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 93