From 5eaf1a9e233d61438377f57facb167f8208ba9fd Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 21 Jan 2014 15:49:04 -0800 Subject: [PATCH] mm: thp: turn compound_head() into BUG_ON(!PageTail) in get_huge_page_tail() get_huge_page_tail()->compound_head() looks confusing. Every caller must check PageTail(page), otherwise atomic_inc(&page->_mapcount) is simply wrong if this page is compound-trans-head. Signed-off-by: Oleg Nesterov Cc: Thomas Gleixner Cc: Dave Jones Cc: Darren Hart Cc: Peter Zijlstra Cc: Mel Gorman Acked-by: Andrea Arcangeli Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mm.h | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index f95c71b7c1fd..58202c26c559 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -445,13 +445,12 @@ static inline bool compound_tail_refcounted(struct page *page) static inline void get_huge_page_tail(struct page *page) { /* - * __split_huge_page_refcount() cannot run - * from under us. - * In turn no need of compound_trans_head here. + * __split_huge_page_refcount() cannot run from under us. */ + VM_BUG_ON(!PageTail(page)); VM_BUG_ON(page_mapcount(page) < 0); VM_BUG_ON(atomic_read(&page->_count) != 0); - if (compound_tail_refcounted(compound_head(page))) + if (compound_tail_refcounted(page->first_page)) atomic_inc(&page->_mapcount); } -- 2.30.2