linux-kernel - [PATCH 4.13 097/160] mm, hugetlb, soft_offline: save compound page order before page migration

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Date:   Tue, 10 Oct 2017 21:50:25 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Alexandru Moise <00moses.alexander00@...il.com>,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        Michal Hocko <mhocko@...e.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Minchan Kim <minchan@...nel.org>,
        Hillf Danton <hdanton@...a.com>, Shaohua Li <shli@...com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        David Rientjes <rientjes@...gle.com>,
        Rik van Riel <riel@...hat.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.13 097/160] mm, hugetlb, soft_offline: save compound page order before page migration

4.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alexandru Moise <00moses.alexander00@...il.com>

commit 19bfbe22f59a207417b2679e7e83c180419c9ec5 upstream.

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@...il.com>
Cc: Anshuman Khandual <khandual@...ux.vnet.ibm.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: Minchan Kim <minchan@...nel.org>
Cc: Hillf Danton <hdanton@...a.com>
Cc: Shaohua Li <shli@...com>
Cc: Mike Rapoport <rppt@...ux.vnet.ibm.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: Mel Gorman <mgorman@...hsingularity.net>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Rik van Riel <riel@...hat.com>
Cc: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 mm/madvise.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -614,18 +614,26 @@ static int madvise_inject_error(int beha
 {
 	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;