1#include <linux/kernel.h>
 2#include <linux/threads.h>
 3#include <linux/module.h>
 4#include <linux/mm.h>
 5#include <linux/smp.h>
 6#include <linux/cpu.h>
 7
 8#include <linux/blk-mq.h>
 9#include "blk.h"
10#include "blk-mq.h"
11
12static int cpu_to_queue_index(unsigned int nr_cpus, unsigned int nr_queues,
13			      const int cpu)
14{
15	return cpu / ((nr_cpus + nr_queues - 1) / nr_queues);
16}
17
18static int get_first_sibling(unsigned int cpu)
19{
20	unsigned int ret;
21
22	ret = cpumask_first(topology_thread_cpumask(cpu));
23	if (ret < nr_cpu_ids)
24		return ret;
25
26	return cpu;
27}
28
29int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues)
30{
31	unsigned int i, nr_cpus, nr_uniq_cpus, queue, first_sibling;
32	cpumask_var_t cpus;
33
34	if (!alloc_cpumask_var(&cpus, GFP_ATOMIC))
35		return 1;
36
37	cpumask_clear(cpus);
38	nr_cpus = nr_uniq_cpus = 0;
39	for_each_online_cpu(i) {
40		nr_cpus++;
41		first_sibling = get_first_sibling(i);
42		if (!cpumask_test_cpu(first_sibling, cpus))
43			nr_uniq_cpus++;
44		cpumask_set_cpu(i, cpus);
45	}
46
47	queue = 0;
48	for_each_possible_cpu(i) {
49		if (!cpu_online(i)) {
50			map[i] = 0;
51			continue;
52		}
53
54		/*
55		 * Easy case - we have equal or more hardware queues. Or
56		 * there are no thread siblings to take into account. Do
57		 * 1:1 if enough, or sequential mapping if less.
58		 */
59		if (nr_queues >= nr_cpus || nr_cpus == nr_uniq_cpus) {
60			map[i] = cpu_to_queue_index(nr_cpus, nr_queues, queue);
61			queue++;
62			continue;
63		}
64
65		/*
66		 * Less then nr_cpus queues, and we have some number of
67		 * threads per cores. Map sibling threads to the same
68		 * queue.
69		 */
70		first_sibling = get_first_sibling(i);
71		if (first_sibling == i) {
72			map[i] = cpu_to_queue_index(nr_uniq_cpus, nr_queues,
73							queue);
74			queue++;
75		} else
76			map[i] = map[first_sibling];
77	}
78
79	free_cpumask_var(cpus);
80	return 0;
81}
82
83unsigned int *blk_mq_make_queue_map(struct blk_mq_reg *reg)
84{
85	unsigned int *map;
86
87	/* If cpus are offline, map them to first hctx */
88	map = kzalloc_node(sizeof(*map) * num_possible_cpus(), GFP_KERNEL,
89				reg->numa_node);
90	if (!map)
91		return NULL;
92
93	if (!blk_mq_update_queue_map(map, reg->nr_hw_queues))
94		return map;
95
96	kfree(map);
97	return NULL;
98}