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From:   Olga Kornievskaia <olga.kornievskaia@gmail.com>
Date:   Thu, 25 Oct 2018 12:00:44 -0400
Message-ID: <CAN-5tyH93_iLCKYazWoLNeFv=jLZiekYsNShwB1dj=HGBcGeuQ@mail.gmail.com>
Subject: Re: [PATCH v1 02/11] VFS permit cross device vfs_copy_file_range
To:     Amir Goldstein <amir73il@gmail.com>
Cc:     Jeff Layton <jlayton@redhat.com>, willy@infradead.org,
        viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org,
        linux-nfs <linux-nfs@vger.kernel.org>, fweimer@redhat.com,
        Steve French <smfrench@gmail.com>,
        "Darrick J. Wong" <darrick.wong@oracle.com>,
        Christoph Hellwig <hch@lst.de>,
        Linux API <linux-api@vger.kernel.org>
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Sender: linux-nfs-owner@vger.kernel.org
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On Thu, Oct 25, 2018 at 11:58 AM Olga Kornievskaia
<olga.kornievskaia@gmail.com> wrote:
>
> On Thu, Oct 25, 2018 at 12:59 AM Amir Goldstein <amir73il@gmail.com> wrote:
> >
> > On Wed, Oct 24, 2018 at 10:59 PM Olga Kornievskaia
> > <olga.kornievskaia@gmail.com> wrote:
> > >
> > [...]
> > > It feels like folks are now ok with either the check being in the
> > > drivers or doing the check in the VFS layer.
> > >
> > > I'm picking the choice of not doing the check in the VFS layer because
> > > it allows for do_splice_direct() by any caller.
> >
> > I'm sorry, but this reasoning in flawed and this is not the reason that
> > Matthew promoted not doing same fs type check in vfs.
>
> I stated the reason why I picked to do the check at the driver layer.
> Looking at your version of the sb type check to be only applied to the
> copy_file_range indeed makes my argument invalid. I was under the
> impression that sb type check was being proposed as a standalone check
> (just like the sb check was standalone). Thus, yes I didn't completely
> understand what you proposed.
>
> > You did not understand the option that I was promoting to begin with.
> > What I suggested was:
> >
> > 1. Remove current same sb check in beginning of vfs_copy_file_range()
> > 2. Check sb && ->clone_file_range
> > 3. Check same sb type && ->copy_file_range
> > 4. Cross fs do_splice_direct()
> >
> > It's fine that you chose not to check for same fs type in VFS before calling
> > copy_file_range() method, but still requires an ACK from Al that he agrees
> > with passing in file * of another filesystem on the interface.
>
> Al, can you please provide a final decision as to which way you would
> prefer for this to be done.
>
> > > I'm about to submit
> > > the new version of the patches (this time I will include the NFS patch
> > > series). We can continue with the discussion on the new version.
> > >
> > > I have added checks for the CIFS and OverlayFS to be consistent with
> > > the previous behavior -- no cross-device copy_offload, I assume if and
> > > when those file systems are ready to make use of it they'll remove the
> > > check.
> > >
> >
> > Actually overlayfs code is "ready" for cross sb copy, but neither nfs nor
> > cifs are supported as upper file system, so it doesn't matter much.
>
> So then the commit statement is still true. When overlayfs will have
> upper file systems that do support it, this check can be removed.

Ops sorry I meant them as questions. Do you feel that commit message
needs to be changed then?
>
> >
> > Thanks,
> > Amir.