From b968dd7650c8075de1fb74569a736f1daaa4459c Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Fri, 1 Jun 2018 16:50:50 -0700 Subject: [PATCH] mm: fix the NULL mapping case in __isolate_lru_page() commit 145e1a71e090575c74969e3daa8136d1e5b99fc8 upstream. George Boole would have noticed a slight error in 4.16 commit 69d763fc6d3a ("mm: pin address_space before dereferencing it while isolating an LRU page"). Fix it, to match both the comment above it, and the original behaviour. Although anonymous pages are not marked PageDirty at first, we have an old habit of calling SetPageDirty when a page is removed from swap cache: so there's a category of ex-swap pages that are easily migratable, but were inadvertently excluded from compaction's async migration in 4.16. Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1805302014001.12558@eggly.anvils Fixes: 69d763fc6d3a ("mm: pin address_space before dereferencing it while isolating an LRU page") Signed-off-by: Hugh Dickins Acked-by: Minchan Kim Acked-by: Mel Gorman Reported-by: Ivan Kalvachev Cc: "Huang, Ying" Cc: Jan Kara Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/vmscan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 1a581468a9cf..be56e2e1931e 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1451,7 +1451,7 @@ int __isolate_lru_page(struct page *page, isolate_mode_t mode) return ret; mapping = page_mapping(page); - migrate_dirty = mapping && mapping->a_ops->migratepage; + migrate_dirty = !mapping || mapping->a_ops->migratepage; unlock_page(page); if (!migrate_dirty) return ret;