Patch "mm: fix check for reclaimable pages in PF_MEMALLOC reclaim throttling" 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: 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 <[email protected]> know about it.

From: Johannes Weiner <[email protected]>
Date: Wed, 3 May 2017 14:51:54 -0700
Subject: mm: fix check for reclaimable pages in PF_MEMALLOC reclaim throttling

From: Johannes Weiner <[email protected]>

[ 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.

---
 mm/vmscan.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

@@ -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 [email protected] 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