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