On 2013-10-03 21:33, Christoffer Dall wrote:
On Mon, Sep 23, 2013 at 11:11:07AM +0100, Marc Zyngier wrote:
[...]
>
> +static bool transparent_hugepage_adjust(pfn_t *pfnp, phys_addr_t
*ipap)
> +{
> + pfn_t pfn = *pfnp;
> + gfn_t gfn = *ipap >> PAGE_SHIFT;
> +
> + if (PageTransCompound(pfn_to_page(pfn))) {
> + unsigned long mask;
> + /*
> + * mmu_notifier_retry was successful and we hold
the
> + * mmu_lock here, so the pmd can't become
splitting
> + * from under us, and in turn
> + * __split_huge_page_refcount() can't run from
under
> + * us and we can safely transfer the refcount from
> + * PG_tail to PG_head as we switch the pfn from
tail to
> + * head.
> + */
-ECANTPARSE. Well, I sort of can, but this deserves a clearer
explanation.
> + mask = (PMD_SIZE / PAGE_SIZE) - 1;
mask = PTRS_PER_PMD -1;
> + VM_BUG_ON((gfn & mask) != (pfn & mask));
> + if (pfn & mask) {
> + gfn &= ~mask;
This doesn't seem to be used later on.
> + *ipap &= ~(PMD_SIZE - 1);
*ipap &= ~PMD_MASK;
damn, I trust you too much, you surely meant
*ipap &= PMD_MASK;
right?
Indeed. Just keeping you on your toes ;-)
M.
--
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