Re: [PATCH v6 5/9] Documentation: add a new file documenting multigrain timestamps

Jan Kara
2024-07-17T11:31:38Z

On Mon 15-07-24 08:48:56, Jeff Layton wrote:
> Add a high-level document that describes how multigrain timestamps work,
> rationale for them, and some info about implementation and tradeoffs.
>
> Reviewed-by: Josef Bacik <josef@toxicpanda.com>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>

One comment below. With that fixed feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

> +Implementation Notes
> +====================
> +Multigrain timestamps are intended for use by local filesystems that get
> +ctime values from the local clock. This is in contrast to network filesystems
> +and the like that just mirror timestamp values from a server.
> +
> +For most filesystems, it's sufficient to just set the FS_MGTIME flag in the
> +fstype->fs_flags in order to opt-in, providing the ctime is only ever set via
> +inode_set_ctime_current(). If the filesystem has a ->getattr routine that
> +doesn't call generic_fillattr, then you should have it call fill_mg_cmtime to
> +fill those values.

I think you should explicitely mention that ->setattr() implementation
needs to use setattr_copy() or otherwise mimic its behavior...

Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR