[PATCH 1/4] block: introduce bvec_nth_page()
From: Ming Lei <hidden>
Date: 2019-02-27 12:40:34
Subsystem:
block layer, the rest · Maintainers:
Jens Axboe, Linus Torvalds
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 <redacted> --- 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