[PATCH 5.7 109/112] mm/hugetlb.c: fix pages per hugetlb calculation

[Greg Kroah-Hartman]

From: Mike Kravetz <mike.kravetz@xxxxxxxxxx>

commit 1139d336fff425f9a20374945cdd28eb44d09fa8 upstream.

The routine hpage_nr_pages() was incorrectly used to calculate the number
of base pages in a hugetlb page.  hpage_nr_pages is designed to be called
for THP pages and will return HPAGE_PMD_NR for hugetlb pages of any size.

Due to the context in which hpage_nr_pages was called, it is unlikely to
produce a user visible error.  The routine with the incorrect call is only
exercised in the case of hugetlb memory error or migration.  In addition,
this would need to be on an architecture which supports huge page sizes
less than PMD_SIZE.  And, the vma containing the huge page would also need
to smaller than PMD_SIZE.

Fixes: c0d0381ade79 ("hugetlbfs: use i_mmap_rwsem for more pmd sharing synchronization")
Reported-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: "Kirill A . Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20200629185003.97202-1-mike.kravetz@xxxxxxxxxx
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 mm/hugetlb.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1594,7 +1594,7 @@ static struct address_space *_get_hugetl
 
 	/* Use first found vma */
 	pgoff_start = page_to_pgoff(hpage);
-	pgoff_end = pgoff_start + hpage_nr_pages(hpage) - 1;
+	pgoff_end = pgoff_start + pages_per_huge_page(page_hstate(hpage)) - 1;
 	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root,
 					pgoff_start, pgoff_end) {
 		struct vm_area_struct *vma = avc->vma;