linux-ext4 - Re: [PATCH v7 0/9] fs: clean up handling of i

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Date:   Wed, 19 Oct 2022 08:18:15 -0400
From:   Jeff Layton <jlayton@...nel.org>
To:     Christian Brauner <brauner@...nel.org>
Cc:     tytso@....edu, adilger.kernel@...ger.ca, djwong@...nel.org,
        david@...morbit.com, trondmy@...merspace.com, neilb@...e.de,
        viro@...iv.linux.org.uk, zohar@...ux.ibm.com, xiubli@...hat.com,
        chuck.lever@...cle.com, lczerner@...hat.com, jack@...e.cz,
        bfields@...ldses.org, fweimer@...hat.com,
        linux-btrfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, ceph-devel@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-xfs@...r.kernel.org
Subject: Re: [PATCH v7 0/9] fs: clean up handling of i_version counter

On Wed, 2022-10-19 at 13:13 +0200, Christian Brauner wrote:
> On Mon, Oct 17, 2022 at 06:57:00AM -0400, Jeff Layton wrote:
> > This patchset is intended to clean up the handling of the i_version
> > counter by nfsd. Most of the changes are to internal interfaces.
> > 
> > This set is not intended to address crash resilience, or the fact that
> > the counter is bumped before a change and not after. I intend to tackle
> > those in follow-on patchsets.
> > 
> > My intention is to get this series included into linux-next soon, with
> > an eye toward merging most of it during the v6.2 merge window. The last
> > patch in the series is probably not suitable for merge as-is, at least
> > until we sort out the semantics we want to present to userland for it.
> 
> Over the course of the series I struggled a bit - and sorry for losing
> focus - with what i_version is supposed to represent for userspace. So I
> would support not exposing it to userspace before that. But that
> shouldn't affect your other changes iiuc.

Thanks Christian,

It has been a real struggle to nail this down, and yeah I too am not
planning to expose this to userland until we have this much better
defined. Patch #9 is just to give you an idea of what this would
ultimately look like. I intend to re-post the first 8 patches with an
eye toward merge in v6.2, once we've settled on the naming. On that
note...

I believe you had mentioned that you didn't like STATX_CHANGE_ATTR for
the name, and suggested STATX_I_VERSION (or something similar), which I
later shortened to STATX_VERSION.

Dave C. objected to STATX_VERSION, as "version" fields in a struct
usually refer to the version of the struct itself rather than the
version of the thing it describes. It also sort of implies a monotonic
counter, and I'm not ready to require that just yet.

What about STATX_CHANGE for the name (with corresponding names for the
field and other flags)? That drops the redundant "_ATTR" postfix, while
being sufficiently vague to allow for alternative implementations in the
future.

Do you (or anyone else) have other suggestions for a name?
-- 
Jeff Layton <jlayton@...nel.org>