F2FS_GET_BLOCK_PRE_DIO
if (flag == F2FS_GET_BLOCK_PRE_DIO)
case F2FS_GET_BLOCK_PRE_DIO:
err = f2fs_map_blocks(inode, &map, F2FS_GET_BLOCK_PRE_DIO);
flag = F2FS_GET_BLOCK_PRE_DIO;