/*
   * 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 <linux/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

  struct fdtable {
  	unsigned int max_fds;

  	struct file __rcu **fd;      /* current fd array */

  	unsigned long *close_on_exec;
  	unsigned long *open_fds;

  	struct rcu_head rcu;

  };

  static inline bool close_on_exec(int fd, const struct fdtable *fdt)
  {

  	return test_bit(fd, fdt->close_on_exec);

  }

  static inline bool fd_is_open(int fd, const struct fdtable *fdt)
  {

  	return test_bit(fd, fdt->open_fds);

  }

  /*
   * Open file table structure
   */
  struct files_struct {
    /*
     * read mostly part
     */
  	atomic_t count;

  	struct fdtable __rcu *fdt;

  	struct fdtable fdtab;
    /*
     * written part on a separate cache line in SMP
     */
  	spinlock_t file_lock ____cacheline_aligned_in_smp;
  	int next_fd;

  	unsigned long close_on_exec_init[1];
  	unsigned long open_fds_init[1];

  	struct file __rcu * fd_array[NR_OPEN_DEFAULT];

  };

  struct file_operations;
  struct vfsmount;
  struct dentry;

  #define rcu_dereference_check_fdtable(files, fdtfd) \
  	rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock))
  
  #define files_fdtable(files) \
  	rcu_dereference_check_fdtable((files), (files)->fdt)
  
  /*
   * The caller must ensure that fd table isn't shared or hold rcu or file lock
   */
  static inline struct file *__fcheck_files(struct files_struct *files, unsigned int fd)

  {

  	struct fdtable *fdt = rcu_dereference_raw(files->fdt);

  
  	if (fd < fdt->max_fds)

  		return rcu_dereference_raw(fdt->fd[fd]);
  	return NULL;
  }
  
  static inline struct file *fcheck_files(struct files_struct *files, unsigned int fd)
  {
  	rcu_lockdep_assert(rcu_read_lock_held() ||
  			   lockdep_is_held(&files->file_lock),
  			   "suspicious rcu_dereference_check() usage");
  	return __fcheck_files(files, fd);

  }
  
  /*
   * 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 *);

  void do_close_on_exec(struct files_struct *);

  int iterate_fd(struct files_struct *, unsigned,
  		int (*)(const void *, struct file *, unsigned),
  		const void *);

  extern int __alloc_fd(struct files_struct *files,
  		      unsigned start, unsigned end, unsigned flags);

  extern void __fd_install(struct files_struct *files,
  		      unsigned int fd, struct file *file);

  extern int __close_fd(struct files_struct *files,
  		      unsigned int fd);

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