3.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Joe Thornber <ejt@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/persistent-data/dm-array.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
--- 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
* 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;
}
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