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dm thin: avoid unnecessarily breaking sharing for flushes

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There's no need to break sharing, triggering a copy, for a write that has no
data (i.e. a flush).

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Joe Thornber 2012-07-27 15:08:06 +01:00 committed by Alasdair G Kergon
parent 905386f82d
commit 6004970136
1 changed files with 1 additions and 1 deletions
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2
drivers/md/dm-thin.c
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@ -1315,7 +1315,7 @@ static void process_shared_bio(struct thin_c *tc, struct bio *bio,
if (bio_detain(pool->prison, &key, bio, &cell))
return;
if (bio_data_dir(bio) == WRITE)
if (bio_data_dir(bio) == WRITE && bio->bi_size)
break_sharing(tc, bio, block, &key, lookup_result, cell);
else {
struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;