LXR linux/include/linux/nsproxy.h

   1#ifndef _LINUX_NSPROXY_H
   2#define _LINUX_NSPROXY_H
   3
   4#include <linux/spinlock.h>
   5#include <linux/sched.h>
   6
   7struct mnt_namespace;
   8struct uts_namespace;
   9struct ipc_namespace;
  10struct pid_namespace;
  11
  12/*
  13 * A structure to contain pointers to all per-process
  14 * namespaces - fs (mount), uts, network, sysvipc, etc.
  15 *
  16 * 'count' is the number of tasks holding a reference.
  17 * The count for each namespace, then, will be the number
  18 * of nsproxies pointing to it, not the number of tasks.
  19 *
  20 * The nsproxy is shared by tasks which share all namespaces.
  21 * As soon as a single namespace is cloned or unshared, the
  22 * nsproxy is copied.
  23 */
  24struct nsproxy {
  25        atomic_t count;
  26        struct uts_namespace *uts_ns;
  27        struct ipc_namespace *ipc_ns;
  28        struct mnt_namespace *mnt_ns;
  29        struct pid_namespace *pid_ns;
  30        struct net           *net_ns;
  31};
  32extern struct nsproxy init_nsproxy;
  33
  34/*
  35 * the namespaces access rules are:
  36 *
  37 *  1. only current task is allowed to change tsk->nsproxy pointer or
  38 *     any pointer on the nsproxy itself
  39 *
  40 *  2. when accessing (i.e. reading) current task's namespaces - no
  41 *     precautions should be taken - just dereference the pointers
  42 *
  43 *  3. the access to other task namespaces is performed like this
  44 *     rcu_read_lock();
  45 *     nsproxy = task_nsproxy(tsk);
  46 *     if (nsproxy != NULL) {
  47 *             / *
  48 *               * work with the namespaces here
  49 *               * e.g. get the reference on one of them
  50 *               * /
  51 *     } / *
  52 *         * NULL task_nsproxy() means that this task is
  53 *         * almost dead (zombie)
  54 *         * /
  55 *     rcu_read_unlock();
  56 *
  57 */
  58
  59static inline struct nsproxy *task_nsproxy(struct task_struct *tsk)
  60{
  61        return rcu_dereference(tsk->nsproxy);
  62}
  63
  64int copy_namespaces(unsigned long flags, struct task_struct *tsk);
  65void exit_task_namespaces(struct task_struct *tsk);
  66void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new);
  67void free_nsproxy(struct nsproxy *ns);
  68int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
  69        struct fs_struct *);
  70
  71static inline void put_nsproxy(struct nsproxy *ns)
  72{
  73        if (atomic_dec_and_test(&ns->count)) {
  74                free_nsproxy(ns);
  75        }
  76}
  77
  78static inline void get_nsproxy(struct nsproxy *ns)
  79{
  80        atomic_inc(&ns->count);
  81}
  82
  83#ifdef CONFIG_CGROUP_NS
  84int ns_cgroup_clone(struct task_struct *tsk, struct pid *pid);
  85#else
  86static inline int ns_cgroup_clone(struct task_struct *tsk, struct pid *pid)
  87{
  88        return 0;
  89}
  90#endif
  91
  92#endif
  93