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