[PATCH 8/8] res_counter: Allow charge failure pointer to be null

[Frederic Weisbecker <fweisbec@gmail.com>]

So that callers of res_counter_charge() don't have to create and
pass this pointer even if they aren't interested in it.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Aditya Kali <adityakali@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
---
 kernel/cgroup_task_counter.c |    6 ++----
 kernel/res_counter.c         |    6 ++++--
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/cgroup_task_counter.c b/kernel/cgroup_task_counter.c
index 7f12ac9..dacc4a9 100644
--- a/kernel/cgroup_task_counter.c
+++ b/kernel/cgroup_task_counter.c
@@ -93,11 +93,10 @@ static int task_counter_can_attach_task(struct cgroup *cgrp, struct cgroup *old_
 {
 	struct res_counter *res = cgroup_task_counter_res(cgrp);
 	struct res_counter *old_res = cgroup_task_counter_res(old_cgrp);
-	struct res_counter *limit_fail_at;
 
 	common_ancestor = res_counter_common_ancestor(res, old_res);
 
-	return res_counter_charge_until(res, common_ancestor, 1, &limit_fail_at);
+	return res_counter_charge_until(res, common_ancestor, 1, NULL);
 }
 
 static void task_counter_cancel_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
@@ -154,13 +153,12 @@ int cgroup_task_counter_fork(struct task_struct *child)
 {
 	struct cgroup_subsys_state *css = child->cgroups->subsys[tasks_subsys_id];
 	struct cgroup *cgrp = css->cgroup;
-	struct res_counter *limit_fail_at;
 
 	/* Optimize for the root cgroup case, which doesn't have a limit */
 	if (!cgrp->parent)
 		return 0;
 
-	return res_counter_charge(cgroup_task_counter_res(cgrp), 1, &limit_fail_at);
+	return res_counter_charge(cgroup_task_counter_res(cgrp), 1, NULL);
 }
 
 struct cgroup_subsys tasks_subsys = {
diff --git a/kernel/res_counter.c b/kernel/res_counter.c
index 725dfa6..7eac803 100644
--- a/kernel/res_counter.c
+++ b/kernel/res_counter.c
@@ -43,14 +43,16 @@ int res_counter_charge_until(struct res_counter *counter,
 	unsigned long flags;
 	struct res_counter *c, *u;
 
-	*limit_fail_at = NULL;
+	if (limit_fail_at)
+		*limit_fail_at = NULL;
 	local_irq_save(flags);
 	for (c = counter; c != limit; c = c->parent) {
 		spin_lock(&c->lock);
 		ret = res_counter_charge_locked(c, val);
 		spin_unlock(&c->lock);
 		if (ret < 0) {
-			*limit_fail_at = c;
+			if (limit_fail_at)
+				*limit_fail_at = c;
 			goto undo;
 		}
 	}
-- 
1.7.5.4