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

BugLink: http://bugs.launchpad.net/bugs/1807469
commit f21c601a2bb319ec19eb4562eadc7797d90fd90e upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 437b26488b0ef3059e84a9313701d08ee798a43f..6ce83e619663fcdbe6d4501a89f48580feb72742 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1513,10 +1513,9 @@ static void __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);
                                generic_make_request(bio);
                                break;