linux-kernel - Re: [PATCH v12] vfs: fix copy_file_range regression in cross-fs copies

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Date:   Fri, 2 Jul 2021 14:02:08 +0100
From:   Luis Henriques <lhenriques@...e.de>
To:     Amir Goldstein <amir73il@...il.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Nicolas Boichat <drinkcat@...omium.org>,
        Olga Kornievskaia <aglo@...ch.edu>,
        Petr Vorel <pvorel@...e.cz>, Steve French <sfrench@...ba.org>,
        Trond Myklebust <trondmy@...merspace.com>,
        Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
        kernel test robot <oliver.sang@...el.com>
Subject: Re: [PATCH v12] vfs: fix copy_file_range regression in cross-fs
 copies

On Fri, Jul 02, 2021 at 02:12:29PM +0300, Amir Goldstein wrote:
<snip>
> I guess there was miscommunication
> 
> As Olga wrote, you have to place this short-circuit in
> nfs4_copy_file_range() if you remove it from here.
> It is NOT SAFE to pass zero length to nfs4_copy_file_range().
> 
> I apologize if you inferred from my response that you don't need to
> do that.

Yeah, I totally misread your email.  But yeah I understand the issue and
I'll take a look into that.  Although this will need to go back to my TODO
pile for next week.

> My intention was, not knowing if and when your patch will be picked up,
> (a volunteer to pick it pick never showed up...)

Right, and this brings the question that this has been dragging already
for a while now.  And I feel like I'm approaching my last attempt before
giving up.  If no one is picking this patch there's no point continue
wasting more time with it (mine and all the other people helping with
reviews and testing).

Anyway... I'll try to get back to this during next week.

Cheers,
--
Luís

> I think that nfs client developers should make sure that the zero length
> check is added to nfs code as fail safety, because the semantics
> of the vfs method and the NFS protocol command do not match.
> 
> Thanks,
> Amir.