linux-kernel - [PATCH 4.17 210/220] dm: use bio_split() when splitting out the already processed bio

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Date:   Sun,  1 Jul 2018 18:23:54 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Christoph Hellwig <hch@....de>,
        NeilBrown <neilb@...e.com>, Mike Snitzer <snitzer@...hat.com>
Subject: [PATCH 4.17 210/220] dm: use bio_split() when splitting out the already processed bio

4.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mike Snitzer <snitzer@...hat.com>

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@...r.kernel.org # 4.15+, requires removal of '&' before md->queue->bio_split
Reported-by: Christoph Hellwig <hch@....de>
Reviewed-by: NeilBrown <neilb@...e.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/dm.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1582,10 +1582,9 @@ static blk_qc_t __split_and_process_bio(
 				 * 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;