hugetlb: do not use vma_hugecache_offset() for vma_prio_tree_foreach

Commit 0c176d52b0b2 ("mm: hugetlb: fix pgoff computation when unmapping
page from vma") fixed pgoff calculation but it has replaced it by
vma_hugecache_offset() which is not approapriate for offsets used for
vma_prio_tree_foreach() because that one expects index in page units
rather than in huge_page_shift.

Johannes said:

: The resulting index may not be too big, but it can be too small: assume
: hpage size of 2M and the address to unmap to be 0x200000.  This is regular
: page index 512 and hpage index 1.  If you have a VMA that maps the file
: only starting at the second huge page, that VMAs vm_pgoff will be 512 but
: you ask for offset 1 and miss it even though it does map the page of
: interest.  hugetlb_cow() will try to unmap, miss the vma, and retry the
: cow until the allocation succeeds or the skipped vma(s) go away.

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Hillf Danton <dhillf@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 8536741f069b..de5d1dcf34fe 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2480,7 +2480,8 @@ 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 = vma_hugecache_offset(h, vma, address);
+        pgoff = ((address - vma->vm_start) >> PAGE_SHIFT) +
+                        vma->vm_pgoff;
         mapping = vma->vm_file->f_dentry->d_inode->i_mapping;
 
         /*