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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 "blk-cgroup.h"
  17 #include "cfq-iosched.h"
  18
  19 struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
  20
  21 struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
  22 {
  23         return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
  24                             struct blkio_cgroup, css);
  25 }
  26
  27 void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
  28                         unsigned long time, unsigned long sectors)
  29 {
  30         blkg->time += time;
  31         blkg->sectors += sectors;
  32 }
  33
  34 void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
  35                         struct blkio_group *blkg, void *key, dev_t dev)
  36 {
  37         unsigned long flags;
  38
  39         spin_lock_irqsave(&blkcg->lock, flags);
  40         rcu_assign_pointer(blkg->key, key);
  41         blkg->blkcg_id = css_id(&blkcg->css);
  42         hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
  43         spin_unlock_irqrestore(&blkcg->lock, flags);
  44 #ifdef CONFIG_DEBUG_BLK_CGROUP
  45         /* Need to take css reference ? */
  46         cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
  47 #endif
  48         blkg->dev = dev;
  49 }
  50
  51 static void __blkiocg_del_blkio_group(struct blkio_group *blkg)
  52 {
  53         hlist_del_init_rcu(&blkg->blkcg_node);
  54         blkg->blkcg_id = 0;
  55 }
  56
  57 /*
  58  * returns 0 if blkio_group was still on cgroup list. Otherwise returns 1
  59  * indicating that blk_group was unhashed by the time we got to it.
  60  */
  61 int blkiocg_del_blkio_group(struct blkio_group *blkg)
  62 {
  63         struct blkio_cgroup *blkcg;
  64         unsigned long flags;
  65         struct cgroup_subsys_state *css;
  66         int ret = 1;
  67
  68         rcu_read_lock();
  69         css = css_lookup(&blkio_subsys, blkg->blkcg_id);
  70         if (!css)
  71                 goto out;
  72
  73         blkcg = container_of(css, struct blkio_cgroup, css);
  74         spin_lock_irqsave(&blkcg->lock, flags);
  75         if (!hlist_unhashed(&blkg->blkcg_node)) {
  76                 __blkiocg_del_blkio_group(blkg);
  77                 ret = 0;
  78         }
  79         spin_unlock_irqrestore(&blkcg->lock, flags);
  80 out:
  81         rcu_read_unlock();
  82         return ret;
  83 }
  84
  85 /* called under rcu_read_lock(). */
  86 struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key)
  87 {
  88         struct blkio_group *blkg;
  89         struct hlist_node *n;
  90         void *__key;
  91
  92         hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
  93                 __key = blkg->key;
  94                 if (__key == key)
  95                         return blkg;
  96         }
  97
  98         return NULL;
  99 }
 100
 101 #define SHOW_FUNCTION(__VAR)                                            \
 102 static u64 blkiocg_##__VAR##_read(struct cgroup *cgroup,                \
 103                                        struct cftype *cftype)           \
 104 {                                                                       \
 105         struct blkio_cgroup *blkcg;                                     \
 106                                                                         \
 107         blkcg = cgroup_to_blkio_cgroup(cgroup);                         \
 108         return (u64)blkcg->__VAR;                                       \
 109 }
 110
 111 SHOW_FUNCTION(weight);
 112 #undef SHOW_FUNCTION
 113
 114 static int
 115 blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
 116 {
 117         struct blkio_cgroup *blkcg;
 118         struct blkio_group *blkg;
 119         struct hlist_node *n;
 120
 121         if (val < BLKIO_WEIGHT_MIN || val > BLKIO_WEIGHT_MAX)
 122                 return -EINVAL;
 123
 124         blkcg = cgroup_to_blkio_cgroup(cgroup);
 125         spin_lock_irq(&blkcg->lock);
 126         blkcg->weight = (unsigned int)val;
 127         hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
 128                 cfq_update_blkio_group_weight(blkg, blkcg->weight);
 129         spin_unlock_irq(&blkcg->lock);
 130         return 0;
 131 }
 132
 133 #define SHOW_FUNCTION_PER_GROUP(__VAR)                                  \
 134 static int blkiocg_##__VAR##_read(struct cgroup *cgroup,                \
 135                         struct cftype *cftype, struct seq_file *m)      \
 136 {                                                                       \
 137         struct blkio_cgroup *blkcg;                                     \
 138         struct blkio_group *blkg;                                       \
 139         struct hlist_node *n;                                           \
 140                                                                         \
 141         if (!cgroup_lock_live_group(cgroup))                            \
 142                 return -ENODEV;                                         \
 143                                                                         \
 144         blkcg = cgroup_to_blkio_cgroup(cgroup);                         \
 145         rcu_read_lock();                                                \
 146         hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {\
 147                 if (blkg->dev)                                          \
 148                         seq_printf(m, "%u:%u %lu\n", MAJOR(blkg->dev),  \
 149                                  MINOR(blkg->dev), blkg->__VAR);        \
 150         }                                                               \
 151         rcu_read_unlock();                                              \
 152         cgroup_unlock();                                                \
 153         return 0;                                                       \
 154 }
 155
 156 SHOW_FUNCTION_PER_GROUP(time);
 157 SHOW_FUNCTION_PER_GROUP(sectors);
 158 #ifdef CONFIG_DEBUG_BLK_CGROUP
 159 SHOW_FUNCTION_PER_GROUP(dequeue);
 160 #endif
 161 #undef SHOW_FUNCTION_PER_GROUP
 162
 163 #ifdef CONFIG_DEBUG_BLK_CGROUP
 164 void blkiocg_update_blkio_group_dequeue_stats(struct blkio_group *blkg,
 165                         unsigned long dequeue)
 166 {
 167         blkg->dequeue += dequeue;
 168 }
 169 #endif
 170
 171 struct cftype blkio_files[] = {
 172         {
 173                 .name = "weight",
 174                 .read_u64 = blkiocg_weight_read,
 175                 .write_u64 = blkiocg_weight_write,
 176         },
 177         {
 178                 .name = "time",
 179                 .read_seq_string = blkiocg_time_read,
 180         },
 181         {
 182                 .name = "sectors",
 183                 .read_seq_string = blkiocg_sectors_read,
 184         },
 185 #ifdef CONFIG_DEBUG_BLK_CGROUP
 186        {
 187                 .name = "dequeue",
 188                 .read_seq_string = blkiocg_dequeue_read,
 189        },
 190 #endif
 191 };
 192
 193 static int blkiocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 194 {
 195         return cgroup_add_files(cgroup, subsys, blkio_files,
 196                                 ARRAY_SIZE(blkio_files));
 197 }
 198
 199 static void blkiocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 200 {
 201         struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
 202         unsigned long flags;
 203         struct blkio_group *blkg;
 204         void *key;
 205
 206         rcu_read_lock();
 207 remove_entry:
 208         spin_lock_irqsave(&blkcg->lock, flags);
 209
 210         if (hlist_empty(&blkcg->blkg_list)) {
 211                 spin_unlock_irqrestore(&blkcg->lock, flags);
 212                 goto done;
 213         }
 214
 215         blkg = hlist_entry(blkcg->blkg_list.first, struct blkio_group,
 216                                 blkcg_node);
 217         key = rcu_dereference(blkg->key);
 218         __blkiocg_del_blkio_group(blkg);
 219
 220         spin_unlock_irqrestore(&blkcg->lock, flags);
 221
 222         /*
 223          * This blkio_group is being unlinked as associated cgroup is going
 224          * away. Let all the IO controlling policies know about this event.
 225          *
 226          * Currently this is static call to one io controlling policy. Once
 227          * we have more policies in place, we need some dynamic registration
 228          * of callback function.
 229          */
 230         cfq_unlink_blkio_group(key, blkg);
 231         goto remove_entry;
 232 done:
 233         free_css_id(&blkio_subsys, &blkcg->css);
 234         rcu_read_unlock();
 235         kfree(blkcg);
 236 }
 237
 238 static struct cgroup_subsys_state *
 239 blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 240 {
 241         struct blkio_cgroup *blkcg, *parent_blkcg;
 242
 243         if (!cgroup->parent) {
 244                 blkcg = &blkio_root_cgroup;
 245                 goto done;
 246         }
 247
 248         /* Currently we do not support hierarchy deeper than two level (0,1) */
 249         parent_blkcg = cgroup_to_blkio_cgroup(cgroup->parent);
 250         if (css_depth(&parent_blkcg->css) > 0)
 251                 return ERR_PTR(-EINVAL);
 252
 253         blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
 254         if (!blkcg)
 255                 return ERR_PTR(-ENOMEM);
 256
 257         blkcg->weight = BLKIO_WEIGHT_DEFAULT;
 258 done:
 259         spin_lock_init(&blkcg->lock);
 260         INIT_HLIST_HEAD(&blkcg->blkg_list);
 261
 262         return &blkcg->css;
 263 }
 264
 265 /*
 266  * We cannot support shared io contexts, as we have no mean to support
 267  * two tasks with the same ioc in two different groups without major rework
 268  * of the main cic data structures.  For now we allow a task to change
 269  * its cgroup only if it's the only owner of its ioc.
 270  */
 271 static int blkiocg_can_attach(struct cgroup_subsys *subsys,
 272                                 struct cgroup *cgroup, struct task_struct *tsk,
 273                                 bool threadgroup)
 274 {
 275         struct io_context *ioc;
 276         int ret = 0;
 277
 278         /* task_lock() is needed to avoid races with exit_io_context() */
 279         task_lock(tsk);
 280         ioc = tsk->io_context;
 281         if (ioc && atomic_read(&ioc->nr_tasks) > 1)
 282                 ret = -EINVAL;
 283         task_unlock(tsk);
 284
 285         return ret;
 286 }
 287
 288 static void blkiocg_attach(struct cgroup_subsys *subsys, struct cgroup *cgroup,
 289                                 struct cgroup *prev, struct task_struct *tsk,
 290                                 bool threadgroup)
 291 {
 292         struct io_context *ioc;
 293
 294         task_lock(tsk);
 295         ioc = tsk->io_context;
 296         if (ioc)
 297                 ioc->cgroup_changed = 1;
 298         task_unlock(tsk);
 299 }
 300
 301 struct cgroup_subsys blkio_subsys = {
 302         .name = "blkio",
 303         .create = blkiocg_create,
 304         .can_attach = blkiocg_can_attach,
 305         .attach = blkiocg_attach,
 306         .destroy = blkiocg_destroy,
 307         .populate = blkiocg_populate,
 308         .subsys_id = blkio_subsys_id,
 309         .use_id = 1,
 310 };