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 #include <linux/prio_heap.h>
  18
  19 #ifdef CONFIG_CGROUPS
  20
  21 struct cgroupfs_root;
  22 struct cgroup_subsys;
  23 struct inode;
  24
  25 extern int cgroup_init_early(void);
  26 extern int cgroup_init(void);
  27 extern void cgroup_init_smp(void);
  28 extern void cgroup_lock(void);
  29 extern void cgroup_unlock(void);
  30 extern void cgroup_fork(struct task_struct *p);
  31 extern void cgroup_fork_callbacks(struct task_struct *p);
  32 extern void cgroup_post_fork(struct task_struct *p);
  33 extern void cgroup_exit(struct task_struct *p, int run_callbacks);
  34 extern int cgroupstats_build(struct cgroupstats *stats,
  35                                 struct dentry *dentry);
  36
  37 extern struct file_operations proc_cgroup_operations;
  38
  39 /* Define the enumeration of all cgroup subsystems */
  40 #define SUBSYS(_x) _x ## _subsys_id,
  41 enum cgroup_subsys_id {
  42 #include <linux/cgroup_subsys.h>
  43         CGROUP_SUBSYS_COUNT
  44 };
  45 #undef SUBSYS
  46
  47 /* Per-subsystem/per-cgroup state maintained by the system. */
  48 struct cgroup_subsys_state {
  49         /* The cgroup that this subsystem is attached to. Useful
  50          * for subsystems that want to know about the cgroup
  51          * hierarchy structure */
  52         struct cgroup *cgroup;
  53
  54         /* State maintained by the cgroup system to allow
  55          * subsystems to be "busy". Should be accessed via css_get()
  56          * and css_put() */
  57
  58         atomic_t refcnt;
  59
  60         unsigned long flags;
  61 };
  62
  63 /* bits in struct cgroup_subsys_state flags field */
  64 enum {
  65         CSS_ROOT, /* This CSS is the root of the subsystem */
  66 };
  67
  68 /*
  69  * Call css_get() to hold a reference on the cgroup;
  70  *
  71  */
  72
  73 static inline void css_get(struct cgroup_subsys_state *css)
  74 {
  75         /* We don't need to reference count the root state */
  76         if (!test_bit(CSS_ROOT, &css->flags))
  77                 atomic_inc(&css->refcnt);
  78 }
  79 /*
  80  * css_put() should be called to release a reference taken by
  81  * css_get()
  82  */
  83
  84 extern void __css_put(struct cgroup_subsys_state *css);
  85 static inline void css_put(struct cgroup_subsys_state *css)
  86 {
  87         if (!test_bit(CSS_ROOT, &css->flags))
  88                 __css_put(css);
  89 }
  90
  91 struct cgroup {
  92         unsigned long flags;            /* "unsigned long" so bitops work */
  93
  94         /* count users of this cgroup. >0 means busy, but doesn't
  95          * necessarily indicate the number of tasks in the
  96          * cgroup */
  97         atomic_t count;
  98
  99         /*
 100          * We link our 'sibling' struct into our parent's 'children'.
 101          * Our children link their 'sibling' into our 'children'.
 102          */
 103         struct list_head sibling;       /* my parent's children */
 104         struct list_head children;      /* my children */
 105
 106         struct cgroup *parent;  /* my parent */
 107         struct dentry *dentry;          /* cgroup fs entry */
 108
 109         /* Private pointers for each registered subsystem */
 110         struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
 111
 112         struct cgroupfs_root *root;
 113         struct cgroup *top_cgroup;
 114
 115         /*
 116          * List of cg_cgroup_links pointing at css_sets with
 117          * tasks in this cgroup. Protected by css_set_lock
 118          */
 119         struct list_head css_sets;
 120
 121         /*
 122          * Linked list running through all cgroups that can
 123          * potentially be reaped by the release agent. Protected by
 124          * release_list_lock
 125          */
 126         struct list_head release_list;
 127 };
 128
 129 /* A css_set is a structure holding pointers to a set of
 130  * cgroup_subsys_state objects. This saves space in the task struct
 131  * object and speeds up fork()/exit(), since a single inc/dec and a
 132  * list_add()/del() can bump the reference count on the entire
 133  * cgroup set for a task.
 134  */
 135
 136 struct css_set {
 137
 138         /* Reference count */
 139         struct kref ref;
 140
 141         /*
 142          * List running through all cgroup groups. Protected by
 143          * css_set_lock
 144          */
 145         struct list_head list;
 146
 147         /*
 148          * List running through all tasks using this cgroup
 149          * group. Protected by css_set_lock
 150          */
 151         struct list_head tasks;
 152
 153         /*
 154          * List of cg_cgroup_link objects on link chains from
 155          * cgroups referenced from this css_set. Protected by
 156          * css_set_lock
 157          */
 158         struct list_head cg_links;
 159
 160         /*
 161          * Set of subsystem states, one for each subsystem. This array
 162          * is immutable after creation apart from the init_css_set
 163          * during subsystem registration (at boot time).
 164          */
 165         struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
 166
 167 };
 168
 169 /* struct cftype:
 170  *
 171  * The files in the cgroup filesystem mostly have a very simple read/write
 172  * handling, some common function will take care of it. Nevertheless some cases
 173  * (read tasks) are special and therefore I define this structure for every
 174  * kind of file.
 175  *
 176  *
 177  * When reading/writing to a file:
 178  *      - the cgroup to use is file->f_dentry->d_parent->d_fsdata
 179  *      - the 'cftype' of the file is file->f_dentry->d_fsdata
 180  */
 181
 182 #define MAX_CFTYPE_NAME 64
 183 struct cftype {
 184         /* By convention, the name should begin with the name of the
 185          * subsystem, followed by a period */
 186         char name[MAX_CFTYPE_NAME];
 187         int private;
 188         int (*open) (struct inode *inode, struct file *file);
 189         ssize_t (*read) (struct cgroup *cgrp, struct cftype *cft,
 190                          struct file *file,
 191                          char __user *buf, size_t nbytes, loff_t *ppos);
 192         /*
 193          * read_uint() is a shortcut for the common case of returning a
 194          * single integer. Use it in place of read()
 195          */
 196         u64 (*read_uint) (struct cgroup *cgrp, struct cftype *cft);
 197         ssize_t (*write) (struct cgroup *cgrp, struct cftype *cft,
 198                           struct file *file,
 199                           const char __user *buf, size_t nbytes, loff_t *ppos);
 200
 201         /*
 202          * write_uint() is a shortcut for the common case of accepting
 203          * a single integer (as parsed by simple_strtoull) from
 204          * userspace. Use in place of write(); return 0 or error.
 205          */
 206         int (*write_uint) (struct cgroup *cgrp, struct cftype *cft, u64 val);
 207
 208         int (*release) (struct inode *inode, struct file *file);
 209 };
 210
 211 struct cgroup_scanner {
 212         struct cgroup *cg;
 213         int (*test_task)(struct task_struct *p, struct cgroup_scanner *scan);
 214         void (*process_task)(struct task_struct *p,
 215                         struct cgroup_scanner *scan);
 216         struct ptr_heap *heap;
 217 };
 218
 219 /* Add a new file to the given cgroup directory. Should only be
 220  * called by subsystems from within a populate() method */
 221 int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
 222                        const struct cftype *cft);
 223
 224 /* Add a set of new files to the given cgroup directory. Should
 225  * only be called by subsystems from within a populate() method */
 226 int cgroup_add_files(struct cgroup *cgrp,
 227                         struct cgroup_subsys *subsys,
 228                         const struct cftype cft[],
 229                         int count);
 230
 231 int cgroup_is_removed(const struct cgroup *cgrp);
 232
 233 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
 234
 235 int cgroup_task_count(const struct cgroup *cgrp);
 236
 237 /* Return true if the cgroup is a descendant of the current cgroup */
 238 int cgroup_is_descendant(const struct cgroup *cgrp);
 239
 240 /* Control Group subsystem type. See Documentation/cgroups.txt for details */
 241
 242 struct cgroup_subsys {
 243         struct cgroup_subsys_state *(*create)(struct cgroup_subsys *ss,
 244                                                   struct cgroup *cgrp);
 245         void (*pre_destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
 246         void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
 247         int (*can_attach)(struct cgroup_subsys *ss,
 248                           struct cgroup *cgrp, struct task_struct *tsk);
 249         void (*attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
 250                         struct cgroup *old_cgrp, struct task_struct *tsk);
 251         void (*fork)(struct cgroup_subsys *ss, struct task_struct *task);
 252         void (*exit)(struct cgroup_subsys *ss, struct task_struct *task);
 253         int (*populate)(struct cgroup_subsys *ss,
 254                         struct cgroup *cgrp);
 255         void (*post_clone)(struct cgroup_subsys *ss, struct cgroup *cgrp);
 256         void (*bind)(struct cgroup_subsys *ss, struct cgroup *root);
 257         int subsys_id;
 258         int active;
 259         int early_init;
 260 #define MAX_CGROUP_TYPE_NAMELEN 32
 261         const char *name;
 262
 263         /* Protected by RCU */
 264         struct cgroupfs_root *root;
 265
 266         struct list_head sibling;
 267
 268         void *private;
 269 };
 270
 271 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
 272 #include <linux/cgroup_subsys.h>
 273 #undef SUBSYS
 274
 275 static inline struct cgroup_subsys_state *cgroup_subsys_state(
 276         struct cgroup *cgrp, int subsys_id)
 277 {
 278         return cgrp->subsys[subsys_id];
 279 }
 280
 281 static inline struct cgroup_subsys_state *task_subsys_state(
 282         struct task_struct *task, int subsys_id)
 283 {
 284         return rcu_dereference(task->cgroups->subsys[subsys_id]);
 285 }
 286
 287 static inline struct cgroup* task_cgroup(struct task_struct *task,
 288                                                int subsys_id)
 289 {
 290         return task_subsys_state(task, subsys_id)->cgroup;
 291 }
 292
 293 int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *ss);
 294
 295 /* A cgroup_iter should be treated as an opaque object */
 296 struct cgroup_iter {
 297         struct list_head *cg_link;
 298         struct list_head *task;
 299 };
 300
 301 /* To iterate across the tasks in a cgroup:
 302  *
 303  * 1) call cgroup_iter_start to intialize an iterator
 304  *
 305  * 2) call cgroup_iter_next() to retrieve member tasks until it
 306  *    returns NULL or until you want to end the iteration
 307  *
 308  * 3) call cgroup_iter_end() to destroy the iterator.
 309  *
 310  * Or, call cgroup_scan_tasks() to iterate through every task in a cpuset.
 311  *    - cgroup_scan_tasks() holds the css_set_lock when calling the test_task()
 312  *      callback, but not while calling the process_task() callback.
 313  */
 314 void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it);
 315 struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
 316                                         struct cgroup_iter *it);
 317 void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it);
 318 int cgroup_scan_tasks(struct cgroup_scanner *scan);
 319 int cgroup_attach_task(struct cgroup *, struct task_struct *);
 320
 321 #else /* !CONFIG_CGROUPS */
 322
 323 static inline int cgroup_init_early(void) { return 0; }
 324 static inline int cgroup_init(void) { return 0; }
 325 static inline void cgroup_init_smp(void) {}
 326 static inline void cgroup_fork(struct task_struct *p) {}
 327 static inline void cgroup_fork_callbacks(struct task_struct *p) {}
 328 static inline void cgroup_post_fork(struct task_struct *p) {}
 329 static inline void cgroup_exit(struct task_struct *p, int callbacks) {}
 330
 331 static inline void cgroup_lock(void) {}
 332 static inline void cgroup_unlock(void) {}
 333 static inline int cgroupstats_build(struct cgroupstats *stats,
 334                                         struct dentry *dentry)
 335 {
 336         return -EINVAL;
 337 }
 338
 339 #endif /* !CONFIG_CGROUPS */
 340
 341 #endif /* _LINUX_CGROUP_H */