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authorJoe Thornber <ejt@redhat.com>2013-12-13 14:55:55 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-12-20 07:45:11 -0800
commit1cfc4552917a128e0cdf15f57abfe60a30f5eaec (patch)
tree9b247d08e99c49e3d1a3f87b9f861184a139deff /drivers/md
parent20d68d38efd83f2bb598d7b3655a5c230ccc17e8 (diff)
dm array: fix a reference counting bug in shadow_ablock
commit ed9571f0cf1fe09d3506302610f3ccdfa1d22c4a upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/persistent-data/dm-array.c10
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;
}