On Wed 19-10-16 11:21:52, Ross Zwisler wrote:
> On Wed, Oct 19, 2016 at 09:16:00AM +0200, Jan Kara wrote:
> > > > @@ -2315,26 +2335,17 @@ static int wp_page_shared(struct vm_fault *vmf)
> > > > put_page(vmf->page);
> > > > return tmp;
> > > > }
> > > > - /*
> > > > - * 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)))) {
> > >
> > > The 'tmp' return from finish_mkwrite_fault() can only be 0 or
> > > VM_FAULT_WRITE.
> > > I think this test should just be
> > >
> > > if (unlikely(!tmp)) {
> >
> > Right, finish_mkwrite_fault() cannot currently throw other errors than
> > "retry needed" which is indicated by tmp == 0. However I'd prefer to keep
> > symmetry with finish_fault() handler which can throw other errors and
> > better be prepared to handle them from finish_mkwrite_fault() as well.
>
> Fair enough. You can add:
>
> Reviewed-by: Ross Zwisler <[email protected]>
Thanks. Actually, your question made me have a harder look at return values
from finish_mkwrite_fault() and I've added one more commit switching the
return values so that finish_mkwrite_fault() returns 0 on success and
VM_FAULT_NOPAGE if PTE changed. That is less confusing and even more
consistent with what finish_fault() returns.
Honza
--
Jan Kara <[email protected]>
SUSE Labs, CR
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