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| author | Joe Thornber <ejt@redhat.com> | 2013-12-13 14:55:55 +0000 |
|---|---|---|
| committer | Mike Snitzer <snitzer@redhat.com> | 2013-12-13 14:22:10 -0500 |
| commit | ed9571f0cf1fe09d3506302610f3ccdfa1d22c4a (patch) | |
| tree | ec013b939d466fbd06d3c62a5a0de5ca9e5a3ae1 | |
| parent | 5b564d80f8bc21094c0cd2b19b679d983aabcc29 (diff) | |
| download | lwn-ed9571f0cf1fe09d3506302610f3ccdfa1d22c4a.tar.gz lwn-ed9571f0cf1fe09d3506302610f3ccdfa1d22c4a.zip | |
dm array: fix a reference counting bug in shadow_ablock
An old array block could have its reference count decremented below
zero when it is being replaced in the btree by a new array block.
The fix is to increment the old ablock's reference count just before
inserting a new ablock into the btree.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 3.9+
| -rw-r--r-- | drivers/md/persistent-data/dm-array.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/drivers/md/persistent-data/dm-array.c b/drivers/md/persistent-data/dm-array.c index af96e24ec328..1d75b1dc1e2e 100644 --- a/drivers/md/persistent-data/dm-array.c +++ b/drivers/md/persistent-data/dm-array.c @@ -317,8 +317,16 @@ static int shadow_ablock(struct dm_array_info *info, dm_block_t *root, * The shadow op will often be a noop. Only insert if it really * copied data. */ - if (dm_block_location(*block) != b) + if (dm_block_location(*block) != b) { + /* + * dm_tm_shadow_block will have already decremented the old + * block, but it is still referenced by the btree. We + * increment to stop the insert decrementing it below zero + * when overwriting the old value. + */ + dm_tm_inc(info->btree_info.tm, b); r = insert_ablock(info, index, *block, root); + } return r; } |