hugetlb: make unmap_ref_private multi-size-aware

Oops.  Part of the hugetlb private reservation code was not fully
converted to use hstates.

When a huge page must be unmapped from VMAs due to a failed COW,
HPAGE_SIZE is used in the call to unmap_hugepage_range() regardless of
the page size being used.  This works if the VMA is using the default
huge page size.  Otherwise we might unmap too much, too little, or
trigger a BUG_ON.  Rare but serious -- fix it.

Signed-off-by: Adam Litke <agl@us.ibm.com>
Cc: Jon Tollefson <kniht@linux.vnet.ibm.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index d143ab67be4..6058b53dcb8 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1796,6 +1796,7 @@ void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 static int unmap_ref_private(struct mm_struct *mm, struct vm_area_struct *vma,
                                 struct page *page, unsigned long address)
 {
+        struct hstate *h = hstate_vma(vma);
         struct vm_area_struct *iter_vma;
         struct address_space *mapping;
         struct prio_tree_iter iter;
@@ -1805,7 +1806,7 @@ static int unmap_ref_private(struct mm_struct *mm, struct vm_area_struct *vma,
          * vm_pgoff is in PAGE_SIZE units, hence the different calculation
          * from page cache lookup which is in HPAGE_SIZE units.
          */
-        address = address & huge_page_mask(hstate_vma(vma));
+        address = address & huge_page_mask(h);
         pgoff = ((address - vma->vm_start) >> PAGE_SHIFT)
                 + (vma->vm_pgoff >> PAGE_SHIFT);
         mapping = (struct address_space *)page_private(page);
@@ -1824,7 +1825,7 @@ static int unmap_ref_private(struct mm_struct *mm, struct vm_area_struct *vma,
                  */
                 if (!is_vma_resv_set(iter_vma, HPAGE_RESV_OWNER))
                         unmap_hugepage_range(iter_vma,
-                                address, address + HPAGE_SIZE,
+                                address, address + huge_page_size(h),
                                 page);
         }