Add a VM_WARN_ON for tracking. and updated comments for the code.
Thanks
---
>From f1381a1547625a6521777bf9235823d8fbd00dac Mon Sep 17 00:00:00 2001
From: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Date: Fri, 10 Jul 2020 16:54:37 +0800
Subject: [PATCH v16 14/22] mm/thp: add tail pages into lru anyway in
split_huge_page()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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Split_huge_page() must start with PageLRU(head), and we are holding the
lru_lock here. If the head was cleared lru bit unexpected, tracking it.
Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Mika Penttilä <mika.penttila@xxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
mm/huge_memory.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index d866b6e43434..28538444197b 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2348,15 +2348,19 @@ 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), and we are holding the
+ * lru_lock.
+ * Do a warning if the head's lru bit was cleared unexpected.
+ */
+ VM_WARN_ON(!PageLRU(head));
+ SetPageLRU(page_tail);
+ list_add_tail(&page_tail->lru, &head->lru);
}
}
--
1.8.3.1
