// SPDX-License-Identifier: GPL-2.0

  /*
   * Copyright (C) 2016 CNEX Labs
   * Initial release: Javier Gonzalez <javier@cnexlabs.com>
   *                  Matias Bjorling <matias@cnexlabs.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.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * pblk-rl.c - pblk's rate limiter for user I/O
   *
   */
  
  #include "pblk.h"
  
  static void pblk_rl_kick_u_timer(struct pblk_rl *rl)
  {
  	mod_timer(&rl->u_timer, jiffies + msecs_to_jiffies(5000));
  }

  int pblk_rl_is_limit(struct pblk_rl *rl)
  {
  	int rb_space;
  
  	rb_space = atomic_read(&rl->rb_space);
  
  	return (rb_space == 0);
  }

  int pblk_rl_user_may_insert(struct pblk_rl *rl, int nr_entries)
  {
  	int rb_user_cnt = atomic_read(&rl->rb_user_cnt);

  	int rb_space = atomic_read(&rl->rb_space);
  
  	if (unlikely(rb_space >= 0) && (rb_space - nr_entries < 0))
  		return NVM_IO_ERR;
  
  	if (rb_user_cnt >= rl->rb_user_max)
  		return NVM_IO_REQUEUE;

  	return NVM_IO_OK;
  }
  
  void pblk_rl_inserted(struct pblk_rl *rl, int nr_entries)
  {
  	int rb_space = atomic_read(&rl->rb_space);
  
  	if (unlikely(rb_space >= 0))
  		atomic_sub(nr_entries, &rl->rb_space);

  }
  
  int pblk_rl_gc_may_insert(struct pblk_rl *rl, int nr_entries)
  {
  	int rb_gc_cnt = atomic_read(&rl->rb_gc_cnt);
  	int rb_user_active;
  
  	/* If there is no user I/O let GC take over space on the write buffer */
  	rb_user_active = READ_ONCE(rl->rb_user_active);

  	return (!(rb_gc_cnt >= rl->rb_gc_max && rb_user_active));

  }
  
  void pblk_rl_user_in(struct pblk_rl *rl, int nr_entries)
  {
  	atomic_add(nr_entries, &rl->rb_user_cnt);
  
  	/* Release user I/O state. Protect from GC */
  	smp_store_release(&rl->rb_user_active, 1);
  	pblk_rl_kick_u_timer(rl);
  }

  void pblk_rl_werr_line_in(struct pblk_rl *rl)
  {
  	atomic_inc(&rl->werr_lines);
  }
  
  void pblk_rl_werr_line_out(struct pblk_rl *rl)
  {
  	atomic_dec(&rl->werr_lines);
  }

  void pblk_rl_gc_in(struct pblk_rl *rl, int nr_entries)
  {
  	atomic_add(nr_entries, &rl->rb_gc_cnt);
  }
  
  void pblk_rl_out(struct pblk_rl *rl, int nr_user, int nr_gc)
  {
  	atomic_sub(nr_user, &rl->rb_user_cnt);
  	atomic_sub(nr_gc, &rl->rb_gc_cnt);
  }
  
  unsigned long pblk_rl_nr_free_blks(struct pblk_rl *rl)
  {
  	return atomic_read(&rl->free_blocks);
  }

  unsigned long pblk_rl_nr_user_free_blks(struct pblk_rl *rl)
  {
  	return atomic_read(&rl->free_user_blocks);
  }
  
  static void __pblk_rl_update_rates(struct pblk_rl *rl,
  				   unsigned long free_blocks)

  {

  	struct pblk *pblk = container_of(rl, struct pblk, rl);

  	int max = rl->rb_budget;

  	int werr_gc_needed = atomic_read(&rl->werr_lines);

  
  	if (free_blocks >= rl->high) {

  		if (werr_gc_needed) {
  			/* Allocate a small budget for recovering
  			 * lines with write errors
  			 */
  			rl->rb_gc_max = 1 << rl->rb_windows_pw;
  			rl->rb_user_max = max - rl->rb_gc_max;
  			rl->rb_state = PBLK_RL_WERR;
  		} else {
  			rl->rb_user_max = max;
  			rl->rb_gc_max = 0;
  			rl->rb_state = PBLK_RL_OFF;
  		}

  	} else if (free_blocks < rl->high) {
  		int shift = rl->high_pw - rl->rb_windows_pw;
  		int user_windows = free_blocks >> shift;

  		int user_max = user_windows << ilog2(NVM_MAX_VLBA);

  
  		rl->rb_user_max = user_max;

  		rl->rb_gc_max = max - user_max;
  
  		if (free_blocks <= rl->rsv_blocks) {
  			rl->rb_user_max = 0;
  			rl->rb_gc_max = max;
  		}
  
  		/* In the worst case, we will need to GC lines in the low list
  		 * (high valid sector count). If there are lines to GC on high
  		 * or mid lists, these will be prioritized
  		 */
  		rl->rb_state = PBLK_RL_LOW;

  	}

  	if (rl->rb_state != PBLK_RL_OFF)

  		pblk_gc_should_start(pblk);
  	else
  		pblk_gc_should_stop(pblk);

  }

  void pblk_rl_update_rates(struct pblk_rl *rl)
  {
  	__pblk_rl_update_rates(rl, pblk_rl_nr_user_free_blks(rl));
  }

  void pblk_rl_free_lines_inc(struct pblk_rl *rl, struct pblk_line *line)
  {

  	int blk_in_line = atomic_read(&line->blk_in_line);

  	int free_blocks;

  	atomic_add(blk_in_line, &rl->free_blocks);

  	free_blocks = atomic_add_return(blk_in_line, &rl->free_user_blocks);
  
  	__pblk_rl_update_rates(rl, free_blocks);

  }

  void pblk_rl_free_lines_dec(struct pblk_rl *rl, struct pblk_line *line,
  			    bool used)

  {

  	int blk_in_line = atomic_read(&line->blk_in_line);

  	int free_blocks;

  	atomic_sub(blk_in_line, &rl->free_blocks);

  
  	if (used)
  		free_blocks = atomic_sub_return(blk_in_line,
  							&rl->free_user_blocks);
  	else
  		free_blocks = atomic_read(&rl->free_user_blocks);
  
  	__pblk_rl_update_rates(rl, free_blocks);

  }

  int pblk_rl_high_thrs(struct pblk_rl *rl)

  {
  	return rl->high;
  }

  int pblk_rl_max_io(struct pblk_rl *rl)
  {
  	return rl->rb_max_io;
  }

  static void pblk_rl_u_timer(struct timer_list *t)

  {

  	struct pblk_rl *rl = from_timer(rl, t, u_timer);

  
  	/* Release user I/O state. Protect from GC */
  	smp_store_release(&rl->rb_user_active, 0);
  }
  
  void pblk_rl_free(struct pblk_rl *rl)
  {
  	del_timer(&rl->u_timer);
  }

  void pblk_rl_init(struct pblk_rl *rl, int budget, int threshold)

  {

  	struct pblk *pblk = container_of(rl, struct pblk, rl);

  	struct nvm_tgt_dev *dev = pblk->dev;
  	struct nvm_geo *geo = &dev->geo;
  	struct pblk_line_mgmt *l_mg = &pblk->l_mg;

  	struct pblk_line_meta *lm = &pblk->lm;

  	int sec_meta, blk_meta;

  	unsigned int rb_windows;

  	/* Consider sectors used for metadata */
  	sec_meta = (lm->smeta_sec + lm->emeta_sec[0]) * l_mg->nr_free_lines;

  	blk_meta = DIV_ROUND_UP(sec_meta, geo->clba);

  	rl->high = pblk->op_blks - blk_meta - lm->blk_per_line;
  	rl->high_pw = get_count_order(rl->high);

  	rl->rsv_blocks = pblk_get_min_chks(pblk);

  	/* This will always be a power-of-2 */

  	rb_windows = budget / NVM_MAX_VLBA;

  	rl->rb_windows_pw = get_count_order(rb_windows);

  
  	/* To start with, all buffer is available to user I/O writers */
  	rl->rb_budget = budget;
  	rl->rb_user_max = budget;

  	rl->rb_gc_max = 0;
  	rl->rb_state = PBLK_RL_HIGH;

  	/* Maximize I/O size and ansure that back threshold is respected */
  	if (threshold)
  		rl->rb_max_io = budget - pblk->min_write_pgs_data - threshold;
  	else
  		rl->rb_max_io = budget - pblk->min_write_pgs_data - 1;

  	atomic_set(&rl->rb_user_cnt, 0);

  	atomic_set(&rl->rb_gc_cnt, 0);

  	atomic_set(&rl->rb_space, -1);

  	atomic_set(&rl->werr_lines, 0);

  	timer_setup(&rl->u_timer, pblk_rl_u_timer, 0);

  	rl->rb_user_active = 0;

  	rl->rb_gc_active = 0;

  }