hugetlb: Make unmap_ref_private multi-size-aware

[Adam Litke <agl@us.ibm.com>]

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>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 421aee9..070150b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1751,6 +1751,7 @@ 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;
@@ -1760,7 +1761,7 @@ 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);
@@ -1779,7 +1780,7 @@ 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);
 	}
 

-- 
Adam Litke - (agl at us.ibm.com)
IBM Linux Technology Center

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