linux-kernel - [PATCH] rmap: fix pgoff calculation to handle hugepage correctly

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Message-Id: <1404225982-22739-1-git-send-email-n-horiguchi@ah.jp.nec.com>
Date:	Tue,  1 Jul 2014 10:46:22 -0400
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Hugh Dickins <hughd@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Hillf Danton <dhillf@...il.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Naoya Horiguchi <nao.horiguchi@...il.com>
Subject: [PATCH] rmap: fix pgoff calculation to handle hugepage correctly

I triggered VM_BUG_ON() in vma_address() when I try to migrate an anonymous
hugepage with mbind() in the kernel v3.16-rc3. This is because pgoff's
calculation in rmap_walk_anon() fails to consider compound_order() only to
have an incorrect value. So this patch fixes it.

Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
---
 mm/rmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git v3.16-rc3.orig/mm/rmap.c v3.16-rc3/mm/rmap.c
index b7e94ebbd09e..8cc964c6bd8d 100644
--- v3.16-rc3.orig/mm/rmap.c
+++ v3.16-rc3/mm/rmap.c
@@ -1639,7 +1639,7 @@ static struct anon_vma *rmap_walk_anon_lock(struct page *page,
 static int rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc)
 {
 	struct anon_vma *anon_vma;
-	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
+	pgoff_t pgoff = page->index << compound_order(page);
 	struct anon_vma_chain *avc;
 	int ret = SWAP_AGAIN;
 
-- 
1.9.3

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