Re: [PATCH v4 01/10] ext4: remove writable userspace mappings before truncating page cache

[Matthew Wilcox]

On Mon, Dec 16, 2024 at 09:39:06AM +0800, Zhang Yi wrote:
>  $mkfs.ext4 -b 1024 /dev/vdb
>  $mount /dev/vdb /mnt
>  $xfs_io -t -f -c "pwrite -S 0x58 0 4096" -c "mmap -rw 0 4096" \
>                -c "mwrite -S 0x5a 2048 2048" -c "fzero 2048 2048" \
>                -c "mwrite -S 0x59 2048 2048" -c "close" /mnt/foo
> 
>  $od -Ax -t x1z /mnt/foo
>  000000 58 58 58 58 58 58 58 58 58 58 58 58 58 58 58 58
>  *
>  000800 59 59 59 59 59 59 59 59 59 59 59 59 59 59 59 59
>  *
>  001000
> 
>  $umount /mnt && mount /dev/vdb /mnt
>  $od -Ax -t x1z /mnt/foo
>  000000 58 58 58 58 58 58 58 58 58 58 58 58 58 58 58 58
>  *
>  000800 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>  *
>  001000

Can you add this to fstests please so we can be sure other filesystems
don't have the same problem?