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

[Nicolas Boichat]

On Wed, Feb 24, 2021 at 6:44 PM Nicolas Boichat <drinkcat@xxxxxxxxxxxx> wrote:
>
> On Wed, Feb 24, 2021 at 6:22 PM Luis Henriques <lhenriques@xxxxxxx> 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@xxxxxxx> 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@xxxxxxxxxxxx/
> > > > Link: https://lore.kernel.org/linux-fsdevel/CANMq1KDZuxir2LM5jOTm0xx+BnvW=ZmpsG47CyHFJwnw7zSX6Q@xxxxxxxxxxxxxx/
> > > > Link: https://lore.kernel.org/linux-fsdevel/20210126135012.1.If45b7cdc3ff707bc1efa17f5366057d60603c45f@changeid/
> > > > Reported-by: Nicolas Boichat <drinkcat@xxxxxxxxxxxx>
> > > > Signed-off-by: Luis Henriques <lhenriques@xxxxxxx>
> > >
> > > 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@xxxxxxxxxxxx>

What happened to this patch? It does not seem to have been picked up
yet? Any reason why?

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