From: Jeremy Fitzhardinge on
On 07/09/2010 09:22 AM, Andrea Arcangeli wrote:
> mmu notifier only relevant for userland mappings, not kernel
> mappings. I don't know about the xen use, but for vmalloc certainly it
> can't be a problem to remove those two mmu notifier invalidates.
>
> Only bit that is worrysome is the mm == &init_mm
> pte_alloc_kernel|pte_alloc_map_lock. That seems to imply it may also
> be used to mangle over userland. But apparently all users are passing
> &init_mm as expected. I guess if you remove the mm parameter and you
> default to &init_mm definitely there will be no risk in removing the
> mmu notifier range_start/end invalidates.
>

No, we do have some users which use it on user memory. But those users
are using it as part of their own mmu notifier backend, so the recursive
calls are causing a problem. My point is that anyone using
apply_to_page_range should be making their own calls to mmu notifiers as
appropriate to whatever they're doing.

J

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From: Jeremy Fitzhardinge on
On 07/09/2010 10:36 AM, Andrea Arcangeli wrote:
> I'm not opposed to removing it, I've been wondering if it made any
> sense in the first place but then there was no point not to add
> it. Just calling apply_to_page_range in non blocking context doesn't
> look so good.
>

That's a good point. It should be safe if the pagetable is already
fully populated; I should double-check that's true in our case.

J

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From: Andrea Arcangeli on
On Fri, Jul 09, 2010 at 10:41:51AM -0700, Jeremy Fitzhardinge wrote:
> On 07/09/2010 10:36 AM, Andrea Arcangeli wrote:
> > I'm not opposed to removing it, I've been wondering if it made any
> > sense in the first place but then there was no point not to add
> > it. Just calling apply_to_page_range in non blocking context doesn't
> > look so good.
> >
>
> That's a good point. It should be safe if the pagetable is already
> fully populated; I should double-check that's true in our case.

Yes in that case is safe, but it'd be more strict to use pmd/*_offset
then.
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