linux-kernel - Re: [PATCH v8] vfs: fix copy_file_range regression in cross-fs copies

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Message-ID: <8735vzfugn.fsf@suse.de>
Date:   Fri, 09 Apr 2021 14:39:20 +0100
From:   Luis Henriques <lhenriques@...e.de>
To:     Nicolas Boichat <drinkcat@...omium.org>
Cc:     Olga Kornievskaia <aglo@...ch.edu>,
        Amir Goldstein <amir73il@...il.com>,
        Jeff Layton <jlayton@...nel.org>,
        Steve French <sfrench@...ba.org>,
        Miklos Szeredi <miklos@...redi.hu>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Dave Chinner <dchinner@...hat.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Ian Lance Taylor <iant@...gle.com>,
        Luis Lozano <llozano@...omium.org>,
        Andreas Dilger <adilger@...ger.ca>,
        Christoph Hellwig <hch@...radead.org>,
        ceph-devel <ceph-devel@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        CIFS <linux-cifs@...r.kernel.org>,
        samba-technical <samba-technical@...ts.samba.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-nfs <linux-nfs@...r.kernel.org>
Subject: Re: [PATCH v8] vfs: fix copy_file_range regression in cross-fs copies

Nicolas Boichat <drinkcat@...omium.org> writes:

> On Wed, Feb 24, 2021 at 6:44 PM Nicolas Boichat <drinkcat@...omium.org> wrote:
>>
>> On Wed, Feb 24, 2021 at 6:22 PM Luis Henriques <lhenriques@...e.de> wrote:
>> >
>> > On Tue, Feb 23, 2021 at 08:00:54PM -0500, Olga Kornievskaia wrote:
>> > > On Mon, Feb 22, 2021 at 5:25 AM Luis Henriques <lhenriques@...e.de> wrote:
>> > > >
>> > > > A regression has been reported by Nicolas Boichat, found while using the
>> > > > copy_file_range syscall to copy a tracefs file.  Before commit
>> > > > 5dae222a5ff0 ("vfs: allow copy_file_range to copy across devices") the
>> > > > kernel would return -EXDEV to userspace when trying to copy a file across
>> > > > different filesystems.  After this commit, the syscall doesn't fail anymore
>> > > > and instead returns zero (zero bytes copied), as this file's content is
>> > > > generated on-the-fly and thus reports a size of zero.
>> > > >
>> > > > This patch restores some cross-filesystem copy restrictions that existed
>> > > > prior to commit 5dae222a5ff0 ("vfs: allow copy_file_range to copy across
>> > > > devices").  Filesystems are still allowed to fall-back to the VFS
>> > > > generic_copy_file_range() implementation, but that has now to be done
>> > > > explicitly.
>> > > >
>> > > > nfsd is also modified to fall-back into generic_copy_file_range() in case
>> > > > vfs_copy_file_range() fails with -EOPNOTSUPP or -EXDEV.
>> > > >
>> > > > Fixes: 5dae222a5ff0 ("vfs: allow copy_file_range to copy across devices")
>> > > > Link: https://lore.kernel.org/linux-fsdevel/20210212044405.4120619-1-drinkcat@chromium.org/
>> > > > Link: https://lore.kernel.org/linux-fsdevel/CANMq1KDZuxir2LM5jOTm0xx+BnvW=ZmpsG47CyHFJwnw7zSX6Q@mail.gmail.com/
>> > > > Link: https://lore.kernel.org/linux-fsdevel/20210126135012.1.If45b7cdc3ff707bc1efa17f5366057d60603c45f@changeid/
>> > > > Reported-by: Nicolas Boichat <drinkcat@...omium.org>
>> > > > Signed-off-by: Luis Henriques <lhenriques@...e.de>
>> > >
>> > > I tested v8 and I believe it works for NFS.
>> >
>> > Thanks a lot for the testing.  And to everyone else for reviews,
>> > feedback,... and patience.
>>
>> Thanks so much to you!!!
>>
>> Works here, you can add my
>> Tested-by: Nicolas Boichat <drinkcat@...omium.org>
>
> What happened to this patch? It does not seem to have been picked up
> yet? Any reason why?

Hmm... good question.  I'm not actually sure who would be picking it.  Al,
maybe...?

Cheers,
-- 
Luis

>
>> >
>> > I'll now go look into the manpage and see what needs to be changed.
>> >
>> > Cheers,
>> > --
>> > Luís