#ifndef _LINUX_PID_NS_H
  #define _LINUX_PID_NS_H

  
  #include <linux/sched.h>
  #include <linux/mm.h>
  #include <linux/threads.h>

  #include <linux/nsproxy.h>
  #include <linux/kref.h>

  
  struct pidmap {
         atomic_t nr_free;
         void *page;
  };
  
  #define PIDMAP_ENTRIES         ((PID_MAX_LIMIT + 8*PAGE_SIZE - 1)/PAGE_SIZE/8)

  struct bsd_acct_struct;

  struct pid_namespace {

  	struct kref kref;
  	struct pidmap pidmap[PIDMAP_ENTRIES];
  	int last_pid;

  	struct task_struct *child_reaper;

  	struct kmem_cache *pid_cachep;

  	unsigned int level;

  	struct pid_namespace *parent;

  #ifdef CONFIG_PROC_FS
  	struct vfsmount *proc_mnt;
  #endif

  #ifdef CONFIG_BSD_PROCESS_ACCT
  	struct bsd_acct_struct *bacct;
  #endif

  	gid_t pid_gid;
  	int hide_pid;

  };

  extern struct pid_namespace init_pid_ns;

  #ifdef CONFIG_PID_NS

  static inline struct pid_namespace *get_pid_ns(struct pid_namespace *ns)

  {

  	if (ns != &init_pid_ns)
  		kref_get(&ns->kref);

  	return ns;

  }

  extern struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *ns);

  extern void free_pid_ns(struct kref *kref);

  extern void zap_pid_ns_processes(struct pid_namespace *pid_ns);

  
  static inline void put_pid_ns(struct pid_namespace *ns)
  {

  	if (ns != &init_pid_ns)
  		kref_put(&ns->kref, free_pid_ns);

  }

  #else /* !CONFIG_PID_NS */
  #include <linux/err.h>
  
  static inline struct pid_namespace *get_pid_ns(struct pid_namespace *ns)
  {
  	return ns;
  }
  
  static inline struct pid_namespace *
  copy_pid_ns(unsigned long flags, struct pid_namespace *ns)
  {
  	if (flags & CLONE_NEWPID)
  		ns = ERR_PTR(-EINVAL);
  	return ns;
  }
  
  static inline void put_pid_ns(struct pid_namespace *ns)
  {
  }

  
  static inline void zap_pid_ns_processes(struct pid_namespace *ns)
  {
  	BUG();
  }

  #endif /* CONFIG_PID_NS */

  extern struct pid_namespace *task_active_pid_ns(struct task_struct *tsk);

  void pidhash_init(void);
  void pidmap_init(void);

  #endif /* _LINUX_PID_NS_H */