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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 "blk-cgroup.h"
  15
  16 struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
  17
  18 struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
  19 {
  20         return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
  21                             struct blkio_cgroup, css);
  22 }
  23
  24 void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
  25                                 struct blkio_group *blkg, void *key)
  26 {
  27         unsigned long flags;
  28
  29         spin_lock_irqsave(&blkcg->lock, flags);
  30         rcu_assign_pointer(blkg->key, key);
  31         hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
  32         spin_unlock_irqrestore(&blkcg->lock, flags);
  33 }
  34
  35 int blkiocg_del_blkio_group(struct blkio_group *blkg)
  36 {
  37         /* Implemented later */
  38         return 0;
  39 }
  40
  41 /* called under rcu_read_lock(). */
  42 struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key)
  43 {
  44         struct blkio_group *blkg;
  45         struct hlist_node *n;
  46         void *__key;
  47
  48         hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
  49                 __key = blkg->key;
  50                 if (__key == key)
  51                         return blkg;
  52         }
  53
  54         return NULL;
  55 }
  56
  57 #define SHOW_FUNCTION(__VAR)                                            \
  58 static u64 blkiocg_##__VAR##_read(struct cgroup *cgroup,                \
  59                                        struct cftype *cftype)           \
  60 {                                                                       \
  61         struct blkio_cgroup *blkcg;                                     \
  62                                                                         \
  63         blkcg = cgroup_to_blkio_cgroup(cgroup);                         \
  64         return (u64)blkcg->__VAR;                                       \
  65 }
  66
  67 SHOW_FUNCTION(weight);
  68 #undef SHOW_FUNCTION
  69
  70 static int
  71 blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
  72 {
  73         struct blkio_cgroup *blkcg;
  74
  75         if (val < BLKIO_WEIGHT_MIN || val > BLKIO_WEIGHT_MAX)
  76                 return -EINVAL;
  77
  78         blkcg = cgroup_to_blkio_cgroup(cgroup);
  79         blkcg->weight = (unsigned int)val;
  80         return 0;
  81 }
  82
  83 struct cftype blkio_files[] = {
  84         {
  85                 .name = "weight",
  86                 .read_u64 = blkiocg_weight_read,
  87                 .write_u64 = blkiocg_weight_write,
  88         },
  89 };
  90
  91 static int blkiocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
  92 {
  93         return cgroup_add_files(cgroup, subsys, blkio_files,
  94                                 ARRAY_SIZE(blkio_files));
  95 }
  96
  97 static void blkiocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
  98 {
  99         struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
 100
 101         free_css_id(&blkio_subsys, &blkcg->css);
 102         kfree(blkcg);
 103 }
 104
 105 static struct cgroup_subsys_state *
 106 blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 107 {
 108         struct blkio_cgroup *blkcg, *parent_blkcg;
 109
 110         if (!cgroup->parent) {
 111                 blkcg = &blkio_root_cgroup;
 112                 goto done;
 113         }
 114
 115         /* Currently we do not support hierarchy deeper than two level (0,1) */
 116         parent_blkcg = cgroup_to_blkio_cgroup(cgroup->parent);
 117         if (css_depth(&parent_blkcg->css) > 0)
 118                 return ERR_PTR(-EINVAL);
 119
 120         blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
 121         if (!blkcg)
 122                 return ERR_PTR(-ENOMEM);
 123
 124         blkcg->weight = BLKIO_WEIGHT_DEFAULT;
 125 done:
 126         spin_lock_init(&blkcg->lock);
 127         INIT_HLIST_HEAD(&blkcg->blkg_list);
 128
 129         return &blkcg->css;
 130 }
 131
 132 /*
 133  * We cannot support shared io contexts, as we have no mean to support
 134  * two tasks with the same ioc in two different groups without major rework
 135  * of the main cic data structures.  For now we allow a task to change
 136  * its cgroup only if it's the only owner of its ioc.
 137  */
 138 static int blkiocg_can_attach(struct cgroup_subsys *subsys,
 139                                 struct cgroup *cgroup, struct task_struct *tsk,
 140                                 bool threadgroup)
 141 {
 142         struct io_context *ioc;
 143         int ret = 0;
 144
 145         /* task_lock() is needed to avoid races with exit_io_context() */
 146         task_lock(tsk);
 147         ioc = tsk->io_context;
 148         if (ioc && atomic_read(&ioc->nr_tasks) > 1)
 149                 ret = -EINVAL;
 150         task_unlock(tsk);
 151
 152         return ret;
 153 }
 154
 155 static void blkiocg_attach(struct cgroup_subsys *subsys, struct cgroup *cgroup,
 156                                 struct cgroup *prev, struct task_struct *tsk,
 157                                 bool threadgroup)
 158 {
 159         struct io_context *ioc;
 160
 161         task_lock(tsk);
 162         ioc = tsk->io_context;
 163         if (ioc)
 164                 ioc->cgroup_changed = 1;
 165         task_unlock(tsk);
 166 }
 167
 168 struct cgroup_subsys blkio_subsys = {
 169         .name = "blkio",
 170         .create = blkiocg_create,
 171         .can_attach = blkiocg_can_attach,
 172         .attach = blkiocg_attach,
 173         .destroy = blkiocg_destroy,
 174         .populate = blkiocg_populate,
 175         .subsys_id = blkio_subsys_id,
 176         .use_id = 1,
 177 };