Re: [man-pages RFC PATCH v4] statx, inode: document the new STATX_INO_VERSION field

Jeff Layton
2022-09-09T14:43:43Z

On Fri, 2022-09-09 at 09:48 -0400, Theodore Ts'o wrote:
> On Fri, Sep 09, 2022 at 08:47:17AM -0400, Jeff Layton wrote:
> >
> > i_version only changes now if someone has queried it since it was last
> > changed. That makes a huge difference in performance. We can try to
> > optimize it further, but it probably wouldn't move the needle much under
> > real workloads.
>
> Good point. And to be clear, from NFS's perspective, you only need to
> have i_version bumped if there is a user-visible change to the
> file. --- with an explicit exception here of the FIEMAP system call,
> since in the case of a delayed allocation, FIEMAP might change from
> reporting:
>
> ext: logical_offset: physical_offset: length: expected: flags:
> 0: 0.. 0: 0.. 0: 0: last,unknown_loc,delalloc,eof
>
> to this:
>
> ext: logical_offset: physical_offset: length: expected: flags:
> 0: 0.. 0: 190087172.. 190087172: 1: last,eof
>
> after a sync(2) or fsync(2) call, or after time passes.
>

In general, we want to bump i_version if the ctime changes. I'm guessing
that we don't change ctime on a delalloc? If it's not visible to NFS,
then NFS won't care about it. We can't project FIEMAP info across the
wire at this time, so we'd probably like to avoid seeing an i_version
bump in due to delalloc.

> > Great! That's what I was hoping for with ext4. Would you be willing to
> > pick up these two patches for v6.1?
> >
> > https://lore.kernel.org/linux-ext4/20220908172448.208585-3-jlayton@kernel.org/T/#u
> > https://lore.kernel.org/linux-ext4/20220908172448.208585-4-jlayton@kernel.org/T/#u
>
> I think you mean:
>
> https://lore.kernel.org/linux-ext4/20220908172448.208585-2-jlayton@kernel.org/T/#u
> https://lore.kernel.org/linux-ext4/20220908172448.208585-3-jlayton@kernel.org/T/#u
>
> Right?
>
> BTW, sorry for not responding to these patches earlier; between
> preparing for the various Linux conferences in Dublin next week, and
> being in Zurich and meeting with colleagues at $WORK all of this week,
> I'm a bit behind on my patch reviews.
>

No worries. As long as they're on your radar, that's fine.

Thanks!
--
Jeff Layton <jlayton@kernel.org>