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
   7 struct mnt_namespace;
   8 struct uts_namespace;
   9 struct ipc_namespace;
  10 struct pid_namespace;
  11 struct fs_struct;
  12
  13 /*
  14  * A structure to contain pointers to all per-process
  15  * namespaces - fs (mount), uts, network, sysvipc, etc.
  16  *
  17  * 'count' is the number of tasks holding a reference.
  18  * The count for each namespace, then, will be the number
  19  * of nsproxies pointing to it, not the number of tasks.
  20  *
  21  * The nsproxy is shared by tasks which share all namespaces.
  22  * As soon as a single namespace is cloned or unshared, the
  23  * nsproxy is copied.
  24  */
  25 struct nsproxy {
  26         atomic_t count;
  27         struct uts_namespace *uts_ns;
  28         struct ipc_namespace *ipc_ns;
  29         struct mnt_namespace *mnt_ns;
  30         struct pid_namespace *pid_ns;
  31         struct net           *net_ns;
  32 };
  33 extern 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
  60 static inline struct nsproxy *task_nsproxy(struct task_struct *tsk)
  61 {
  62         return rcu_dereference(tsk->nsproxy);
  63 }
  64
  65 int copy_namespaces(unsigned long flags, struct task_struct *tsk);
  66 void exit_task_namespaces(struct task_struct *tsk);
  67 void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new);
  68 void free_nsproxy(struct nsproxy *ns);
  69 int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
  70         struct fs_struct *);
  71 int __init nsproxy_cache_init(void);
  72
  73 static inline void put_nsproxy(struct nsproxy *ns)
  74 {
  75         if (atomic_dec_and_test(&ns->count)) {
  76                 free_nsproxy(ns);
  77         }
  78 }
  79
  80 static inline void get_nsproxy(struct nsproxy *ns)
  81 {
  82         atomic_inc(&ns->count);
  83 }
  84
  85 #endif