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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/blk-iopoll.h>
13#include <linux/delay.h>
14
15#include "blk.h"
16
17int blk_iopoll_enabled = 1;
18EXPORT_SYMBOL(blk_iopoll_enabled);
19
20static unsigned int blk_iopoll_budget __read_mostly = 256;
21
22static DEFINE_PER_CPU(struct list_head, blk_cpu_iopoll);
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32
33void blk_iopoll_sched(struct blk_iopoll *iop)
34{
35 unsigned long flags;
36
37 local_irq_save(flags);
38 list_add_tail(&iop->list, &__get_cpu_var(blk_cpu_iopoll));
39 __raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ);
40 local_irq_restore(flags);
41}
42EXPORT_SYMBOL(blk_iopoll_sched);
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51
52void __blk_iopoll_complete(struct blk_iopoll *iop)
53{
54 list_del(&iop->list);
55 smp_mb__before_clear_bit();
56 clear_bit_unlock(IOPOLL_F_SCHED, &iop->state);
57}
58EXPORT_SYMBOL(__blk_iopoll_complete);
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69
70void blk_iopoll_complete(struct blk_iopoll *iopoll)
71{
72 unsigned long flags;
73
74 local_irq_save(flags);
75 __blk_iopoll_complete(iopoll);
76 local_irq_restore(flags);
77}
78EXPORT_SYMBOL(blk_iopoll_complete);
79
80static void blk_iopoll_softirq(struct softirq_action *h)
81{
82 struct list_head *list = &__get_cpu_var(blk_cpu_iopoll);
83 int rearm = 0, budget = blk_iopoll_budget;
84 unsigned long start_time = jiffies;
85
86 local_irq_disable();
87
88 while (!list_empty(list)) {
89 struct blk_iopoll *iop;
90 int work, weight;
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94
95 if (budget <= 0 || time_after(jiffies, start_time)) {
96 rearm = 1;
97 break;
98 }
99
100 local_irq_enable();
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107 iop = list_entry(list->next, struct blk_iopoll, list);
108
109 weight = iop->weight;
110 work = 0;
111 if (test_bit(IOPOLL_F_SCHED, &iop->state))
112 work = iop->poll(iop, weight);
113
114 budget -= work;
115
116 local_irq_disable();
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125
126 if (work >= weight) {
127 if (blk_iopoll_disable_pending(iop))
128 __blk_iopoll_complete(iop);
129 else
130 list_move_tail(&iop->list, list);
131 }
132 }
133
134 if (rearm)
135 __raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ);
136
137 local_irq_enable();
138}
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146
147void blk_iopoll_disable(struct blk_iopoll *iop)
148{
149 set_bit(IOPOLL_F_DISABLE, &iop->state);
150 while (test_and_set_bit(IOPOLL_F_SCHED, &iop->state))
151 msleep(1);
152 clear_bit(IOPOLL_F_DISABLE, &iop->state);
153}
154EXPORT_SYMBOL(blk_iopoll_disable);
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163
164void blk_iopoll_enable(struct blk_iopoll *iop)
165{
166 BUG_ON(!test_bit(IOPOLL_F_SCHED, &iop->state));
167 smp_mb__before_clear_bit();
168 clear_bit_unlock(IOPOLL_F_SCHED, &iop->state);
169}
170EXPORT_SYMBOL(blk_iopoll_enable);
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181
182void blk_iopoll_init(struct blk_iopoll *iop, int weight, blk_iopoll_fn *poll_fn)
183{
184 memset(iop, 0, sizeof(*iop));
185 INIT_LIST_HEAD(&iop->list);
186 iop->weight = weight;
187 iop->poll = poll_fn;
188 set_bit(IOPOLL_F_SCHED, &iop->state);
189}
190EXPORT_SYMBOL(blk_iopoll_init);
191
192static int blk_iopoll_cpu_notify(struct notifier_block *self,
193 unsigned long action, void *hcpu)
194{
195
196
197
198
199 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
200 int cpu = (unsigned long) hcpu;
201
202 local_irq_disable();
203 list_splice_init(&per_cpu(blk_cpu_iopoll, cpu),
204 &__get_cpu_var(blk_cpu_iopoll));
205 __raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ);
206 local_irq_enable();
207 }
208
209 return NOTIFY_OK;
210}
211
212static struct notifier_block blk_iopoll_cpu_notifier = {
213 .notifier_call = blk_iopoll_cpu_notify,
214};
215
216static __init int blk_iopoll_setup(void)
217{
218 int i;
219
220 for_each_possible_cpu(i)
221 INIT_LIST_HEAD(&per_cpu(blk_cpu_iopoll, i));
222
223 open_softirq(BLOCK_IOPOLL_SOFTIRQ, blk_iopoll_softirq);
224 register_hotcpu_notifier(&blk_iopoll_cpu_notifier);
225 return 0;
226}
227subsys_initcall(blk_iopoll_setup);
228