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