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 "blk-cgroup.h"
  17
  18 extern void cfq_unlink_blkio_group(void *, struct blkio_group *);
  19 extern void cfq_update_blkio_group_weight(struct blkio_group *, unsigned int);
  20
  21 struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
  22
  23 struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
  24 {
  25         return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
  26                             struct blkio_cgroup, css);
  27 }
  28
  29 void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
  30                         unsigned long time, unsigned long sectors)
  31 {
  32         blkg->time += time;
  33         blkg->sectors += sectors;
  34 }
  35
  36 void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
  37                         struct blkio_group *blkg, void *key, dev_t dev)
  38 {
  39         unsigned long flags;
  40
  41         spin_lock_irqsave(&blkcg->lock, flags);
  42         rcu_assign_pointer(blkg->key, key);
  43         blkg->blkcg_id = css_id(&blkcg->css);
  44         hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
  45         spin_unlock_irqrestore(&blkcg->lock, flags);
  46 #ifdef CONFIG_DEBUG_BLK_CGROUP
  47         /* Need to take css reference ? */
  48         cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
  49 #endif
  50         blkg->dev = dev;
  51 }
  52
  53 static void __blkiocg_del_blkio_group(struct blkio_group *blkg)
  54 {
  55         hlist_del_init_rcu(&blkg->blkcg_node);
  56         blkg->blkcg_id = 0;
  57 }
  58
  59 /*
  60  * returns 0 if blkio_group was still on cgroup list. Otherwise returns 1
  61  * indicating that blk_group was unhashed by the time we got to it.
  62  */
  63 int blkiocg_del_blkio_group(struct blkio_group *blkg)
  64 {
  65         struct blkio_cgroup *blkcg;
  66         unsigned long flags;
  67         struct cgroup_subsys_state *css;
  68         int ret = 1;
  69
  70         rcu_read_lock();
  71         css = css_lookup(&blkio_subsys, blkg->blkcg_id);
  72         if (!css)
  73                 goto out;
  74
  75         blkcg = container_of(css, struct blkio_cgroup, css);
  76         spin_lock_irqsave(&blkcg->lock, flags);
  77         if (!hlist_unhashed(&blkg->blkcg_node)) {
  78                 __blkiocg_del_blkio_group(blkg);
  79                 ret = 0;
  80         }
  81         spin_unlock_irqrestore(&blkcg->lock, flags);
  82 out:
  83         rcu_read_unlock();
  84         return ret;
  85 }
  86
  87 /* called under rcu_read_lock(). */
  88 struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key)
  89 {
  90         struct blkio_group *blkg;
  91         struct hlist_node *n;
  92         void *__key;
  93
  94         hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
  95                 __key = blkg->key;
  96                 if (__key == key)
  97                         return blkg;
  98         }
  99
 100         return NULL;
 101 }
 102
 103 #define SHOW_FUNCTION(__VAR)                                            \
 104 static u64 blkiocg_##__VAR##_read(struct cgroup *cgroup,                \
 105                                        struct cftype *cftype)           \
 106 {                                                                       \
 107         struct blkio_cgroup *blkcg;                                     \
 108                                                                         \
 109         blkcg = cgroup_to_blkio_cgroup(cgroup);                         \
 110         return (u64)blkcg->__VAR;                                       \
 111 }
 112
 113 SHOW_FUNCTION(weight);
 114 #undef SHOW_FUNCTION
 115
 116 static int
 117 blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
 118 {
 119         struct blkio_cgroup *blkcg;
 120         struct blkio_group *blkg;
 121         struct hlist_node *n;
 122
 123         if (val < BLKIO_WEIGHT_MIN || val > BLKIO_WEIGHT_MAX)
 124                 return -EINVAL;
 125
 126         blkcg = cgroup_to_blkio_cgroup(cgroup);
 127         spin_lock_irq(&blkcg->lock);
 128         blkcg->weight = (unsigned int)val;
 129         hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
 130                 cfq_update_blkio_group_weight(blkg, blkcg->weight);
 131         spin_unlock_irq(&blkcg->lock);
 132         return 0;
 133 }
 134
 135 #define SHOW_FUNCTION_PER_GROUP(__VAR)                                  \
 136 static int blkiocg_##__VAR##_read(struct cgroup *cgroup,                \
 137                         struct cftype *cftype, struct seq_file *m)      \
 138 {                                                                       \
 139         struct blkio_cgroup *blkcg;                                     \
 140         struct blkio_group *blkg;                                       \
 141         struct hlist_node *n;                                           \
 142                                                                         \
 143         if (!cgroup_lock_live_group(cgroup))                            \
 144                 return -ENODEV;                                         \
 145                                                                         \
 146         blkcg = cgroup_to_blkio_cgroup(cgroup);                         \
 147         rcu_read_lock();                                                \
 148         hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {\
 149                 if (blkg->dev)                                          \
 150                         seq_printf(m, "%u:%u %lu\n", MAJOR(blkg->dev),  \
 151                                  MINOR(blkg->dev), blkg->__VAR);        \
 152         }                                                               \
 153         rcu_read_unlock();                                              \
 154         cgroup_unlock();                                                \
 155         return 0;                                                       \
 156 }
 157
 158 SHOW_FUNCTION_PER_GROUP(time);
 159 SHOW_FUNCTION_PER_GROUP(sectors);
 160 #ifdef CONFIG_DEBUG_BLK_CGROUP
 161 SHOW_FUNCTION_PER_GROUP(dequeue);
 162 #endif
 163 #undef SHOW_FUNCTION_PER_GROUP
 164
 165 #ifdef CONFIG_DEBUG_BLK_CGROUP
 166 void blkiocg_update_blkio_group_dequeue_stats(struct blkio_group *blkg,
 167                         unsigned long dequeue)
 168 {
 169         blkg->dequeue += dequeue;
 170 }
 171 #endif
 172
 173 struct cftype blkio_files[] = {
 174         {
 175                 .name = "weight",
 176                 .read_u64 = blkiocg_weight_read,
 177                 .write_u64 = blkiocg_weight_write,
 178         },
 179         {
 180                 .name = "time",
 181                 .read_seq_string = blkiocg_time_read,
 182         },
 183         {
 184                 .name = "sectors",
 185                 .read_seq_string = blkiocg_sectors_read,
 186         },
 187 #ifdef CONFIG_DEBUG_BLK_CGROUP
 188        {
 189                 .name = "dequeue",
 190                 .read_seq_string = blkiocg_dequeue_read,
 191        },
 192 #endif
 193 };
 194
 195 static int blkiocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 196 {
 197         return cgroup_add_files(cgroup, subsys, blkio_files,
 198                                 ARRAY_SIZE(blkio_files));
 199 }
 200
 201 static void blkiocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 202 {
 203         struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
 204         unsigned long flags;
 205         struct blkio_group *blkg;
 206         void *key;
 207
 208         rcu_read_lock();
 209 remove_entry:
 210         spin_lock_irqsave(&blkcg->lock, flags);
 211
 212         if (hlist_empty(&blkcg->blkg_list)) {
 213                 spin_unlock_irqrestore(&blkcg->lock, flags);
 214                 goto done;
 215         }
 216
 217         blkg = hlist_entry(blkcg->blkg_list.first, struct blkio_group,
 218                                 blkcg_node);
 219         key = rcu_dereference(blkg->key);
 220         __blkiocg_del_blkio_group(blkg);
 221
 222         spin_unlock_irqrestore(&blkcg->lock, flags);
 223
 224         /*
 225          * This blkio_group is being unlinked as associated cgroup is going
 226          * away. Let all the IO controlling policies know about this event.
 227          *
 228          * Currently this is static call to one io controlling policy. Once
 229          * we have more policies in place, we need some dynamic registration
 230          * of callback function.
 231          */
 232         cfq_unlink_blkio_group(key, blkg);
 233         goto remove_entry;
 234 done:
 235         free_css_id(&blkio_subsys, &blkcg->css);
 236         rcu_read_unlock();
 237         kfree(blkcg);
 238 }
 239
 240 static struct cgroup_subsys_state *
 241 blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 242 {
 243         struct blkio_cgroup *blkcg, *parent_blkcg;
 244
 245         if (!cgroup->parent) {
 246                 blkcg = &blkio_root_cgroup;
 247                 goto done;
 248         }
 249
 250         /* Currently we do not support hierarchy deeper than two level (0,1) */
 251         parent_blkcg = cgroup_to_blkio_cgroup(cgroup->parent);
 252         if (css_depth(&parent_blkcg->css) > 0)
 253                 return ERR_PTR(-EINVAL);
 254
 255         blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
 256         if (!blkcg)
 257                 return ERR_PTR(-ENOMEM);
 258
 259         blkcg->weight = BLKIO_WEIGHT_DEFAULT;
 260 done:
 261         spin_lock_init(&blkcg->lock);
 262         INIT_HLIST_HEAD(&blkcg->blkg_list);
 263
 264         return &blkcg->css;
 265 }
 266
 267 /*
 268  * We cannot support shared io contexts, as we have no mean to support
 269  * two tasks with the same ioc in two different groups without major rework
 270  * of the main cic data structures.  For now we allow a task to change
 271  * its cgroup only if it's the only owner of its ioc.
 272  */
 273 static int blkiocg_can_attach(struct cgroup_subsys *subsys,
 274                                 struct cgroup *cgroup, struct task_struct *tsk,
 275                                 bool threadgroup)
 276 {
 277         struct io_context *ioc;
 278         int ret = 0;
 279
 280         /* task_lock() is needed to avoid races with exit_io_context() */
 281         task_lock(tsk);
 282         ioc = tsk->io_context;
 283         if (ioc && atomic_read(&ioc->nr_tasks) > 1)
 284                 ret = -EINVAL;
 285         task_unlock(tsk);
 286
 287         return ret;
 288 }
 289
 290 static void blkiocg_attach(struct cgroup_subsys *subsys, struct cgroup *cgroup,
 291                                 struct cgroup *prev, struct task_struct *tsk,
 292                                 bool threadgroup)
 293 {
 294         struct io_context *ioc;
 295
 296         task_lock(tsk);
 297         ioc = tsk->io_context;
 298         if (ioc)
 299                 ioc->cgroup_changed = 1;
 300         task_unlock(tsk);
 301 }
 302
 303 struct cgroup_subsys blkio_subsys = {
 304         .name = "blkio",
 305         .create = blkiocg_create,
 306         .can_attach = blkiocg_can_attach,
 307         .attach = blkiocg_attach,
 308         .destroy = blkiocg_destroy,
 309         .populate = blkiocg_populate,
 310         .subsys_id = blkio_subsys_id,
 311         .use_id = 1,
 312 };