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Date: Fri, 26 Oct 2018 05:54:43 -0700
From: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH v3 11/11] NFS replace cross device with cross filesystem
 check in copy_file_range
Message-ID: <20181026125443.GR25444@bombadil.infradead.org>
References: <20181025215147.36248-1-olga.kornievskaia@gmail.com>
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To: Olga Kornievskaia <olga.kornievskaia@gmail.com>
Cc: trond.myklebust@hammerspace.com, Anna Schumaker <anna.schumaker@netapp.com>, viro@zeniv.linux.org.uk, Steve French <smfrench@gmail.com>, Miklos Szeredi <miklos@szeredi.hu>, linux-nfs <linux-nfs@vger.kernel.org>, linux-fsdevel@vger.kernel.org, linux-cifs@vger.kernel.org, linux-unionfs@vger.kernel.org, linux-man@vger.kernel.org
List-ID: <linux-unionfs@vger.kernel.org>

On Fri, Oct 26, 2018 at 08:45:38AM -0400, Olga Kornievskaia wrote:
> On Thu, Oct 25, 2018 at 6:27 PM Matthew Wilcox <willy@infradead.org> wrote:
> >
> > On Thu, Oct 25, 2018 at 05:51:47PM -0400, Olga Kornievskaia wrote:
> > > -     if (file_in->f_inode->i_sb != file_out->f_inode->i_sb)
> > > +     if (file_in->f_inode->i_sb->s_type != file_out->f_inode->i_sb->s_type)
> >
> > Isn't it simpler to do:
> >
> >         if (file_in->f_inode->i_sb->s_type != &nfs4_fs_type)
> 
> I don't believe that's sufficient. What if "in"  fs was NFS and "out"
> fs was CIFS?

This is the NFS implementation, so you know that 'out' is an NFS file.

> > But now I've done some grepping, and I wonder whether it's possible
> > / desirable to also copy between inodes on a nfs4_remote_fs_type,
> > nfs4_remote_referral_fs_type, nfs4_referral_fs_type or nfs4_xdev_fs_type.
> > I haven't kept up with NFS development for a while, so maybe none of
> > those are possible.
> 
> Thank you for pointing it out. Grepping thru the code, don't believe
> the last one is used but for the migration and replication types, I
> don't know if there are any caveats that would preclude support for
> copy offload I'll check with Chuck Lever. Then the check should be
> that "in" and "out" are any of the 4 NFS types.