From: Mike Kravetz mike.kravetz@oracle.com Subject: mm/hugetlb.c: fix pages per hugetlb calculation

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.

Link: http://lkml.kernel.org/r/20200629185003.97202-1-mike.kravetz@oracle.com Fixes: c0d0381ade79 ("hugetlbfs: use i_mmap_rwsem for more pmd sharing synchronization") Signed-off-by: Mike Kravetz mike.kravetz@oracle.com Reviewed-by: Matthew Wilcox (Oracle) willy@infradead.org Reported-by: Matthew Wilcox (Oracle) willy@infradead.org Cc: Michal Hocko mhocko@kernel.org Cc: "Kirill A . Shutemov" kirill.shutemov@linux.intel.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

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

--- a/mm/hugetlb.c~hugetlb-fix-pages-per-hugetlb-calculation +++ a/mm/hugetlb.c @@ -1593,7 +1593,7 @@ 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; _