Commit f21c601a authored Jun 15, 2018 by Mike Snitzer

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>

parent ce397d21

drivers/md/dm.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -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;

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