[RFC 3/6] misc: introduce misc_cg_charge()

[Tycho Andersen <tycho@tycho.pizza>]

From: Tycho Andersen <tandersen@netflix.com>

Similar to cases in e.g. the pids cgroup with pids_charge(), if a migration
fails we will need to force-unwind it, which may put misc cgroups over
their limits. We need to charge them anyway, which is what this helper is
for.

Signed-off-by: Tycho Andersen <tandersen@netflix.com>
---
 include/linux/misc_cgroup.h |  1 +
 kernel/cgroup/misc.c        | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/include/linux/misc_cgroup.h b/include/linux/misc_cgroup.h
index e799b1f8d05b..6ddffeeb6f97 100644
--- a/include/linux/misc_cgroup.h
+++ b/include/linux/misc_cgroup.h
@@ -57,6 +57,7 @@ struct misc_cg {
 u64 misc_cg_res_total_usage(enum misc_res_type type);
 int misc_cg_set_capacity(enum misc_res_type type, u64 capacity);
 int misc_cg_try_charge(enum misc_res_type type, struct misc_cg *cg, u64 amount);
+void misc_cg_charge(enum misc_res_type type, struct misc_cg *cg, u64 amount);
 void misc_cg_uncharge(enum misc_res_type type, struct misc_cg *cg, u64 amount);
 
 /**
diff --git a/kernel/cgroup/misc.c b/kernel/cgroup/misc.c
index 79a3717a5803..bbce097270cf 100644
--- a/kernel/cgroup/misc.c
+++ b/kernel/cgroup/misc.c
@@ -121,6 +121,38 @@ static void misc_cg_cancel_charge(enum misc_res_type type, struct misc_cg *cg,
 		  misc_res_name[type]);
 }
 
+/**
+ * misc_cg_charge() - Charge the cgroup, ignoring limits/capacity.
+ * @type: Misc res type to charge.
+ * @cg: Misc cgroup which will be charged.
+ * @amount: Amount to charge.
+ *
+ * Charge @amount to the misc cgroup. Caller must use the same cgroup during
+ * the uncharge call.
+ *
+ * Context: Any context.
+ */
+void misc_cg_charge(enum misc_res_type type, struct misc_cg *cg, u64 amount)
+{
+	struct misc_res *res;
+	struct misc_cg *i;
+
+	if (!(valid_type(type) && cg && READ_ONCE(misc_res_capacity[type]))) {
+		WARN_ON_ONCE(!valid_type(type));
+		return;
+	}
+
+	if (!amount)
+		return;
+
+	for (i = cg; i; i = parent_misc(i)) {
+		res = &i->res[type];
+
+		atomic_long_add(amount, &res->usage);
+	}
+}
+EXPORT_SYMBOL_GPL(misc_cg_charge);
+
 /**
  * misc_cg_try_charge() - Try charging the misc cgroup.
  * @type: Misc res type to charge.
-- 
2.34.1