dm cache metadata: do not allow the data block size to change

The block size for the dm-cache's data device must remained fixed for
the life of the cache.  Disallow any attempt to change the cache's data
block size.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
Cc: stable@vger.kernel.org

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/md/dm-cache-metadata.c b/drivers/md/dm-cache-metadata.c
index 4ead4ba60656..d2899e7eb3aa 100644
--- a/drivers/md/dm-cache-metadata.c
+++ b/drivers/md/dm-cache-metadata.c
@@ -425,6 +425,15 @@ static int __open_metadata(struct dm_cache_metadata *cmd)
 
         disk_super = dm_block_data(sblock);
 
+        /* Verify the data block size hasn't changed */
+        if (le32_to_cpu(disk_super->data_block_size) != cmd->data_block_size) {
+                DMERR("changing the data block size (from %u to %llu) is not supported",
+                      le32_to_cpu(disk_super->data_block_size),
+                      (unsigned long long)cmd->data_block_size);
+                r = -EINVAL;
+                goto bad;
+        }
+
         r = __check_incompat_features(disk_super, cmd);
         if (r < 0)
                 goto bad;