[PATCH v17 15/21] mm/thp: add tail pages into lru anyway in split_huge_page()

Alex Shi
2020-07-25T13:00:52Z

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@linux.alibaba.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.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 | 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