btrfs: fix missing error handling when searching for inode refs during log replay

During log replay, at __add_inode_ref(), when we are searching for inode
ref keys we totally ignore if btrfs_search_slot() returns an error. This
may make a log replay succeed when there was an actual error and leave
some metadata inconsistency in a subvolume tree. Fix this by checking if
an error was returned from btrfs_search_slot() and if so, return it to
the caller.

Fixes: e02119d ("Btrfs: Add a write ahead tree log to optimize synchronous operations")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: fdmanana

fs/btrfs/tree-log.c

@@ -1073,7 +1073,9 @@ static inline int __add_inode_ref(struct btrfs_trans_handle *trans,
 	search_key.type = BTRFS_INODE_REF_KEY;
 	search_key.offset = parent_objectid;
 	ret = btrfs_search_slot(NULL, root, &search_key, path, 0, 0);
-	if (ret == 0) {
+	if (ret < 0) {
+		return ret;
+	} else if (ret == 0) {
 		struct btrfs_inode_ref *victim_ref;
 		unsigned long ptr;
 		unsigned long ptr_end;