On Wed 16-11-16 01:52:10, Kirill A. Shutemov wrote:
> On Fri, Nov 04, 2016 at 05:25:12AM +0100, Jan Kara wrote:
> > Provide a helper function for finishing write faults due to PTE being
> > read-only. The helper will be used by DAX to avoid the need of
> > complicating generic MM code with DAX locking specifics.
> >
> > Reviewed-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
> > Signed-off-by: Jan Kara <jack@xxxxxxx>
...
> > - /*
> > - * Since we dropped the lock we need to revalidate
> > - * the PTE as someone else may have changed it. If
> > - * they did, we just return, as we can count on the
> > - * MMU to tell us if they didn't also make it writable.
> > - */
> > - vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
> > - vmf->address, &vmf->ptl);
> > - if (!pte_same(*vmf->pte, vmf->orig_pte)) {
> > + tmp = finish_mkwrite_fault(vmf);
> > + if (unlikely(!tmp || (tmp &
> > + (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
>
> Looks like the second part of condition is never true here, right? Not
> that it would matter, having the next patch in the queue.
Yeah, I had the condition like this to handle the standard set of return
values. And as you say, the next patch even makes this condition have a
real effect.
> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Thanks.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
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