[PATCH 2/6] add res_counter_uncharge_until()

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

From: Frederic Weisbecker <fweisbec@gmail.com>

At killing res_counter which is a child of other counter,
we need to do
	res_counter_uncharge(child, xxx)
	res_counter_charge(parent, xxx)

This is not atomic and wasting cpu. This patch adds
res_counter_uncharge_until(). This function's uncharge propagates
to ancestors until specified res_counter.

	res_counter_uncharge_until(child, parent, xxx)

Now, ops is atomic and efficient.

Changelog since v2
 - removed unnecessary lines.
 - Fixed 'From' , this patch comes from his series. Please signed-off-by if good.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 Documentation/cgroups/resource_counter.txt |    8 ++++++++
 include/linux/res_counter.h                |    3 +++
 kernel/res_counter.c                       |   10 ++++++++--
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/Documentation/cgroups/resource_counter.txt b/Documentation/cgroups/resource_counter.txt
index 95b24d7..703103a 100644
--- a/Documentation/cgroups/resource_counter.txt
+++ b/Documentation/cgroups/resource_counter.txt
@@ -92,6 +92,14 @@ to work with it.
 
 	The _locked routines imply that the res_counter->lock is taken.
 
+ f. void res_counter_uncharge_until
+		(struct res_counter *rc, struct res_counter *top,
+		 unsinged long val)
+
+	Almost same as res_cunter_uncharge() but propagation of uncharge
+	stops when rc == top. This is useful when kill a res_coutner in
+	child cgroup.
+
  2.1 Other accounting routines
 
     There are more routines that may help you with common needs, like
diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h
index da81af0..d11c1cd 100644
--- a/include/linux/res_counter.h
+++ b/include/linux/res_counter.h
@@ -135,6 +135,9 @@ int __must_check res_counter_charge_nofail(struct res_counter *counter,
 void res_counter_uncharge_locked(struct res_counter *counter, unsigned long val);
 void res_counter_uncharge(struct res_counter *counter, unsigned long val);
 
+void res_counter_uncharge_until(struct res_counter *counter,
+				struct res_counter *top,
+				unsigned long val);
 /**
  * res_counter_margin - calculate chargeable space of a counter
  * @cnt: the counter
diff --git a/kernel/res_counter.c b/kernel/res_counter.c
index d508363..d9ea45e 100644
--- a/kernel/res_counter.c
+++ b/kernel/res_counter.c
@@ -99,13 +99,15 @@ void res_counter_uncharge_locked(struct res_counter *counter, unsigned long val)
 	counter->usage -= val;
 }
 
-void res_counter_uncharge(struct res_counter *counter, unsigned long val)
+void res_counter_uncharge_until(struct res_counter *counter,
+				struct res_counter *top,
+				unsigned long val)
 {
 	unsigned long flags;
 	struct res_counter *c;
 
 	local_irq_save(flags);
-	for (c = counter; c != NULL; c = c->parent) {
+	for (c = counter; c != top; c = c->parent) {
 		spin_lock(&c->lock);
 		res_counter_uncharge_locked(c, val);
 		spin_unlock(&c->lock);
@@ -113,6 +115,10 @@ void res_counter_uncharge(struct res_counter *counter, unsigned long val)
 	local_irq_restore(flags);
 }
 
+void res_counter_uncharge(struct res_counter *counter, unsigned long val)
+{
+	res_counter_uncharge_until(counter, NULL, val);
+}
 
 static inline unsigned long long *
 res_counter_member(struct res_counter *counter, int member)
-- 
1.7.4.1


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