/* SPDX-License-Identifier: GPL-2.0-or-later */
  /*
   *  include/linux/eventpoll.h ( Efficient event polling implementation )
   *  Copyright (C) 2001,...,2006	 Davide Libenzi
   *
   *  Davide Libenzi <davidel@xmailserver.org>
   */
  #ifndef _LINUX_EVENTPOLL_H
  #define _LINUX_EVENTPOLL_H
  
  #include <uapi/linux/eventpoll.h>
  #include <uapi/linux/kcmp.h>
  
  
  /* Forward declarations to avoid compiler errors */
  struct file;
  
  
  #ifdef CONFIG_EPOLL
  
  #ifdef CONFIG_CHECKPOINT_RESTORE
  struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long toff);
  #endif
  
  /* Used to initialize the epoll bits inside the "struct file" */
  static inline void eventpoll_init_file(struct file *file)
  {
  	INIT_LIST_HEAD(&file->f_ep_links);
  	INIT_LIST_HEAD(&file->f_tfile_llink);
  }
  
  
  /* Used to release the epoll bits inside the "struct file" */
  void eventpoll_release_file(struct file *file);
  
  /*
   * This is called from inside fs/file_table.c:__fput() to unlink files
   * from the eventpoll interface. We need to have this facility to cleanup
   * correctly files that are closed without being removed from the eventpoll
   * interface.
   */
  static inline void eventpoll_release(struct file *file)
  {
  
  	/*
  	 * Fast check to avoid the get/release of the semaphore. Since
  	 * we're doing this outside the semaphore lock, it might return
  	 * false negatives, but we don't care. It'll help in 99.99% of cases
  	 * to avoid the semaphore lock. False positives simply cannot happen
  	 * because the file in on the way to be removed and nobody ( but
  	 * eventpoll ) has still a reference to this file.
  	 */
  	if (likely(list_empty(&file->f_ep_links)))
  		return;
  
  	/*
  	 * The file is being closed while it is still linked to an epoll
  	 * descriptor. We need to handle this by correctly unlinking it
  	 * from its containers.
  	 */
  	eventpoll_release_file(file);
  }
  
  #else
  
  static inline void eventpoll_init_file(struct file *file) {}
  static inline void eventpoll_release(struct file *file) {}
  
  #endif
  
  #endif /* #ifndef _LINUX_EVENTPOLL_H */