ext4: fix invalid inode checksum

stable inclusion
from linux-4.19.155
commit 7b97149296ef752a1576d0939f629dd30e83e03d

--------------------------------

commit 13221811 upstream.

During the stability test, there are some errors:
  ext4_lookup:1590: inode #6967: comm fsstress: iget: checksum invalid.

If the inode->i_iblocks too big and doesn't set huge file flag, checksum
will not be recalculated when update the inode information to it's buffer.
If other inode marks the buffer dirty, then the inconsistent inode will
be flushed to disk.

Fix this problem by checking i_blocks in advance.

Cc: stable@kernel.org
Signed-off-by: Luo Meng <luomeng12@huawei.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Link: https://lore.kernel.org/r/20201020013631.3796673-1-luomeng12@huawei.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>