Because of how for_each_bvec() works it never advances across multiple entries at a time, so bvec_iter_advance() is an overkill. Add specialised bvec_iter_advance_single() that is faster. It also handles zero-len bvecs, so can kill bvec_iter_skip_zero_bvec().
text data bss dec hex filename before: 23977 805 0 24782 60ce lib/iov_iter.o before, bvec_iter_advance() w/o WARN_ONCE() 22886 600 0 23486 5bbe ./lib/iov_iter.o after: 21862 600 0 22462 57be lib/iov_iter.o Signed-off-by: Pavel Begunkov <[email protected]> --- include/linux/bvec.h | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/include/linux/bvec.h b/include/linux/bvec.h index 2efec10bf792..4a304dfafa18 100644 --- a/include/linux/bvec.h +++ b/include/linux/bvec.h @@ -121,18 +121,24 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv, return true; } -static inline void bvec_iter_skip_zero_bvec(struct bvec_iter *iter) +static inline void bvec_iter_advance_single(const struct bio_vec *bv, + struct bvec_iter *iter, unsigned int bytes) { - iter->bi_bvec_done = 0; - iter->bi_idx++; + unsigned int done = iter->bi_bvec_done + bytes; + + if (done == bv[iter->bi_idx].bv_len) { + done = 0; + iter->bi_idx++; + } + iter->bi_bvec_done = done; + iter->bi_size -= bytes; } #define for_each_bvec(bvl, bio_vec, iter, start) \ for (iter = (start); \ (iter).bi_size && \ ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \ - (bvl).bv_len ? (void)bvec_iter_advance((bio_vec), &(iter), \ - (bvl).bv_len) : bvec_iter_skip_zero_bvec(&(iter))) + bvec_iter_advance_single((bio_vec), &(iter), (bvl).bv_len)) /* for iterating one bio from start to end */ #define BVEC_ITER_ALL_INIT (struct bvec_iter) \ -- 2.24.0
