Re: [PATCH] mmu_notifier, kvm: Introduce dirty bit tracking in spteand mmu notifier to help KSM dirty bit tracking

From: Andrea Arcangeli
Date: Wed Jun 22 2011 - 19:45:10 EST

On Thu, Jun 23, 2011 at 07:19:06AM +0800, Nai Xia wrote:
> OK, I'll have a try over other workarounds.
> I am not feeling good about need_pte_unmap myself. :-)

The usual way is to check VM_HUGETLB in the caller and to call another
function that doesn't kmap. Casting pmd_t to pte_t isn't really nice
(but hey we're also doing that exceptionally in smaps_pte_range for
THP, but it safe there because we're casting the value of the pmd, not
the pointer to the pmd, so the kmap is done by the pte version of the
caller and not done by the pmd version of the caller).

Is it done for migrate? Surely it's not for swapout ;).

> Thanks for viewing!

You're welcome!

JFYI I'll be offline on vacation for a week, starting tomorrow, so if
I don't answer in the next few days that's the reason but I'll follow
the progress in a week.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at