Root/block/blk-cgroup.c

Source at commit 0341509fdfc9519f7de6aabc5dd23217cef72b73 created 13 years 7 months ago.
By Li Zefan, blk-cgroup: Fix an RCU warning in blkiocg_create()
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
21static DEFINE_SPINLOCK(blkio_list_lock);
22static LIST_HEAD(blkio_list);
23
24struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
25EXPORT_SYMBOL_GPL(blkio_root_cgroup);
26
27static struct cgroup_subsys_state *blkiocg_create(struct cgroup_subsys *,
28                          struct cgroup *);
29static int blkiocg_can_attach(struct cgroup_subsys *, struct cgroup *,
30                  struct task_struct *, bool);
31static void blkiocg_attach(struct cgroup_subsys *, struct cgroup *,
32               struct cgroup *, struct task_struct *, bool);
33static void blkiocg_destroy(struct cgroup_subsys *, struct cgroup *);
34static int blkiocg_populate(struct cgroup_subsys *, struct cgroup *);
35
36struct 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};
50EXPORT_SYMBOL_GPL(blkio_subsys);
51
52struct 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}
57EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup);
58
59void 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}
65EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_stats);
66
67void 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}
83EXPORT_SYMBOL_GPL(blkiocg_add_blkio_group);
84
85static 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 */
95int 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);
114out:
115    rcu_read_unlock();
116    return ret;
117}
118EXPORT_SYMBOL_GPL(blkiocg_del_blkio_group);
119
120/* called under rcu_read_lock(). */
121struct 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}
135EXPORT_SYMBOL_GPL(blkiocg_lookup_group);
136
137#define SHOW_FUNCTION(__VAR) \
138static 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
147SHOW_FUNCTION(weight);
148#undef SHOW_FUNCTION
149
150static int
151blkiocg_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) \
176static 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
198SHOW_FUNCTION_PER_GROUP(time);
199SHOW_FUNCTION_PER_GROUP(sectors);
200#ifdef CONFIG_DEBUG_BLK_CGROUP
201SHOW_FUNCTION_PER_GROUP(dequeue);
202#endif
203#undef SHOW_FUNCTION_PER_GROUP
204
205#ifdef CONFIG_DEBUG_BLK_CGROUP
206void blkiocg_update_blkio_group_dequeue_stats(struct blkio_group *blkg,
207            unsigned long dequeue)
208{
209    blkg->dequeue += dequeue;
210}
211EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_dequeue_stats);
212#endif
213
214struct 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
236static 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
242static 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();
251remove_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;
279done:
280    free_css_id(&blkio_subsys, &blkcg->css);
281    rcu_read_unlock();
282    if (blkcg != &blkio_root_cgroup)
283        kfree(blkcg);
284}
285
286static struct cgroup_subsys_state *
287blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
288{
289    struct blkio_cgroup *blkcg;
290    struct cgroup *parent = cgroup->parent;
291
292    if (!parent) {
293        blkcg = &blkio_root_cgroup;
294        goto done;
295    }
296
297    /* Currently we do not support hierarchy deeper than two level (0,1) */
298    if (parent != cgroup->top_cgroup)
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;
306done:
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 */
319static 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
336static 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
349void 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}
355EXPORT_SYMBOL_GPL(blkio_policy_register);
356
357void 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}
363EXPORT_SYMBOL_GPL(blkio_policy_unregister);
364
365static int __init init_cgroup_blkio(void)
366{
367    return cgroup_load_subsys(&blkio_subsys);
368}
369
370static void __exit exit_cgroup_blkio(void)
371{
372    cgroup_unload_subsys(&blkio_subsys);
373}
374
375module_init(init_cgroup_blkio);
376module_exit(exit_cgroup_blkio);
377MODULE_LICENSE("GPL");
378

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