Re: [PATCH] hugetlb: call mmu notifiers on hugepage cow
From: Doug Doan
Date: Fri May 28 2010 - 12:41:26 EST
On 05/28/2010 02:59 AM, Mel Gorman wrote:
On Thu, May 27, 2010 at 01:43:00PM -0700, Doug Doan wrote:
From: Doug Doan<dougd@xxxxxxxx>
When a copy-on-write occurs, we take one of two paths in handle_mm_fault:
through handle_pte_fault for normal pages, or through hugetlb_fault for
huge pages.
In the normal page case, we eventually get to do_wp_page and call mmu
notifiers via ptep_clear_flush_notify. There is no callout to the mmmu
notifiers in the huge page case. This patch fixes that.
Signed-off-by: Doug Doan<dougd@xxxxxxxx>
---
--- mm/hugetlb.c.orig 2010-05-27 13:07:58.569546314 -0700
+++ mm/hugetlb.c 2010-05-26 14:41:06.449296524 -0700
@@ -2345,11 +2345,17 @@ retry_avoidcopy:
ptep = huge_pte_offset(mm, address& huge_page_mask(h));
if (likely(pte_same(huge_ptep_get(ptep), pte))) {
/* Break COW */
+ mmu_notifier_invalidate_range_start(mm,
+ address& huge_page_mask(h),
+ (address& huge_page_mask(h)) + huge_page_size(h));
Should the address not already be aligned?
I'm not seeing where the address was aligned before this point. The code just
above aligns it:
ptep = huge_pte_offset(mm, address& huge_page_mask(h));
if (likely(pte_same(huge_ptep_get(ptep), pte))) {
/* Break COW */
Otherwise, I don't see any problem.
huge_ptep_clear_flush(vma, address, ptep);
set_huge_pte_at(mm, address, ptep,
make_huge_pte(vma, new_page, 1));
/* Make the old page be freed below */
new_page = old_page;
+ mmu_notifier_invalidate_range_end(mm,
+ address& huge_page_mask(h),
+ (address& huge_page_mask(h)) + huge_page_size(h));
}
page_cache_release(new_page);
page_cache_release(old_page);
--
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