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
  17 #ifdef CONFIG_CGROUPS
  18
  19 struct cgroupfs_root;
  20 struct cgroup_subsys;
  21 struct inode;
  22
  23 extern int cgroup_init_early(void);
  24 extern int cgroup_init(void);
  25 extern void cgroup_init_smp(void);
  26 extern void cgroup_lock(void);
  27 extern void cgroup_unlock(void);
  28
  29 /* Per-subsystem/per-cgroup state maintained by the system. */
  30 struct cgroup_subsys_state {
  31         /* The cgroup that this subsystem is attached to. Useful
  32          * for subsystems that want to know about the cgroup
  33          * hierarchy structure */
  34         struct cgroup *cgroup;
  35
  36         /* State maintained by the cgroup system to allow
  37          * subsystems to be "busy". Should be accessed via css_get()
  38          * and css_put() */
  39
  40         atomic_t refcnt;
  41
  42         unsigned long flags;
  43 };
  44
  45 /* bits in struct cgroup_subsys_state flags field */
  46 enum {
  47         CSS_ROOT, /* This CSS is the root of the subsystem */
  48 };
  49
  50 /*
  51  * Call css_get() to hold a reference on the cgroup;
  52  *
  53  */
  54
  55 static inline void css_get(struct cgroup_subsys_state *css)
  56 {
  57         /* We don't need to reference count the root state */
  58         if (!test_bit(CSS_ROOT, &css->flags))
  59                 atomic_inc(&css->refcnt);
  60 }
  61 /*
  62  * css_put() should be called to release a reference taken by
  63  * css_get()
  64  */
  65
  66 static inline void css_put(struct cgroup_subsys_state *css)
  67 {
  68         if (!test_bit(CSS_ROOT, &css->flags))
  69                 atomic_dec(&css->refcnt);
  70 }
  71
  72 struct cgroup {
  73         unsigned long flags;            /* "unsigned long" so bitops work */
  74
  75         /* count users of this cgroup. >0 means busy, but doesn't
  76          * necessarily indicate the number of tasks in the
  77          * cgroup */
  78         atomic_t count;
  79
  80         /*
  81          * We link our 'sibling' struct into our parent's 'children'.
  82          * Our children link their 'sibling' into our 'children'.
  83          */
  84         struct list_head sibling;       /* my parent's children */
  85         struct list_head children;      /* my children */
  86
  87         struct cgroup *parent;  /* my parent */
  88         struct dentry *dentry;          /* cgroup fs entry */
  89
  90         /* Private pointers for each registered subsystem */
  91         struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
  92
  93         struct cgroupfs_root *root;
  94         struct cgroup *top_cgroup;
  95 };
  96
  97 /* struct cftype:
  98  *
  99  * The files in the cgroup filesystem mostly have a very simple read/write
 100  * handling, some common function will take care of it. Nevertheless some cases
 101  * (read tasks) are special and therefore I define this structure for every
 102  * kind of file.
 103  *
 104  *
 105  * When reading/writing to a file:
 106  *      - the cgroup to use in file->f_dentry->d_parent->d_fsdata
 107  *      - the 'cftype' of the file is file->f_dentry->d_fsdata
 108  */
 109
 110 #define MAX_CFTYPE_NAME 64
 111 struct cftype {
 112         /* By convention, the name should begin with the name of the
 113          * subsystem, followed by a period */
 114         char name[MAX_CFTYPE_NAME];
 115         int private;
 116         int (*open) (struct inode *inode, struct file *file);
 117         ssize_t (*read) (struct cgroup *cont, struct cftype *cft,
 118                          struct file *file,
 119                          char __user *buf, size_t nbytes, loff_t *ppos);
 120         /*
 121          * read_uint() is a shortcut for the common case of returning a
 122          * single integer. Use it in place of read()
 123          */
 124         u64 (*read_uint) (struct cgroup *cont, struct cftype *cft);
 125         ssize_t (*write) (struct cgroup *cont, struct cftype *cft,
 126                           struct file *file,
 127                           const char __user *buf, size_t nbytes, loff_t *ppos);
 128
 129         /*
 130          * write_uint() is a shortcut for the common case of accepting
 131          * a single integer (as parsed by simple_strtoull) from
 132          * userspace. Use in place of write(); return 0 or error.
 133          */
 134         int (*write_uint) (struct cgroup *cont, struct cftype *cft, u64 val);
 135
 136         int (*release) (struct inode *inode, struct file *file);
 137 };
 138
 139 /* Add a new file to the given cgroup directory. Should only be
 140  * called by subsystems from within a populate() method */
 141 int cgroup_add_file(struct cgroup *cont, struct cgroup_subsys *subsys,
 142                        const struct cftype *cft);
 143
 144 /* Add a set of new files to the given cgroup directory. Should
 145  * only be called by subsystems from within a populate() method */
 146 int cgroup_add_files(struct cgroup *cont,
 147                         struct cgroup_subsys *subsys,
 148                         const struct cftype cft[],
 149                         int count);
 150
 151 int cgroup_is_removed(const struct cgroup *cont);
 152
 153 int cgroup_path(const struct cgroup *cont, char *buf, int buflen);
 154
 155 int __cgroup_task_count(const struct cgroup *cont);
 156 static inline int cgroup_task_count(const struct cgroup *cont)
 157 {
 158         int task_count;
 159         rcu_read_lock();
 160         task_count = __cgroup_task_count(cont);
 161         rcu_read_unlock();
 162         return task_count;
 163 }
 164
 165 /* Return true if the cgroup is a descendant of the current cgroup */
 166 int cgroup_is_descendant(const struct cgroup *cont);
 167
 168 /* Control Group subsystem type. See Documentation/cgroups.txt for details */
 169
 170 struct cgroup_subsys {
 171         struct cgroup_subsys_state *(*create)(struct cgroup_subsys *ss,
 172                                                   struct cgroup *cont);
 173         void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cont);
 174         int (*can_attach)(struct cgroup_subsys *ss,
 175                           struct cgroup *cont, struct task_struct *tsk);
 176         void (*attach)(struct cgroup_subsys *ss, struct cgroup *cont,
 177                         struct cgroup *old_cont, struct task_struct *tsk);
 178         void (*fork)(struct cgroup_subsys *ss, struct task_struct *task);
 179         void (*exit)(struct cgroup_subsys *ss, struct task_struct *task);
 180         int (*populate)(struct cgroup_subsys *ss,
 181                         struct cgroup *cont);
 182         void (*bind)(struct cgroup_subsys *ss, struct cgroup *root);
 183         int subsys_id;
 184         int active;
 185         int early_init;
 186 #define MAX_CGROUP_TYPE_NAMELEN 32
 187         const char *name;
 188
 189         /* Protected by RCU */
 190         struct cgroupfs_root *root;
 191
 192         struct list_head sibling;
 193
 194         void *private;
 195 };
 196
 197 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
 198 #include <linux/cgroup_subsys.h>
 199 #undef SUBSYS
 200
 201 static inline struct cgroup_subsys_state *cgroup_subsys_state(
 202         struct cgroup *cont, int subsys_id)
 203 {
 204         return cont->subsys[subsys_id];
 205 }
 206
 207 static inline struct cgroup_subsys_state *task_subsys_state(
 208         struct task_struct *task, int subsys_id)
 209 {
 210         return rcu_dereference(task->cgroups.subsys[subsys_id]);
 211 }
 212
 213 static inline struct cgroup* task_cgroup(struct task_struct *task,
 214                                                int subsys_id)
 215 {
 216         return task_subsys_state(task, subsys_id)->cgroup;
 217 }
 218
 219 int cgroup_path(const struct cgroup *cont, char *buf, int buflen);
 220
 221 #else /* !CONFIG_CGROUPS */
 222
 223 static inline int cgroup_init_early(void) { return 0; }
 224 static inline int cgroup_init(void) { return 0; }
 225 static inline void cgroup_init_smp(void) {}
 226
 227 static inline void cgroup_lock(void) {}
 228 static inline void cgroup_unlock(void) {}
 229
 230 #endif /* !CONFIG_CGROUPS */
 231
 232 #endif /* _LINUX_CGROUP_H */