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

[Amir Goldstein]

On Fri, Apr 9, 2021 at 4:39 PM Luis Henriques <lhenriques@xxxxxxx> wrote:
>
> Nicolas Boichat <drinkcat@xxxxxxxxxxxx> writes:
>
> > 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?
>
> Hmm... good question.  I'm not actually sure who would be picking it.  Al,
> maybe...?
>

Darrick,

Would you mind taking this through your tree in case Al doesn't pick it up?

Thanks,
Amir.