From 19bfbe22f59a207417b2679e7e83c180419c9ec5 Mon Sep 17 00:00:00 2001 From: Alexandru Moise <00moses.alexander00@gmail.com> Date: Tue, 3 Oct 2017 16:14:31 -0700 Subject: [PATCH] mm, hugetlb, soft_offline: save compound page order before page migration This fixes a bug in madvise() where if you'd try to soft offline a hugepage via madvise(), while walking the address range you'd end up, using the wrong page offset due to attempting to get the compound order of a former but presently not compound page, due to dissolving the huge page (since commit c3114a84f7f9: "mm: hugetlb: soft-offline: dissolve source hugepage after successful migration"). As a result I ended up with all my free pages except one being offlined. Link: http://lkml.kernel.org/r/20170912204306.GA12053@gmail.com Fixes: c3114a84f7f9 ("mm: hugetlb: soft-offline: dissolve source hugepage after successful migration") Signed-off-by: Alexandru Moise <00moses.alexander00@gmail.com> Cc: Anshuman Khandual Cc: Michal Hocko Cc: Andrea Arcangeli Cc: Minchan Kim Cc: Hillf Danton Cc: Shaohua Li Cc: Mike Rapoport Cc: "Kirill A. Shutemov" Cc: Mel Gorman Cc: David Rientjes Cc: Rik van Riel Cc: Naoya Horiguchi Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/madvise.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index 21261ff0466f..25bade36e9ca 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -625,18 +625,26 @@ static int madvise_inject_error(int behavior, { struct page *page; struct zone *zone; + unsigned int order; if (!capable(CAP_SYS_ADMIN)) return -EPERM; - for (; start < end; start += PAGE_SIZE << - compound_order(compound_head(page))) { + + for (; start < end; start += PAGE_SIZE << order) { int ret; ret = get_user_pages_fast(start, 1, 0, &page); if (ret != 1) return ret; + /* + * When soft offlining hugepages, after migrating the page + * we dissolve it, therefore in the second loop "page" will + * no longer be a compound page, and order will be 0. + */ + order = compound_order(compound_head(page)); + if (PageHWPoison(page)) { put_page(page); continue; -- 2.20.1