1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Functions related to softirq rq completions
4 */
5#include <linux/kernel.h>
6#include <linux/module.h>
7#include <linux/init.h>
8#include <linux/bio.h>
9#include <linux/blkdev.h>
10#include <linux/interrupt.h>
11#include <linux/cpu.h>
12#include <linux/sched.h>
13#include <linux/sched/topology.h>
14
15#include "blk.h"
16
17static DEFINE_PER_CPU(struct list_head, blk_cpu_done);
18
19/*
20 * Softirq action handler - move entries to local list and loop over them
21 * while passing them to the queue registered handler.
22 */
23static __latent_entropy void blk_done_softirq(struct softirq_action *h)
24{
25 struct list_head *cpu_list, local_list;
26
27 local_irq_disable();
28 cpu_list = this_cpu_ptr(&blk_cpu_done);
29 list_replace_init(cpu_list, &local_list);
30 local_irq_enable();
31
32 while (!list_empty(&local_list)) {
33 struct request *rq;
34
35 rq = list_entry(local_list.next, struct request, ipi_list);
36 list_del_init(&rq->ipi_list);
37 rq->q->mq_ops->complete(rq);
38 }
39}
40
41#ifdef CONFIG_SMP
42static void trigger_softirq(void *data)
43{
44 struct request *rq = data;
45 unsigned long flags;
46 struct list_head *list;
47
48 local_irq_save(flags);
49 list = this_cpu_ptr(&blk_cpu_done);
50 list_add_tail(&rq->ipi_list, list);
51
52 if (list->next == &rq->ipi_list)
53 raise_softirq_irqoff(BLOCK_SOFTIRQ);
54
55 local_irq_restore(flags);
56}
57
58/*
59 * Setup and invoke a run of 'trigger_softirq' on the given cpu.
60 */
61static int raise_blk_irq(int cpu, struct request *rq)
62{
63 if (cpu_online(cpu)) {
64 call_single_data_t *data = &rq->csd;
65
66 data->func = trigger_softirq;
67 data->info = rq;
68 data->flags = 0;
69
70 smp_call_function_single_async(cpu, data);
71 return 0;
72 }
73
74 return 1;
75}
76#else /* CONFIG_SMP */
77static int raise_blk_irq(int cpu, struct request *rq)
78{
79 return 1;
80}
81#endif
82
83static int blk_softirq_cpu_dead(unsigned int cpu)
84{
85 /*
86 * If a CPU goes away, splice its entries to the current CPU
87 * and trigger a run of the softirq
88 */
89 local_irq_disable();
90 list_splice_init(&per_cpu(blk_cpu_done, cpu),
91 this_cpu_ptr(&blk_cpu_done));
92 raise_softirq_irqoff(BLOCK_SOFTIRQ);
93 local_irq_enable();
94
95 return 0;
96}
97
98void __blk_complete_request(struct request *req)
99{
100 struct request_queue *q = req->q;
101 int cpu, ccpu = req->mq_ctx->cpu;
102 unsigned long flags;
103 bool shared = false;
104
105 BUG_ON(!q->mq_ops->complete);
106
107 local_irq_save(flags);
108 cpu = smp_processor_id();
109
110 /*
111 * Select completion CPU
112 */
113 if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) && ccpu != -1) {
114 if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
115 shared = cpus_share_cache(cpu, ccpu);
116 } else
117 ccpu = cpu;
118
119 /*
120 * If current CPU and requested CPU share a cache, run the softirq on
121 * the current CPU. One might concern this is just like
122 * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is
123 * running in interrupt handler, and currently I/O controller doesn't
124 * support multiple interrupts, so current CPU is unique actually. This
125 * avoids IPI sending from current CPU to the first CPU of a group.
126 */
127 if (ccpu == cpu || shared) {
128 struct list_head *list;
129do_local:
130 list = this_cpu_ptr(&blk_cpu_done);
131 list_add_tail(&req->ipi_list, list);
132
133 /*
134 * if the list only contains our just added request,
135 * signal a raise of the softirq. If there are already
136 * entries there, someone already raised the irq but it
137 * hasn't run yet.
138 */
139 if (list->next == &req->ipi_list)
140 raise_softirq_irqoff(BLOCK_SOFTIRQ);
141 } else if (raise_blk_irq(ccpu, req))
142 goto do_local;
143
144 local_irq_restore(flags);
145}
146
147static __init int blk_softirq_init(void)
148{
149 int i;
150
151 for_each_possible_cpu(i)
152 INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
153
154 open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
155 cpuhp_setup_state_nocalls(CPUHP_BLOCK_SOFTIRQ_DEAD,
156 "block/softirq:dead", NULL,
157 blk_softirq_cpu_dead);
158 return 0;
159}
160subsys_initcall(blk_softirq_init);
161