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
  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  */
  24 struct 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 };
  32 extern 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
  59 static inline struct nsproxy *task_nsproxy(struct task_struct *tsk)
  60 {
  61         return rcu_dereference(tsk->nsproxy);
  62 }
  63
  64 int copy_namespaces(unsigned long flags, struct task_struct *tsk);
  65 void exit_task_namespaces(struct task_struct *tsk);
  66 void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new);
  67 void free_nsproxy(struct nsproxy *ns);
  68 int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
  69         struct fs_struct *);
  70
  71 static inline void put_nsproxy(struct nsproxy *ns)
  72 {
  73         if (atomic_dec_and_test(&ns->count)) {
  74                 free_nsproxy(ns);
  75         }
  76 }
  77
  78 static inline void get_nsproxy(struct nsproxy *ns)
  79 {
  80         atomic_inc(&ns->count);
  81 }
  82
  83 #ifdef CONFIG_CGROUP_NS
  84 int ns_cgroup_clone(struct task_struct *tsk, struct pid *pid);
  85 #else
  86 static inline int ns_cgroup_clone(struct task_struct *tsk, struct pid *pid)
  87 {
  88         return 0;
  89 }
  90 #endif
  91
  92 #endif