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