Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/evalenti/linux...
[sfrench/cifs-2.6.git] / block / blk-softirq.c
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
17 static 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  */
23 static __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
42 static 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  */
61 static 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 */
77 static int raise_blk_irq(int cpu, struct request *rq)
78 {
79         return 1;
80 }
81 #endif
82
83 static 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
98 void __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;
129 do_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
147 static __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 }
160 subsys_initcall(blk_softirq_init);