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// SPDX-License-Identifier: GPL-2.0-only
/*
* 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>
*/
#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
|