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