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.
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