Btrfs: send, build path string only once in send_hole

There's no point building the path string in each iteration of the
send_hole loop, as it produces always the same string.
Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/send.c

@@ -4436,14 +4436,14 @@ static int send_hole(struct send_ctx *sctx, u64 end)
 	p = fs_path_alloc();
 	if (!p)
 		return -ENOMEM;
+	ret = get_cur_path(sctx, sctx->cur_ino, sctx->cur_inode_gen, p);
+	if (ret < 0)
+		goto tlv_put_failure;
 	memset(sctx->read_buf, 0, BTRFS_SEND_READ_SIZE);
 	while (offset < end) {
 		len = min_t(u64, end - offset, BTRFS_SEND_READ_SIZE);
 
 		ret = begin_cmd(sctx, BTRFS_SEND_C_WRITE);
-		if (ret < 0)
-			break;
-		ret = get_cur_path(sctx, sctx->cur_ino, sctx->cur_inode_gen, p);
 		if (ret < 0)
 			break;
 		TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);