diff --git a/include/linux/cgroup_rdma.h b/include/linux/cgroup_rdma.h
new file mode 100644
index 0000000..e94290b
--- /dev/null
+++ b/include/linux/cgroup_rdma.h
@@ -0,0 +1,53 @@
+/*
+ * 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 */
diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
index 0df0336a..d0e597c 100644
--- a/include/linux/cgroup_subsys.h
+++ b/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.
  */
diff --git a/init/Kconfig b/init/Kconfig
index 34407f1..351bcac 100644
--- a/init/Kconfig
+++ b/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
diff --git a/kernel/Makefile b/kernel/Makefile
index eb26e12c..04b6f78 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -67,6 +67,7 @@ obj-$(CONFIG_COMPAT) += compat.o
 obj-$(CONFIG_CGROUPS) += cgroup.o
 obj-$(CONFIG_CGROUP_FREEZER) += cgroup_freezer.o
 obj-$(CONFIG_CGROUP_PIDS) += cgroup_pids.o
+obj-$(CONFIG_CGROUP_RDMA) += cgroup_rdma.o
 obj-$(CONFIG_CPUSETS) += cpuset.o
 obj-$(CONFIG_UTS_NS) += utsname.o
 obj-$(CONFIG_USER_NS) += user_namespace.o
diff --git a/kernel/cgroup_rdma.c b/kernel/cgroup_rdma.c
new file mode 100644
index 0000000..38ce5bb
--- /dev/null
+++ b/kernel/cgroup_rdma.c
@@ -0,0 +1,617 @@
+/*
+ * 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_hirerchy - 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_hirerchy(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_hirerchy(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_hirerchy(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;
+		}
+
+		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,
+};
