mm: hugetlb: fix pgoff computation when unmapping page from vma

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>

1 files changed, 1 insertions, 2 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index ab89d6f382d1..bb7dc405634f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2315,8 +2315,7 @@ static int unmap_ref_private(struct mm_struct *mm, struct vm_area_struct *vma,
          * 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 = (struct address_space *)page_private(page);
 
         /*