cfq-iosched: move IO controller declerations to a header file
[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 "blk-cgroup.h"
17 #include "cfq-iosched.h"
18
19 struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
20
21 struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
22 {
23         return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
24                             struct blkio_cgroup, css);
25 }
26
27 void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
28                         unsigned long time, unsigned long sectors)
29 {
30         blkg->time += time;
31         blkg->sectors += sectors;
32 }
33
34 void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
35                         struct blkio_group *blkg, void *key, dev_t dev)
36 {
37         unsigned long flags;
38
39         spin_lock_irqsave(&blkcg->lock, flags);
40         rcu_assign_pointer(blkg->key, key);
41         blkg->blkcg_id = css_id(&blkcg->css);
42         hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
43         spin_unlock_irqrestore(&blkcg->lock, flags);
44 #ifdef CONFIG_DEBUG_BLK_CGROUP
45         /* Need to take css reference ? */
46         cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
47 #endif
48         blkg->dev = dev;
49 }
50
51 static void __blkiocg_del_blkio_group(struct blkio_group *blkg)
52 {
53         hlist_del_init_rcu(&blkg->blkcg_node);
54         blkg->blkcg_id = 0;
55 }
56
57 /*
58  * returns 0 if blkio_group was still on cgroup list. Otherwise returns 1
59  * indicating that blk_group was unhashed by the time we got to it.
60  */
61 int blkiocg_del_blkio_group(struct blkio_group *blkg)
62 {
63         struct blkio_cgroup *blkcg;
64         unsigned long flags;
65         struct cgroup_subsys_state *css;
66         int ret = 1;
67
68         rcu_read_lock();
69         css = css_lookup(&blkio_subsys, blkg->blkcg_id);
70         if (!css)
71                 goto out;
72
73         blkcg = container_of(css, struct blkio_cgroup, css);
74         spin_lock_irqsave(&blkcg->lock, flags);
75         if (!hlist_unhashed(&blkg->blkcg_node)) {
76                 __blkiocg_del_blkio_group(blkg);
77                 ret = 0;
78         }
79         spin_unlock_irqrestore(&blkcg->lock, flags);
80 out:
81         rcu_read_unlock();
82         return ret;
83 }
84
85 /* called under rcu_read_lock(). */
86 struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key)
87 {
88         struct blkio_group *blkg;
89         struct hlist_node *n;
90         void *__key;
91
92         hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
93                 __key = blkg->key;
94                 if (__key == key)
95                         return blkg;
96         }
97
98         return NULL;
99 }
100
101 #define SHOW_FUNCTION(__VAR)                                            \
102 static u64 blkiocg_##__VAR##_read(struct cgroup *cgroup,                \
103                                        struct cftype *cftype)           \
104 {                                                                       \
105         struct blkio_cgroup *blkcg;                                     \
106                                                                         \
107         blkcg = cgroup_to_blkio_cgroup(cgroup);                         \
108         return (u64)blkcg->__VAR;                                       \
109 }
110
111 SHOW_FUNCTION(weight);
112 #undef SHOW_FUNCTION
113
114 static int
115 blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
116 {
117         struct blkio_cgroup *blkcg;
118         struct blkio_group *blkg;
119         struct hlist_node *n;
120
121         if (val < BLKIO_WEIGHT_MIN || val > BLKIO_WEIGHT_MAX)
122                 return -EINVAL;
123
124         blkcg = cgroup_to_blkio_cgroup(cgroup);
125         spin_lock_irq(&blkcg->lock);
126         blkcg->weight = (unsigned int)val;
127         hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
128                 cfq_update_blkio_group_weight(blkg, blkcg->weight);
129         spin_unlock_irq(&blkcg->lock);
130         return 0;
131 }
132
133 #define SHOW_FUNCTION_PER_GROUP(__VAR)                                  \
134 static int blkiocg_##__VAR##_read(struct cgroup *cgroup,                \
135                         struct cftype *cftype, struct seq_file *m)      \
136 {                                                                       \
137         struct blkio_cgroup *blkcg;                                     \
138         struct blkio_group *blkg;                                       \
139         struct hlist_node *n;                                           \
140                                                                         \
141         if (!cgroup_lock_live_group(cgroup))                            \
142                 return -ENODEV;                                         \
143                                                                         \
144         blkcg = cgroup_to_blkio_cgroup(cgroup);                         \
145         rcu_read_lock();                                                \
146         hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {\
147                 if (blkg->dev)                                          \
148                         seq_printf(m, "%u:%u %lu\n", MAJOR(blkg->dev),  \
149                                  MINOR(blkg->dev), blkg->__VAR);        \
150         }                                                               \
151         rcu_read_unlock();                                              \
152         cgroup_unlock();                                                \
153         return 0;                                                       \
154 }
155
156 SHOW_FUNCTION_PER_GROUP(time);
157 SHOW_FUNCTION_PER_GROUP(sectors);
158 #ifdef CONFIG_DEBUG_BLK_CGROUP
159 SHOW_FUNCTION_PER_GROUP(dequeue);
160 #endif
161 #undef SHOW_FUNCTION_PER_GROUP
162
163 #ifdef CONFIG_DEBUG_BLK_CGROUP
164 void blkiocg_update_blkio_group_dequeue_stats(struct blkio_group *blkg,
165                         unsigned long dequeue)
166 {
167         blkg->dequeue += dequeue;
168 }
169 #endif
170
171 struct cftype blkio_files[] = {
172         {
173                 .name = "weight",
174                 .read_u64 = blkiocg_weight_read,
175                 .write_u64 = blkiocg_weight_write,
176         },
177         {
178                 .name = "time",
179                 .read_seq_string = blkiocg_time_read,
180         },
181         {
182                 .name = "sectors",
183                 .read_seq_string = blkiocg_sectors_read,
184         },
185 #ifdef CONFIG_DEBUG_BLK_CGROUP
186        {
187                 .name = "dequeue",
188                 .read_seq_string = blkiocg_dequeue_read,
189        },
190 #endif
191 };
192
193 static int blkiocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
194 {
195         return cgroup_add_files(cgroup, subsys, blkio_files,
196                                 ARRAY_SIZE(blkio_files));
197 }
198
199 static void blkiocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
200 {
201         struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
202         unsigned long flags;
203         struct blkio_group *blkg;
204         void *key;
205
206         rcu_read_lock();
207 remove_entry:
208         spin_lock_irqsave(&blkcg->lock, flags);
209
210         if (hlist_empty(&blkcg->blkg_list)) {
211                 spin_unlock_irqrestore(&blkcg->lock, flags);
212                 goto done;
213         }
214
215         blkg = hlist_entry(blkcg->blkg_list.first, struct blkio_group,
216                                 blkcg_node);
217         key = rcu_dereference(blkg->key);
218         __blkiocg_del_blkio_group(blkg);
219
220         spin_unlock_irqrestore(&blkcg->lock, flags);
221
222         /*
223          * This blkio_group is being unlinked as associated cgroup is going
224          * away. Let all the IO controlling policies know about this event.
225          *
226          * Currently this is static call to one io controlling policy. Once
227          * we have more policies in place, we need some dynamic registration
228          * of callback function.
229          */
230         cfq_unlink_blkio_group(key, blkg);
231         goto remove_entry;
232 done:
233         free_css_id(&blkio_subsys, &blkcg->css);
234         rcu_read_unlock();
235         kfree(blkcg);
236 }
237
238 static struct cgroup_subsys_state *
239 blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
240 {
241         struct blkio_cgroup *blkcg, *parent_blkcg;
242
243         if (!cgroup->parent) {
244                 blkcg = &blkio_root_cgroup;
245                 goto done;
246         }
247
248         /* Currently we do not support hierarchy deeper than two level (0,1) */
249         parent_blkcg = cgroup_to_blkio_cgroup(cgroup->parent);
250         if (css_depth(&parent_blkcg->css) > 0)
251                 return ERR_PTR(-EINVAL);
252
253         blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
254         if (!blkcg)
255                 return ERR_PTR(-ENOMEM);
256
257         blkcg->weight = BLKIO_WEIGHT_DEFAULT;
258 done:
259         spin_lock_init(&blkcg->lock);
260         INIT_HLIST_HEAD(&blkcg->blkg_list);
261
262         return &blkcg->css;
263 }
264
265 /*
266  * We cannot support shared io contexts, as we have no mean to support
267  * two tasks with the same ioc in two different groups without major rework
268  * of the main cic data structures.  For now we allow a task to change
269  * its cgroup only if it's the only owner of its ioc.
270  */
271 static int blkiocg_can_attach(struct cgroup_subsys *subsys,
272                                 struct cgroup *cgroup, struct task_struct *tsk,
273                                 bool threadgroup)
274 {
275         struct io_context *ioc;
276         int ret = 0;
277
278         /* task_lock() is needed to avoid races with exit_io_context() */
279         task_lock(tsk);
280         ioc = tsk->io_context;
281         if (ioc && atomic_read(&ioc->nr_tasks) > 1)
282                 ret = -EINVAL;
283         task_unlock(tsk);
284
285         return ret;
286 }
287
288 static void blkiocg_attach(struct cgroup_subsys *subsys, struct cgroup *cgroup,
289                                 struct cgroup *prev, struct task_struct *tsk,
290                                 bool threadgroup)
291 {
292         struct io_context *ioc;
293
294         task_lock(tsk);
295         ioc = tsk->io_context;
296         if (ioc)
297                 ioc->cgroup_changed = 1;
298         task_unlock(tsk);
299 }
300
301 struct cgroup_subsys blkio_subsys = {
302         .name = "blkio",
303         .create = blkiocg_create,
304         .can_attach = blkiocg_can_attach,
305         .attach = blkiocg_attach,
306         .destroy = blkiocg_destroy,
307         .populate = blkiocg_populate,
308         .subsys_id = blkio_subsys_id,
309         .use_id = 1,
310 };