Merge branch 'cgroup/for-4.11-rdmacg' into cgroup/for-4.11

Merge in to resolve conflicts in Documentation/cgroup-v2.txt.  The
conflicts are from multiple section additions and trivial to resolve.
Signed-off-by: Tejun Heo <tj@kernel.org>

Documentation/cgroup-v1/rdma.txt

+				RDMA Controller
+				----------------
+
+Contents
+--------
+
+1. Overview
+  1-1. What is RDMA controller?
+  1-2. Why RDMA controller needed?
+  1-3. How is RDMA controller implemented?
+2. Usage Examples
+
+1. Overview
+
+1-1. What is RDMA controller?
+-----------------------------
+
+RDMA controller allows user to limit RDMA/IB specific resources that a given
+set of processes can use. These processes are grouped using RDMA controller.
+
+RDMA controller defines two resources which can be limited for processes of a
+cgroup.
+
+1-2. Why RDMA controller needed?
+--------------------------------
+
+Currently user space applications can easily take away all the rdma verb
+specific resources such as AH, CQ, QP, MR etc. Due to which other applications
+in other cgroup or kernel space ULPs may not even get chance to allocate any
+rdma resources. This can leads to service unavailability.
+
+Therefore RDMA controller is needed through which resource consumption
+of processes can be limited. Through this controller different rdma
+resources can be accounted.
+
+1-3. How is RDMA controller implemented?
+----------------------------------------
+
+RDMA cgroup allows limit configuration of resources. Rdma cgroup maintains
+resource accounting per cgroup, per device using resource pool structure.
+Each such resource pool is limited up to 64 resources in given resource pool
+by rdma cgroup, which can be extended later if required.
+
+This resource pool object is linked to the cgroup css. Typically there
+are 0 to 4 resource pool instances per cgroup, per device in most use cases.
+But nothing limits to have it more. At present hundreds of RDMA devices per
+single cgroup may not be handled optimally, however there is no
+known use case or requirement for such configuration either.
+
+Since RDMA resources can be allocated from any process and can be freed by any
+of the child processes which shares the address space, rdma resources are
+always owned by the creator cgroup css. This allows process migration from one
+to other cgroup without major complexity of transferring resource ownership;
+because such ownership is not really present due to shared nature of
+rdma resources. Linking resources around css also ensures that cgroups can be
+deleted after processes migrated. This allow progress migration as well with
+active resources, even though that is not a primary use case.
+
+Whenever RDMA resource charging occurs, owner rdma cgroup is returned to
+the caller. Same rdma cgroup should be passed while uncharging the resource.
+This also allows process migrated with active RDMA resource to charge
+to new owner cgroup for new resource. It also allows to uncharge resource of
+a process from previously charged cgroup which is migrated to new cgroup,
+even though that is not a primary use case.
+
+Resource pool object is created in following situations.
+(a) User sets the limit and no previous resource pool exist for the device
+of interest for the cgroup.
+(b) No resource limits were configured, but IB/RDMA stack tries to
+charge the resource. So that it correctly uncharge them when applications are
+running without limits and later on when limits are enforced during uncharging,
+otherwise usage count will drop to negative.
+
+Resource pool is destroyed if all the resource limits are set to max and
+it is the last resource getting deallocated.
+
+User should set all the limit to max value if it intents to remove/unconfigure
+the resource pool for a particular device.
+
+IB stack honors limits enforced by the rdma controller. When application
+query about maximum resource limits of IB device, it returns minimum of
+what is configured by user for a given cgroup and what is supported by
+IB device.
+
+Following resources can be accounted by rdma controller.
+  hca_handle	Maximum number of HCA Handles
+  hca_object 	Maximum number of HCA Objects
+
+2. Usage Examples
+-----------------
+
+(a) Configure resource limit:
+echo mlx4_0 hca_handle=2 hca_object=2000 > /sys/fs/cgroup/rdma/1/rdma.max
+echo ocrdma1 hca_handle=3 > /sys/fs/cgroup/rdma/2/rdma.max
+
+(b) Query resource limit:
+cat /sys/fs/cgroup/rdma/2/rdma.max
+#Output:
+mlx4_0 hca_handle=2 hca_object=2000
+ocrdma1 hca_handle=3 hca_object=max
+
+(c) Query current usage:
+cat /sys/fs/cgroup/rdma/2/rdma.current
+#Output:
+mlx4_0 hca_handle=1 hca_object=20
+ocrdma1 hca_handle=1 hca_object=23
+
+(d) Delete resource limit:
+echo echo mlx4_0 hca_handle=max hca_object=max > /sys/fs/cgroup/rdma/1/rdma.max

Documentation/cgroup-v2.txt

@@ -49,8 +49,10 @@ CONTENTS
     5-3-2. Writeback
   5-4. PID
     5-4-1. PID Interface Files
-  5-5. Misc
-    5-5-1. perf_event
+  5-5. RDMA
+    5-5-1. RDMA Interface Files
+  5-6. Misc
+    5-6-1. perf_event
 6. Namespace
   6-1. Basics
   6-2. The Root and Views
@@ -1160,9 +1162,45 @@ through fork() or clone(). These will return -EAGAIN if the creation
 of a new process would cause a cgroup policy to be violated.
 
 
-5-5. Misc
+5-5. RDMA
 
-5-5-1. perf_event
+The "rdma" controller regulates the distribution and accounting of
+of RDMA resources.
+
+5-5-1. RDMA Interface Files
+
+  rdma.max
+	A readwrite nested-keyed file that exists for all the cgroups
+	except root that describes current configured resource limit
+	for a RDMA/IB device.
+
+	Lines are keyed by device name and are not ordered.
+	Each line contains space separated resource name and its configured
+	limit that can be distributed.
+
+	The following nested keys are defined.
+
+	  hca_handle	Maximum number of HCA Handles
+	  hca_object 	Maximum number of HCA Objects
+
+	An example for mlx4 and ocrdma device follows.
+
+	  mlx4_0 hca_handle=2 hca_object=2000
+	  ocrdma1 hca_handle=3 hca_object=max
+
+  rdma.current
+	A read-only file that describes current resource usage.
+	It exists for all the cgroup except root.
+
+	An example for mlx4 and ocrdma device follows.
+
+	  mlx4_0 hca_handle=1 hca_object=20
+	  ocrdma1 hca_handle=1 hca_object=23
+
+
+5-6. Misc
+
+5-6-1. perf_event
 
 perf_event controller, if not mounted on a legacy hierarchy, is
 automatically enabled on the v2 hierarchy so that perf events can

drivers/infiniband/core/Makefile

@@ -13,6 +13,7 @@ ib_core-y :=			packer.o ud_header.o verbs.o cq.o rw.o sysfs.o \
 				multicast.o mad.o smi.o agent.o mad_rmpp.o
 ib_core-$(CONFIG_INFINIBAND_USER_MEM) += umem.o
 ib_core-$(CONFIG_INFINIBAND_ON_DEMAND_PAGING) += umem_odp.o umem_rbtree.o
+ib_core-$(CONFIG_CGROUP_RDMA) += cgroup.o
 
 ib_cm-y :=			cm.o
 

drivers/infiniband/core/cgroup.c

+/*
+ * Copyright (C) 2016 Parav Pandit <pandit.parav@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+
+#include "core_priv.h"
+
+/**
+ * ib_device_register_rdmacg - register with rdma cgroup.
+ * @device: device to register to participate in resource
+ *          accounting by rdma cgroup.
+ *
+ * Register with the rdma cgroup. Should be called before
+ * exposing rdma device to user space applications to avoid
+ * resource accounting leak.
+ * Returns 0 on success or otherwise failure code.
+ */
+int ib_device_register_rdmacg(struct ib_device *device)
+{
+	device->cg_device.name = device->name;
+	return rdmacg_register_device(&device->cg_device);
+}
+
+/**
+ * ib_device_unregister_rdmacg - unregister with rdma cgroup.
+ * @device: device to unregister.
+ *
+ * Unregister with the rdma cgroup. Should be called after
+ * all the resources are deallocated, and after a stage when any
+ * other resource allocation by user application cannot be done
+ * for this device to avoid any leak in accounting.
+ */
+void ib_device_unregister_rdmacg(struct ib_device *device)
+{
+	rdmacg_unregister_device(&device->cg_device);
+}
+
+int ib_rdmacg_try_charge(struct ib_rdmacg_object *cg_obj,
+			 struct ib_device *device,
+			 enum rdmacg_resource_type resource_index)
+{
+	return rdmacg_try_charge(&cg_obj->cg, &device->cg_device,
+				 resource_index);
+}
+EXPORT_SYMBOL(ib_rdmacg_try_charge);
+
+void ib_rdmacg_uncharge(struct ib_rdmacg_object *cg_obj,
+			struct ib_device *device,
+			enum rdmacg_resource_type resource_index)
+{
+	rdmacg_uncharge(cg_obj->cg, &device->cg_device,
+			resource_index);
+}
+EXPORT_SYMBOL(ib_rdmacg_uncharge);

drivers/infiniband/core/core_priv.h

@@ -35,6 +35,7 @@
 
 #include <linux/list.h>
 #include <linux/spinlock.h>
+#include <linux/cgroup_rdma.h>
 
 #include <rdma/ib_verbs.h>
 
@@ -121,6 +122,35 @@ int ib_cache_setup_one(struct ib_device *device);
 void ib_cache_cleanup_one(struct ib_device *device);
 void ib_cache_release_one(struct ib_device *device);
 
+#ifdef CONFIG_CGROUP_RDMA
+int ib_device_register_rdmacg(struct ib_device *device);
+void ib_device_unregister_rdmacg(struct ib_device *device);
+
+int ib_rdmacg_try_charge(struct ib_rdmacg_object *cg_obj,
+			 struct ib_device *device,
+			 enum rdmacg_resource_type resource_index);
+
+void ib_rdmacg_uncharge(struct ib_rdmacg_object *cg_obj,
+			struct ib_device *device,
+			enum rdmacg_resource_type resource_index);
+#else
+static inline int ib_device_register_rdmacg(struct ib_device *device)
+{ return 0; }
+
+static inline void ib_device_unregister_rdmacg(struct ib_device *device)
+{ }
+
+static inline int ib_rdmacg_try_charge(struct ib_rdmacg_object *cg_obj,
+				       struct ib_device *device,
+				       enum rdmacg_resource_type resource_index)
+{ return 0; }
+
+static inline void ib_rdmacg_uncharge(struct ib_rdmacg_object *cg_obj,
+				      struct ib_device *device,
+				      enum rdmacg_resource_type resource_index)
+{ }
+#endif
+
 static inline bool rdma_is_upper_dev_rcu(struct net_device *dev,
 					 struct net_device *upper)
 {

drivers/infiniband/core/device.c

@@ -360,10 +360,18 @@ int ib_register_device(struct ib_device *device,
 		goto out;
 	}
 
+	ret = ib_device_register_rdmacg(device);
+	if (ret) {
+		pr_warn("Couldn't register device with rdma cgroup\n");
+		ib_cache_cleanup_one(device);
+		goto out;
+	}
+
 	memset(&device->attrs, 0, sizeof(device->attrs));
 	ret = device->query_device(device, &device->attrs, &uhw);
 	if (ret) {
 		pr_warn("Couldn't query the device attributes\n");
+		ib_device_unregister_rdmacg(device);
 		ib_cache_cleanup_one(device);
 		goto out;
 	}
@@ -372,6 +380,7 @@ int ib_register_device(struct ib_device *device,
 	if (ret) {
 		pr_warn("Couldn't register device %s with driver model\n",
 			device->name);
+		ib_device_unregister_rdmacg(device);
 		ib_cache_cleanup_one(device);
 		goto out;
 	}
@@ -421,6 +430,7 @@ void ib_unregister_device(struct ib_device *device)
 
 	mutex_unlock(&device_mutex);
 
+	ib_device_unregister_rdmacg(device);
 	ib_device_unregister_sysfs(device);
 	ib_cache_cleanup_one(device);
 

drivers/infiniband/core/uverbs_cmd.c

@@ -316,6 +316,7 @@ ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
 	struct ib_udata                   udata;
 	struct ib_ucontext		 *ucontext;
 	struct file			 *filp;
+	struct ib_rdmacg_object		 cg_obj;
 	int ret;
 
 	if (out_len < sizeof resp)
@@ -335,13 +336,18 @@ ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
 		   (unsigned long) cmd.response + sizeof resp,
 		   in_len - sizeof cmd, out_len - sizeof resp);
 
+	ret = ib_rdmacg_try_charge(&cg_obj, ib_dev, RDMACG_RESOURCE_HCA_HANDLE);
+	if (ret)
+		goto err;
+
 	ucontext = ib_dev->alloc_ucontext(ib_dev, &udata);
 	if (IS_ERR(ucontext)) {
 		ret = PTR_ERR(ucontext);
-		goto err;
+		goto err_alloc;
 	}
 
 	ucontext->device = ib_dev;
+	ucontext->cg_obj = cg_obj;
 	INIT_LIST_HEAD(&ucontext->pd_list);
 	INIT_LIST_HEAD(&ucontext->mr_list);
 	INIT_LIST_HEAD(&ucontext->mw_list);
@@ -407,6 +413,9 @@ ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
 	put_pid(ucontext->tgid);
 	ib_dev->dealloc_ucontext(ucontext);
 
+err_alloc:
+	ib_rdmacg_uncharge(&cg_obj, ib_dev, RDMACG_RESOURCE_HCA_HANDLE);
+
 err:
 	mutex_unlock(&file->mutex);
 	return ret;
@@ -561,6 +570,13 @@ ssize_t ib_uverbs_alloc_pd(struct ib_uverbs_file *file,
 		return -ENOMEM;
 
 	init_uobj(uobj, 0, file->ucontext, &pd_lock_class);
+	ret = ib_rdmacg_try_charge(&uobj->cg_obj, ib_dev,
+				   RDMACG_RESOURCE_HCA_OBJECT);
+	if (ret) {
+		kfree(uobj);
+		return ret;
+	}
+
 	down_write(&uobj->mutex);
 
 	pd = ib_dev->alloc_pd(ib_dev, file->ucontext, &udata);
@@ -605,6 +621,7 @@ ssize_t ib_uverbs_alloc_pd(struct ib_uverbs_file *file,
 	ib_dealloc_pd(pd);
 
 err:
+	ib_rdmacg_uncharge(&uobj->cg_obj, ib_dev, RDMACG_RESOURCE_HCA_OBJECT);
 	put_uobj_write(uobj);
 	return ret;
 }
@@ -637,6 +654,8 @@ ssize_t ib_uverbs_dealloc_pd(struct ib_uverbs_file *file,
 	if (ret)
 		goto err_put;
 
+	ib_rdmacg_uncharge(&uobj->cg_obj, ib_dev, RDMACG_RESOURCE_HCA_OBJECT);
+
 	uobj->live = 0;
 	put_uobj_write(uobj);
 
@@ -1006,6 +1025,10 @@ ssize_t ib_uverbs_reg_mr(struct ib_uverbs_file *file,
 			goto err_put;
 		}
 	}
+	ret = ib_rdmacg_try_charge(&uobj->cg_obj, ib_dev,
+				   RDMACG_RESOURCE_HCA_OBJECT);
+	if (ret)
+		goto err_charge;
 
 	mr = pd->device->reg_user_mr(pd, cmd.start, cmd.length, cmd.hca_va,
 				     cmd.access_flags, &udata);
@@ -1054,6 +1077,9 @@ ssize_t ib_uverbs_reg_mr(struct ib_uverbs_file *file,
 	ib_dereg_mr(mr);
 
 err_put:
+	ib_rdmacg_uncharge(&uobj->cg_obj, ib_dev, RDMACG_RESOURCE_HCA_OBJECT);
+
+err_charge:
 	put_pd_read(pd);
 
 err_free:
@@ -1178,6 +1204,8 @@ ssize_t ib_uverbs_dereg_mr(struct ib_uverbs_file *file,
 	if (ret)
 		return ret;
 
+	ib_rdmacg_uncharge(&uobj->cg_obj, ib_dev, RDMACG_RESOURCE_HCA_OBJECT);
+
 	idr_remove_uobj(&ib_uverbs_mr_idr, uobj);
 
 	mutex_lock(&file->mutex);
@@ -1226,6 +1254,11 @@ ssize_t ib_uverbs_alloc_mw(struct ib_uverbs_file *file,
 		   in_len - sizeof(cmd) - sizeof(struct ib_uverbs_cmd_hdr),
 		   out_len - sizeof(resp));
 
+	ret = ib_rdmacg_try_charge(&uobj->cg_obj, ib_dev,
+				   RDMACG_RESOURCE_HCA_OBJECT);
+	if (ret)
+		goto err_charge;
+
 	mw = pd->device->alloc_mw(pd, cmd.mw_type, &udata);
 	if (IS_ERR(mw)) {
 		ret = PTR_ERR(mw);
@@ -1271,6 +1304,9 @@ ssize_t ib_uverbs_alloc_mw(struct ib_uverbs_file *file,
 	uverbs_dealloc_mw(mw);
 
 err_put:
+	ib_rdmacg_uncharge(&uobj->cg_obj, ib_dev, RDMACG_RESOURCE_HCA_OBJECT);
+
+err_charge:
 	put_pd_read(pd);
 
 err_free:
@@ -1306,6 +1342,8 @@ ssize_t ib_uverbs_dealloc_mw(struct ib_uverbs_file *file,
 	if (ret)
 		return ret;
 
+	ib_rdmacg_uncharge(&uobj->cg_obj, ib_dev, RDMACG_RESOURCE_HCA_OBJECT);
+
 	idr_remove_uobj(&ib_uverbs_mw_idr, uobj);
 
 	mutex_lock(&file->mutex);
@@ -1405,6 +1443,11 @@ static struct ib_ucq_object *create_cq(struct ib_uverbs_file *file,
 	if (cmd_sz > offsetof(typeof(*cmd), flags) + sizeof(cmd->flags))
 		attr.flags = cmd->flags;
 
+	ret = ib_rdmacg_try_charge(&obj->uobject.cg_obj, ib_dev,
+				   RDMACG_RESOURCE_HCA_OBJECT);
+	if (ret)
+		goto err_charge;
+
 	cq = ib_dev->create_cq(ib_dev, &attr,
 					     file->ucontext, uhw);
 	if (IS_ERR(cq)) {
@@ -1452,6 +1495,10 @@ static struct ib_ucq_object *create_cq(struct ib_uverbs_file *file,
 	ib_destroy_cq(cq);
 
 err_file:
+	ib_rdmacg_uncharge(&obj->uobject.cg_obj, ib_dev,
+			   RDMACG_RESOURCE_HCA_OBJECT);
+
+err_charge:
 	if (ev_file)
 		ib_uverbs_release_ucq(file, ev_file, obj);
 
@@ -1732,6 +1779,8 @@ ssize_t ib_uverbs_destroy_cq(struct ib_uverbs_file *file,
 	if (ret)
 		return ret;
 
+	ib_rdmacg_uncharge(&uobj->cg_obj, ib_dev, RDMACG_RESOURCE_HCA_OBJECT);
+
 	idr_remove_uobj(&ib_uverbs_cq_idr, uobj);
 
 	mutex_lock(&file->mutex);
@@ -1904,6 +1953,11 @@ static int create_qp(struct ib_uverbs_file *file,
 			goto err_put;
 		}
 
+	ret = ib_rdmacg_try_charge(&obj->uevent.uobject.cg_obj, device,
+				   RDMACG_RESOURCE_HCA_OBJECT);
+	if (ret)
+		goto err_put;
+
 	if (cmd->qp_type == IB_QPT_XRC_TGT)
 		qp = ib_create_qp(pd, &attr);
 	else
@@ -1911,7 +1965,7 @@ static int create_qp(struct ib_uverbs_file *file,
 
 	if (IS_ERR(qp)) {
 		ret = PTR_ERR(qp);
-		goto err_put;
+		goto err_create;
 	}
 
 	if (cmd->qp_type != IB_QPT_XRC_TGT) {
@@ -1992,6 +2046,10 @@ static int create_qp(struct ib_uverbs_file *file,
 err_destroy:
 	ib_destroy_qp(qp);
 
+err_create:
+	ib_rdmacg_uncharge(&obj->uevent.uobject.cg_obj, device,
+			   RDMACG_RESOURCE_HCA_OBJECT);
+
 err_put:
 	if (xrcd)
 		put_xrcd_read(xrcd_uobj);
@@ -2518,6 +2576,8 @@ ssize_t ib_uverbs_destroy_qp(struct ib_uverbs_file *file,
 	if (ret)
 		return ret;
 
+	ib_rdmacg_uncharge(&uobj->cg_obj, ib_dev, RDMACG_RESOURCE_HCA_OBJECT);
+
 	if (obj->uxrcd)
 		atomic_dec(&obj->uxrcd->refcnt);
 
@@ -2969,11 +3029,16 @@ ssize_t ib_uverbs_create_ah(struct ib_uverbs_file *file,
 	memset(&attr.dmac, 0, sizeof(attr.dmac));
 	memcpy(attr.grh.dgid.raw, cmd.attr.grh.dgid, 16);
 
+	ret = ib_rdmacg_try_charge(&uobj->cg_obj, ib_dev,
+				   RDMACG_RESOURCE_HCA_OBJECT);
+	if (ret)
+		goto err_charge;
+
 	ah = pd->device->create_ah(pd, &attr, &udata);
 
 	if (IS_ERR(ah)) {
 		ret = PTR_ERR(ah);
-		goto err_put;
+		goto err_create;
 	}
 
 	ah->device  = pd->device;
@@ -3012,7 +3077,10 @@ ssize_t ib_uverbs_create_ah(struct ib_uverbs_file *file,
 err_destroy:
 	ib_destroy_ah(ah);
 
-err_put:
+err_create:
+	ib_rdmacg_uncharge(&uobj->cg_obj, ib_dev, RDMACG_RESOURCE_HCA_OBJECT);
+
+err_charge:
 	put_pd_read(pd);
 
 err:
@@ -3046,6 +3114,8 @@ ssize_t ib_uverbs_destroy_ah(struct ib_uverbs_file *file,
 	if (ret)
 		return ret;
 
+	ib_rdmacg_uncharge(&uobj->cg_obj, ib_dev, RDMACG_RESOURCE_HCA_OBJECT);
+
 	idr_remove_uobj(&ib_uverbs_ah_idr, uobj);
 
 	mutex_lock(&file->mutex);
@@ -3822,10 +3892,16 @@ int ib_uverbs_ex_create_flow(struct ib_uverbs_file *file,
 		err = -EINVAL;
 		goto err_free;
 	}
+
+	err = ib_rdmacg_try_charge(&uobj->cg_obj, ib_dev,
+				   RDMACG_RESOURCE_HCA_OBJECT);
+	if (err)
+		goto err_free;
+
 	flow_id = ib_create_flow(qp, flow_attr, IB_FLOW_DOMAIN_USER);
 	if (IS_ERR(flow_id)) {
 		err = PTR_ERR(flow_id);
-		goto err_free;
+		goto err_create;
 	}
 	flow_id->uobject = uobj;
 	uobj->object = flow_id;
@@ -3858,6 +3934,8 @@ int ib_uverbs_ex_create_flow(struct ib_uverbs_file *file,
 	idr_remove_uobj(&ib_uverbs_rule_idr, uobj);
 destroy_flow:
 	ib_destroy_flow(flow_id);
+err_create:
+	ib_rdmacg_uncharge(&uobj->cg_obj, ib_dev, RDMACG_RESOURCE_HCA_OBJECT);
 err_free:
 	kfree(flow_attr);
 err_put:
@@ -3897,8 +3975,11 @@ int ib_uverbs_ex_destroy_flow(struct ib_uverbs_file *file,
 	flow_id = uobj->object;
 
 	ret = ib_destroy_flow(flow_id);
-	if (!ret)
+	if (!ret) {
+		ib_rdmacg_uncharge(&uobj->cg_obj, ib_dev,
+				   RDMACG_RESOURCE_HCA_OBJECT);
 		uobj->live = 0;
+	}
 
 	put_uobj_write(uobj);
 
@@ -3966,6 +4047,11 @@ static int __uverbs_create_xsrq(struct ib_uverbs_file *file,
 	obj->uevent.events_reported = 0;
 	INIT_LIST_HEAD(&obj->uevent.event_list);
 
+	ret = ib_rdmacg_try_charge(&obj->uevent.uobject.cg_obj, ib_dev,
+				   RDMACG_RESOURCE_HCA_OBJECT);
+	if (ret)
+		goto err_put_cq;
+
 	srq = pd->device->create_srq(pd, &attr, udata);
 	if (IS_ERR(srq)) {
 		ret = PTR_ERR(srq);
@@ -4030,6 +4116,8 @@ static int __uverbs_create_xsrq(struct ib_uverbs_file *file,
 	ib_destroy_srq(srq);
 
 err_put:
+	ib_rdmacg_uncharge(&obj->uevent.uobject.cg_obj, ib_dev,
+			   RDMACG_RESOURCE_HCA_OBJECT);
 	put_pd_read(pd);
 
 err_put_cq:
@@ -4216,6 +4304,8 @@ ssize_t ib_uverbs_destroy_srq(struct ib_uverbs_file *file,
 	if (ret)
 		return ret;
 
+	ib_rdmacg_uncharge(&uobj->cg_obj, ib_dev, RDMACG_RESOURCE_HCA_OBJECT);
+
 	if (srq_type == IB_SRQT_XRC) {
 		us = container_of(obj, struct ib_usrq_object, uevent);
 		atomic_dec(&us->uxrcd->refcnt);

drivers/infiniband/core/uverbs_main.c

@@ -51,6 +51,7 @@
 #include <rdma/ib.h>
 
 #include "uverbs.h"
+#include "core_priv.h"
 
 MODULE_AUTHOR("Roland Dreier");
 MODULE_DESCRIPTION("InfiniBand userspace verbs access");
@@ -237,6 +238,8 @@ static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file,
 
 		idr_remove_uobj(&ib_uverbs_ah_idr, uobj);
 		ib_destroy_ah(ah);
+		ib_rdmacg_uncharge(&uobj->cg_obj, context->device,
+				   RDMACG_RESOURCE_HCA_OBJECT);
 		kfree(uobj);
 	}
 
@@ -246,6 +249,8 @@ static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file,
 
 		idr_remove_uobj(&ib_uverbs_mw_idr, uobj);
 		uverbs_dealloc_mw(mw);
+		ib_rdmacg_uncharge(&uobj->cg_obj, context->device,
+				   RDMACG_RESOURCE_HCA_OBJECT);
 		kfree(uobj);
 	}
 
@@ -254,6 +259,8 @@ static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file,
 
 		idr_remove_uobj(&ib_uverbs_rule_idr, uobj);
 		ib_destroy_flow(flow_id);
+		ib_rdmacg_uncharge(&uobj->cg_obj, context->device,
+				   RDMACG_RESOURCE_HCA_OBJECT);
 		kfree(uobj);
 	}
 
@@ -266,6 +273,8 @@ static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file,
 		if (qp == qp->real_qp)
 			ib_uverbs_detach_umcast(qp, uqp);
 		ib_destroy_qp(qp);
+		ib_rdmacg_uncharge(&uobj->cg_obj, context->device,
+				   RDMACG_RESOURCE_HCA_OBJECT);
 		ib_uverbs_release_uevent(file, &uqp->uevent);
 		kfree(uqp);
 	}
@@ -298,6 +307,8 @@ static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file,
 
 		idr_remove_uobj(&ib_uverbs_srq_idr, uobj);
 		ib_destroy_srq(srq);
+		ib_rdmacg_uncharge(&uobj->cg_obj, context->device,
+				   RDMACG_RESOURCE_HCA_OBJECT);
 		ib_uverbs_release_uevent(file, uevent);
 		kfree(uevent);
 	}
@@ -310,6 +321,8 @@ static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file,
 
 		idr_remove_uobj(&ib_uverbs_cq_idr, uobj);
 		ib_destroy_cq(cq);
+		ib_rdmacg_uncharge(&uobj->cg_obj, context->device,
+				   RDMACG_RESOURCE_HCA_OBJECT);
 		ib_uverbs_release_ucq(file, ev_file, ucq);
 		kfree(ucq);
 	}
@@ -319,6 +332,8 @@ static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file,
 
 		idr_remove_uobj(&ib_uverbs_mr_idr, uobj);
 		ib_dereg_mr(mr);
+		ib_rdmacg_uncharge(&uobj->cg_obj, context->device,
+				   RDMACG_RESOURCE_HCA_OBJECT);
 		kfree(uobj);
 	}
 
@@ -339,11 +354,16 @@ static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file,
 
 		idr_remove_uobj(&ib_uverbs_pd_idr, uobj);
 		ib_dealloc_pd(pd);
+		ib_rdmacg_uncharge(&uobj->cg_obj, context->device,
+				   RDMACG_RESOURCE_HCA_OBJECT);
 		kfree(uobj);
 	}
 
 	put_pid(context->tgid);
 
+	ib_rdmacg_uncharge(&context->cg_obj, context->device,
+			   RDMACG_RESOURCE_HCA_HANDLE);
+
 	return context->device->dealloc_ucontext(context);
 }
 

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.
  */

include/rdma/ib_verbs.h

@@ -60,6 +60,7 @@
 #include <linux/atomic.h>
 #include <linux/mmu_notifier.h>
 #include <linux/uaccess.h>
+#include <linux/cgroup_rdma.h>
 
 extern struct workqueue_struct *ib_wq;
 extern struct workqueue_struct *ib_comp_wq;
@@ -1331,6 +1332,12 @@ struct ib_fmr_attr {
 
 struct ib_umem;
 
+struct ib_rdmacg_object {
+#ifdef CONFIG_CGROUP_RDMA
+	struct rdma_cgroup	*cg;		/* owner rdma cgroup */
+#endif
+};
+
 struct ib_ucontext {
 	struct ib_device       *device;
 	struct list_head	pd_list;
@@ -1363,6 +1370,8 @@ struct ib_ucontext {
 	struct list_head	no_private_counters;
 	int                     odp_mrs_count;
 #endif
+
+	struct ib_rdmacg_object	cg_obj;
 };
 
 struct ib_uobject {
@@ -1370,6 +1379,7 @@ struct ib_uobject {
 	struct ib_ucontext     *context;	/* associated user context */
 	void		       *object;		/* containing object */
 	struct list_head	list;		/* link to context's list */
+	struct ib_rdmacg_object	cg_obj;		/* rdmacg object */
 	int			id;		/* index into kernel idr */
 	struct kref		ref;
 	struct rw_semaphore	mutex;		/* protects .live */
@@ -2118,6 +2128,10 @@ struct ib_device {
 	struct attribute_group	     *hw_stats_ag;
 	struct rdma_hw_stats         *hw_stats;
 
+#ifdef CONFIG_CGROUP_RDMA
+	struct rdmacg_device         cg_device;
+#endif
+
 	/**
 	 * The following mandatory functions are used only at device
 	 * registration.  Keep functions such as these at the end of this

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

kernel/cgroup/rdma.c

+/*
+ * RDMA resource limiting controller for cgroups.
+ *
+ * Used to allow a cgroup hierarchy to stop processes from consuming
+ * additional RDMA resources after a certain limit is reached.
+ *
+ * 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.
+ */
+
+#include <linux/bitops.h>
+#include <linux/slab.h>
+#include <linux/seq_file.h>
+#include <linux/cgroup.h>
+#include <linux/parser.h>
+#include <linux/cgroup_rdma.h>
+
+#define RDMACG_MAX_STR "max"
+
+/*
+ * Protects list of resource pools maintained on per cgroup basis
+ * and rdma device list.
+ */
+static DEFINE_MUTEX(rdmacg_mutex);
+static LIST_HEAD(rdmacg_devices);
+
+enum rdmacg_file_type {
+	RDMACG_RESOURCE_TYPE_MAX,
+	RDMACG_RESOURCE_TYPE_STAT,
+};
+
+/*
+ * resource table definition as to be seen by the user.
+ * Need to add entries to it when more resources are
+ * added/defined at IB verb/core layer.
+ */
+static char const *rdmacg_resource_names[] = {
+	[RDMACG_RESOURCE_HCA_HANDLE]	= "hca_handle",
+	[RDMACG_RESOURCE_HCA_OBJECT]	= "hca_object",
+};
+
+/* resource tracker for each resource of rdma cgroup */
+struct rdmacg_resource {
+	int max;
+	int usage;
+};
+
+/*
+ * resource pool object which represents per cgroup, per device
+ * resources. There are multiple instances of this object per cgroup,
+ * therefore it cannot be embedded within rdma_cgroup structure. It
+ * is maintained as list.
+ */
+struct rdmacg_resource_pool {
+	struct rdmacg_device	*device;
+	struct rdmacg_resource	resources[RDMACG_RESOURCE_MAX];
+
+	struct list_head	cg_node;
+	struct list_head	dev_node;
+
+	/* count active user tasks of this pool */
+	u64			usage_sum;
+	/* total number counts which are set to max */
+	int			num_max_cnt;
+};
+
+static struct rdma_cgroup *css_rdmacg(struct cgroup_subsys_state *css)
+{
+	return container_of(css, struct rdma_cgroup, css);
+}
+
+static struct rdma_cgroup *parent_rdmacg(struct rdma_cgroup *cg)
+{
+	return css_rdmacg(cg->css.parent);
+}
+
+static inline struct rdma_cgroup *get_current_rdmacg(void)
+{
+	return css_rdmacg(task_get_css(current, rdma_cgrp_id));
+}
+
+static void set_resource_limit(struct rdmacg_resource_pool *rpool,
+			       int index, int new_max)
+{
+	if (new_max == S32_MAX) {
+		if (rpool->resources[index].max != S32_MAX)
+			rpool->num_max_cnt++;
+	} else {
+		if (rpool->resources[index].max == S32_MAX)
+			rpool->num_max_cnt--;
+	}
+	rpool->resources[index].max = new_max;
+}
+
+static void set_all_resource_max_limit(struct rdmacg_resource_pool *rpool)
+{
+	int i;
+
+	for (i = 0; i < RDMACG_RESOURCE_MAX; i++)
+		set_resource_limit(rpool, i, S32_MAX);
+}
+
+static void free_cg_rpool_locked(struct rdmacg_resource_pool *rpool)
+{
+	lockdep_assert_held(&rdmacg_mutex);
+
+	list_del(&rpool->cg_node);
+	list_del(&rpool->dev_node);
+	kfree(rpool);
+}
+
+static struct rdmacg_resource_pool *
+find_cg_rpool_locked(struct rdma_cgroup *cg,
+		     struct rdmacg_device *device)
+
+{
+	struct rdmacg_resource_pool *pool;
+
+	lockdep_assert_held(&rdmacg_mutex);
+
+	list_for_each_entry(pool, &cg->rpools, cg_node)
+		if (pool->device == device)
+			return pool;
+
+	return NULL;
+}
+
+static struct rdmacg_resource_pool *
+get_cg_rpool_locked(struct rdma_cgroup *cg, struct rdmacg_device *device)
+{
+	struct rdmacg_resource_pool *rpool;
+
+	rpool = find_cg_rpool_locked(cg, device);
+	if (rpool)
+		return rpool;
+
+	rpool = kzalloc(sizeof(*rpool), GFP_KERNEL);
+	if (!rpool)
+		return ERR_PTR(-ENOMEM);
+
+	rpool->device = device;
+	set_all_resource_max_limit(rpool);
+
+	INIT_LIST_HEAD(&rpool->cg_node);
+	INIT_LIST_HEAD(&rpool->dev_node);
+	list_add_tail(&rpool->cg_node, &cg->rpools);
+	list_add_tail(&rpool->dev_node, &device->rpools);
+	return rpool;
+}
+
+/**
+ * uncharge_cg_locked - uncharge resource for rdma cgroup
+ * @cg: pointer to cg to uncharge and all parents in hierarchy
+ * @device: pointer to rdmacg device
+ * @index: index of the resource to uncharge in cg (resource pool)
+ *
+ * It also frees the resource pool which was created as part of
+ * charging operation when there are no resources attached to
+ * resource pool.
+ */
+static void
+uncharge_cg_locked(struct rdma_cgroup *cg,
+		   struct rdmacg_device *device,
+		   enum rdmacg_resource_type index)
+{
+	struct rdmacg_resource_pool *rpool;
+
+	rpool = find_cg_rpool_locked(cg, device);
+
+	/*
+	 * rpool cannot be null at this stage. Let kernel operate in case
+	 * if there a bug in IB stack or rdma controller, instead of crashing
+	 * the system.
+	 */
+	if (unlikely(!rpool)) {
+		pr_warn("Invalid device %p or rdma cgroup %p\n", cg, device);
+		return;
+	}
+
+	rpool->resources[index].usage--;
+
+	/*
+	 * A negative count (or overflow) is invalid,
+	 * it indicates a bug in the rdma controller.
+	 */
+	WARN_ON_ONCE(rpool->resources[index].usage < 0);
+	rpool->usage_sum--;
+	if (rpool->usage_sum == 0 &&
+	    rpool->num_max_cnt == RDMACG_RESOURCE_MAX) {
+		/*
+		 * No user of the rpool and all entries are set to max, so
+		 * safe to delete this rpool.
+		 */
+		free_cg_rpool_locked(rpool);
+	}
+}
+
+/**
+ * rdmacg_uncharge_hierarchy - hierarchically uncharge rdma resource count
+ * @device: pointer to rdmacg device
+ * @stop_cg: while traversing hirerchy, when meet with stop_cg cgroup
+ *           stop uncharging
+ * @index: index of the resource to uncharge in cg in given resource pool
+ */
+static void rdmacg_uncharge_hierarchy(struct rdma_cgroup *cg,
+				     struct rdmacg_device *device,
+				     struct rdma_cgroup *stop_cg,
+				     enum rdmacg_resource_type index)
+{
+	struct rdma_cgroup *p;
+
+	mutex_lock(&rdmacg_mutex);
+
+	for (p = cg; p != stop_cg; p = parent_rdmacg(p))
+		uncharge_cg_locked(p, device, index);
+
+	mutex_unlock(&rdmacg_mutex);
+
+	css_put(&cg->css);
+}
+
+/**
+ * rdmacg_uncharge - hierarchically uncharge rdma resource count
+ * @device: pointer to rdmacg device
+ * @index: index of the resource to uncharge in cgroup in given resource pool
+ */
+void rdmacg_uncharge(struct rdma_cgroup *cg,
+		     struct rdmacg_device *device,
+		     enum rdmacg_resource_type index)
+{
+	if (index >= RDMACG_RESOURCE_MAX)
+		return;
+
+	rdmacg_uncharge_hierarchy(cg, device, NULL, index);
+}
+EXPORT_SYMBOL(rdmacg_uncharge);
+
+/**
+ * rdmacg_try_charge - hierarchically try to charge the rdma resource
+ * @rdmacg: pointer to rdma cgroup which will own this resource
+ * @device: pointer to rdmacg device
+ * @index: index of the resource to charge in cgroup (resource pool)
+ *
+ * This function follows charging resource in hierarchical way.
+ * It will fail if the charge would cause the new value to exceed the
+ * hierarchical limit.
+ * Returns 0 if the charge succeded, otherwise -EAGAIN, -ENOMEM or -EINVAL.
+ * Returns pointer to rdmacg for this resource when charging is successful.
+ *
+ * Charger needs to account resources on two criteria.
+ * (a) per cgroup & (b) per device resource usage.
+ * Per cgroup resource usage ensures that tasks of cgroup doesn't cross
+ * the configured limits. Per device provides granular configuration
+ * in multi device usage. It allocates resource pool in the hierarchy
+ * for each parent it come across for first resource. Later on resource
+ * pool will be available. Therefore it will be much faster thereon
+ * to charge/uncharge.
+ */
+int rdmacg_try_charge(struct rdma_cgroup **rdmacg,
+		      struct rdmacg_device *device,
+		      enum rdmacg_resource_type index)
+{
+	struct rdma_cgroup *cg, *p;
+	struct rdmacg_resource_pool *rpool;
+	s64 new;
+	int ret = 0;
+
+	if (index >= RDMACG_RESOURCE_MAX)
+		return -EINVAL;
+
+	/*
+	 * hold on to css, as cgroup can be removed but resource
+	 * accounting happens on css.
+	 */
+	cg = get_current_rdmacg();
+
+	mutex_lock(&rdmacg_mutex);
+	for (p = cg; p; p = parent_rdmacg(p)) {
+		rpool = get_cg_rpool_locked(p, device);
+		if (IS_ERR(rpool)) {
+			ret = PTR_ERR(rpool);
+			goto err;
+		} else {
+			new = rpool->resources[index].usage + 1;
+			if (new > rpool->resources[index].max) {
+				ret = -EAGAIN;
+				goto err;
+			} else {
+				rpool->resources[index].usage = new;
+				rpool->usage_sum++;
+			}
+		}
+	}
+	mutex_unlock(&rdmacg_mutex);
+
+	*rdmacg = cg;
+	return 0;
+
+err:
+	mutex_unlock(&rdmacg_mutex);
+	rdmacg_uncharge_hierarchy(cg, device, p, index);
+	return ret;
+}
+EXPORT_SYMBOL(rdmacg_try_charge);
+
+/**
+ * rdmacg_register_device - register rdmacg device to rdma controller.
+ * @device: pointer to rdmacg device whose resources need to be accounted.
+ *
+ * If IB stack wish a device to participate in rdma cgroup resource
+ * tracking, it must invoke this API to register with rdma cgroup before
+ * any user space application can start using the RDMA resources.
+ * Returns 0 on success or EINVAL when table length given is beyond
+ * supported size.
+ */
+int rdmacg_register_device(struct rdmacg_device *device)
+{
+	INIT_LIST_HEAD(&device->dev_node);
+	INIT_LIST_HEAD(&device->rpools);
+
+	mutex_lock(&rdmacg_mutex);
+	list_add_tail(&device->dev_node, &rdmacg_devices);
+	mutex_unlock(&rdmacg_mutex);
+	return 0;
+}
+EXPORT_SYMBOL(rdmacg_register_device);
+
+/**
+ * rdmacg_unregister_device - unregister rdmacg device from rdma controller.
+ * @device: pointer to rdmacg device which was previously registered with rdma
+ *          controller using rdmacg_register_device().
+ *
+ * IB stack must invoke this after all the resources of the IB device
+ * are destroyed and after ensuring that no more resources will be created
+ * when this API is invoked.
+ */
+void rdmacg_unregister_device(struct rdmacg_device *device)
+{
+	struct rdmacg_resource_pool *rpool, *tmp;
+
+	/*
+	 * Synchronize with any active resource settings,
+	 * usage query happening via configfs.
+	 */
+	mutex_lock(&rdmacg_mutex);
+	list_del_init(&device->dev_node);
+
+	/*
+	 * Now that this device is off the cgroup list, its safe to free
+	 * all the rpool resources.
+	 */
+	list_for_each_entry_safe(rpool, tmp, &device->rpools, dev_node)
+		free_cg_rpool_locked(rpool);
+
+	mutex_unlock(&rdmacg_mutex);
+}
+EXPORT_SYMBOL(rdmacg_unregister_device);
+
+static int parse_resource(char *c, int *intval)
+{
+	substring_t argstr;
+	const char **table = &rdmacg_resource_names[0];
+	char *name, *value = c;
+	size_t len;
+	int ret, i = 0;
+
+	name = strsep(&value, "=");
+	if (!name || !value)
+		return -EINVAL;
+
+	len = strlen(value);
+
+	for (i = 0; i < RDMACG_RESOURCE_MAX; i++) {
+		if (strcmp(table[i], name))
+			continue;
+
+		argstr.from = value;
+		argstr.to = value + len;
+
+		ret = match_int(&argstr, intval);
+		if (ret >= 0) {
+			if (*intval < 0)
+				break;
+			return i;
+		}
+		if (strncmp(value, RDMACG_MAX_STR, len) == 0) {
+			*intval = S32_MAX;
+			return i;
+		}
+		break;
+	}
+	return -EINVAL;
+}
+
+static int rdmacg_parse_limits(char *options,
+			       int *new_limits, unsigned long *enables)
+{
+	char *c;
+	int err = -EINVAL;
+
+	/* parse resource options */
+	while ((c = strsep(&options, " ")) != NULL) {
+		int index, intval;
+
+		index = parse_resource(c, &intval);
+		if (index < 0)
+			goto err;
+
+		new_limits[index] = intval;
+		*enables |= BIT(index);
+	}
+	return 0;
+
+err:
+	return err;
+}
+
+static struct rdmacg_device *rdmacg_get_device_locked(const char *name)
+{
+	struct rdmacg_device *device;
+
+	lockdep_assert_held(&rdmacg_mutex);
+
+	list_for_each_entry(device, &rdmacg_devices, dev_node)
+		if (!strcmp(name, device->name))
+			return device;
+
+	return NULL;
+}
+
+static ssize_t rdmacg_resource_set_max(struct kernfs_open_file *of,
+				       char *buf, size_t nbytes, loff_t off)
+{
+	struct rdma_cgroup *cg = css_rdmacg(of_css(of));
+	const char *dev_name;
+	struct rdmacg_resource_pool *rpool;
+	struct rdmacg_device *device;
+	char *options = strstrip(buf);
+	int *new_limits;
+	unsigned long enables = 0;
+	int i = 0, ret = 0;
+
+	/* extract the device name first */
+	dev_name = strsep(&options, " ");
+	if (!dev_name) {
+		ret = -EINVAL;
+		goto err;
+	}
+
+	new_limits = kcalloc(RDMACG_RESOURCE_MAX, sizeof(int), GFP_KERNEL);
+	if (!new_limits) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	ret = rdmacg_parse_limits(options, new_limits, &enables);
+	if (ret)
+		goto parse_err;
+
+	/* acquire lock to synchronize with hot plug devices */
+	mutex_lock(&rdmacg_mutex);
+
+	device = rdmacg_get_device_locked(dev_name);
+	if (!device) {
+		ret = -ENODEV;
+		goto dev_err;
+	}
+
+	rpool = get_cg_rpool_locked(cg, device);
+	if (IS_ERR(rpool)) {
+		ret = PTR_ERR(rpool);
+		goto dev_err;
+	}
+
+	/* now set the new limits of the rpool */
+	for_each_set_bit(i, &enables, RDMACG_RESOURCE_MAX)
+		set_resource_limit(rpool, i, new_limits[i]);
+
+	if (rpool->usage_sum == 0 &&
+	    rpool->num_max_cnt == RDMACG_RESOURCE_MAX) {
+		/*
+		 * No user of the rpool and all entries are set to max, so
+		 * safe to delete this rpool.
+		 */
+		free_cg_rpool_locked(rpool);
+	}
+
+dev_err:
+	mutex_unlock(&rdmacg_mutex);
+
+parse_err:
+	kfree(new_limits);
+
+err:
+	return ret ?: nbytes;
+}
+
+static void print_rpool_values(struct seq_file *sf,
+			       struct rdmacg_resource_pool *rpool)
+{
+	enum rdmacg_file_type sf_type;
+	int i;
+	u32 value;
+
+	sf_type = seq_cft(sf)->private;
+
+	for (i = 0; i < RDMACG_RESOURCE_MAX; i++) {
+		seq_puts(sf, rdmacg_resource_names[i]);
+		seq_putc(sf, '=');
+		if (sf_type == RDMACG_RESOURCE_TYPE_MAX) {
+			if (rpool)
+				value = rpool->resources[i].max;
+			else
+				value = S32_MAX;
+		} else {
+			if (rpool)
+				value = rpool->resources[i].usage;
+			else
+				value = 0;
+		}
+
+		if (value == S32_MAX)
+			seq_puts(sf, RDMACG_MAX_STR);
+		else
+			seq_printf(sf, "%d", value);
+		seq_putc(sf, ' ');
+	}
+}
+
+static int rdmacg_resource_read(struct seq_file *sf, void *v)
+{
+	struct rdmacg_device *device;
+	struct rdmacg_resource_pool *rpool;
+	struct rdma_cgroup *cg = css_rdmacg(seq_css(sf));
+
+	mutex_lock(&rdmacg_mutex);
+
+	list_for_each_entry(device, &rdmacg_devices, dev_node) {
+		seq_printf(sf, "%s ", device->name);
+
+		rpool = find_cg_rpool_locked(cg, device);
+		print_rpool_values(sf, rpool);
+
+		seq_putc(sf, '\n');
+	}
+
+	mutex_unlock(&rdmacg_mutex);
+	return 0;
+}
+
+static struct cftype rdmacg_files[] = {
+	{
+		.name = "max",
+		.write = rdmacg_resource_set_max,
+		.seq_show = rdmacg_resource_read,
+		.private = RDMACG_RESOURCE_TYPE_MAX,
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	{
+		.name = "current",
+		.seq_show = rdmacg_resource_read,
+		.private = RDMACG_RESOURCE_TYPE_STAT,
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	{ }	/* terminate */
+};
+
+static struct cgroup_subsys_state *
+rdmacg_css_alloc(struct cgroup_subsys_state *parent)
+{
+	struct rdma_cgroup *cg;
+
+	cg = kzalloc(sizeof(*cg), GFP_KERNEL);
+	if (!cg)
+		return ERR_PTR(-ENOMEM);
+
+	INIT_LIST_HEAD(&cg->rpools);
+	return &cg->css;
+}
+
+static void rdmacg_css_free(struct cgroup_subsys_state *css)
+{
+	struct rdma_cgroup *cg = css_rdmacg(css);
+
+	kfree(cg);
+}
+
+/**
+ * rdmacg_css_offline - cgroup css_offline callback
+ * @css: css of interest
+ *
+ * This function is called when @css is about to go away and responsible
+ * for shooting down all rdmacg associated with @css. As part of that it
+ * marks all the resource pool entries to max value, so that when resources are
+ * uncharged, associated resource pool can be freed as well.
+ */
+static void rdmacg_css_offline(struct cgroup_subsys_state *css)
+{
+	struct rdma_cgroup *cg = css_rdmacg(css);
+	struct rdmacg_resource_pool *rpool;
+
+	mutex_lock(&rdmacg_mutex);
+
+	list_for_each_entry(rpool, &cg->rpools, cg_node)
+		set_all_resource_max_limit(rpool);
+
+	mutex_unlock(&rdmacg_mutex);
+}
+
+struct cgroup_subsys rdma_cgrp_subsys = {
+	.css_alloc	= rdmacg_css_alloc,
+	.css_free	= rdmacg_css_free,
+	.css_offline	= rdmacg_css_offline,
+	.legacy_cftypes	= rdmacg_files,
+	.dfl_cftypes	= rdmacg_files,
+};