[PATCH] hugetlb: call mmu notifiers on hugepage cow

[Doug Doan <dougd@cray.com>]

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From: Doug Doan <dougd@cray.com>

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@cray.com>
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--- 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));
 		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);