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;
 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;
 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");