mm: VM_BUG_ON lru page flags

Move scattered VM_BUG_ONs to two essential places that cover all
lru list additions and deletions.

Link: https://lore.kernel.org/linux-mm/20201207220949.830352-8-yuzhao@google.com/
Link: https://lkml.kernel.org/r/20210122220600.906146-8-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@google.com>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mm_inline.h

@@ -66,6 +66,8 @@ static inline enum lru_list page_lru_base_type(struct page *page)
  */
 static __always_inline void __clear_page_lru_flags(struct page *page)
 {
+	VM_BUG_ON_PAGE(!PageLRU(page), page);
+
 	__ClearPageLRU(page);
 
 	/* this shouldn't happen, so leave the flags to bad_page() */
@@ -87,6 +89,8 @@ static __always_inline enum lru_list page_lru(struct page *page)
 {
 	enum lru_list lru;
 
+	VM_BUG_ON_PAGE(PageActive(page) && PageUnevictable(page), page);
+
 	if (PageUnevictable(page))
 		lru = LRU_UNEVICTABLE;
 	else {

mm/swap.c

@@ -83,7 +83,6 @@ static void __page_cache_release(struct page *page)
 		unsigned long flags;
 
 		lruvec = lock_page_lruvec_irqsave(page, &flags);
-		VM_BUG_ON_PAGE(!PageLRU(page), page);
 		del_page_from_lru_list(page, lruvec);
 		__clear_page_lru_flags(page);
 		unlock_page_lruvec_irqrestore(lruvec, flags);
@@ -909,7 +908,6 @@ void release_pages(struct page **pages, int nr)
 			if (prev_lruvec != lruvec)
 				lock_batch = 0;
 
-			VM_BUG_ON_PAGE(!PageLRU(page), page);
 			del_page_from_lru_list(page, lruvec);
 			__clear_page_lru_flags(page);
 		}

mm/vmscan.c

@@ -4281,7 +4281,6 @@ void check_move_unevictable_pages(struct pagevec *pvec)
 
 		lruvec = relock_page_lruvec_irq(page, lruvec);
 		if (page_evictable(page) && PageUnevictable(page)) {
-			VM_BUG_ON_PAGE(PageActive(page), page);
 			del_page_from_lru_list(page, lruvec);
 			ClearPageUnevictable(page);
 			add_page_to_lru_list(page, lruvec);