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

[Naoya Horiguchi]

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@xxxxxxxxxxxxx>
---
 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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