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         int (*release) (struct inode *inode, struct file *file);
 129 };
 130
 131 /* Add a new file to the given cgroup directory. Should only be
 132  * called by subsystems from within a populate() method */
 133 int cgroup_add_file(struct cgroup *cont, struct cgroup_subsys *subsys,
 134                        const struct cftype *cft);
 135
 136 /* Add a set of new files to the given cgroup directory. Should
 137  * only be called by subsystems from within a populate() method */
 138 int cgroup_add_files(struct cgroup *cont,
 139                         struct cgroup_subsys *subsys,
 140                         const struct cftype cft[],
 141                         int count);
 142
 143 int cgroup_is_removed(const struct cgroup *cont);
 144
 145 int cgroup_path(const struct cgroup *cont, char *buf, int buflen);
 146
 147 /* Return true if the cgroup is a descendant of the current cgroup */
 148 int cgroup_is_descendant(const struct cgroup *cont);
 149
 150 /* Control Group subsystem type. See Documentation/cgroups.txt for details */
 151
 152 struct cgroup_subsys {
 153         struct cgroup_subsys_state *(*create)(struct cgroup_subsys *ss,
 154                                                   struct cgroup *cont);
 155         void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cont);
 156         int (*can_attach)(struct cgroup_subsys *ss,
 157                           struct cgroup *cont, struct task_struct *tsk);
 158         void (*attach)(struct cgroup_subsys *ss, struct cgroup *cont,
 159                         struct cgroup *old_cont, struct task_struct *tsk);
 160         void (*fork)(struct cgroup_subsys *ss, struct task_struct *task);
 161         void (*exit)(struct cgroup_subsys *ss, struct task_struct *task);
 162         int (*populate)(struct cgroup_subsys *ss,
 163                         struct cgroup *cont);
 164         void (*bind)(struct cgroup_subsys *ss, struct cgroup *root);
 165         int subsys_id;
 166         int active;
 167         int early_init;
 168 #define MAX_CGROUP_TYPE_NAMELEN 32
 169         const char *name;
 170
 171         /* Protected by RCU */
 172         struct cgroupfs_root *root;
 173
 174         struct list_head sibling;
 175
 176         void *private;
 177 };
 178
 179 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
 180 #include <linux/cgroup_subsys.h>
 181 #undef SUBSYS
 182
 183 static inline struct cgroup_subsys_state *cgroup_subsys_state(
 184         struct cgroup *cont, int subsys_id)
 185 {
 186         return cont->subsys[subsys_id];
 187 }
 188
 189 static inline struct cgroup_subsys_state *task_subsys_state(
 190         struct task_struct *task, int subsys_id)
 191 {
 192         return rcu_dereference(task->cgroups.subsys[subsys_id]);
 193 }
 194
 195 static inline struct cgroup* task_cgroup(struct task_struct *task,
 196                                                int subsys_id)
 197 {
 198         return task_subsys_state(task, subsys_id)->cgroup;
 199 }
 200
 201 int cgroup_path(const struct cgroup *cont, char *buf, int buflen);
 202
 203 #else /* !CONFIG_CGROUPS */
 204
 205 static inline int cgroup_init_early(void) { return 0; }
 206 static inline int cgroup_init(void) { return 0; }
 207 static inline void cgroup_init_smp(void) {}
 208
 209 static inline void cgroup_lock(void) {}
 210 static inline void cgroup_unlock(void) {}
 211
 212 #endif /* !CONFIG_CGROUPS */
 213
 214 #endif /* _LINUX_CGROUP_H */