On Tue, 2008-04-22 at 11:46 +0200, Nick Piggin wrote:
> On Tue, Apr 22, 2008 at 11:42:36AM +0200, Peter Zijlstra wrote:
> > On Fri, 2008-03-28 at 04:00 +0100, Nick Piggin wrote:
> >
> > > +static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
> > > + unsigned long end, int write, struct page **pages, int *nr)
> > > +{
> > > + unsigned long mask, result;
> > > + pte_t *ptep;
> > > +
> > > + result = _PAGE_PRESENT|_PAGE_USER;
> > > + if (write)
> > > + result |= _PAGE_RW;
> > > + mask = result | _PAGE_SPECIAL;
> > > +
> > > + ptep = pte_offset_map(&pmd, addr);
> > > + do {
> > > + /*
> > > + * XXX: careful. On 3-level 32-bit, the pte is 64 bits, and
> > > + * we need to make sure we load the low word first, then the
> > > + * high. This means _PAGE_PRESENT should be clear if the high
> > > + * word was not valid. Currently, the C compiler can issue
> > > + * the loads in any order, and I don't know of a wrapper
> > > + * function that will do this properly, so it is broken on
> > > + * 32-bit 3-level for the moment.
> > > + */
> > > + pte_t pte = *ptep;
> > > + struct page *page;
> > > +
> > > + if ((pte_val(pte) & mask) != result)
> > > + return 0;
> >
> > This return path fails to unmap the pmd.
>
> Ah good catch. As you can see I haven't done any highmem testing ;)
> Which I will do so before sending upstream.
Which will be when? We'd really like to see this in mainline as soon as
possible and in -mm in the meanwhile.
Thanks,
Shaggy
--
David Kleikamp
IBM Linux Technology Center
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