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Subject: Re: [PATCH v4 4/9] nfsd: ensure we use ctime_peek to grab the
 inode->i_ctime
From:   Jeff Layton <jlayton@kernel.org>
To:     Christian Brauner <brauner@kernel.org>
Cc:     Chuck Lever III <chuck.lever@oracle.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        "Darrick J. Wong" <djwong@kernel.org>,
        Hugh Dickins <hughd@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Dave Chinner <david@fromorbit.com>, Jan Kara <jack@suse.cz>,
        Amir Goldstein <amir73il@gmail.com>,
        David Howells <dhowells@redhat.com>,
        Neil Brown <neilb@suse.de>,
        Matthew Wilcox <willy@infradead.org>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        Theodore T'so <tytso@mit.edu>, Chris Mason <clm@fb.com>,
        Josef Bacik <josef@toxicpanda.com>,
        David Sterba <dsterba@suse.com>,
        Namjae Jeon <linkinjeon@kernel.org>,
        Steve French <sfrench@samba.org>,
        Sergey Senozhatsky <senozhatsky@chromium.org>,
        Tom Talpey <tom@talpey.com>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
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        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
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Date:   Fri, 19 May 2023 07:22:40 -0400
In-Reply-To: <20230519-zierde-legieren-e769c19a29cb@brauner>
References: <20230518114742.128950-1-jlayton@kernel.org>
         <20230518114742.128950-5-jlayton@kernel.org>
         <2B6A4DDD-0356-4765-9CED-B22A29767254@oracle.com>
         <b046f7e3c86d1c9dd45e932d3f25785fce921f4a.camel@kernel.org>
         <20230519-zierde-legieren-e769c19a29cb@brauner>
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On Fri, 2023-05-19 at 12:36 +0200, Christian Brauner wrote:
> On Thu, May 18, 2023 at 11:31:45AM -0400, Jeff Layton wrote:
> > On Thu, 2023-05-18 at 13:43 +0000, Chuck Lever III wrote:
> > >=20
> > > > On May 18, 2023, at 7:47 AM, Jeff Layton <jlayton@kernel.org> wrote=
:
> > > >=20
> > > > If getattr fails, then nfsd can end up scraping the time values dir=
ectly
> > > > out of the inode for pre and post-op attrs. This may or may not be =
the
> > > > right thing to do, but for now make it at least use ctime_peek in t=
his
> > > > situation to ensure that the QUERIED flag is masked.
> > >=20
> > > That code comes from:
> > >=20
> > > commit 39ca1bf624b6b82cc895b0217889eaaf572a7913
> > > Author:     Amir Goldstein <amir73il@gmail.com>
> > > AuthorDate: Wed Jan 3 17:14:35 2018 +0200
> > > Commit:     J. Bruce Fields <bfields@redhat.com>
> > > CommitDate: Thu Feb 8 13:40:17 2018 -0500
> > >=20
> > >     nfsd: store stat times in fill_pre_wcc() instead of inode times
> > >=20
> > >     The time values in stat and inode may differ for overlayfs and st=
at time
> > >     values are the correct ones to use. This is also consistent with =
the fact
> > >     that fill_post_wcc() also stores stat time values.
> > >=20
> > >     This means introducing a stat call that could fail, where previou=
sly we
> > >     were just copying values out of the inode.  To be conservative ab=
out
> > >     changing behavior, we fall back to copying values out of the inod=
e in
> > >     the error case.  It might be better just to clear fh_pre_saved (t=
hough
> > >     note the BUG_ON in set_change_info).
> > >=20
> > >     Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> > >     Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> > >=20
> > > I was thinking it might have been added to handle odd corner
> > > cases around re-exporting NFS mounts, but that does not seem
> > > to be the case.
> > >=20
> > > The fh_getattr() can fail for legitimate reasons -- like the
> > > file is in the middle of being deleted or renamed over -- I
> > > would think. This code should really deal with that by not
> > > adding pre-op attrs, since they are optional.
> > >=20
> >=20
> > That sounds fine to me. I'll plan to drop this patch from the series an=
d
> > I'll send a separate patch to just remove those branches altogether
> > (which should DTRT).
>=20
> I'll wait with reviewing this until you send the next version then.

I don't have any other big changes queued up. So far, this would just be
the exact same set, without this patch.

FWIW, I'm mostly interested in your review of patches #1 and 2. Is
altering prototype for generic_fillattr, and changing the logic in
current_time the right approach here?

--=20
Jeff Layton <jlayton@kernel.org>