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From:   Alex Shi <alex.shi@linux.alibaba.com>
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Subject: [PATCH v16 14/22] mm/thp: add tail pages into lru anyway in split_huge_page()
Date:   Sat, 11 Jul 2020 08:58:48 +0800
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split_huge_page() must start with PageLRU(head), but lru bit *maybe*
cleared by isolate_lru_page, anyway the head still in lru list, since we
still held the lru_lock.

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mika Penttilä <mika.penttila@nextfour.com>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
 mm/huge_memory.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index d866b6e43434..4fe7b92c9330 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2348,15 +2348,18 @@ static void lru_add_page_tail(struct page *head, struct page *page_tail,
 	VM_BUG_ON_PAGE(PageLRU(page_tail), head);
 	lockdep_assert_held(&lruvec_pgdat(lruvec)->lru_lock);
 
-	if (!list)
-		SetPageLRU(page_tail);
-
-	if (likely(PageLRU(head)))
-		list_add_tail(&page_tail->lru, &head->lru);
-	else if (list) {
+	if (list) {
 		/* page reclaim is reclaiming a huge page */
 		get_page(page_tail);
 		list_add_tail(&page_tail->lru, list);
+	} else {
+		/*
+		 * Split start from PageLRU(head), but lru bit maybe cleared
+		 * by isolate_lru_page, but head still in lru list, since we
+		 * held the lru_lock.
+		 */
+		SetPageLRU(page_tail);
+		list_add_tail(&page_tail->lru, &head->lru);
 	}
 }
 
-- 
1.8.3.1