/*

   * fs/f2fs/gc.h
   *
   * Copyright (c) 2012 Samsung Electronics Co., Ltd.
   *             http://www.samsung.com/
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   */

  #define GC_THREAD_MIN_WB_PAGES		1	/*
  						 * a threshold to determine
  						 * whether IO subsystem is idle
  						 * or not
  						 */

  #define DEF_GC_THREAD_MIN_SLEEP_TIME	30000	/* milliseconds */
  #define DEF_GC_THREAD_MAX_SLEEP_TIME	60000
  #define DEF_GC_THREAD_NOGC_SLEEP_TIME	300000	/* wait 5 min */

  #define LIMIT_INVALID_BLOCK	40 /* percentage over total user space */
  #define LIMIT_FREE_BLOCK	40 /* percentage over invalid + free space */
  
  /* Search max. number of dirty segments to select a victim segment */

  #define DEF_MAX_VICTIM_SEARCH 4096 /* covers 8GB */

  struct f2fs_gc_kthread {
  	struct task_struct *f2fs_gc_task;
  	wait_queue_head_t gc_wait_queue_head;

  
  	/* for gc sleep time */
  	unsigned int min_sleep_time;
  	unsigned int max_sleep_time;
  	unsigned int no_gc_sleep_time;

  
  	/* for changing gc mode */
  	unsigned int gc_idle;

  };

  struct gc_inode_list {
  	struct list_head ilist;
  	struct radix_tree_root iroot;
  };

  /*

   * inline functions
   */
  static inline block_t free_user_blocks(struct f2fs_sb_info *sbi)
  {
  	if (free_segments(sbi) < overprovision_segments(sbi))
  		return 0;
  	else
  		return (free_segments(sbi) - overprovision_segments(sbi))
  			<< sbi->log_blocks_per_seg;
  }
  
  static inline block_t limit_invalid_user_blocks(struct f2fs_sb_info *sbi)
  {
  	return (long)(sbi->user_block_count * LIMIT_INVALID_BLOCK) / 100;
  }
  
  static inline block_t limit_free_user_blocks(struct f2fs_sb_info *sbi)
  {
  	block_t reclaimable_user_blocks = sbi->user_block_count -
  		written_block_count(sbi);
  	return (long)(reclaimable_user_blocks * LIMIT_FREE_BLOCK) / 100;
  }

  static inline void increase_sleep_time(struct f2fs_gc_kthread *gc_th,
  								long *wait)

  {

  	if (*wait == gc_th->no_gc_sleep_time)
  		return;

  	*wait += gc_th->min_sleep_time;
  	if (*wait > gc_th->max_sleep_time)
  		*wait = gc_th->max_sleep_time;

  }

  static inline void decrease_sleep_time(struct f2fs_gc_kthread *gc_th,
  								long *wait)

  {

  	if (*wait == gc_th->no_gc_sleep_time)
  		*wait = gc_th->max_sleep_time;

  	*wait -= gc_th->min_sleep_time;
  	if (*wait <= gc_th->min_sleep_time)
  		*wait = gc_th->min_sleep_time;

  }
  
  static inline bool has_enough_invalid_blocks(struct f2fs_sb_info *sbi)
  {
  	block_t invalid_user_blocks = sbi->user_block_count -
  					written_block_count(sbi);
  	/*

  	 * Background GC is triggered with the following conditions.

  	 * 1. There are a number of invalid blocks.
  	 * 2. There is not enough free space.
  	 */
  	if (invalid_user_blocks > limit_invalid_user_blocks(sbi) &&
  			free_user_blocks(sbi) < limit_free_user_blocks(sbi))
  		return true;
  	return false;
  }