dm cache: fix NULL pointer when switching from cleaner policy

[ Upstream commit 2bffa1503c5c06192eb1459180fac4416575a966 ]

The cleaner policy doesn't make use of the per cache block hint space in
the metadata (unlike the other policies).  When switching from the
cleaner policy to mq or smq a NULL pointer crash (in dm_tm_new_block)
was observed.  The crash was caused by bugs in dm-cache-metadata.c
when trying to skip creation of the hint btree.

The minimal fix is to change hint size for the cleaner policy to 4 bytes
(only hint size supported).

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

diff --git a/drivers/md/dm-cache-policy-cleaner.c b/drivers/md/dm-cache-policy-cleaner.c
index b04d1f904d0763c43870e38c857fcd25baad4b7e..2eca9084defeea717ed7ee3f2be6f96e64039cd3 100644 (file)
--- a/drivers/md/dm-cache-policy-cleaner.c
+++ b/drivers/md/dm-cache-policy-cleaner.c
@@ -434,7 +434,7 @@ static struct dm_cache_policy *wb_create(dm_cblock_t cache_size,
 static struct dm_cache_policy_type wb_policy_type = {
        .name = "cleaner",
        .version = {1, 0, 0},
-       .hint_size = 0,
+       .hint_size = 4,
        .owner = THIS_MODULE,
        .create = wb_create
 };