[PATCH v7 12/13] ext4: switch to multigrain timestamps

[Xi Ruoyao]

On Mon, 2023-08-07 at 15:38 -0400, Jeff Layton wrote:
> Enable multigrain timestamps, which should ensure that there is an
> apparent change to the timestamp whenever it has been written after
> being actively observed via getattr.
> 
> For ext4, we only need to enable the FS_MGTIME flag.

Hi Jeff,

This patch causes a gnulib test failure:

$ ~/sources/lfs/grep-3.11/gnulib-tests/test-stat-time
test-stat-time.c:141: assertion 'statinfo[0].st_mtime < statinfo[2].st_mtime || (statinfo[0].st_mtime == statinfo[2].st_mtime && (get_stat_mtime_ns (&statinfo[0]) < get_stat_mtime_ns (&statinfo[2])))' failed
Aborted (core dumped)

The source code of the test:
https://git.savannah.gnu.org/cgit/gnulib.git/tree/tests/test-stat-time.c

Is this an expected change?

> Acked-by: Theodore Ts'o <tytso at mit.edu>
> Reviewed-by: Jan Kara <jack at suse.cz>
> Signed-off-by: Jeff Layton <jlayton at kernel.org>
> ---
>  fs/ext4/super.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index b54c70e1a74e..cb1ff47af156 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -7279,7 +7279,7 @@ static struct file_system_type ext4_fs_type = {
>  	.init_fs_context	= ext4_init_fs_context,
>  	.parameters		= ext4_param_specs,
>  	.kill_sb		= kill_block_super,
> -	.fs_flags		= FS_REQUIRES_DEV | FS_ALLOW_IDMAP,
> +	.fs_flags		= FS_REQUIRES_DEV | FS_ALLOW_IDMAP |
> FS_MGTIME,
>  };
>  MODULE_ALIAS_FS("ext4");
>  
>