[RFC 2/7] consolidate all res_counter manipulation

[Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>]

This patch moves all the locked updates done to res_counter to
__res_counter_add(). It gets flags for the special cases like nofail(),
and a negative value of the increment means uncharge.

This will be useful later when we start doing percpu_counter updates.

Signed-off-by: Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
---
 kernel/res_counter.c |   59 +++++++++++++++++++++++--------------------------
 1 files changed, 28 insertions(+), 31 deletions(-)

diff --git a/kernel/res_counter.c b/kernel/res_counter.c
index b8a3d6a..ecb4aad 100644
--- a/kernel/res_counter.c
+++ b/kernel/res_counter.c
@@ -22,17 +22,32 @@ void res_counter_init(struct res_counter *counter, struct res_counter *parent)
 	counter->parent = parent;
 }
 
-int res_counter_charge_locked(struct res_counter *counter, unsigned long val)
+int __res_counter_add(struct res_counter *c, long val, bool fail)
 {
-	if (counter->usage + val > counter->limit) {
-		counter->failcnt++;
-		return -ENOMEM;
+	int ret = 0;
+	u64 usage;
+
+	spin_lock(&c->lock);
+
+	usage = c->usage;
+
+	if (usage + val > c->limit) {
+		c->failcnt++;
+		ret = -ENOMEM;
+		if (fail)
+			goto out;
 	}
 
-	counter->usage += val;
-	if (counter->usage > counter->max_usage)
-		counter->max_usage = counter->usage;
-	return 0;
+	usage += val;
+
+	c->usage = usage;
+	if (usage > c->max_usage)
+		c->max_usage = usage;
+
+out:
+	spin_unlock(&c->lock);
+	return ret;
+
 }
 
 int res_counter_charge(struct res_counter *counter, unsigned long val,
@@ -45,9 +60,7 @@ int res_counter_charge(struct res_counter *counter, unsigned long val,
 	*limit_fail_at = NULL;
 	local_irq_save(flags);
 	for (c = counter; c != NULL; c = c->parent) {
-		spin_lock(&c->lock);
-		ret = res_counter_charge_locked(c, val);
-		spin_unlock(&c->lock);
+		ret = __res_counter_add(c, val, true);
 		if (ret < 0) {
 			*limit_fail_at = c;
 			goto undo;
@@ -57,9 +70,7 @@ int res_counter_charge(struct res_counter *counter, unsigned long val,
 	goto done;
 undo:
 	for (u = counter; u != c; u = u->parent) {
-		spin_lock(&u->lock);
-		res_counter_uncharge_locked(u, val);
-		spin_unlock(&u->lock);
+		__res_counter_add(u, -val, false);
 	}
 done:
 	local_irq_restore(flags);
@@ -77,11 +88,7 @@ int res_counter_charge_nofail(struct res_counter *counter, unsigned long val,
 	*limit_fail_at = NULL;
 	local_irq_save(flags);
 	for (c = counter; c != NULL; c = c->parent) {
-		spin_lock(&c->lock);
-		r = res_counter_charge_locked(c, val);
-		if (r)
-			c->usage += val;
-		spin_unlock(&c->lock);
+		r = __res_counter_add(c, val, false);
 		if (r < 0 && ret == 0) {
 			*limit_fail_at = c;
 			ret = r;
@@ -91,13 +98,6 @@ int res_counter_charge_nofail(struct res_counter *counter, unsigned long val,
 
 	return ret;
 }
-void res_counter_uncharge_locked(struct res_counter *counter, unsigned long val)
-{
-	if (WARN_ON(counter->usage < val))
-		val = counter->usage;
-
-	counter->usage -= val;
-}
 
 void res_counter_uncharge(struct res_counter *counter, unsigned long val)
 {
@@ -105,11 +105,8 @@ void res_counter_uncharge(struct res_counter *counter, unsigned long val)
 	struct res_counter *c;
 
 	local_irq_save(flags);
-	for (c = counter; c != NULL; c = c->parent) {
-		spin_lock(&c->lock);
-		res_counter_uncharge_locked(c, val);
-		spin_unlock(&c->lock);
-	}
+	for (c = counter; c != NULL; c = c->parent)
+		__res_counter_add(c, -val, false);
 	local_irq_restore(flags);
 }
 
-- 
1.7.4.1