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/disk-io.c b/fs/btrfs/disk-io.c
index 8c63419..6182e54 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1630,6 +1630,7 @@
 				     bool check_ref)
 {
 	struct btrfs_root *root;
+	struct btrfs_path *path;
 	int ret;
 
 	if (location->objectid == BTRFS_ROOT_TREE_OBJECTID)
@@ -1669,8 +1670,14 @@
 	if (ret)
 		goto fail;
 
-	ret = btrfs_find_item(fs_info->tree_root, NULL, BTRFS_ORPHAN_OBJECTID,
+	path = btrfs_alloc_path();
+	if (!path) {
+		ret = -ENOMEM;
+		goto fail;
+	}
+	ret = btrfs_find_item(fs_info->tree_root, path, BTRFS_ORPHAN_OBJECTID,
 			location->objectid, BTRFS_ORPHAN_ITEM_KEY, NULL);
+	btrfs_free_path(path);
 	if (ret < 0)
 		goto fail;
 	if (ret == 0)