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

[ Upstream commit 588083bb37a3cea8533c392370a554417c8f29cb ]

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index aac1c98..221762e 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5289,6 +5289,7 @@ static ssize_t memory_high_write(struct kernfs_open_file *of,
                                 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;
 
@@ -5299,6 +5300,11 @@ static ssize_t memory_high_write(struct kernfs_open_file *of,
 
        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);
+
        return nbytes;
 }