f2fs: fix return value of move_data_block()

If f2fs_grab_cache_page() fails, it needs to return -ENOMEM.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/gc.c

@@ -849,8 +849,10 @@ static int move_data_block(struct inode *inode, block_t bidx,
 
 	mpage = f2fs_grab_cache_page(META_MAPPING(fio.sbi),
 					fio.old_blkaddr, false);
-	if (!mpage)
+	if (!mpage) {
+		err = -ENOMEM;
 		goto up_out;
+	}
 
 	fio.encrypted_page = mpage;