[PATCH 1/2] Add the max_usage member on the res_counter

[Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>]

This is a very usefull feature. E.g. one may set the
limit to "unlimited" value and check for the memory
requirements of a new container.

Signed-off-by: Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>

---
 include/linux/res_counter.h |    5 +++++
 kernel/res_counter.c        |    4 ++++
 mm/memcontrol.c             |    5 +++++
 3 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h
index 8cb1ecd..2c4deb5 100644
--- a/include/linux/res_counter.h
+++ b/include/linux/res_counter.h
@@ -25,6 +25,10 @@ struct res_counter {
 	 */
 	unsigned long long usage;
 	/*
+	 * the maximal value of the usage from the counter creation
+	 */
+	unsigned long long max_usage;
+	/*
 	 * the limit that usage cannot exceed
 	 */
 	unsigned long long limit;
@@ -67,6 +71,7 @@ ssize_t res_counter_write(struct res_counter *counter, int member,
 
 enum {
 	RES_USAGE,
+	RES_MAX_USAGE,
 	RES_LIMIT,
 	RES_FAILCNT,
 };
diff --git a/kernel/res_counter.c b/kernel/res_counter.c
index 791ff2b..f1f20c2 100644
--- a/kernel/res_counter.c
+++ b/kernel/res_counter.c
@@ -27,6 +27,8 @@ int res_counter_charge_locked(struct res_counter *counter, unsigned long val)
 	}
 
 	counter->usage += val;
+	if (counter->usage > counter->max_usage)
+		counter->max_usage = counter->usage;
 	return 0;
 }
 
@@ -65,6 +67,8 @@ res_counter_member(struct res_counter *counter, int member)
 	switch (member) {
 	case RES_USAGE:
 		return &counter->usage;
+	case RES_MAX_USAGE:
+		return &counter->max_usage;
 	case RES_LIMIT:
 		return &counter->limit;
 	case RES_FAILCNT:
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2d59163..e5c741a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -911,6 +911,11 @@ static struct cftype mem_cgroup_files[] = {
 		.read_u64 = mem_cgroup_read,
 	},
 	{
+		.name = "max_usage_in_bytes",
+		.private = RES_MAX_USAGE,
+		.read_u64 = mem_cgroup_read,
+	},
+	{
 		.name = "limit_in_bytes",
 		.private = RES_LIMIT,
 		.write = mem_cgroup_write,
-- 
1.5.3.4