Patch "mm: memcontrol: reclaim when shrinking memory.high below usage" has been added to the 4.4-stable tree

Patch "mm: memcontrol: reclaim when shrinking memory.high below usage" has been added to the 4.4-stable tree

[gregkh]

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

    mm: memcontrol: reclaim when shrinking memory.high below usage

to the 4.4-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-memcontrol-reclaim-when-shrinking-memory.high-below-usage.patch
and it can be found in the queue-4.4 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 588083bb37a3cea8533c392370a554417c8f29cb Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@cmpxchg.org>
Date: Thu, 17 Mar 2016 14:20:25 -0700
Subject: mm: memcontrol: reclaim when shrinking memory.high below usage

From: Johannes Weiner <hannes@cmpxchg.org>

commit 588083bb37a3cea8533c392370a554417c8f29cb upstream.

When setting memory.high below usage, nothing happens until the next
charge comes along, and then it will only reclaim its own charge and not
the now potentially huge excess of the new memory.high.  This can cause
groups to stay in excess of their memory.high indefinitely.

To fix that, when shrinking memory.high, kick off a reclaim cycle that
goes after the delta.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 mm/memcontrol.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5121,6 +5121,7 @@ static ssize_t memory_high_write(struct
 				 char *buf, size_t nbytes, loff_t off)
 {
 	struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
+	unsigned long nr_pages;
 	unsigned long high;
 	int err;
 
@@ -5131,6 +5132,11 @@ static ssize_t memory_high_write(struct
 
 	memcg->high = high;
 
+	nr_pages = page_counter_read(&memcg->memory);
+	if (nr_pages > high)
+		try_to_free_mem_cgroup_pages(memcg, nr_pages - high,
+					     GFP_KERNEL, true);
+
 	memcg_wb_domain_size_changed(memcg);
 	return nbytes;
 }


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

queue-4.4/mm-memcontrol-reclaim-when-shrinking-memory.high-below-usage.patch
queue-4.4/mm-memcontrol-reclaim-and-oom-kill-when-shrinking-memory.max-below-usage.patch