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Linux/net/core/netprio_cgroup.c

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  1 /*
  2  * net/core/netprio_cgroup.c    Priority Control Group
  3  *
  4  *              This program is free software; you can redistribute it and/or
  5  *              modify it under the terms of the GNU General Public License
  6  *              as published by the Free Software Foundation; either version
  7  *              2 of the License, or (at your option) any later version.
  8  *
  9  * Authors:     Neil Horman <nhorman@tuxdriver.com>
 10  */
 11 
 12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 13 
 14 #include <linux/module.h>
 15 #include <linux/slab.h>
 16 #include <linux/types.h>
 17 #include <linux/string.h>
 18 #include <linux/errno.h>
 19 #include <linux/skbuff.h>
 20 #include <linux/cgroup.h>
 21 #include <linux/rcupdate.h>
 22 #include <linux/atomic.h>
 23 #include <linux/sched/task.h>
 24 
 25 #include <net/rtnetlink.h>
 26 #include <net/pkt_cls.h>
 27 #include <net/sock.h>
 28 #include <net/netprio_cgroup.h>
 29 
 30 #include <linux/fdtable.h>
 31 
 32 /*
 33  * netprio allocates per-net_device priomap array which is indexed by
 34  * css->id.  Limiting css ID to 16bits doesn't lose anything.
 35  */
 36 #define NETPRIO_ID_MAX          USHRT_MAX
 37 
 38 #define PRIOMAP_MIN_SZ          128
 39 
 40 /*
 41  * Extend @dev->priomap so that it's large enough to accommodate
 42  * @target_idx.  @dev->priomap.priomap_len > @target_idx after successful
 43  * return.  Must be called under rtnl lock.
 44  */
 45 static int extend_netdev_table(struct net_device *dev, u32 target_idx)
 46 {
 47         struct netprio_map *old, *new;
 48         size_t new_sz, new_len;
 49 
 50         /* is the existing priomap large enough? */
 51         old = rtnl_dereference(dev->priomap);
 52         if (old && old->priomap_len > target_idx)
 53                 return 0;
 54 
 55         /*
 56          * Determine the new size.  Let's keep it power-of-two.  We start
 57          * from PRIOMAP_MIN_SZ and double it until it's large enough to
 58          * accommodate @target_idx.
 59          */
 60         new_sz = PRIOMAP_MIN_SZ;
 61         while (true) {
 62                 new_len = (new_sz - offsetof(struct netprio_map, priomap)) /
 63                         sizeof(new->priomap[0]);
 64                 if (new_len > target_idx)
 65                         break;
 66                 new_sz *= 2;
 67                 /* overflowed? */
 68                 if (WARN_ON(new_sz < PRIOMAP_MIN_SZ))
 69                         return -ENOSPC;
 70         }
 71 
 72         /* allocate & copy */
 73         new = kzalloc(new_sz, GFP_KERNEL);
 74         if (!new)
 75                 return -ENOMEM;
 76 
 77         if (old)
 78                 memcpy(new->priomap, old->priomap,
 79                        old->priomap_len * sizeof(old->priomap[0]));
 80 
 81         new->priomap_len = new_len;
 82 
 83         /* install the new priomap */
 84         rcu_assign_pointer(dev->priomap, new);
 85         if (old)
 86                 kfree_rcu(old, rcu);
 87         return 0;
 88 }
 89 
 90 /**
 91  * netprio_prio - return the effective netprio of a cgroup-net_device pair
 92  * @css: css part of the target pair
 93  * @dev: net_device part of the target pair
 94  *
 95  * Should be called under RCU read or rtnl lock.
 96  */
 97 static u32 netprio_prio(struct cgroup_subsys_state *css, struct net_device *dev)
 98 {
 99         struct netprio_map *map = rcu_dereference_rtnl(dev->priomap);
100         int id = css->cgroup->id;
101 
102         if (map && id < map->priomap_len)
103                 return map->priomap[id];
104         return 0;
105 }
106 
107 /**
108  * netprio_set_prio - set netprio on a cgroup-net_device pair
109  * @css: css part of the target pair
110  * @dev: net_device part of the target pair
111  * @prio: prio to set
112  *
113  * Set netprio to @prio on @css-@dev pair.  Should be called under rtnl
114  * lock and may fail under memory pressure for non-zero @prio.
115  */
116 static int netprio_set_prio(struct cgroup_subsys_state *css,
117                             struct net_device *dev, u32 prio)
118 {
119         struct netprio_map *map;
120         int id = css->cgroup->id;
121         int ret;
122 
123         /* avoid extending priomap for zero writes */
124         map = rtnl_dereference(dev->priomap);
125         if (!prio && (!map || map->priomap_len <= id))
126                 return 0;
127 
128         ret = extend_netdev_table(dev, id);
129         if (ret)
130                 return ret;
131 
132         map = rtnl_dereference(dev->priomap);
133         map->priomap[id] = prio;
134         return 0;
135 }
136 
137 static struct cgroup_subsys_state *
138 cgrp_css_alloc(struct cgroup_subsys_state *parent_css)
139 {
140         struct cgroup_subsys_state *css;
141 
142         css = kzalloc(sizeof(*css), GFP_KERNEL);
143         if (!css)
144                 return ERR_PTR(-ENOMEM);
145 
146         return css;
147 }
148 
149 static int cgrp_css_online(struct cgroup_subsys_state *css)
150 {
151         struct cgroup_subsys_state *parent_css = css->parent;
152         struct net_device *dev;
153         int ret = 0;
154 
155         if (css->id > NETPRIO_ID_MAX)
156                 return -ENOSPC;
157 
158         if (!parent_css)
159                 return 0;
160 
161         rtnl_lock();
162         /*
163          * Inherit prios from the parent.  As all prios are set during
164          * onlining, there is no need to clear them on offline.
165          */
166         for_each_netdev(&init_net, dev) {
167                 u32 prio = netprio_prio(parent_css, dev);
168 
169                 ret = netprio_set_prio(css, dev, prio);
170                 if (ret)
171                         break;
172         }
173         rtnl_unlock();
174         return ret;
175 }
176 
177 static void cgrp_css_free(struct cgroup_subsys_state *css)
178 {
179         kfree(css);
180 }
181 
182 static u64 read_prioidx(struct cgroup_subsys_state *css, struct cftype *cft)
183 {
184         return css->cgroup->id;
185 }
186 
187 static int read_priomap(struct seq_file *sf, void *v)
188 {
189         struct net_device *dev;
190 
191         rcu_read_lock();
192         for_each_netdev_rcu(&init_net, dev)
193                 seq_printf(sf, "%s %u\n", dev->name,
194                            netprio_prio(seq_css(sf), dev));
195         rcu_read_unlock();
196         return 0;
197 }
198 
199 static ssize_t write_priomap(struct kernfs_open_file *of,
200                              char *buf, size_t nbytes, loff_t off)
201 {
202         char devname[IFNAMSIZ + 1];
203         struct net_device *dev;
204         u32 prio;
205         int ret;
206 
207         if (sscanf(buf, "%"__stringify(IFNAMSIZ)"s %u", devname, &prio) != 2)
208                 return -EINVAL;
209 
210         dev = dev_get_by_name(&init_net, devname);
211         if (!dev)
212                 return -ENODEV;
213 
214         cgroup_sk_alloc_disable();
215 
216         rtnl_lock();
217 
218         ret = netprio_set_prio(of_css(of), dev, prio);
219 
220         rtnl_unlock();
221         dev_put(dev);
222         return ret ?: nbytes;
223 }
224 
225 static int update_netprio(const void *v, struct file *file, unsigned n)
226 {
227         int err;
228         struct socket *sock = sock_from_file(file, &err);
229         if (sock) {
230                 spin_lock(&cgroup_sk_update_lock);
231                 sock_cgroup_set_prioidx(&sock->sk->sk_cgrp_data,
232                                         (unsigned long)v);
233                 spin_unlock(&cgroup_sk_update_lock);
234         }
235         return 0;
236 }
237 
238 static void net_prio_attach(struct cgroup_taskset *tset)
239 {
240         struct task_struct *p;
241         struct cgroup_subsys_state *css;
242 
243         cgroup_taskset_for_each(p, css, tset) {
244                 void *v = (void *)(unsigned long)css->cgroup->id;
245 
246                 task_lock(p);
247                 iterate_fd(p->files, 0, update_netprio, v);
248                 task_unlock(p);
249         }
250 }
251 
252 static struct cftype ss_files[] = {
253         {
254                 .name = "prioidx",
255                 .read_u64 = read_prioidx,
256         },
257         {
258                 .name = "ifpriomap",
259                 .seq_show = read_priomap,
260                 .write = write_priomap,
261         },
262         { }     /* terminate */
263 };
264 
265 struct cgroup_subsys net_prio_cgrp_subsys = {
266         .css_alloc      = cgrp_css_alloc,
267         .css_online     = cgrp_css_online,
268         .css_free       = cgrp_css_free,
269         .attach         = net_prio_attach,
270         .legacy_cftypes = ss_files,
271 };
272 
273 static int netprio_device_event(struct notifier_block *unused,
274                                 unsigned long event, void *ptr)
275 {
276         struct net_device *dev = netdev_notifier_info_to_dev(ptr);
277         struct netprio_map *old;
278 
279         /*
280          * Note this is called with rtnl_lock held so we have update side
281          * protection on our rcu assignments
282          */
283 
284         switch (event) {
285         case NETDEV_UNREGISTER:
286                 old = rtnl_dereference(dev->priomap);
287                 RCU_INIT_POINTER(dev->priomap, NULL);
288                 if (old)
289                         kfree_rcu(old, rcu);
290                 break;
291         }
292         return NOTIFY_DONE;
293 }
294 
295 static struct notifier_block netprio_device_notifier = {
296         .notifier_call = netprio_device_event
297 };
298 
299 static int __init init_cgroup_netprio(void)
300 {
301         register_netdevice_notifier(&netprio_device_notifier);
302         return 0;
303 }
304 
305 subsys_initcall(init_cgroup_netprio);
306 MODULE_LICENSE("GPL v2");
307 

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