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