xref: /linux/block/blk-cgroup.c (revision a33f32244d8550da8b4a26e277ce07d5c6d158b5) 
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");
378