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