blkio: Export some symbols from blkio as its user CFQ can be a module
[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 "blk-cgroup.h"
18 #include "cfq-iosched.h"
19
20 struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
21 EXPORT_SYMBOL_GPL(blkio_root_cgroup);
22
23 bool blkiocg_css_tryget(struct blkio_cgroup *blkcg)
24 {
25         if (!css_tryget(&blkcg->css))
26                 return false;
27         return true;
28 }
29 EXPORT_SYMBOL_GPL(blkiocg_css_tryget);
30
31 void blkiocg_css_put(struct blkio_cgroup *blkcg)
32 {
33         css_put(&blkcg->css);
34 }
35 EXPORT_SYMBOL_GPL(blkiocg_css_put);
36
37 struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
38 {
39         return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
40                             struct blkio_cgroup, css);
41 }
42 EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup);
43
44 void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
45                         unsigned long time, unsigned long sectors)
46 {
47         blkg->time += time;
48         blkg->sectors += sectors;
49 }
50 EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_stats);
51
52 void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
53                         struct blkio_group *blkg, void *key, dev_t dev)
54 {
55         unsigned long flags;
56
57         spin_lock_irqsave(&blkcg->lock, flags);
58         rcu_assign_pointer(blkg->key, key);
59         blkg->blkcg_id = css_id(&blkcg->css);
60         hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
61         spin_unlock_irqrestore(&blkcg->lock, flags);
62 #ifdef CONFIG_DEBUG_BLK_CGROUP
63         /* Need to take css reference ? */
64         cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
65 #endif
66         blkg->dev = dev;
67 }
68 EXPORT_SYMBOL_GPL(blkiocg_add_blkio_group);
69
70 static void __blkiocg_del_blkio_group(struct blkio_group *blkg)
71 {
72         hlist_del_init_rcu(&blkg->blkcg_node);
73         blkg->blkcg_id = 0;
74 }
75
76 /*
77  * returns 0 if blkio_group was still on cgroup list. Otherwise returns 1
78  * indicating that blk_group was unhashed by the time we got to it.
79  */
80 int blkiocg_del_blkio_group(struct blkio_group *blkg)
81 {
82         struct blkio_cgroup *blkcg;
83         unsigned long flags;
84         struct cgroup_subsys_state *css;
85         int ret = 1;
86
87         rcu_read_lock();
88         css = css_lookup(&blkio_subsys, blkg->blkcg_id);
89         if (!css)
90                 goto out;
91
92         blkcg = container_of(css, struct blkio_cgroup, css);
93         spin_lock_irqsave(&blkcg->lock, flags);
94         if (!hlist_unhashed(&blkg->blkcg_node)) {
95                 __blkiocg_del_blkio_group(blkg);
96                 ret = 0;
97         }
98         spin_unlock_irqrestore(&blkcg->lock, flags);
99 out:
100         rcu_read_unlock();
101         return ret;
102 }
103 EXPORT_SYMBOL_GPL(blkiocg_del_blkio_group);
104
105 /* called under rcu_read_lock(). */
106 struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key)
107 {
108         struct blkio_group *blkg;
109         struct hlist_node *n;
110         void *__key;
111
112         hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
113                 __key = blkg->key;
114                 if (__key == key)
115                         return blkg;
116         }
117
118         return NULL;
119 }
120 EXPORT_SYMBOL_GPL(blkiocg_lookup_group);
121
122 #define SHOW_FUNCTION(__VAR)                                            \
123 static u64 blkiocg_##__VAR##_read(struct cgroup *cgroup,                \
124                                        struct cftype *cftype)           \
125 {                                                                       \
126         struct blkio_cgroup *blkcg;                                     \
127                                                                         \
128         blkcg = cgroup_to_blkio_cgroup(cgroup);                         \
129         return (u64)blkcg->__VAR;                                       \
130 }
131
132 SHOW_FUNCTION(weight);
133 #undef SHOW_FUNCTION
134
135 static int
136 blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
137 {
138         struct blkio_cgroup *blkcg;
139         struct blkio_group *blkg;
140         struct hlist_node *n;
141
142         if (val < BLKIO_WEIGHT_MIN || val > BLKIO_WEIGHT_MAX)
143                 return -EINVAL;
144
145         blkcg = cgroup_to_blkio_cgroup(cgroup);
146         spin_lock_irq(&blkcg->lock);
147         blkcg->weight = (unsigned int)val;
148         hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
149                 cfq_update_blkio_group_weight(blkg, blkcg->weight);
150         spin_unlock_irq(&blkcg->lock);
151         return 0;
152 }
153
154 #define SHOW_FUNCTION_PER_GROUP(__VAR)                                  \
155 static int blkiocg_##__VAR##_read(struct cgroup *cgroup,                \
156                         struct cftype *cftype, struct seq_file *m)      \
157 {                                                                       \
158         struct blkio_cgroup *blkcg;                                     \
159         struct blkio_group *blkg;                                       \
160         struct hlist_node *n;                                           \
161                                                                         \
162         if (!cgroup_lock_live_group(cgroup))                            \
163                 return -ENODEV;                                         \
164                                                                         \
165         blkcg = cgroup_to_blkio_cgroup(cgroup);                         \
166         rcu_read_lock();                                                \
167         hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {\
168                 if (blkg->dev)                                          \
169                         seq_printf(m, "%u:%u %lu\n", MAJOR(blkg->dev),  \
170                                  MINOR(blkg->dev), blkg->__VAR);        \
171         }                                                               \
172         rcu_read_unlock();                                              \
173         cgroup_unlock();                                                \
174         return 0;                                                       \
175 }
176
177 SHOW_FUNCTION_PER_GROUP(time);
178 SHOW_FUNCTION_PER_GROUP(sectors);
179 #ifdef CONFIG_DEBUG_BLK_CGROUP
180 SHOW_FUNCTION_PER_GROUP(dequeue);
181 #endif
182 #undef SHOW_FUNCTION_PER_GROUP
183
184 #ifdef CONFIG_DEBUG_BLK_CGROUP
185 void blkiocg_update_blkio_group_dequeue_stats(struct blkio_group *blkg,
186                         unsigned long dequeue)
187 {
188         blkg->dequeue += dequeue;
189 }
190 EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_dequeue_stats);
191 #endif
192
193 struct cftype blkio_files[] = {
194         {
195                 .name = "weight",
196                 .read_u64 = blkiocg_weight_read,
197                 .write_u64 = blkiocg_weight_write,
198         },
199         {
200                 .name = "time",
201                 .read_seq_string = blkiocg_time_read,
202         },
203         {
204                 .name = "sectors",
205                 .read_seq_string = blkiocg_sectors_read,
206         },
207 #ifdef CONFIG_DEBUG_BLK_CGROUP
208        {
209                 .name = "dequeue",
210                 .read_seq_string = blkiocg_dequeue_read,
211        },
212 #endif
213 };
214
215 static int blkiocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
216 {
217         return cgroup_add_files(cgroup, subsys, blkio_files,
218                                 ARRAY_SIZE(blkio_files));
219 }
220
221 static void blkiocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
222 {
223         struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
224         unsigned long flags;
225         struct blkio_group *blkg;
226         void *key;
227
228         rcu_read_lock();
229 remove_entry:
230         spin_lock_irqsave(&blkcg->lock, flags);
231
232         if (hlist_empty(&blkcg->blkg_list)) {
233                 spin_unlock_irqrestore(&blkcg->lock, flags);
234                 goto done;
235         }
236
237         blkg = hlist_entry(blkcg->blkg_list.first, struct blkio_group,
238                                 blkcg_node);
239         key = rcu_dereference(blkg->key);
240         __blkiocg_del_blkio_group(blkg);
241
242         spin_unlock_irqrestore(&blkcg->lock, flags);
243
244         /*
245          * This blkio_group is being unlinked as associated cgroup is going
246          * away. Let all the IO controlling policies know about this event.
247          *
248          * Currently this is static call to one io controlling policy. Once
249          * we have more policies in place, we need some dynamic registration
250          * of callback function.
251          */
252         cfq_unlink_blkio_group(key, blkg);
253         goto remove_entry;
254 done:
255         free_css_id(&blkio_subsys, &blkcg->css);
256         rcu_read_unlock();
257         kfree(blkcg);
258 }
259
260 static struct cgroup_subsys_state *
261 blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
262 {
263         struct blkio_cgroup *blkcg, *parent_blkcg;
264
265         if (!cgroup->parent) {
266                 blkcg = &blkio_root_cgroup;
267                 goto done;
268         }
269
270         /* Currently we do not support hierarchy deeper than two level (0,1) */
271         parent_blkcg = cgroup_to_blkio_cgroup(cgroup->parent);
272         if (css_depth(&parent_blkcg->css) > 0)
273                 return ERR_PTR(-EINVAL);
274
275         blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
276         if (!blkcg)
277                 return ERR_PTR(-ENOMEM);
278
279         blkcg->weight = BLKIO_WEIGHT_DEFAULT;
280 done:
281         spin_lock_init(&blkcg->lock);
282         INIT_HLIST_HEAD(&blkcg->blkg_list);
283
284         return &blkcg->css;
285 }
286
287 /*
288  * We cannot support shared io contexts, as we have no mean to support
289  * two tasks with the same ioc in two different groups without major rework
290  * of the main cic data structures.  For now we allow a task to change
291  * its cgroup only if it's the only owner of its ioc.
292  */
293 static int blkiocg_can_attach(struct cgroup_subsys *subsys,
294                                 struct cgroup *cgroup, struct task_struct *tsk,
295                                 bool threadgroup)
296 {
297         struct io_context *ioc;
298         int ret = 0;
299
300         /* task_lock() is needed to avoid races with exit_io_context() */
301         task_lock(tsk);
302         ioc = tsk->io_context;
303         if (ioc && atomic_read(&ioc->nr_tasks) > 1)
304                 ret = -EINVAL;
305         task_unlock(tsk);
306
307         return ret;
308 }
309
310 static void blkiocg_attach(struct cgroup_subsys *subsys, struct cgroup *cgroup,
311                                 struct cgroup *prev, struct task_struct *tsk,
312                                 bool threadgroup)
313 {
314         struct io_context *ioc;
315
316         task_lock(tsk);
317         ioc = tsk->io_context;
318         if (ioc)
319                 ioc->cgroup_changed = 1;
320         task_unlock(tsk);
321 }
322
323 struct cgroup_subsys blkio_subsys = {
324         .name = "blkio",
325         .create = blkiocg_create,
326         .can_attach = blkiocg_can_attach,
327         .attach = blkiocg_attach,
328         .destroy = blkiocg_destroy,
329         .populate = blkiocg_populate,
330         .subsys_id = blkio_subsys_id,
331         .use_id = 1,
332 };