[PATCH V10 10/19] block: loop: pass multi-page bvec to iov_iter

[Ming Lei]

iov_iter is implemented with bvec itererator, so it is safe to pass
multipage bvec to it, and this way is much more efficient than
passing one page in each bvec.

Cc: Dave Chinner <dchinner at redhat.com>
Cc: Kent Overstreet <kent.overstreet at gmail.com>
Cc: Mike Snitzer <snitzer at redhat.com>
Cc: dm-devel at redhat.com
Cc: Alexander Viro <viro at zeniv.linux.org.uk>
Cc: linux-fsdevel at vger.kernel.org
Cc: Shaohua Li <shli at kernel.org>
Cc: linux-raid at vger.kernel.org
Cc: linux-erofs at lists.ozlabs.org
Cc: David Sterba <dsterba at suse.com>
Cc: linux-btrfs at vger.kernel.org
Cc: Darrick J. Wong <darrick.wong at oracle.com>
Cc: linux-xfs at vger.kernel.org
Cc: Gao Xiang <gaoxiang25 at huawei.com>
Cc: Christoph Hellwig <hch at lst.de>
Cc: Theodore Ts'o <tytso at mit.edu>
Cc: linux-ext4 at vger.kernel.org
Cc: Coly Li <colyli at suse.de>
Cc: linux-bcache at vger.kernel.org
Cc: Boaz Harrosh <ooo at electrozaur.com>
Cc: Bob Peterson <rpeterso at redhat.com>
Cc: cluster-devel at redhat.com
Signed-off-by: Ming Lei <ming.lei at redhat.com>
---
 drivers/block/loop.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index bf6bc35aaf88..a3fd418ec637 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -515,16 +515,16 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
 	struct bio *bio = rq->bio;
 	struct file *file = lo->lo_backing_file;
 	unsigned int offset;
-	int segments = 0;
+	int nr_bvec = 0;
 	int ret;
 
 	if (rq->bio != rq->biotail) {
-		struct req_iterator iter;
+		struct bvec_iter iter;
 		struct bio_vec tmp;
 
 		__rq_for_each_bio(bio, rq)
-			segments += bio_segments(bio);
-		bvec = kmalloc_array(segments, sizeof(struct bio_vec),
+			nr_bvec += bio_bvecs(bio);
+		bvec = kmalloc_array(nr_bvec, sizeof(struct bio_vec),
 				     GFP_NOIO);
 		if (!bvec)
 			return -EIO;
@@ -533,13 +533,14 @@ 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 bio_for_each_bvec
 		 * API will take care of all details for us.
 		 */
-		rq_for_each_segment(tmp, rq, iter) {
-			*bvec = tmp;
-			bvec++;
-		}
+		__rq_for_each_bio(bio, rq)
+			bio_for_each_bvec(tmp, bio, iter) {
+				*bvec = tmp;
+				bvec++;
+			}
 		bvec = cmd->bvec;
 		offset = 0;
 	} else {
@@ -550,11 +551,11 @@ 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);
+		nr_bvec = bio_bvecs(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