linux-kernel - Re: [PATCH] xfs: reinstate the old i_version counter as STATX_CHANGE

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Date:   Wed, 11 Oct 2023 12:12:00 -0700
From:   "Darrick J. Wong" <djwong@...nel.org>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     Chandan Babu R <chandan.babu@...cle.com>,
        Chuck Lever <chuck.lever@...cle.com>,
        linux-nfs@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        brauner@...nel.org
Subject: Re: [PATCH] xfs: reinstate the old i_version counter as
 STATX_CHANGE_COOKIE

On Wed, Oct 11, 2023 at 11:51:08AM -0400, Jeff Layton wrote:
> On Wed, 2023-10-11 at 08:49 -0700, Darrick J. Wong wrote:
> > On Wed, Oct 11, 2023 at 09:09:38AM -0400, Jeff Layton wrote:
> > > On Fri, 2023-09-29 at 14:43 -0400, Jeff Layton wrote:
> > > > The handling of STATX_CHANGE_COOKIE was moved into generic_fillattr in
> > > > commit 0d72b92883c6 (fs: pass the request_mask to generic_fillattr), but
> > > > we didn't account for the fact that xfs doesn't call generic_fillattr at
> > > > all.
> > > > 
> > > > Make XFS report its i_version as the STATX_CHANGE_COOKIE.
> > > > 
> > > > Fixes: 0d72b92883c6 (fs: pass the request_mask to generic_fillattr)
> > > > Signed-off-by: Jeff Layton <jlayton@...nel.org>
> > > > ---
> > > > I had hoped to fix this in a better way with the multigrain patches, but
> > > > it's taking longer than expected (if it even pans out at this point).
> > > > 
> > > > Until then, make sure we use XFS's i_version as the STATX_CHANGE_COOKIE,
> > > > even if it's bumped due to atime updates. Too many invalidations is
> > > > preferable to not enough.
> > > > ---
> > > >  fs/xfs/xfs_iops.c | 5 +++++
> > > >  1 file changed, 5 insertions(+)
> > > > 
> > > > diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> > > > index 1c1e6171209d..2b3b05c28e9e 100644
> > > > --- a/fs/xfs/xfs_iops.c
> > > > +++ b/fs/xfs/xfs_iops.c
> > > > @@ -584,6 +584,11 @@ xfs_vn_getattr(
> > > >  		}
> > > >  	}
> > > >  
> > > > +	if ((request_mask & STATX_CHANGE_COOKIE) && IS_I_VERSION(inode)) {
> > > > +		stat->change_cookie = inode_query_iversion(inode);
> > > > +		stat->result_mask |= STATX_CHANGE_COOKIE;
> > > > +	}
> > > > +
> > > >  	/*
> > > >  	 * Note: If you add another clause to set an attribute flag, please
> > > >  	 * update attributes_mask below.
> > > > 
> > > > ---
> > > > base-commit: df964ce9ef9fea10cf131bf6bad8658fde7956f6
> > > > change-id: 20230929-xfs-iversion-819fa2c18591
> > > > 
> > > > Best regards,
> > > 
> > > Ping?
> > > 
> > > This patch is needed in v6.6 to prevent a regression when serving XFS
> > > via NFSD. I'd prefer this go in via the xfs tree, but let me know if
> > > you need me to get this merged this via a different one.
> > 
> > Oh!   Right, this is needed because the "hide a state in the high bit of
> > tv_nsec" stuff got reverted in -rc3, correct?  So now nfsd needs some
> > way to know that something changed in the file, and better to have too
> > many client invalidations than not enough?  And I guess bumping
> > i_version will keep nfsd sane for now?
> > 
> > If the answers are [yes, yes, yes] then:
> > Reviewed-by: Darrick J. Wong <djwong@...nel.org>
> 
> Yes, yes, and yes. Can you guys shepherd this into mainline?

Chandan, can you queue this (and the other xfs fixes I sent) for -rc6?

--D

> Thanks for the R-b!
> -- 
> Jeff Layton <jlayton@...nel.org>
>