Patch "mm: fix check for reclaimable pages in PF_MEMALLOC reclaim throttling" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

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

    mm: fix check for reclaimable pages in PF_MEMALLOC reclaim throttling

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-fix-check-for-reclaimable-pages-in-pf_memalloc-reclaim-throttling.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 <stable@vger.kernel.org> know about it.


>From foo@baz Thu Mar 22 14:40:24 CET 2018
From: Johannes Weiner <hannes@cmpxchg.org>
Date: Wed, 3 May 2017 14:51:54 -0700
Subject: mm: fix check for reclaimable pages in PF_MEMALLOC reclaim throttling

From: Johannes Weiner <hannes@cmpxchg.org>


[ Upstream commit d450abd81b081d45adb12f303a07dd44b15eb1bc ]

PF_MEMALLOC direct reclaimers get throttled on a node when the sum of
all free pages in each zone fall below half the min watermark.  During
the summation, we want to exclude zones that don't have reclaimables.
Checking the same pgdat over and over again doesn't make sense.

Fixes: 599d0c954f91 ("mm, vmscan: move LRU lists to node")
Link: http://lkml.kernel.org/r/20170228214007.5621-3-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Jia He <hejianet@gmail.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 mm/vmscan.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2841,8 +2841,10 @@ static bool allow_direct_reclaim(pg_data
 
 	for (i = 0; i <= ZONE_NORMAL; i++) {
 		zone = &pgdat->node_zones[i];
-		if (!managed_zone(zone) ||
-		    pgdat_reclaimable_pages(pgdat) == 0)
+		if (!managed_zone(zone))
+			continue;
+
+		if (!zone_reclaimable_pages(zone))
 			continue;
 
 		pfmemalloc_reserve += min_wmark_pages(zone);


Patches currently in stable-queue which might be from hannes@cmpxchg.org are

queue-4.9/mm-fix-check-for-reclaimable-pages-in-pf_memalloc-reclaim-throttling.patch
queue-4.9/mm-vmstat-suppress-pcp-stats-for-unpopulated-zones-in-zoneinfo.patch