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1/*
2 * Functions related to softirq rq completions
3 */
4#include <linux/kernel.h>
5#include <linux/module.h>
6#include <linux/init.h>
7#include <linux/bio.h>
8#include <linux/blkdev.h>
9#include <linux/interrupt.h>
10#include <linux/cpu.h>
11#include <linux/sched.h>
12
13#include "blk.h"
14
15static DEFINE_PER_CPU(struct list_head, blk_cpu_done);
16
17/*
18 * Softirq action handler - move entries to local list and loop over them
19 * while passing them to the queue registered handler.
20 */
21static void blk_done_softirq(struct softirq_action *h)
22{
23 struct list_head *cpu_list, local_list;
24
25 local_irq_disable();
26 cpu_list = this_cpu_ptr(&blk_cpu_done);
27 list_replace_init(cpu_list, &local_list);
28 local_irq_enable();
29
30 while (!list_empty(&local_list)) {
31 struct request *rq;
32
33 rq = list_entry(local_list.next, struct request, ipi_list);
34 list_del_init(&rq->ipi_list);
35 rq->q->softirq_done_fn(rq);
36 }
37}
38
39#ifdef CONFIG_SMP
40static void trigger_softirq(void *data)
41{
42 struct request *rq = data;
43 unsigned long flags;
44 struct list_head *list;
45
46 local_irq_save(flags);
47 list = this_cpu_ptr(&blk_cpu_done);
48 list_add_tail(&rq->ipi_list, list);
49
50 if (list->next == &rq->ipi_list)
51 raise_softirq_irqoff(BLOCK_SOFTIRQ);
52
53 local_irq_restore(flags);
54}
55
56/*
57 * Setup and invoke a run of 'trigger_softirq' on the given cpu.
58 */
59static int raise_blk_irq(int cpu, struct request *rq)
60{
61 if (cpu_online(cpu)) {
62 struct call_single_data *data = &rq->csd;
63
64 data->func = trigger_softirq;
65 data->info = rq;
66 data->flags = 0;
67
68 smp_call_function_single_async(cpu, data);
69 return 0;
70 }
71
72 return 1;
73}
74#else /* CONFIG_SMP */
75static int raise_blk_irq(int cpu, struct request *rq)
76{
77 return 1;
78}
79#endif
80
81static int blk_cpu_notify(struct notifier_block *self, unsigned long action,
82 void *hcpu)
83{
84 /*
85 * If a CPU goes away, splice its entries to the current CPU
86 * and trigger a run of the softirq
87 */
88 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
89 int cpu = (unsigned long) hcpu;
90
91 local_irq_disable();
92 list_splice_init(&per_cpu(blk_cpu_done, cpu),
93 this_cpu_ptr(&blk_cpu_done));
94 raise_softirq_irqoff(BLOCK_SOFTIRQ);
95 local_irq_enable();
96 }
97
98 return NOTIFY_OK;
99}
100
101static struct notifier_block blk_cpu_notifier = {
102 .notifier_call = blk_cpu_notify,
103};
104
105void __blk_complete_request(struct request *req)
106{
107 int ccpu, cpu;
108 struct request_queue *q = req->q;
109 unsigned long flags;
110 bool shared = false;
111
112 BUG_ON(!q->softirq_done_fn);
113
114 local_irq_save(flags);
115 cpu = smp_processor_id();
116
117 /*
118 * Select completion CPU
119 */
120 if (req->cpu != -1) {
121 ccpu = req->cpu;
122 if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
123 shared = cpus_share_cache(cpu, ccpu);
124 } else
125 ccpu = cpu;
126
127 /*
128 * If current CPU and requested CPU share a cache, run the softirq on
129 * the current CPU. One might concern this is just like
130 * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is
131 * running in interrupt handler, and currently I/O controller doesn't
132 * support multiple interrupts, so current CPU is unique actually. This
133 * avoids IPI sending from current CPU to the first CPU of a group.
134 */
135 if (ccpu == cpu || shared) {
136 struct list_head *list;
137do_local:
138 list = this_cpu_ptr(&blk_cpu_done);
139 list_add_tail(&req->ipi_list, list);
140
141 /*
142 * if the list only contains our just added request,
143 * signal a raise of the softirq. If there are already
144 * entries there, someone already raised the irq but it
145 * hasn't run yet.
146 */
147 if (list->next == &req->ipi_list)
148 raise_softirq_irqoff(BLOCK_SOFTIRQ);
149 } else if (raise_blk_irq(ccpu, req))
150 goto do_local;
151
152 local_irq_restore(flags);
153}
154
155/**
156 * blk_complete_request - end I/O on a request
157 * @req: the request being processed
158 *
159 * Description:
160 * Ends all I/O on a request. It does not handle partial completions,
161 * unless the driver actually implements this in its completion callback
162 * through requeueing. The actual completion happens out-of-order,
163 * through a softirq handler. The user must have registered a completion
164 * callback through blk_queue_softirq_done().
165 **/
166void blk_complete_request(struct request *req)
167{
168 if (unlikely(blk_should_fake_timeout(req->q)))
169 return;
170 if (!blk_mark_rq_complete(req))
171 __blk_complete_request(req);
172}
173EXPORT_SYMBOL(blk_complete_request);
174
175static __init int blk_softirq_init(void)
176{
177 int i;
178
179 for_each_possible_cpu(i)
180 INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
181
182 open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
183 register_hotcpu_notifier(&blk_cpu_notifier);
184 return 0;
185}
186subsys_initcall(blk_softirq_init);
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->softirq_done_fn(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 int ccpu, cpu;
101 struct request_queue *q = req->q;
102 unsigned long flags;
103 bool shared = false;
104
105 BUG_ON(!q->softirq_done_fn);
106
107 local_irq_save(flags);
108 cpu = smp_processor_id();
109
110 /*
111 * Select completion CPU
112 */
113 if (req->cpu != -1) {
114 ccpu = req->cpu;
115 if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
116 shared = cpus_share_cache(cpu, ccpu);
117 } else
118 ccpu = cpu;
119
120 /*
121 * If current CPU and requested CPU share a cache, run the softirq on
122 * the current CPU. One might concern this is just like
123 * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is
124 * running in interrupt handler, and currently I/O controller doesn't
125 * support multiple interrupts, so current CPU is unique actually. This
126 * avoids IPI sending from current CPU to the first CPU of a group.
127 */
128 if (ccpu == cpu || shared) {
129 struct list_head *list;
130do_local:
131 list = this_cpu_ptr(&blk_cpu_done);
132 list_add_tail(&req->ipi_list, list);
133
134 /*
135 * if the list only contains our just added request,
136 * signal a raise of the softirq. If there are already
137 * entries there, someone already raised the irq but it
138 * hasn't run yet.
139 */
140 if (list->next == &req->ipi_list)
141 raise_softirq_irqoff(BLOCK_SOFTIRQ);
142 } else if (raise_blk_irq(ccpu, req))
143 goto do_local;
144
145 local_irq_restore(flags);
146}
147
148/**
149 * blk_complete_request - end I/O on a request
150 * @req: the request being processed
151 *
152 * Description:
153 * Ends all I/O on a request. It does not handle partial completions,
154 * unless the driver actually implements this in its completion callback
155 * through requeueing. The actual completion happens out-of-order,
156 * through a softirq handler. The user must have registered a completion
157 * callback through blk_queue_softirq_done().
158 **/
159void blk_complete_request(struct request *req)
160{
161 if (unlikely(blk_should_fake_timeout(req->q)))
162 return;
163 if (!blk_mark_rq_complete(req))
164 __blk_complete_request(req);
165}
166EXPORT_SYMBOL(blk_complete_request);
167
168static __init int blk_softirq_init(void)
169{
170 int i;
171
172 for_each_possible_cpu(i)
173 INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
174
175 open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
176 cpuhp_setup_state_nocalls(CPUHP_BLOCK_SOFTIRQ_DEAD,
177 "block/softirq:dead", NULL,
178 blk_softirq_cpu_dead);
179 return 0;
180}
181subsys_initcall(blk_softirq_init);