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 "blk-cgroup.h"
  19
  20 static DEFINE_SPINLOCK(blkio_list_lock);
  21 static LIST_HEAD(blkio_list);
  22
  23 struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
  24 EXPORT_SYMBOL_GPL(blkio_root_cgroup);
  25
  26 static struct cgroup_subsys_state *blkiocg_create(struct cgroup_subsys *,
  27                                                   struct cgroup *);
  28 static int blkiocg_can_attach(struct cgroup_subsys *, struct cgroup *,
  29                               struct task_struct *, bool);
  30 static void blkiocg_attach(struct cgroup_subsys *, struct cgroup *,
  31                            struct cgroup *, struct task_struct *, bool);
  32 static void blkiocg_destroy(struct cgroup_subsys *, struct cgroup *);
  33 static int blkiocg_populate(struct cgroup_subsys *, struct cgroup *);
  34
  35 struct cgroup_subsys blkio_subsys = {
  36         .name = "blkio",
  37         .create = blkiocg_create,
  38         .can_attach = blkiocg_can_attach,
  39         .attach = blkiocg_attach,
  40         .destroy = blkiocg_destroy,
  41         .populate = blkiocg_populate,
  42 #ifdef CONFIG_BLK_CGROUP
  43         /* note: blkio_subsys_id is otherwise defined in blk-cgroup.h */
  44         .subsys_id = blkio_subsys_id,
  45 #endif
  46         .use_id = 1,
  47         .module = THIS_MODULE,
  48 };
  49 EXPORT_SYMBOL_GPL(blkio_subsys);
  50
  51 struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
  52 {
  53         return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
  54                             struct blkio_cgroup, css);
  55 }
  56 EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup);
  57
  58 void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
  59                         unsigned long time, unsigned long sectors)
  60 {
  61         blkg->time += time;
  62         blkg->sectors += sectors;
  63 }
  64 EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_stats);
  65
  66 void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
  67                         struct blkio_group *blkg, void *key, dev_t dev)
  68 {
  69         unsigned long flags;
  70
  71         spin_lock_irqsave(&blkcg->lock, flags);
  72         rcu_assign_pointer(blkg->key, key);
  73         blkg->blkcg_id = css_id(&blkcg->css);
  74         hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
  75         spin_unlock_irqrestore(&blkcg->lock, flags);
  76 #ifdef CONFIG_DEBUG_BLK_CGROUP
  77         /* Need to take css reference ? */
  78         cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
  79 #endif
  80         blkg->dev = dev;
  81 }
  82 EXPORT_SYMBOL_GPL(blkiocg_add_blkio_group);
  83
  84 static void __blkiocg_del_blkio_group(struct blkio_group *blkg)
  85 {
  86         hlist_del_init_rcu(&blkg->blkcg_node);
  87         blkg->blkcg_id = 0;
  88 }
  89
  90 /*
  91  * returns 0 if blkio_group was still on cgroup list. Otherwise returns 1
  92  * indicating that blk_group was unhashed by the time we got to it.
  93  */
  94 int blkiocg_del_blkio_group(struct blkio_group *blkg)
  95 {
  96         struct blkio_cgroup *blkcg;
  97         unsigned long flags;
  98         struct cgroup_subsys_state *css;
  99         int ret = 1;
 100
 101         rcu_read_lock();
 102         css = css_lookup(&blkio_subsys, blkg->blkcg_id);
 103         if (!css)
 104                 goto out;
 105
 106         blkcg = container_of(css, struct blkio_cgroup, css);
 107         spin_lock_irqsave(&blkcg->lock, flags);
 108         if (!hlist_unhashed(&blkg->blkcg_node)) {
 109                 __blkiocg_del_blkio_group(blkg);
 110                 ret = 0;
 111         }
 112         spin_unlock_irqrestore(&blkcg->lock, flags);
 113 out:
 114         rcu_read_unlock();
 115         return ret;
 116 }
 117 EXPORT_SYMBOL_GPL(blkiocg_del_blkio_group);
 118
 119 /* called under rcu_read_lock(). */
 120 struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key)
 121 {
 122         struct blkio_group *blkg;
 123         struct hlist_node *n;
 124         void *__key;
 125
 126         hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
 127                 __key = blkg->key;
 128                 if (__key == key)
 129                         return blkg;
 130         }
 131
 132         return NULL;
 133 }
 134 EXPORT_SYMBOL_GPL(blkiocg_lookup_group);
 135
 136 #define SHOW_FUNCTION(__VAR)                                            \
 137 static u64 blkiocg_##__VAR##_read(struct cgroup *cgroup,                \
 138                                        struct cftype *cftype)           \
 139 {                                                                       \
 140         struct blkio_cgroup *blkcg;                                     \
 141                                                                         \
 142         blkcg = cgroup_to_blkio_cgroup(cgroup);                         \
 143         return (u64)blkcg->__VAR;                                       \
 144 }
 145
 146 SHOW_FUNCTION(weight);
 147 #undef SHOW_FUNCTION
 148
 149 static int
 150 blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
 151 {
 152         struct blkio_cgroup *blkcg;
 153         struct blkio_group *blkg;
 154         struct hlist_node *n;
 155         struct blkio_policy_type *blkiop;
 156
 157         if (val < BLKIO_WEIGHT_MIN || val > BLKIO_WEIGHT_MAX)
 158                 return -EINVAL;
 159
 160         blkcg = cgroup_to_blkio_cgroup(cgroup);
 161         spin_lock(&blkio_list_lock);
 162         spin_lock_irq(&blkcg->lock);
 163         blkcg->weight = (unsigned int)val;
 164         hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
 165                 list_for_each_entry(blkiop, &blkio_list, list)
 166                         blkiop->ops.blkio_update_group_weight_fn(blkg,
 167                                         blkcg->weight);
 168         }
 169         spin_unlock_irq(&blkcg->lock);
 170         spin_unlock(&blkio_list_lock);
 171         return 0;
 172 }
 173
 174 #define SHOW_FUNCTION_PER_GROUP(__VAR)                                  \
 175 static int blkiocg_##__VAR##_read(struct cgroup *cgroup,                \
 176                         struct cftype *cftype, struct seq_file *m)      \
 177 {                                                                       \
 178         struct blkio_cgroup *blkcg;                                     \
 179         struct blkio_group *blkg;                                       \
 180         struct hlist_node *n;                                           \
 181                                                                         \
 182         if (!cgroup_lock_live_group(cgroup))                            \
 183                 return -ENODEV;                                         \
 184                                                                         \
 185         blkcg = cgroup_to_blkio_cgroup(cgroup);                         \
 186         rcu_read_lock();                                                \
 187         hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {\
 188                 if (blkg->dev)                                          \
 189                         seq_printf(m, "%u:%u %lu\n", MAJOR(blkg->dev),  \
 190                                  MINOR(blkg->dev), blkg->__VAR);        \
 191         }                                                               \
 192         rcu_read_unlock();                                              \
 193         cgroup_unlock();                                                \
 194         return 0;                                                       \
 195 }
 196
 197 SHOW_FUNCTION_PER_GROUP(time);
 198 SHOW_FUNCTION_PER_GROUP(sectors);
 199 #ifdef CONFIG_DEBUG_BLK_CGROUP
 200 SHOW_FUNCTION_PER_GROUP(dequeue);
 201 #endif
 202 #undef SHOW_FUNCTION_PER_GROUP
 203
 204 #ifdef CONFIG_DEBUG_BLK_CGROUP
 205 void blkiocg_update_blkio_group_dequeue_stats(struct blkio_group *blkg,
 206                         unsigned long dequeue)
 207 {
 208         blkg->dequeue += dequeue;
 209 }
 210 EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_dequeue_stats);
 211 #endif
 212
 213 struct cftype blkio_files[] = {
 214         {
 215                 .name = "weight",
 216                 .read_u64 = blkiocg_weight_read,
 217                 .write_u64 = blkiocg_weight_write,
 218         },
 219         {
 220                 .name = "time",
 221                 .read_seq_string = blkiocg_time_read,
 222         },
 223         {
 224                 .name = "sectors",
 225                 .read_seq_string = blkiocg_sectors_read,
 226         },
 227 #ifdef CONFIG_DEBUG_BLK_CGROUP
 228        {
 229                 .name = "dequeue",
 230                 .read_seq_string = blkiocg_dequeue_read,
 231        },
 232 #endif
 233 };
 234
 235 static int blkiocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 236 {
 237         return cgroup_add_files(cgroup, subsys, blkio_files,
 238                                 ARRAY_SIZE(blkio_files));
 239 }
 240
 241 static void blkiocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 242 {
 243         struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
 244         unsigned long flags;
 245         struct blkio_group *blkg;
 246         void *key;
 247         struct blkio_policy_type *blkiop;
 248
 249         rcu_read_lock();
 250 remove_entry:
 251         spin_lock_irqsave(&blkcg->lock, flags);
 252
 253         if (hlist_empty(&blkcg->blkg_list)) {
 254                 spin_unlock_irqrestore(&blkcg->lock, flags);
 255                 goto done;
 256         }
 257
 258         blkg = hlist_entry(blkcg->blkg_list.first, struct blkio_group,
 259                                 blkcg_node);
 260         key = rcu_dereference(blkg->key);
 261         __blkiocg_del_blkio_group(blkg);
 262
 263         spin_unlock_irqrestore(&blkcg->lock, flags);
 264
 265         /*
 266          * This blkio_group is being unlinked as associated cgroup is going
 267          * away. Let all the IO controlling policies know about this event.
 268          *
 269          * Currently this is static call to one io controlling policy. Once
 270          * we have more policies in place, we need some dynamic registration
 271          * of callback function.
 272          */
 273         spin_lock(&blkio_list_lock);
 274         list_for_each_entry(blkiop, &blkio_list, list)
 275                 blkiop->ops.blkio_unlink_group_fn(key, blkg);
 276         spin_unlock(&blkio_list_lock);
 277         goto remove_entry;
 278 done:
 279         free_css_id(&blkio_subsys, &blkcg->css);
 280         rcu_read_unlock();
 281         if (blkcg != &blkio_root_cgroup)
 282                 kfree(blkcg);
 283 }
 284
 285 static struct cgroup_subsys_state *
 286 blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 287 {
 288         struct blkio_cgroup *blkcg, *parent_blkcg;
 289
 290         if (!cgroup->parent) {
 291                 blkcg = &blkio_root_cgroup;
 292                 goto done;
 293         }
 294
 295         /* Currently we do not support hierarchy deeper than two level (0,1) */
 296         parent_blkcg = cgroup_to_blkio_cgroup(cgroup->parent);
 297         if (css_depth(&parent_blkcg->css) > 0)
 298                 return ERR_PTR(-EINVAL);
 299
 300         blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
 301         if (!blkcg)
 302                 return ERR_PTR(-ENOMEM);
 303
 304         blkcg->weight = BLKIO_WEIGHT_DEFAULT;
 305 done:
 306         spin_lock_init(&blkcg->lock);
 307         INIT_HLIST_HEAD(&blkcg->blkg_list);
 308
 309         return &blkcg->css;
 310 }
 311
 312 /*
 313  * We cannot support shared io contexts, as we have no mean to support
 314  * two tasks with the same ioc in two different groups without major rework
 315  * of the main cic data structures.  For now we allow a task to change
 316  * its cgroup only if it's the only owner of its ioc.
 317  */
 318 static int blkiocg_can_attach(struct cgroup_subsys *subsys,
 319                                 struct cgroup *cgroup, struct task_struct *tsk,
 320                                 bool threadgroup)
 321 {
 322         struct io_context *ioc;
 323         int ret = 0;
 324
 325         /* task_lock() is needed to avoid races with exit_io_context() */
 326         task_lock(tsk);
 327         ioc = tsk->io_context;
 328         if (ioc && atomic_read(&ioc->nr_tasks) > 1)
 329                 ret = -EINVAL;
 330         task_unlock(tsk);
 331
 332         return ret;
 333 }
 334
 335 static void blkiocg_attach(struct cgroup_subsys *subsys, struct cgroup *cgroup,
 336                                 struct cgroup *prev, struct task_struct *tsk,
 337                                 bool threadgroup)
 338 {
 339         struct io_context *ioc;
 340
 341         task_lock(tsk);
 342         ioc = tsk->io_context;
 343         if (ioc)
 344                 ioc->cgroup_changed = 1;
 345         task_unlock(tsk);
 346 }
 347
 348 void blkio_policy_register(struct blkio_policy_type *blkiop)
 349 {
 350         spin_lock(&blkio_list_lock);
 351         list_add_tail(&blkiop->list, &blkio_list);
 352         spin_unlock(&blkio_list_lock);
 353 }
 354 EXPORT_SYMBOL_GPL(blkio_policy_register);
 355
 356 void blkio_policy_unregister(struct blkio_policy_type *blkiop)
 357 {
 358         spin_lock(&blkio_list_lock);
 359         list_del_init(&blkiop->list);
 360         spin_unlock(&blkio_list_lock);
 361 }
 362 EXPORT_SYMBOL_GPL(blkio_policy_unregister);
 363
 364 static int __init init_cgroup_blkio(void)
 365 {
 366         return cgroup_load_subsys(&blkio_subsys);
 367 }
 368
 369 static void __exit exit_cgroup_blkio(void)
 370 {
 371         cgroup_unload_subsys(&blkio_subsys);
 372 }
 373
 374 module_init(init_cgroup_blkio);
 375 module_exit(exit_cgroup_blkio);
 376 MODULE_LICENSE("GPL");