linux-kernel - [PATCH] mm/hugetlb: filter out hugetlb pages if HUGEPAGE migration is not supported.

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Message-Id: <20180824063314.21981-1-aneesh.kumar@linux.ibm.com>
Date:   Fri, 24 Aug 2018 12:03:14 +0530
From:   "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
To:     akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        mhocko@...nel.org, mike.kravetz@...cle.com,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Subject: [PATCH] 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;
	}

We do support hugetlb migration ony if the hugetlb pages are at pmd level. Here
we just check for Kernel config. The gigantic page size check is done in
page_huge_active.

Acked-by: Michal Hocko <mhocko@...e.com>
Reported-by: Haren Myneni <haren@...ux.vnet.ibm.com>
CC: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.ibm.com>
---
 mm/memory_hotplug.c | 3 ++-
 mm/page_alloc.c     | 4 ++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 9eea6e809a4e..38d94b703e9d 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -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,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c677c1506d73..b8d91f59b836 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7709,6 +7709,10 @@ 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;
 		}
-- 
2.17.1