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Subject[PATCH v18 05/32] mm/thp: remove code path which never got into
Date
split_huge_page() will never call on a page which isn't on lru list, so
this code never got a chance to run, and should not be run, to add tail
pages on a lru list which head page isn't there.

Although the bug was never triggered, it'better be removed for code
correctness, and add a warn for unexpected calling.

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: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
mm/huge_memory.c | 13 ++-----------
1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 739497770a3d..247f53def87b 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2330,17 +2330,8 @@ static void lru_add_page_tail(struct page *head, struct page *page_tail,
/* page reclaim is reclaiming a huge page */
get_page(page_tail);
list_add_tail(&page_tail->lru, list);
- } else {
- /*
- * Head page has not yet been counted, as an hpage,
- * so we must account for each subpage individually.
- *
- * Put page_tail on the list at the correct position
- * so they all end up in order.
- */
- add_page_to_lru_list_tail(page_tail, lruvec,
- page_lru(page_tail));
- }
+ } else
+ VM_WARN_ON(!PageLRU(head));
}

static void __split_huge_page_tail(struct page *head, int tail,
--
1.8.3.1
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