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/cpumask.h>
  13 #include <linux/nodemask.h>
  14 #include <linux/rcupdate.h>
  15 #include <linux/cgroupstats.h>
  16 #include <linux/prio_heap.h>
  17 #include <linux/rwsem.h>
  18
  19 #ifdef CONFIG_CGROUPS
  20
  21 struct cgroupfs_root;
  22 struct cgroup_subsys;
  23 struct inode;
  24 struct cgroup;
  25
  26 extern int cgroup_init_early(void);
  27 extern int cgroup_init(void);
  28 extern void cgroup_init_smp(void);
  29 extern void cgroup_lock(void);
  30 extern bool cgroup_lock_live_group(struct cgroup *cgrp);
  31 extern void cgroup_unlock(void);
  32 extern void cgroup_fork(struct task_struct *p);
  33 extern void cgroup_fork_callbacks(struct task_struct *p);
  34 extern void cgroup_post_fork(struct task_struct *p);
  35 extern void cgroup_exit(struct task_struct *p, int run_callbacks);
  36 extern int cgroupstats_build(struct cgroupstats *stats,
  37                                 struct dentry *dentry);
  38
  39 extern struct file_operations proc_cgroup_operations;
  40
  41 /* Define the enumeration of all cgroup subsystems */
  42 #define SUBSYS(_x) _x ## _subsys_id,
  43 enum cgroup_subsys_id {
  44 #include <linux/cgroup_subsys.h>
  45         CGROUP_SUBSYS_COUNT
  46 };
  47 #undef SUBSYS
  48
  49 /* Per-subsystem/per-cgroup state maintained by the system. */
  50 struct cgroup_subsys_state {
  51         /* The cgroup that this subsystem is attached to. Useful
  52          * for subsystems that want to know about the cgroup
  53          * hierarchy structure */
  54         struct cgroup *cgroup;
  55
  56         /* State maintained by the cgroup system to allow
  57          * subsystems to be "busy". Should be accessed via css_get()
  58          * and css_put() */
  59
  60         atomic_t refcnt;
  61
  62         unsigned long flags;
  63 };
  64
  65 /* bits in struct cgroup_subsys_state flags field */
  66 enum {
  67         CSS_ROOT, /* This CSS is the root of the subsystem */
  68 };
  69
  70 /*
  71  * Call css_get() to hold a reference on the cgroup;
  72  *
  73  */
  74
  75 static inline void css_get(struct cgroup_subsys_state *css)
  76 {
  77         /* We don't need to reference count the root state */
  78         if (!test_bit(CSS_ROOT, &css->flags))
  79                 atomic_inc(&css->refcnt);
  80 }
  81 /*
  82  * css_put() should be called to release a reference taken by
  83  * css_get()
  84  */
  85
  86 extern void __css_put(struct cgroup_subsys_state *css);
  87 static inline void css_put(struct cgroup_subsys_state *css)
  88 {
  89         if (!test_bit(CSS_ROOT, &css->flags))
  90                 __css_put(css);
  91 }
  92
  93 /* bits in struct cgroup flags field */
  94 enum {
  95         /* Control Group is dead */
  96         CGRP_REMOVED,
  97         /* Control Group has previously had a child cgroup or a task,
  98          * but no longer (only if CGRP_NOTIFY_ON_RELEASE is set) */
  99         CGRP_RELEASABLE,
 100         /* Control Group requires release notifications to userspace */
 101         CGRP_NOTIFY_ON_RELEASE,
 102 };
 103
 104 struct cgroup {
 105         unsigned long flags;            /* "unsigned long" so bitops work */
 106
 107         /* count users of this cgroup. >0 means busy, but doesn't
 108          * necessarily indicate the number of tasks in the
 109          * cgroup */
 110         atomic_t count;
 111
 112         /*
 113          * We link our 'sibling' struct into our parent's 'children'.
 114          * Our children link their 'sibling' into our 'children'.
 115          */
 116         struct list_head sibling;       /* my parent's children */
 117         struct list_head children;      /* my children */
 118
 119         struct cgroup *parent;  /* my parent */
 120         struct dentry *dentry;          /* cgroup fs entry */
 121
 122         /* Private pointers for each registered subsystem */
 123         struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
 124
 125         struct cgroupfs_root *root;
 126         struct cgroup *top_cgroup;
 127
 128         /*
 129          * List of cg_cgroup_links pointing at css_sets with
 130          * tasks in this cgroup. Protected by css_set_lock
 131          */
 132         struct list_head css_sets;
 133
 134         /*
 135          * Linked list running through all cgroups that can
 136          * potentially be reaped by the release agent. Protected by
 137          * release_list_lock
 138          */
 139         struct list_head release_list;
 140
 141         /* pids_mutex protects the fields below */
 142         struct rw_semaphore pids_mutex;
 143         /* Array of process ids in the cgroup */
 144         pid_t *tasks_pids;
 145         /* How many files are using the current tasks_pids array */
 146         int pids_use_count;
 147         /* Length of the current tasks_pids array */
 148         int pids_length;
 149 };
 150
 151 /* A css_set is a structure holding pointers to a set of
 152  * cgroup_subsys_state objects. This saves space in the task struct
 153  * object and speeds up fork()/exit(), since a single inc/dec and a
 154  * list_add()/del() can bump the reference count on the entire
 155  * cgroup set for a task.
 156  */
 157
 158 struct css_set {
 159
 160         /* Reference count */
 161         atomic_t refcount;
 162
 163         /*
 164          * List running through all cgroup groups in the same hash
 165          * slot. Protected by css_set_lock
 166          */
 167         struct hlist_node hlist;
 168
 169         /*
 170          * List running through all tasks using this cgroup
 171          * group. Protected by css_set_lock
 172          */
 173         struct list_head tasks;
 174
 175         /*
 176          * List of cg_cgroup_link objects on link chains from
 177          * cgroups referenced from this css_set. Protected by
 178          * css_set_lock
 179          */
 180         struct list_head cg_links;
 181
 182         /*
 183          * Set of subsystem states, one for each subsystem. This array
 184          * is immutable after creation apart from the init_css_set
 185          * during subsystem registration (at boot time).
 186          */
 187         struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
 188 };
 189
 190 /*
 191  * cgroup_map_cb is an abstract callback API for reporting map-valued
 192  * control files
 193  */
 194
 195 struct cgroup_map_cb {
 196         int (*fill)(struct cgroup_map_cb *cb, const char *key, u64 value);
 197         void *state;
 198 };
 199
 200 /* struct cftype:
 201  *
 202  * The files in the cgroup filesystem mostly have a very simple read/write
 203  * handling, some common function will take care of it. Nevertheless some cases
 204  * (read tasks) are special and therefore I define this structure for every
 205  * kind of file.
 206  *
 207  *
 208  * When reading/writing to a file:
 209  *      - the cgroup to use is file->f_dentry->d_parent->d_fsdata
 210  *      - the 'cftype' of the file is file->f_dentry->d_fsdata
 211  */
 212
 213 #define MAX_CFTYPE_NAME 64
 214 struct cftype {
 215         /* By convention, the name should begin with the name of the
 216          * subsystem, followed by a period */
 217         char name[MAX_CFTYPE_NAME];
 218         int private;
 219
 220         /*
 221          * If non-zero, defines the maximum length of string that can
 222          * be passed to write_string; defaults to 64
 223          */
 224         size_t max_write_len;
 225
 226         int (*open)(struct inode *inode, struct file *file);
 227         ssize_t (*read)(struct cgroup *cgrp, struct cftype *cft,
 228                         struct file *file,
 229                         char __user *buf, size_t nbytes, loff_t *ppos);
 230         /*
 231          * read_u64() is a shortcut for the common case of returning a
 232          * single integer. Use it in place of read()
 233          */
 234         u64 (*read_u64)(struct cgroup *cgrp, struct cftype *cft);
 235         /*
 236          * read_s64() is a signed version of read_u64()
 237          */
 238         s64 (*read_s64)(struct cgroup *cgrp, struct cftype *cft);
 239         /*
 240          * read_map() is used for defining a map of key/value
 241          * pairs. It should call cb->fill(cb, key, value) for each
 242          * entry. The key/value pairs (and their ordering) should not
 243          * change between reboots.
 244          */
 245         int (*read_map)(struct cgroup *cont, struct cftype *cft,
 246                         struct cgroup_map_cb *cb);
 247         /*
 248          * read_seq_string() is used for outputting a simple sequence
 249          * using seqfile.
 250          */
 251         int (*read_seq_string)(struct cgroup *cont, struct cftype *cft,
 252                                struct seq_file *m);
 253
 254         ssize_t (*write)(struct cgroup *cgrp, struct cftype *cft,
 255                          struct file *file,
 256                          const char __user *buf, size_t nbytes, loff_t *ppos);
 257
 258         /*
 259          * write_u64() is a shortcut for the common case of accepting
 260          * a single integer (as parsed by simple_strtoull) from
 261          * userspace. Use in place of write(); return 0 or error.
 262          */
 263         int (*write_u64)(struct cgroup *cgrp, struct cftype *cft, u64 val);
 264         /*
 265          * write_s64() is a signed version of write_u64()
 266          */
 267         int (*write_s64)(struct cgroup *cgrp, struct cftype *cft, s64 val);
 268
 269         /*
 270          * write_string() is passed a nul-terminated kernelspace
 271          * buffer of maximum length determined by max_write_len.
 272          * Returns 0 or -ve error code.
 273          */
 274         int (*write_string)(struct cgroup *cgrp, struct cftype *cft,
 275                             const char *buffer);
 276         /*
 277          * trigger() callback can be used to get some kick from the
 278          * userspace, when the actual string written is not important
 279          * at all. The private field can be used to determine the
 280          * kick type for multiplexing.
 281          */
 282         int (*trigger)(struct cgroup *cgrp, unsigned int event);
 283
 284         int (*release)(struct inode *inode, struct file *file);
 285 };
 286
 287 struct cgroup_scanner {
 288         struct cgroup *cg;
 289         int (*test_task)(struct task_struct *p, struct cgroup_scanner *scan);
 290         void (*process_task)(struct task_struct *p,
 291                         struct cgroup_scanner *scan);
 292         struct ptr_heap *heap;
 293 };
 294
 295 /* Add a new file to the given cgroup directory. Should only be
 296  * called by subsystems from within a populate() method */
 297 int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
 298                        const struct cftype *cft);
 299
 300 /* Add a set of new files to the given cgroup directory. Should
 301  * only be called by subsystems from within a populate() method */
 302 int cgroup_add_files(struct cgroup *cgrp,
 303                         struct cgroup_subsys *subsys,
 304                         const struct cftype cft[],
 305                         int count);
 306
 307 int cgroup_is_removed(const struct cgroup *cgrp);
 308
 309 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
 310
 311 int cgroup_task_count(const struct cgroup *cgrp);
 312
 313 /* Return true if the cgroup is a descendant of the current cgroup */
 314 int cgroup_is_descendant(const struct cgroup *cgrp);
 315
 316 /* Control Group subsystem type. See Documentation/cgroups.txt for details */
 317
 318 struct cgroup_subsys {
 319         struct cgroup_subsys_state *(*create)(struct cgroup_subsys *ss,
 320                                                   struct cgroup *cgrp);
 321         void (*pre_destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
 322         void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
 323         int (*can_attach)(struct cgroup_subsys *ss,
 324                           struct cgroup *cgrp, struct task_struct *tsk);
 325         void (*attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
 326                         struct cgroup *old_cgrp, struct task_struct *tsk);
 327         void (*fork)(struct cgroup_subsys *ss, struct task_struct *task);
 328         void (*exit)(struct cgroup_subsys *ss, struct task_struct *task);
 329         int (*populate)(struct cgroup_subsys *ss,
 330                         struct cgroup *cgrp);
 331         void (*post_clone)(struct cgroup_subsys *ss, struct cgroup *cgrp);
 332         void (*bind)(struct cgroup_subsys *ss, struct cgroup *root);
 333         /*
 334          * This routine is called with the task_lock of mm->owner held
 335          */
 336         void (*mm_owner_changed)(struct cgroup_subsys *ss,
 337                                         struct cgroup *old,
 338                                         struct cgroup *new,
 339                                         struct task_struct *p);
 340         int subsys_id;
 341         int active;
 342         int disabled;
 343         int early_init;
 344 #define MAX_CGROUP_TYPE_NAMELEN 32
 345         const char *name;
 346
 347         /* Protected by RCU */
 348         struct cgroupfs_root *root;
 349
 350         struct list_head sibling;
 351
 352         void *private;
 353 };
 354
 355 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
 356 #include <linux/cgroup_subsys.h>
 357 #undef SUBSYS
 358
 359 static inline struct cgroup_subsys_state *cgroup_subsys_state(
 360         struct cgroup *cgrp, int subsys_id)
 361 {
 362         return cgrp->subsys[subsys_id];
 363 }
 364
 365 static inline struct cgroup_subsys_state *task_subsys_state(
 366         struct task_struct *task, int subsys_id)
 367 {
 368         return rcu_dereference(task->cgroups->subsys[subsys_id]);
 369 }
 370
 371 static inline struct cgroup* task_cgroup(struct task_struct *task,
 372                                                int subsys_id)
 373 {
 374         return task_subsys_state(task, subsys_id)->cgroup;
 375 }
 376
 377 int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *ss,
 378                                                         char *nodename);
 379
 380 /* A cgroup_iter should be treated as an opaque object */
 381 struct cgroup_iter {
 382         struct list_head *cg_link;
 383         struct list_head *task;
 384 };
 385
 386 /* To iterate across the tasks in a cgroup:
 387  *
 388  * 1) call cgroup_iter_start to intialize an iterator
 389  *
 390  * 2) call cgroup_iter_next() to retrieve member tasks until it
 391  *    returns NULL or until you want to end the iteration
 392  *
 393  * 3) call cgroup_iter_end() to destroy the iterator.
 394  *
 395  * Or, call cgroup_scan_tasks() to iterate through every task in a cpuset.
 396  *    - cgroup_scan_tasks() holds the css_set_lock when calling the test_task()
 397  *      callback, but not while calling the process_task() callback.
 398  */
 399 void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it);
 400 struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
 401                                         struct cgroup_iter *it);
 402 void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it);
 403 int cgroup_scan_tasks(struct cgroup_scanner *scan);
 404 int cgroup_attach_task(struct cgroup *, struct task_struct *);
 405
 406 void cgroup_mm_owner_callbacks(struct task_struct *old,
 407                                struct task_struct *new);
 408
 409 #else /* !CONFIG_CGROUPS */
 410
 411 static inline int cgroup_init_early(void) { return 0; }
 412 static inline int cgroup_init(void) { return 0; }
 413 static inline void cgroup_init_smp(void) {}
 414 static inline void cgroup_fork(struct task_struct *p) {}
 415 static inline void cgroup_fork_callbacks(struct task_struct *p) {}
 416 static inline void cgroup_post_fork(struct task_struct *p) {}
 417 static inline void cgroup_exit(struct task_struct *p, int callbacks) {}
 418
 419 static inline void cgroup_lock(void) {}
 420 static inline void cgroup_unlock(void) {}
 421 static inline int cgroupstats_build(struct cgroupstats *stats,
 422                                         struct dentry *dentry)
 423 {
 424         return -EINVAL;
 425 }
 426
 427 static inline void cgroup_mm_owner_callbacks(struct task_struct *old,
 428                                              struct task_struct *new) {}
 429
 430 #endif /* !CONFIG_CGROUPS */
 431
 432 #endif /* _LINUX_CGROUP_H */