On Thu, Feb 18, 2021 at 5:16 PM Luis Henriques <lhenriq...@suse.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-drink...@chromium.org/
> Link:
> https://lore.kernel.org/linux-fsdevel/CANMq1KDZuxir2LM5jOTm0xx+BnvW=zmpsg47cyhfjwnw7zs...@mail.gmail.com/
> Link:
> https://lore.kernel.org/linux-fsdevel/20210126135012.1.If45b7cdc3ff707bc1efa17f5366057d60603c45f@changeid/
> Reported-by: Nicolas Boichat <drink...@chromium.org>
> Signed-off-by: Luis Henriques <lhenriq...@suse.de>
> ---
> And v5! Sorry. Sure, it makes sense to go through the all the vfs_cfr()
> checks first.
You missed my other comment on v4...
not checking NULL copy_file_range case.
Thanks,
Amir.
