The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f21c601a2bb319ec19eb4562eadc7797d90fd90e Mon Sep 17 00:00:00 2001

From: Mike Snitzer snitzer@redhat.com Date: Fri, 15 Jun 2018 09:35:33 -0400 Subject: [PATCH] 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 e65429a29c06..a3b103e8e3ce 100644 --- 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;