Commit 19bfbe22 authored Oct 03, 2017 by Alexandru Moise Committed by Linus Torvalds Oct 03, 2017

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 c3114a84: "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: c3114a84 ("mm: hugetlb: soft-offline: dissolve source hugepage after successful migration")
Signed-off-by: Alexandru Moise <00moses.alexander00@gmail.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: David Rientjes <rientjes@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 4b22927f

mm/madvise.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -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;