memcg: show real limit under hierarchy mode

Show "real" limit of memcg.  This helps my debugging and maybe useful for
users.

While testing hierarchy like this

	mount -t cgroup none /cgroup -t memory
	mkdir /cgroup/A
	set use_hierarchy==1 to "A"
	mkdir /cgroup/A/01
	mkdir /cgroup/A/01/02
	mkdir /cgroup/A/01/03
	mkdir /cgroup/A/01/03/04
	mkdir /cgroup/A/08
	mkdir /cgroup/A/08/01
	....
and set each own limit to them, "real" limit of each memcg is unclear.
This patch shows real limit by checking all ancestors.

Changelog: (v1) -> (v2)
	- remove "if" and use "min(a,b)"

Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 35 insertions, 0 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c7d78eca836..8d2e5c8a25b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1782,6 +1782,34 @@ static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
         return ret;
 }
 
+static void memcg_get_hierarchical_limit(struct mem_cgroup *memcg,
+                unsigned long long *mem_limit, unsigned long long *memsw_limit)
+{
+        struct cgroup *cgroup;
+        unsigned long long min_limit, min_memsw_limit, tmp;
+
+        min_limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
+        min_memsw_limit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
+        cgroup = memcg->css.cgroup;
+        if (!memcg->use_hierarchy)
+                goto out;
+
+        while (cgroup->parent) {
+                cgroup = cgroup->parent;
+                memcg = mem_cgroup_from_cont(cgroup);
+                if (!memcg->use_hierarchy)
+                        break;
+                tmp = res_counter_read_u64(&memcg->res, RES_LIMIT);
+                min_limit = min(min_limit, tmp);
+                tmp = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
+                min_memsw_limit = min(min_memsw_limit, tmp);
+        }
+out:
+        *mem_limit = min_limit;
+        *memsw_limit = min_memsw_limit;
+        return;
+}
+
 static int mem_cgroup_reset(struct cgroup *cont, unsigned int event)
 {
         struct mem_cgroup *mem;
@@ -1855,6 +1883,13 @@ static int mem_control_stat_show(struct cgroup *cont, struct cftype *cft,
                 cb->fill(cb, "unevictable", unevictable * PAGE_SIZE);
 
         }
+        {
+                unsigned long long limit, memsw_limit;
+                memcg_get_hierarchical_limit(mem_cont, &limit, &memsw_limit);
+                cb->fill(cb, "hierarchical_memory_limit", limit);
+                if (do_swap_account)
+                        cb->fill(cb, "hierarchical_memsw_limit", memsw_limit);
+        }
 
 #ifdef CONFIG_DEBUG_VM
         cb->fill(cb, "inactive_ratio", calc_inactive_ratio(mem_cont, NULL));