btrfs: fix leak of path in btrfs_find_item

If btrfs_find_item is called with NULL path it allocates one locally but
does not free it. Affected paths are inserting an orphan item for a file
and for a subvol root.

Move the path allocation to the callers.

CC: <stable@vger.kernel.org> # 3.14+
Fixes: 3f870c289900 ("btrfs: expand btrfs_find_item() to include find_orphan_item functionality")
Signed-off-by: David Sterba <dsterba@suse.cz>
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 9a02da1..5be45c1 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -1257,10 +1257,19 @@
 			      struct btrfs_root *root, u64 offset)
 {
 	int ret;
-	ret = btrfs_find_item(root, NULL, BTRFS_ORPHAN_OBJECTID,
+	struct btrfs_path *path;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	ret = btrfs_find_item(root, path, BTRFS_ORPHAN_OBJECTID,
 			offset, BTRFS_ORPHAN_ITEM_KEY, NULL);
 	if (ret > 0)
 		ret = btrfs_insert_orphan_item(trans, root, offset);
+
+	btrfs_free_path(path);
+
 	return ret;
 }