dm: use bio_split() when splitting out the already processed bio

Use of bio_clone_bioset() is inefficient if there is no need to clone
the original bio's bio_vec array.  Best to use the bio_clone_fast()
variant.  Also, just using bio_advance() is only part of what is needed
to properly setup the clone -- it doesn't account for the various
bio_integrity() related work that also needs to be performed (see
bio_split).

Address both of these issues by switching from bio_clone_bioset() to
bio_split().

Fixes: 18a25da8 ("dm: ensure bio submission follows a depth-first tree walk")
Cc: stable@vger.kernel.org # 4.15+, requires removal of '&' before md->queue->bio_split
Reported-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index e65429a29c06e2554e8a0e23ba5a0b2a3b18a8c8..a3b103e8e3cef51e4f02d2bc74556fd50bd68672 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1606,10 +1606,9 @@ static blk_qc_t __split_and_process_bio(struct mapped_device *md,
                                 * the usage of io->orig_bio in dm_remap_zone_report()
                                 * won't be affected by this reassignment.
                                 */
-                               struct bio *b = bio_clone_bioset(bio, GFP_NOIO,
-                                                                &md->queue->bio_split);
+                               struct bio *b = bio_split(bio, bio_sectors(bio) - ci.sector_count,
+                                                         GFP_NOIO, &md->queue->bio_split);
                                ci.io->orig_bio = b;
-                               bio_advance(bio, (bio_sectors(bio) - ci.sector_count) << 9);
                                bio_chain(b, bio);
                                ret = generic_make_request(bio);
                                break;