Patch "mm: prevent NR_ISOLATE_* stats from going negative" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

mm: prevent NR_ISOLATE_* stats from going negative

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mm-prevent-nr_isolate_-stats-from-going-negative.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Rabin Vincent <[email protected]>
Date: Thu, 20 Apr 2017 14:37:46 -0700
Subject: mm: prevent NR_ISOLATE_* stats from going negative

From: Rabin Vincent <[email protected]>

commit fc280fe871449ead4bdbd1665fa52c7c01c64765 upstream.

Commit 6afcf8ef0ca0 ("mm, compaction: fix NR_ISOLATED_* stats for pfn based migration") moved the dec_node_page_state() call (along with the page_is_file_cache() call) to after putback_lru_page().

But page_is_file_cache() can change after putback_lru_page() is called, so it should be called before putback_lru_page(), as it was before that patch, to prevent NR_ISOLATE_* stats from going negative.

Without this fix, non-CONFIG_SMP kernels end up hanging in the while(too_many_isolated()) { congestion_wait() } loop in shrink_active_list() due to the negative stats.

Mem-Info:
active_anon:32567 inactive_anon:121 isolated_anon:1 active_file:6066 inactive_file:6639 isolated_file:4294967295

                                                    ^^^^^^^^^^

unevictable:0 dirty:115 writeback:0 unstable:0 slab_reclaimable:2086 slab_unreclaimable:3167 mapped:3398 shmem:18366 pagetables:1145 bounce:0 free:1798 free_pcp:13 free_cma:0

---
 mm/migrate.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -183,9 +183,9 @@ void putback_movable_pages(struct list_h
 			unlock_page(page);
 			put_page(page);
 		} else {
-			putback_lru_page(page);
 			dec_node_page_state(page, NR_ISOLATED_ANON +
 					page_is_file_cache(page));
+			putback_lru_page(page);
 		}
 	}
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/mm-prevent-nr_isolate_-stats-from-going-negative.patch