rdmacg: Added rdma cgroup controller

Added rdma cgroup controller that does accounting, limit enforcement
on rdma/IB resources.

Added rdma cgroup header file which defines its APIs to perform
charging/uncharging functionality. It also defined APIs for RDMA/IB
stack for device registration. Devices which are registered will
participate in controller functions of accounting and limit
enforcements. It define rdmacg_device structure to bind IB stack
and RDMA cgroup controller.

RDMA resources are tracked using resource pool. Resource pool is per
device, per cgroup entity which allows setting up accounting limits
on per device basis.

Currently resources are defined by the RDMA cgroup.

Resource pool is created/destroyed dynamically whenever
charging/uncharging occurs respectively and whenever user
configuration is done. Its a tradeoff of memory vs little more code
space that creates resource pool object whenever necessary, instead of
creating them during cgroup creation and device registration time.
Signed-off-by: Parav Pandit <pandit.parav@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

include/linux/cgroup_rdma.h

+/*
+ * Copyright (C) 2016 Parav Pandit <pandit.parav@gmail.com>
+ *
+ * This file is subject to the terms and conditions of version 2 of the GNU
+ * General Public License. See the file COPYING in the main directory of the
+ * Linux distribution for more details.
+ */
+
+#ifndef _CGROUP_RDMA_H
+#define _CGROUP_RDMA_H
+
+#include <linux/cgroup.h>
+
+enum rdmacg_resource_type {
+	RDMACG_RESOURCE_HCA_HANDLE,
+	RDMACG_RESOURCE_HCA_OBJECT,
+	RDMACG_RESOURCE_MAX,
+};
+
+#ifdef CONFIG_CGROUP_RDMA
+
+struct rdma_cgroup {
+	struct cgroup_subsys_state	css;
+
+	/*
+	 * head to keep track of all resource pools
+	 * that belongs to this cgroup.
+	 */
+	struct list_head		rpools;
+};
+
+struct rdmacg_device {
+	struct list_head	dev_node;
+	struct list_head	rpools;
+	char			*name;
+};
+
+/*
+ * APIs for RDMA/IB stack to publish when a device wants to
+ * participate in resource accounting
+ */
+int rdmacg_register_device(struct rdmacg_device *device);
+void rdmacg_unregister_device(struct rdmacg_device *device);
+
+/* APIs for RDMA/IB stack to charge/uncharge pool specific resources */
+int rdmacg_try_charge(struct rdma_cgroup **rdmacg,
+		      struct rdmacg_device *device,
+		      enum rdmacg_resource_type index);
+void rdmacg_uncharge(struct rdma_cgroup *cg,
+		     struct rdmacg_device *device,
+		     enum rdmacg_resource_type index);
+#endif	/* CONFIG_CGROUP_RDMA */
+#endif	/* _CGROUP_RDMA_H */

include/linux/cgroup_subsys.h

@@ -56,6 +56,10 @@ SUBSYS(hugetlb)
 SUBSYS(pids)
 #endif
 
+#if IS_ENABLED(CONFIG_CGROUP_RDMA)
+SUBSYS(rdma)
+#endif
+
 /*
  * The following subsystems are not supported on the default hierarchy.
  */

init/Kconfig

@@ -1090,6 +1090,16 @@ config CGROUP_PIDS
 	  since the PIDs limit only affects a process's ability to fork, not to
 	  attach to a cgroup.
 
+config CGROUP_RDMA
+	bool "RDMA controller"
+	help
+	  Provides enforcement of RDMA resources defined by IB stack.
+	  It is fairly easy for consumers to exhaust RDMA resources, which
+	  can result into resource unavailability to other consumers.
+	  RDMA controller is designed to stop this from happening.
+	  Attaching processes with active RDMA resources to the cgroup
+	  hierarchy is allowed even if can cross the hierarchy's limit.
+
 config CGROUP_FREEZER
 	bool "Freezer controller"
 	help

kernel/cgroup/Makefile

@@ -2,4 +2,5 @@ obj-y := cgroup.o namespace.o cgroup-v1.o
 
 obj-$(CONFIG_CGROUP_FREEZER) += freezer.o
 obj-$(CONFIG_CGROUP_PIDS) += pids.o
+obj-$(CONFIG_CGROUP_RDMA) += rdma.o
 obj-$(CONFIG_CPUSETS) += cpuset.o