/*
   * descriptor table internals; you almost certainly want file.h instead.
   */
  
  #ifndef __LINUX_FDTABLE_H
  #define __LINUX_FDTABLE_H

  #include <linux/posix_types.h>
  #include <linux/compiler.h>
  #include <linux/spinlock.h>
  #include <linux/rcupdate.h>
  #include <linux/types.h>

  #include <linux/init.h>

  #include <linux/fs.h>

  
  #include <asm/atomic.h>

  
  /*
   * The default fd array needs to be at least BITS_PER_LONG,
   * as this is the granularity returned by copy_fdset().
   */
  #define NR_OPEN_DEFAULT BITS_PER_LONG
  
  /*
   * The embedded_fd_set is a small fd_set,
   * suitable for most tasks (which open <= BITS_PER_LONG files)
   */
  struct embedded_fd_set {
  	unsigned long fds_bits[1];
  };
  
  struct fdtable {
  	unsigned int max_fds;
  	struct file ** fd;      /* current fd array */
  	fd_set *close_on_exec;
  	fd_set *open_fds;
  	struct rcu_head rcu;
  	struct fdtable *next;
  };
  
  /*
   * Open file table structure
   */
  struct files_struct {
    /*
     * read mostly part
     */
  	atomic_t count;
  	struct fdtable *fdt;
  	struct fdtable fdtab;
    /*
     * written part on a separate cache line in SMP
     */
  	spinlock_t file_lock ____cacheline_aligned_in_smp;
  	int next_fd;
  	struct embedded_fd_set close_on_exec_init;
  	struct embedded_fd_set open_fds_init;
  	struct file * fd_array[NR_OPEN_DEFAULT];
  };

  #define rcu_dereference_check_fdtable(files, fdtfd) \
  	(rcu_dereference_check((fdtfd), \

  			       rcu_read_lock_held() || \
  			       lockdep_is_held(&(files)->file_lock) || \

  			       atomic_read(&(files)->count) == 1 || \
  			       rcu_my_thread_group_empty()))

  
  #define files_fdtable(files) \
  		(rcu_dereference_check_fdtable((files), (files)->fdt))

  struct file_operations;
  struct vfsmount;
  struct dentry;
  
  extern int expand_files(struct files_struct *, int nr);
  extern void free_fdtable_rcu(struct rcu_head *rcu);
  extern void __init files_defer_init(void);
  
  static inline void free_fdtable(struct fdtable *fdt)
  {
  	call_rcu(&fdt->rcu, free_fdtable_rcu);
  }
  
  static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
  {
  	struct file * file = NULL;
  	struct fdtable *fdt = files_fdtable(files);
  
  	if (fd < fdt->max_fds)

  		file = rcu_dereference_check_fdtable(files, fdt->fd[fd]);

  	return file;
  }
  
  /*
   * Check whether the specified fd has an open file.
   */
  #define fcheck(fd)	fcheck_files(current->files, fd)
  
  struct task_struct;
  
  struct files_struct *get_files_struct(struct task_struct *);
  void put_files_struct(struct files_struct *fs);
  void reset_files_struct(struct files_struct *);
  int unshare_files(struct files_struct **);

  struct files_struct *dup_fd(struct files_struct *, int *);

  
  extern struct kmem_cache *files_cachep;
  
  #endif /* __LINUX_FDTABLE_H */