge.c b/block/blk-merge.c index 066b66430523..c7e8a8273460 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -483,7 +483,7 @@ static unsigned blk_bvec_map_sg(struct request_queue *q, offset = (total + bvec->bv_offset) % PAGE_SIZE; idx = (total + bvec->bv_offset) / PAGE_SIZE; - pg = nth_page(bvec->bv_page, idx); + pg = bvec_nth_page(bvec->bv_page, idx); sg_set_page(*sg, pg, seg_size, offset); diff --git a/include/linux/bvec.h b/include/linux/bvec.h index 30a57b68d017..4376f683c08a 100644 --- a/include/linux/bvec.h +++ b/include/linux/bvec.h @@ -51,6 +51,11 @@ struct bvec_iter_all { unsigned done; }; +static inline struct page *bvec_nth_page(struct page *page, int idx) +{ + return idx == 0 ? page : nth_page(page, idx); +} + /* * various member access, note that bio_data should of course not be used * on highmem page vectors @@ -87,8 +92,8 @@ struct bvec_iter_all { PAGE_SIZE - bvec_iter_offset((bvec), (iter))) #define bvec_iter_page(bvec, iter) \ - nth_page(mp_bvec_iter_page((bvec), (iter)), \ - mp_bvec_iter_page_idx((bvec), (iter))) + bvec_nth_page(mp_bvec_iter_page((bvec), (iter)), \ + mp_bvec_iter_page_idx((bvec), (iter))) #define bvec_iter_bvec(bvec, iter) \ ((struct bio_vec) { \ @@ -171,7 +176,7 @@ static inline void mp_bvec_last_segment(const struct bio_vec *bvec, unsigned total = bvec->bv_offset + bvec->bv_len; unsigned last_page = (total - 1) / PAGE_SIZE; - seg->bv_page = nth_page(bvec->bv_page, last_page); + seg->bv_page = bvec_nth_page(bvec->bv_page, last_page); /* the whole segment is inside the last page */ if (bvec->bv_offset >= last_page * PAGE_SIZE) { -- 2.9.5
