Commit fa8db494 authored Feb 05, 2019 by Mike Snitzer

dm: don't use bio_trim() afterall



bio_trim() has an early return, which makes it _not_ idempotent, if the
offset is 0 and the bio's bi_size already matches the requested size.
Prior to DM, all users of bio_trim() were fine with this.  But DM has
exposed the fact that bio_trim()'s early return is incompatible with a
cloned bio whose integrity payload must be trimmed via
bio_integrity_trim().

Fix this by reverting DM back to doing the equivalent of bio_trim() but
in an idempotent manner (so bio_integrity_trim is always performed).

Follow-on work is needed to assess what benefit bio_trim()'s early
return is providing to its existing callers.

Reported-by: Milan Broz <gmazyland@gmail.com>
Fixes: 57c36519 ("dm: fix clone_bio() to trigger blk_recount_segments()")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

parent 645efa84

drivers/md/dm.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -1336,7 +1336,11 @@ static int clone_bio(struct dm_target_io tio, struct bio bio,
		return r;
		}

		bio_trim(clone, sector - clone->bi_iter.bi_sector, len);
		bio_advance(clone, to_bytes(sector - clone->bi_iter.bi_sector));
		clone->bi_iter.bi_size = to_bytes(len);

		if (bio_integrity(bio))
		bio_integrity_trim(clone);

		return 0;
		}