linux-kernel - [PATCH] mm/migrate: Split only transparent huge pages when allocation fails

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Date:   Mon, 24 Sep 2018 19:44:55 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     mhocko@...nel.org, akpm@...ux-foundation.org
Subject: [PATCH] mm/migrate: Split only transparent huge pages when allocation fails

When unmap_and_move[_huge_page] function fails due to lack of memory, the
splitting should happen only for transparent huge pages not for HugeTLB
pages. PageTransHuge() returns true for both THP and HugeTLB pages. Hence
the conditonal check should test PagesHuge() flag to make sure that given
pages is not a HugeTLB one.

Fixes: 94723aafb9 ("mm: unclutter THP migration")
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
 mm/migrate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index d6a2e89..d2297fe 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1411,7 +1411,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 				 * we encounter them after the rest of the list
 				 * is processed.
 				 */
-				if (PageTransHuge(page)) {
+				if (PageTransHuge(page) && !PageHuge(page)) {
 					lock_page(page);
 					rc = split_huge_page_to_list(page, from);
 					unlock_page(page);
-- 
2.7.4