[ 116/147] mm: hugetlb: fix pgoff computation when unmapping page from vma

Ben Hutchings
2012-10-14T15:06:43Z

From: Hillf Danton <dhillf@gmail.com>

commit 0c176d52b0b2619f231b2bbf329b90c028134f58 upstream.

The computation for pgoff is incorrect, at least with

(vma->vm_pgoff >> PAGE_SHIFT)

involved. It is fixed with the available method if HPAGE_SIZE is
concerned in page cache lookup.

[akpm@linux-foundation.org: use vma_hugecache_offset() directly, per Michal]
Signed-off-by: Hillf Danton <dhillf@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Michal Hocko <mhocko@suse.cz>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
mm/hugetlb.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2429,8 +2429,7 @@ static int unmap_ref_private(struct mm_s
* from page cache lookup which is in HPAGE_SIZE units.
*/
address = address & huge_page_mask(h);
- pgoff = ((address - vma->vm_start) >> PAGE_SHIFT)
- + (vma->vm_pgoff >> PAGE_SHIFT);
+ pgoff = vma_hugecache_offset(h, vma, address);
mapping = vma->vm_file->f_dentry->d_inode->i_mapping;

/*