linux-kernel - [PATCH 2/2] [PATCH] Align faulting address to a hugepage boundary before unmapping

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Date:	Thu, 10 Jul 2008 18:30:41 +0100 (IST)
From:	Mel Gorman <mel@....ul.ie>
To:	akpm@...ux-foundation.org
Cc:	apw@...dowen.org, linux-mm@...ck.org, agl@...ibm.com,
	linux-kernel@...r.kernel.org, Mel Gorman <mel@....ul.ie>
Subject: [PATCH 2/2] [PATCH] Align faulting address to a hugepage boundary before unmapping


When taking a fault for COW on a private mapping it is possible that the
parent will have to steal the original page from its children due to an
insufficient hugepage pool.  In this case, unmap_ref_private() is called
for the faulting address to unmap via unmap_hugepage_range(). This patch
ensures that the address used for unmapping is hugepage-aligned.

Signed-off-by: Mel Gorman <mel@....ul.ie>
---

 mm/hugetlb.c |    1 +
 1 file changed, 1 insertion(+)

diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.26-rc8-mm1-clean/mm/hugetlb.c linux-2.6.26-rc8-mm1-fix-needsreserve-check/mm/hugetlb.c
--- linux-2.6.26-rc8-mm1-clean/mm/hugetlb.c	2008-07-08 11:54:34.000000000 -0700
+++ linux-2.6.26-rc8-mm1-fix-needsreserve-check/mm/hugetlb.c	2008-07-08 15:50:00.000000000 -0700
@@ -1767,6 +1767,7 @@ int unmap_ref_private(struct mm_struct *
 	 * vm_pgoff is in PAGE_SIZE units, hence the different calculation
 	 * from page cache lookup which is in HPAGE_SIZE units.
 	 */
+	address = address & huge_page_mask(hstate_vma(vma));
 	pgoff = ((address - vma->vm_start) >> PAGE_SHIFT)
 		+ (vma->vm_pgoff >> PAGE_SHIFT);
 	mapping = (struct address_space *)page_private(page);
--
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