include/linux/cgroup.h

   1 #ifndef _LINUX_CGROUP_H
   2 #define _LINUX_CGROUP_H
   3 /*
   4  *  cgroup interface
   5  *
   6  *  Copyright (C) 2003 BULL SA
   7  *  Copyright (C) 2004-2006 Silicon Graphics, Inc.
   8  *
   9  */
  10
  11 #include <linux/sched.h>
  12 #include <linux/kref.h>
  13 #include <linux/cpumask.h>
  14 #include <linux/nodemask.h>
  15 #include <linux/rcupdate.h>
  16 #include <linux/cgroupstats.h>
  17
  18 #ifdef CONFIG_CGROUPS
  19
  20 struct cgroupfs_root;
  21 struct cgroup_subsys;
  22 struct inode;
  23
  24 extern int cgroup_init_early(void);
  25 extern int cgroup_init(void);
  26 extern void cgroup_init_smp(void);
  27 extern void cgroup_lock(void);
  28 extern void cgroup_unlock(void);
  29 extern void cgroup_fork(struct task_struct *p);
  30 extern void cgroup_fork_callbacks(struct task_struct *p);
  31 extern void cgroup_post_fork(struct task_struct *p);
  32 extern void cgroup_exit(struct task_struct *p, int run_callbacks);
  33 extern int cgroupstats_build(struct cgroupstats *stats,
  34                                 struct dentry *dentry);
  35
  36 extern struct file_operations proc_cgroup_operations;
  37
  38 /* Define the enumeration of all cgroup subsystems */
  39 #define SUBSYS(_x) _x ## _subsys_id,
  40 enum cgroup_subsys_id {
  41 #include <linux/cgroup_subsys.h>
  42         CGROUP_SUBSYS_COUNT
  43 };
  44 #undef SUBSYS
  45
  46 /* Per-subsystem/per-cgroup state maintained by the system. */
  47 struct cgroup_subsys_state {
  48         /* The cgroup that this subsystem is attached to. Useful
  49          * for subsystems that want to know about the cgroup
  50          * hierarchy structure */
  51         struct cgroup *cgroup;
  52
  53         /* State maintained by the cgroup system to allow
  54          * subsystems to be "busy". Should be accessed via css_get()
  55          * and css_put() */
  56
  57         atomic_t refcnt;
  58
  59         unsigned long flags;
  60 };
  61
  62 /* bits in struct cgroup_subsys_state flags field */
  63 enum {
  64         CSS_ROOT, /* This CSS is the root of the subsystem */
  65 };
  66
  67 /*
  68  * Call css_get() to hold a reference on the cgroup;
  69  *
  70  */
  71
  72 static inline void css_get(struct cgroup_subsys_state *css)
  73 {
  74         /* We don't need to reference count the root state */
  75         if (!test_bit(CSS_ROOT, &css->flags))
  76                 atomic_inc(&css->refcnt);
  77 }
  78 /*
  79  * css_put() should be called to release a reference taken by
  80  * css_get()
  81  */
  82
  83 extern void __css_put(struct cgroup_subsys_state *css);
  84 static inline void css_put(struct cgroup_subsys_state *css)
  85 {
  86         if (!test_bit(CSS_ROOT, &css->flags))
  87                 __css_put(css);
  88 }
  89
  90 struct cgroup {
  91         unsigned long flags;            /* "unsigned long" so bitops work */
  92
  93         /* count users of this cgroup. >0 means busy, but doesn't
  94          * necessarily indicate the number of tasks in the
  95          * cgroup */
  96         atomic_t count;
  97
  98         /*
  99          * We link our 'sibling' struct into our parent's 'children'.
 100          * Our children link their 'sibling' into our 'children'.
 101          */
 102         struct list_head sibling;       /* my parent's children */
 103         struct list_head children;      /* my children */
 104
 105         struct cgroup *parent;  /* my parent */
 106         struct dentry *dentry;          /* cgroup fs entry */
 107
 108         /* Private pointers for each registered subsystem */
 109         struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
 110
 111         struct cgroupfs_root *root;
 112         struct cgroup *top_cgroup;
 113
 114         /*
 115          * List of cg_cgroup_links pointing at css_sets with
 116          * tasks in this cgroup. Protected by css_set_lock
 117          */
 118         struct list_head css_sets;
 119
 120         /*
 121          * Linked list running through all cgroups that can
 122          * potentially be reaped by the release agent. Protected by
 123          * release_list_lock
 124          */
 125         struct list_head release_list;
 126 };
 127
 128 /* A css_set is a structure holding pointers to a set of
 129  * cgroup_subsys_state objects. This saves space in the task struct
 130  * object and speeds up fork()/exit(), since a single inc/dec and a
 131  * list_add()/del() can bump the reference count on the entire
 132  * cgroup set for a task.
 133  */
 134
 135 struct css_set {
 136
 137         /* Reference count */
 138         struct kref ref;
 139
 140         /*
 141          * List running through all cgroup groups. Protected by
 142          * css_set_lock
 143          */
 144         struct list_head list;
 145
 146         /*
 147          * List running through all tasks using this cgroup
 148          * group. Protected by css_set_lock
 149          */
 150         struct list_head tasks;
 151
 152         /*
 153          * List of cg_cgroup_link objects on link chains from
 154          * cgroups referenced from this css_set. Protected by
 155          * css_set_lock
 156          */
 157         struct list_head cg_links;
 158
 159         /*
 160          * Set of subsystem states, one for each subsystem. This array
 161          * is immutable after creation apart from the init_css_set
 162          * during subsystem registration (at boot time).
 163          */
 164         struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
 165
 166 };
 167
 168 /* struct cftype:
 169  *
 170  * The files in the cgroup filesystem mostly have a very simple read/write
 171  * handling, some common function will take care of it. Nevertheless some cases
 172  * (read tasks) are special and therefore I define this structure for every
 173  * kind of file.
 174  *
 175  *
 176  * When reading/writing to a file:
 177  *      - the cgroup to use in file->f_dentry->d_parent->d_fsdata
 178  *      - the 'cftype' of the file is file->f_dentry->d_fsdata
 179  */
 180
 181 #define MAX_CFTYPE_NAME 64
 182 struct cftype {
 183         /* By convention, the name should begin with the name of the
 184          * subsystem, followed by a period */
 185         char name[MAX_CFTYPE_NAME];
 186         int private;
 187         int (*open) (struct inode *inode, struct file *file);
 188         ssize_t (*read) (struct cgroup *cont, struct cftype *cft,
 189                          struct file *file,
 190                          char __user *buf, size_t nbytes, loff_t *ppos);
 191         /*
 192          * read_uint() is a shortcut for the common case of returning a
 193          * single integer. Use it in place of read()
 194          */
 195         u64 (*read_uint) (struct cgroup *cont, struct cftype *cft);
 196         ssize_t (*write) (struct cgroup *cont, struct cftype *cft,
 197                           struct file *file,
 198                           const char __user *buf, size_t nbytes, loff_t *ppos);
 199
 200         /*
 201          * write_uint() is a shortcut for the common case of accepting
 202          * a single integer (as parsed by simple_strtoull) from
 203          * userspace. Use in place of write(); return 0 or error.
 204          */
 205         int (*write_uint) (struct cgroup *cont, struct cftype *cft, u64 val);
 206
 207         int (*release) (struct inode *inode, struct file *file);
 208 };
 209
 210 /* Add a new file to the given cgroup directory. Should only be
 211  * called by subsystems from within a populate() method */
 212 int cgroup_add_file(struct cgroup *cont, struct cgroup_subsys *subsys,
 213                        const struct cftype *cft);
 214
 215 /* Add a set of new files to the given cgroup directory. Should
 216  * only be called by subsystems from within a populate() method */
 217 int cgroup_add_files(struct cgroup *cont,
 218                         struct cgroup_subsys *subsys,
 219                         const struct cftype cft[],
 220                         int count);
 221
 222 int cgroup_is_removed(const struct cgroup *cont);
 223
 224 int cgroup_path(const struct cgroup *cont, char *buf, int buflen);
 225
 226 int cgroup_task_count(const struct cgroup *cont);
 227
 228 /* Return true if the cgroup is a descendant of the current cgroup */
 229 int cgroup_is_descendant(const struct cgroup *cont);
 230
 231 /* Control Group subsystem type. See Documentation/cgroups.txt for details */
 232
 233 struct cgroup_subsys {
 234         struct cgroup_subsys_state *(*create)(struct cgroup_subsys *ss,
 235                                                   struct cgroup *cont);
 236         void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cont);
 237         int (*can_attach)(struct cgroup_subsys *ss,
 238                           struct cgroup *cont, struct task_struct *tsk);
 239         void (*attach)(struct cgroup_subsys *ss, struct cgroup *cont,
 240                         struct cgroup *old_cont, struct task_struct *tsk);
 241         void (*fork)(struct cgroup_subsys *ss, struct task_struct *task);
 242         void (*exit)(struct cgroup_subsys *ss, struct task_struct *task);
 243         int (*populate)(struct cgroup_subsys *ss,
 244                         struct cgroup *cont);
 245         void (*post_clone)(struct cgroup_subsys *ss, struct cgroup *cont);
 246         void (*bind)(struct cgroup_subsys *ss, struct cgroup *root);
 247         int subsys_id;
 248         int active;
 249         int early_init;
 250 #define MAX_CGROUP_TYPE_NAMELEN 32
 251         const char *name;
 252
 253         /* Protected by RCU */
 254         struct cgroupfs_root *root;
 255
 256         struct list_head sibling;
 257
 258         void *private;
 259 };
 260
 261 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
 262 #include <linux/cgroup_subsys.h>
 263 #undef SUBSYS
 264
 265 static inline struct cgroup_subsys_state *cgroup_subsys_state(
 266         struct cgroup *cont, int subsys_id)
 267 {
 268         return cont->subsys[subsys_id];
 269 }
 270
 271 static inline struct cgroup_subsys_state *task_subsys_state(
 272         struct task_struct *task, int subsys_id)
 273 {
 274         return rcu_dereference(task->cgroups->subsys[subsys_id]);
 275 }
 276
 277 static inline struct cgroup* task_cgroup(struct task_struct *task,
 278                                                int subsys_id)
 279 {
 280         return task_subsys_state(task, subsys_id)->cgroup;
 281 }
 282
 283 int cgroup_path(const struct cgroup *cont, char *buf, int buflen);
 284
 285 int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *ss);
 286
 287 /* A cgroup_iter should be treated as an opaque object */
 288 struct cgroup_iter {
 289         struct list_head *cg_link;
 290         struct list_head *task;
 291 };
 292
 293 /* To iterate across the tasks in a cgroup:
 294  *
 295  * 1) call cgroup_iter_start to intialize an iterator
 296  *
 297  * 2) call cgroup_iter_next() to retrieve member tasks until it
 298  *    returns NULL or until you want to end the iteration
 299  *
 300  * 3) call cgroup_iter_end() to destroy the iterator.
 301  */
 302 void cgroup_iter_start(struct cgroup *cont, struct cgroup_iter *it);
 303 struct task_struct *cgroup_iter_next(struct cgroup *cont,
 304                                         struct cgroup_iter *it);
 305 void cgroup_iter_end(struct cgroup *cont, struct cgroup_iter *it);
 306
 307 #else /* !CONFIG_CGROUPS */
 308
 309 static inline int cgroup_init_early(void) { return 0; }
 310 static inline int cgroup_init(void) { return 0; }
 311 static inline void cgroup_init_smp(void) {}
 312 static inline void cgroup_fork(struct task_struct *p) {}
 313 static inline void cgroup_fork_callbacks(struct task_struct *p) {}
 314 static inline void cgroup_post_fork(struct task_struct *p) {}
 315 static inline void cgroup_exit(struct task_struct *p, int callbacks) {}
 316
 317 static inline void cgroup_lock(void) {}
 318 static inline void cgroup_unlock(void) {}
 319 static inline int cgroupstats_build(struct cgroupstats *stats,
 320                                         struct dentry *dentry)
 321 {
 322         return -EINVAL;
 323 }
 324
 325 #endif /* !CONFIG_CGROUPS */
 326
 327 #endif /* _LINUX_CGROUP_H */