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