FAILED: patch "[PATCH] dm cache metadata: ignore hints array being too small during" failed to apply to 3.18-stable tree

The patch below does not apply to the 3.18-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: Joe Thornber <[email protected]>
Date: Mon, 24 Sep 2018 16:19:30 -0400
Subject: [PATCH] dm cache metadata: ignore hints array being too small during
resize

Commit fd2fa9541 ("dm cache metadata: save in-core policy_hint_size to on-disk superblock") enabled previously written policy hints to be used after a cache is reactivated. But in doing so the cache metadata's hint array was left exposed to out of bounds access because on resize the metadata's on-disk hint array wasn't ever extended.

Fix this by ignoring that there are no on-disk hints associated with the newly added cache blocks. An expanded on-disk hint array is later rewritten upon the next clean shutdown of the cache.

index 69dddeab124c..5936de71883f 100644
@@ -1455,8 +1455,8 @@ static int __load_mappings(struct dm_cache_metadata *cmd,
 		if (hints_valid) {
 			r = dm_array_cursor_next(&cmd->hint_cursor);
 			if (r) {
-				DMERR("dm_array_cursor_next for hint failed");
-				goto out;
+				dm_array_cursor_end(&cmd->hint_cursor);
+				hints_valid = false;
 			}
 		}