[PATCH V13 12/19] block: loop: pass multi-page bvec to iov_iter
From: Ming Lei <hidden>
Date: 2019-01-11 11:01:20
Also in:
dm-devel, linux-bcache, linux-block, linux-btrfs, linux-ext4, linux-fsdevel, linux-mm, linux-xfs, lkml
Subsystem:
block layer, the rest · Maintainers:
Jens Axboe, Linus Torvalds
iov_iter is implemented on bvec itererator helpers, so it is safe to pass multi-page bvec to it, and this way is much more efficient than passing one page in each bvec. Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Omar Sandoval <redacted> Signed-off-by: Ming Lei <redacted> --- drivers/block/loop.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index b8a0720d3653..28dd22c6f83f 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c@@ -511,21 +511,22 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, loff_t pos, bool rw) { struct iov_iter iter; + struct req_iterator rq_iter; struct bio_vec *bvec; struct request *rq = blk_mq_rq_from_pdu(cmd); struct bio *bio = rq->bio; struct file *file = lo->lo_backing_file; + struct bio_vec tmp; unsigned int offset; - int segments = 0; + int nr_bvec = 0; int ret; + rq_for_each_bvec(tmp, rq, rq_iter) + nr_bvec++; + if (rq->bio != rq->biotail) { - struct req_iterator iter; - struct bio_vec tmp; - __rq_for_each_bio(bio, rq) - segments += bio_segments(bio); - bvec = kmalloc_array(segments, sizeof(struct bio_vec), + bvec = kmalloc_array(nr_bvec, sizeof(struct bio_vec), GFP_NOIO); if (!bvec) return -EIO;
@@ -534,10 +535,10 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, /* * The bios of the request may be started from the middle of * the 'bvec' because of bio splitting, so we can't directly - * copy bio->bi_iov_vec to new bvec. The rq_for_each_segment + * copy bio->bi_iov_vec to new bvec. The rq_for_each_bvec * API will take care of all details for us. */ - rq_for_each_segment(tmp, rq, iter) { + rq_for_each_bvec(tmp, rq, rq_iter) { *bvec = tmp; bvec++; }
@@ -551,11 +552,10 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, */ offset = bio->bi_iter.bi_bvec_done; bvec = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter); - segments = bio_segments(bio); } atomic_set(&cmd->ref, 2); - iov_iter_bvec(&iter, rw, bvec, segments, blk_rq_bytes(rq)); + iov_iter_bvec(&iter, rw, bvec, nr_bvec, blk_rq_bytes(rq)); iter.iov_offset = offset; cmd->iocb.ki_pos = pos;
--
2.9.5