[SMB3][PATCH] fix copy_file_range when copying beyond end of source file

[ronnie sahlberg]

Guess we need a fix to the man page.

Reviewed-by: Ronnie Sahlberg <lsahlber at redhat.com>

On Thu, Jun 20, 2019 at 1:19 PM Steve French <smfrench at gmail.com> wrote:
>
> Local file systems that I tried, seem to agree with xfstest and return
> 0 if you try to copy beyond end of src file but do create a zero
> length target file
>
> On Wed, Jun 19, 2019 at 9:14 PM ronnie sahlberg
> <ronniesahlberg at gmail.com> wrote:
> >
> > On Thu, Jun 20, 2019 at 11:45 AM Steve French via samba-technical
> > <samba-technical at lists.samba.org> wrote:
> > >
> > > Patch attached fixes the case where copy_file_range over an SMB3 mount
> > > tries to go beyond the end of file of the source file.  This fixes
> > > xfstests generic/430 and generic/431
> > >
> > > Amir's patches had added a similar change in the VFS layer, but
> > > presumably harmless to have the check in cifs.ko as well to ensure
> > > that we don't try to copy beyond end of the source file (otherwise
> > > SMB3 servers will return an error on copychunk rather than doing the
> > > partial copy (up to end of the source file) that copy_file_range
> > > expects).
> >
> > + if (src_off >= inode->i_size) {
> > + cifs_dbg(FYI, "nothing to do on copychunk\n");
> > + goto cchunk_out; /* nothing to do */
> > + } else if (src_off + len > inode->i_size) {
> > + /* consider adding check to see if src oplocked */
> > + len = inode->i_size - src_off;
> > + cifs_dbg(FYI, "adjust copychunk len %lld less\n", len);
> > + }
> >
> > This makes us return rc == 0 when this triggers. Is that what we want?
> > Looking at "man copy_file_range" suggests we should return -EINVAL in
> > both these cases.
> >
> >
> >
> > >
> > >
> > >
> > > --
> > > Thanks,
> > >
> > > Steve
>
>
>
> --
> Thanks,
>
> Steve