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 user_namespace *user_ns;
  31        struct net           *net_ns;
  32};
  33extern struct nsproxy init_nsproxy;
  34
  35/*
  36 * the namespaces access rules are:
  37 *
  38 *  1. only current task is allowed to change tsk->nsproxy pointer or
  39 *     any pointer on the nsproxy itself
  40 *
  41 *  2. when accessing (i.e. reading) current task's namespaces - no
  42 *     precautions should be taken - just dereference the pointers
  43 *
  44 *  3. the access to other task namespaces is performed like this
  45 *     rcu_read_lock();
  46 *     nsproxy = task_nsproxy(tsk);
  47 *     if (nsproxy != NULL) {
  48 *             / *
  49 *               * work with the namespaces here
  50 *               * e.g. get the reference on one of them
  51 *               * /
  52 *     } / *
  53 *         * NULL task_nsproxy() means that this task is
  54 *         * almost dead (zombie)
  55 *         * /
  56 *     rcu_read_unlock();
  57 *
  58 */
  59
  60static inline struct nsproxy *task_nsproxy(struct task_struct *tsk)
  61{
  62        return rcu_dereference(tsk->nsproxy);
  63}
  64
  65int copy_namespaces(unsigned long flags, struct task_struct *tsk);
  66void exit_task_namespaces(struct task_struct *tsk);
  67void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new);
  68void free_nsproxy(struct nsproxy *ns);
  69int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
  70        struct fs_struct *);
  71
  72static inline void put_nsproxy(struct nsproxy *ns)
  73{
  74        if (atomic_dec_and_test(&ns->count)) {
  75                free_nsproxy(ns);
  76        }
  77}
  78
  79static inline void get_nsproxy(struct nsproxy *ns)
  80{
  81        atomic_inc(&ns->count);
  82}
  83
  84#ifdef CONFIG_CGROUP_NS
  85int ns_cgroup_clone(struct task_struct *tsk);
  86#else
  87static inline int ns_cgroup_clone(struct task_struct *tsk) { return 0; }
  88#endif
  89
  90#endif
  91