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

[Nicolas Boichat]

On Fri, Apr 9, 2021 at 9:50 PM Amir Goldstein <amir73il@xxxxxxxxx> wrote:
>
> 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?

Err, sorry for yet another ping... but it would be good to move
forward with those patches ,-P

Thanks!

> Thanks,
> Amir.