// SPDX-License-Identifier: GPL-2.0

  /*
   * CPU <-> hardware queue mapping helpers
   *
   * Copyright (C) 2013-2014 Jens Axboe
   */

  #include <linux/kernel.h>
  #include <linux/threads.h>
  #include <linux/module.h>
  #include <linux/mm.h>
  #include <linux/smp.h>
  #include <linux/cpu.h>
  
  #include <linux/blk-mq.h>
  #include "blk.h"
  #include "blk-mq.h"

  static int queue_index(struct blk_mq_queue_map *qmap,
  		       unsigned int nr_queues, const int q)

  {

  	return qmap->queue_offset + (q % nr_queues);

  }
  
  static int get_first_sibling(unsigned int cpu)
  {
  	unsigned int ret;

  	ret = cpumask_first(topology_sibling_cpumask(cpu));

  	if (ret < nr_cpu_ids)
  		return ret;
  
  	return cpu;
  }

  int blk_mq_map_queues(struct blk_mq_queue_map *qmap)

  {

  	unsigned int *map = qmap->mq_map;
  	unsigned int nr_queues = qmap->nr_queues;

  	unsigned int cpu, first_sibling, q = 0;
  
  	for_each_possible_cpu(cpu)
  		map[cpu] = -1;
  
  	/*
  	 * Spread queues among present CPUs first for minimizing
  	 * count of dead queues which are mapped by all un-present CPUs
  	 */
  	for_each_present_cpu(cpu) {
  		if (q >= nr_queues)
  			break;
  		map[cpu] = queue_index(qmap, nr_queues, q++);
  	}

  	for_each_possible_cpu(cpu) {

  		if (map[cpu] != -1)
  			continue;

  		/*

  		 * First do sequential mapping between CPUs and queues.
  		 * In case we still have CPUs to map, and we have some number of

  		 * threads per cores then map sibling threads to the same queue
  		 * for performance optimizations.

  		 */

  		if (q < nr_queues) {
  			map[cpu] = queue_index(qmap, nr_queues, q++);

  		} else {
  			first_sibling = get_first_sibling(cpu);
  			if (first_sibling == cpu)

  				map[cpu] = queue_index(qmap, nr_queues, q++);

  			else
  				map[cpu] = map[first_sibling];

  		}

  	}

  	return 0;
  }

  EXPORT_SYMBOL_GPL(blk_mq_map_queues);

  /**
   * blk_mq_hw_queue_to_node - Look up the memory node for a hardware queue index
   * @qmap: CPU to hardware queue map.
   * @index: hardware queue index.
   *

   * We have no quick way of doing reverse lookups. This is only used at
   * queue init time, so runtime isn't important.
   */

  int blk_mq_hw_queue_to_node(struct blk_mq_queue_map *qmap, unsigned int index)

  {
  	int i;
  
  	for_each_possible_cpu(i) {

  		if (index == qmap->mq_map[i])

  			return cpu_to_node(i);

  	}
  
  	return NUMA_NO_NODE;
  }