Re: [PATCH v1 02/11] VFS permit cross device vfs_copy_file_range

[Olga Kornievskaia <olga.kornievskaia@gmail.com>]

On Mon, Oct 22, 2018 at 3:06 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Mon, Oct 22, 2018 at 02:45:04PM -0400, Olga Kornievskaia wrote:
> > On Sat, Oct 20, 2018 at 4:54 AM Amir Goldstein <amir73il@gmail.com> wrote:
> > > Another thing is the commit message claims to:
> > > "Allow copy_file_range to copy between different superblocks but only
> > > of the same file system types"
> > >
> > > But what the patch actually does is:
> > > "Allow copy_file_range() syscall to copy between different filesystems
> > > AND allow calling the filesystems' copy_file_range() method
> > > between different superblocks but only of the same file system types"
> > >
> > > It's probably OK and quite useful to do the former, but maybe man page
> > > should be fixed to explicitly mention that the copy is expected to work
> > > across filesystems since kernel version XXX (?)
> > >
> > > If you don't wish to change cross filesystem type behavior and only
> > > relax cross super block limitation, then you should replace the
> > > same inode->i_sb check above with same inode->i_sb->s_type
> > > check instead of doing the check only for calling the filesystem
> > > copy_file_range() method.
> >
> > Thank you for the feedback. In the next version, I will remove the
> > check for the functions and instead check for the same file system
> > types.
>
> Jeff and I agree that this is the wrong way to go.  Instead, the
> cross-device check should be in the individual instances, not the top
> level code.

So remove the check all together for the VFS (that was my original
patch to begin with (like #1 not this one). So am I missing the point
again, I keep getting different corrections every time.