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);