5fe03def34b24c396f299aa57bda4b1cc5a3df2a
[linux-2.6.git] / block / blk-cgroup.c
1 /*
2  * Common Block IO controller cgroup interface
3  *
4  * Based on ideas and code from CFQ, CFS and BFQ:
5  * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
6  *
7  * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
8  *                    Paolo Valente <paolo.valente@unimore.it>
9  *
10  * Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
11  *                    Nauman Rafique <nauman@google.com>
12  */
13 #include <linux/ioprio.h>
14 #include <linux/seq_file.h>
15 #include <linux/kdev_t.h>
16 #include <linux/module.h>
17 #include <linux/err.h>
18 #include <linux/slab.h>
19 #include "blk-cgroup.h"
20
21 static DEFINE_SPINLOCK(blkio_list_lock);
22 static LIST_HEAD(blkio_list);
23
24 struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
25 EXPORT_SYMBOL_GPL(blkio_root_cgroup);
26
27 static struct cgroup_subsys_state *blkiocg_create(struct cgroup_subsys *,
28                                                   struct cgroup *);
29 static int blkiocg_can_attach(struct cgroup_subsys *, struct cgroup *,
30                               struct task_struct *, bool);
31 static void blkiocg_attach(struct cgroup_subsys *, struct cgroup *,
32                            struct cgroup *, struct task_struct *, bool);
33 static void blkiocg_destroy(struct cgroup_subsys *, struct cgroup *);
34 static int blkiocg_populate(struct cgroup_subsys *, struct cgroup *);
35
36 struct cgroup_subsys blkio_subsys = {
37         .name = "blkio",
38         .create = blkiocg_create,
39         .can_attach = blkiocg_can_attach,
40         .attach = blkiocg_attach,
41         .destroy = blkiocg_destroy,
42         .populate = blkiocg_populate,
43 #ifdef CONFIG_BLK_CGROUP
44         /* note: blkio_subsys_id is otherwise defined in blk-cgroup.h */
45         .subsys_id = blkio_subsys_id,
46 #endif
47         .use_id = 1,
48         .module = THIS_MODULE,
49 };
50 EXPORT_SYMBOL_GPL(blkio_subsys);
51
52 struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
53 {
54         return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
55                             struct blkio_cgroup, css);
56 }
57 EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup);
58
59 void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
60                         unsigned long time, unsigned long sectors)
61 {
62         blkg->time += time;
63         blkg->sectors += sectors;
64 }
65 EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_stats);
66
67 void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
68                         struct blkio_group *blkg, void *key, dev_t dev)
69 {
70         unsigned long flags;
71
72         spin_lock_irqsave(&blkcg->lock, flags);
73         rcu_assign_pointer(blkg->key, key);
74         blkg->blkcg_id = css_id(&blkcg->css);
75         hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
76         spin_unlock_irqrestore(&blkcg->lock, flags);
77 #ifdef CONFIG_DEBUG_BLK_CGROUP
78         /* Need to take css reference ? */
79         cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
80 #endif
81         blkg->dev = dev;
82 }
83 EXPORT_SYMBOL_GPL(blkiocg_add_blkio_group);
84
85 static void __blkiocg_del_blkio_group(struct blkio_group *blkg)
86 {
87         hlist_del_init_rcu(&blkg->blkcg_node);
88         blkg->blkcg_id = 0;
89 }
90
91 /*
92  * returns 0 if blkio_group was still on cgroup list. Otherwise returns 1
93  * indicating that blk_group was unhashed by the time we got to it.
94  */
95 int blkiocg_del_blkio_group(struct blkio_group *blkg)
96 {
97         struct blkio_cgroup *blkcg;
98         unsigned long flags;
99         struct cgroup_subsys_state *css;
100         int ret = 1;
101
102         rcu_read_lock();
103         css = css_lookup(&blkio_subsys, blkg->blkcg_id);
104         if (!css)
105                 goto out;
106
107         blkcg = container_of(css, struct blkio_cgroup, css);
108         spin_lock_irqsave(&blkcg->lock, flags);
109         if (!hlist_unhashed(&blkg->blkcg_node)) {
110                 __blkiocg_del_blkio_group(blkg);
111                 ret = 0;
112         }
113         spin_unlock_irqrestore(&blkcg->lock, flags);
114 out:
115         rcu_read_unlock();
116         return ret;
117 }
118 EXPORT_SYMBOL_GPL(blkiocg_del_blkio_group);
119
120 /* called under rcu_read_lock(). */
121 struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key)
122 {
123         struct blkio_group *blkg;
124         struct hlist_node *n;
125         void *__key;
126
127         hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
128                 __key = blkg->key;
129                 if (__key == key)
130                         return blkg;
131         }
132
133         return NULL;
134 }
135 EXPORT_SYMBOL_GPL(blkiocg_lookup_group);
136
137 #define SHOW_FUNCTION(__VAR)                                            \
138 static u64 blkiocg_##__VAR##_read(struct cgroup *cgroup,                \
139                                        struct cftype *cftype)           \
140 {                                                                       \
141         struct blkio_cgroup *blkcg;                                     \
142                                                                         \
143         blkcg = cgroup_to_blkio_cgroup(cgroup);                         \
144         return (u64)blkcg->__VAR;                                       \
145 }
146
147 SHOW_FUNCTION(weight);
148 #undef SHOW_FUNCTION
149
150 static int
151 blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
152 {
153         struct blkio_cgroup *blkcg;
154         struct blkio_group *blkg;
155         struct hlist_node *n;
156         struct blkio_policy_type *blkiop;
157
158         if (val < BLKIO_WEIGHT_MIN || val > BLKIO_WEIGHT_MAX)
159                 return -EINVAL;
160
161         blkcg = cgroup_to_blkio_cgroup(cgroup);
162         spin_lock(&blkio_list_lock);
163         spin_lock_irq(&blkcg->lock);
164         blkcg->weight = (unsigned int)val;
165         hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
166                 list_for_each_entry(blkiop, &blkio_list, list)
167                         blkiop->ops.blkio_update_group_weight_fn(blkg,
168                                         blkcg->weight);
169         }
170         spin_unlock_irq(&blkcg->lock);
171         spin_unlock(&blkio_list_lock);
172         return 0;
173 }
174
175 #define SHOW_FUNCTION_PER_GROUP(__VAR)                                  \
176 static int blkiocg_##__VAR##_read(struct cgroup *cgroup,                \
177                         struct cftype *cftype, struct seq_file *m)      \
178 {                                                                       \
179         struct blkio_cgroup *blkcg;                                     \
180         struct blkio_group *blkg;                                       \
181         struct hlist_node *n;                                           \
182                                                                         \
183         if (!cgroup_lock_live_group(cgroup))                            \
184                 return -ENODEV;                                         \
185                                                                         \
186         blkcg = cgroup_to_blkio_cgroup(cgroup);                         \
187         rcu_read_lock();                                                \
188         hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {\
189                 if (blkg->dev)                                          \
190                         seq_printf(m, "%u:%u %lu\n", MAJOR(blkg->dev),  \
191                                  MINOR(blkg->dev), blkg->__VAR);        \
192         }                                                               \
193         rcu_read_unlock();                                              \
194         cgroup_unlock();                                                \
195         return 0;                                                       \
196 }
197
198 SHOW_FUNCTION_PER_GROUP(time);
199 SHOW_FUNCTION_PER_GROUP(sectors);
200 #ifdef CONFIG_DEBUG_BLK_CGROUP
201 SHOW_FUNCTION_PER_GROUP(dequeue);
202 #endif
203 #undef SHOW_FUNCTION_PER_GROUP
204
205 #ifdef CONFIG_DEBUG_BLK_CGROUP
206 void blkiocg_update_blkio_group_dequeue_stats(struct blkio_group *blkg,
207                         unsigned long dequeue)
208 {
209         blkg->dequeue += dequeue;
210 }
211 EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_dequeue_stats);
212 #endif
213
214 struct cftype blkio_files[] = {
215         {
216                 .name = "weight",
217                 .read_u64 = blkiocg_weight_read,
218                 .write_u64 = blkiocg_weight_write,
219         },
220         {
221                 .name = "time",
222                 .read_seq_string = blkiocg_time_read,
223         },
224         {
225                 .name = "sectors",
226                 .read_seq_string = blkiocg_sectors_read,
227         },
228 #ifdef CONFIG_DEBUG_BLK_CGROUP
229        {
230                 .name = "dequeue",
231                 .read_seq_string = blkiocg_dequeue_read,
232        },
233 #endif
234 };
235
236 static int blkiocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
237 {
238         return cgroup_add_files(cgroup, subsys, blkio_files,
239                                 ARRAY_SIZE(blkio_files));
240 }
241
242 static void blkiocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
243 {
244         struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
245         unsigned long flags;
246         struct blkio_group *blkg;
247         void *key;
248         struct blkio_policy_type *blkiop;
249
250         rcu_read_lock();
251 remove_entry:
252         spin_lock_irqsave(&blkcg->lock, flags);
253
254         if (hlist_empty(&blkcg->blkg_list)) {
255                 spin_unlock_irqrestore(&blkcg->lock, flags);
256                 goto done;
257         }
258
259         blkg = hlist_entry(blkcg->blkg_list.first, struct blkio_group,
260                                 blkcg_node);
261         key = rcu_dereference(blkg->key);
262         __blkiocg_del_blkio_group(blkg);
263
264         spin_unlock_irqrestore(&blkcg->lock, flags);
265
266         /*
267          * This blkio_group is being unlinked as associated cgroup is going
268          * away. Let all the IO controlling policies know about this event.
269          *
270          * Currently this is static call to one io controlling policy. Once
271          * we have more policies in place, we need some dynamic registration
272          * of callback function.
273          */
274         spin_lock(&blkio_list_lock);
275         list_for_each_entry(blkiop, &blkio_list, list)
276                 blkiop->ops.blkio_unlink_group_fn(key, blkg);
277         spin_unlock(&blkio_list_lock);
278         goto remove_entry;
279 done:
280         free_css_id(&blkio_subsys, &blkcg->css);
281         rcu_read_unlock();
282         if (blkcg != &blkio_root_cgroup)
283                 kfree(blkcg);
284 }
285
286 static struct cgroup_subsys_state *
287 blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
288 {
289         struct blkio_cgroup *blkcg, *parent_blkcg;
290
291         if (!cgroup->parent) {
292                 blkcg = &blkio_root_cgroup;
293                 goto done;
294         }
295
296         /* Currently we do not support hierarchy deeper than two level (0,1) */
297         parent_blkcg = cgroup_to_blkio_cgroup(cgroup->parent);
298         if (css_depth(&parent_blkcg->css) > 0)
299                 return ERR_PTR(-EINVAL);
300
301         blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
302         if (!blkcg)
303                 return ERR_PTR(-ENOMEM);
304
305         blkcg->weight = BLKIO_WEIGHT_DEFAULT;
306 done:
307         spin_lock_init(&blkcg->lock);
308         INIT_HLIST_HEAD(&blkcg->blkg_list);
309
310         return &blkcg->css;
311 }
312
313 /*
314  * We cannot support shared io contexts, as we have no mean to support
315  * two tasks with the same ioc in two different groups without major rework
316  * of the main cic data structures.  For now we allow a task to change
317  * its cgroup only if it's the only owner of its ioc.
318  */
319 static int blkiocg_can_attach(struct cgroup_subsys *subsys,
320                                 struct cgroup *cgroup, struct task_struct *tsk,
321                                 bool threadgroup)
322 {
323         struct io_context *ioc;
324         int ret = 0;
325
326         /* task_lock() is needed to avoid races with exit_io_context() */
327         task_lock(tsk);
328         ioc = tsk->io_context;
329         if (ioc && atomic_read(&ioc->nr_tasks) > 1)
330                 ret = -EINVAL;
331         task_unlock(tsk);
332
333         return ret;
334 }
335
336 static void blkiocg_attach(struct cgroup_subsys *subsys, struct cgroup *cgroup,
337                                 struct cgroup *prev, struct task_struct *tsk,
338                                 bool threadgroup)
339 {
340         struct io_context *ioc;
341
342         task_lock(tsk);
343         ioc = tsk->io_context;
344         if (ioc)
345                 ioc->cgroup_changed = 1;
346         task_unlock(tsk);
347 }
348
349 void blkio_policy_register(struct blkio_policy_type *blkiop)
350 {
351         spin_lock(&blkio_list_lock);
352         list_add_tail(&blkiop->list, &blkio_list);
353         spin_unlock(&blkio_list_lock);
354 }
355 EXPORT_SYMBOL_GPL(blkio_policy_register);
356
357 void blkio_policy_unregister(struct blkio_policy_type *blkiop)
358 {
359         spin_lock(&blkio_list_lock);
360         list_del_init(&blkiop->list);
361         spin_unlock(&blkio_list_lock);
362 }
363 EXPORT_SYMBOL_GPL(blkio_policy_unregister);
364
365 static int __init init_cgroup_blkio(void)
366 {
367         return cgroup_load_subsys(&blkio_subsys);
368 }
369
370 static void __exit exit_cgroup_blkio(void)
371 {
372         cgroup_unload_subsys(&blkio_subsys);
373 }
374
375 module_init(init_cgroup_blkio);
376 module_exit(exit_cgroup_blkio);
377 MODULE_LICENSE("GPL");