Please add 4.17 commit 145e1a71e090575c74969e3daa8136d1e5b99fc8 ("mm: fix the NULL mapping case in __isolate_lru_page()") to the 4.16, 4.14, 4.9, 4.4, 3.18 and 3.2 stable kernel trees.

Two things happened after I'd sent it to Andrew without a stable tag: 1. Ivan posted an equivalent patch: after painstaking bisection, he had found the fixed commit to be what was causing strange blocking (surprising to the rest of us, we had imagined it just suboptimal). 2. The fixed commit arrived in five stable kernel releases (presumably arriving there by auto selection: which will in due course pick up this fix to it, but I don't know its cadence).

Thanks, Hugh

From: Hugh Dickins hughd@google.com Date: Fri, 1 Jun 2018 16:50:50 -0700

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 hughd@google.com Acked-by: Minchan Kim minchan@kernel.org Acked-by: Mel Gorman mgorman@techsingularity.net Reported-by: Ivan Kalvachev ikalvachev@gmail.com Cc: "Huang, Ying" ying.huang@intel.com Cc: Jan Kara jack@suse.cz Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org --- mm/vmscan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c index 9b697323a88c..9270a4370d54 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1418,7 +1418,7 @@ 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;