Re: [PATCH v3 1/7] iversion: update comments with info about atime updates

J. Bruce Fields
2022-08-30T18:32:53Z

On Tue, Aug 30, 2022 at 01:02:50PM -0400, Jeff Layton wrote:
> The fact that NFS kept this more loosely-defined is what allowed us to
> elide some of the i_version bumps and regain a fair bit of performance
> for local filesystems [1]. If the change attribute had been more
> strictly defined like you mention, then that particular optimization
> would not have been possible.
>
> This sort of thing is why I'm a fan of not defining this any more
> strictly than we require. Later on, maybe we'll come up with a way for
> filesystems to advertise that they can offer stronger guarantees.

Yeah, the afs change-attribute-as-counter thing seems ambitious--I
wouldn't even know how to define what exactly you're counting.

My one question is whether it'd be worth just defining the thing as
*increasing*. That's a lower bar.

(Though admittedly we don't quite manage it now--see again 1631087ba872
"Revert "nfsd4: support change_attr_type attribute"".)

--b.