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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: 57c36519e4 ("dm: fix clone_bio() to trigger blk_recount_segments()")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mike Snitzer 2019-02-05 17:07:58 -05:00
parent 645efa84f6
commit fa8db4948f
1 changed files with 5 additions and 1 deletions
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6
drivers/md/dm.c
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@ -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;
}