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);
187