Commit 464c7ffb authored Sep 04, 2018 by Aneesh Kumar K.V Committed by Linus Torvalds Sep 04, 2018

mm/hugetlb: filter out hugetlb pages if HUGEPAGE migration is not supported.

When scanning for movable pages, filter out Hugetlb pages if hugepage
migration is not supported.  Without this we hit infinte loop in
__offline_pages() where we do

	pfn = scan_movable_pages(start_pfn, end_pfn);
	if (pfn) { /* We have movable pages */
		ret = do_migrate_range(pfn, end_pfn);
		goto repeat;
	}

Fix this by checking hugepage_migration_supported both in
has_unmovable_pages which is the primary backoff mechanism for page
offlining and for consistency reasons also into scan_movable_pages
because it doesn't make any sense to return a pfn to non-migrateable
huge page.

This issue was revealed by, but not caused by 72b39cfc ("mm,
memory_hotplug: do not fail offlining too early").

Link: http://lkml.kernel.org/r/20180824063314.21981-1-aneesh.kumar@linux.ibm.com


Fixes: 72b39cfc ("mm, memory_hotplug: do not fail offlining too early")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reported-by: Haren Myneni <haren@linux.vnet.ibm.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: 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 04b8e946

mm/memory_hotplug.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -1333,7 +1333,8 @@ static unsigned long scan_movable_pages(unsigned long start, unsigned long end)
		if (__PageMovable(page))
		return pfn;
		if (PageHuge(page)) {
		if (page_huge_active(page))
		if (hugepage_migration_supported(page_hstate(page)) &&
		page_huge_active(page))
		return pfn;
		else
		pfn = round_up(pfn + 1,

mm/page_alloc.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -7708,6 +7708,10 @@ bool has_unmovable_pages(struct zone zone, struct page page, int count,
		* handle each tail page individually in migration.
		*/
		if (PageHuge(page)) {

		if (!hugepage_migration_supported(page_hstate(page)))
		goto unmovable;

		iter = round_up(iter + 1, 1<<compound_order(page)) - 1;
		continue;
		}

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