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1/*
2 * Functions related to interrupt-poll handling in the block layer. This
3 * is similar to NAPI for network devices.
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/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);
23
24/**
25 * blk_iopoll_sched - Schedule a run of the iopoll handler
26 * @iop: The parent iopoll structure
27 *
28 * Description:
29 * Add this blk_iopoll structure to the pending poll list and trigger the
30 * raise of the blk iopoll softirq. The driver must already have gotten a
31 * successful return from blk_iopoll_sched_prep() before calling this.
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);
43
44/**
45 * __blk_iopoll_complete - Mark this @iop as un-polled again
46 * @iop: The parent iopoll structure
47 *
48 * Description:
49 * See blk_iopoll_complete(). This function must be called with interrupts
50 * disabled.
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);
59
60/**
61 * blk_iopoll_complete - Mark this @iop as un-polled again
62 * @iop: The parent iopoll structure
63 *
64 * Description:
65 * If a driver consumes less than the assigned budget in its run of the
66 * iopoll handler, it'll end the polled mode by calling this function. The
67 * iopoll handler will not be invoked again before blk_iopoll_sched_prep()
68 * is called.
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;
91
92 /*
93 * If softirq window is exhausted then punt.
94 */
95 if (budget <= 0 || time_after(jiffies, start_time)) {
96 rearm = 1;
97 break;
98 }
99
100 local_irq_enable();
101
102 /* Even though interrupts have been re-enabled, this
103 * access is safe because interrupts can only add new
104 * entries to the tail of this list, and only ->poll()
105 * calls can remove this head entry from the list.
106 */
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();
117
118 /*
119 * Drivers must not modify the iopoll state, if they
120 * consume their assigned weight (or more, some drivers can't
121 * easily just stop processing, they have to complete an
122 * entire mask of commands).In such cases this code
123 * still "owns" the iopoll instance and therefore can
124 * move the instance around on the list at-will.
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}
139
140/**
141 * blk_iopoll_disable - Disable iopoll on this @iop
142 * @iop: The parent iopoll structure
143 *
144 * Description:
145 * Disable io polling and wait for any pending callbacks to have completed.
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);
155
156/**
157 * blk_iopoll_enable - Enable iopoll on this @iop
158 * @iop: The parent iopoll structure
159 *
160 * Description:
161 * Enable iopoll on this @iop. Note that the handler run will not be
162 * scheduled, it will only mark it as active.
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);
171
172/**
173 * blk_iopoll_init - Initialize this @iop
174 * @iop: The parent iopoll structure
175 * @weight: The default weight (or command completion budget)
176 * @poll_fn: The handler to invoke
177 *
178 * Description:
179 * Initialize this blk_iopoll structure. Before being actively used, the
180 * driver must call blk_iopoll_enable().
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 __cpuinit blk_iopoll_cpu_notify(struct notifier_block *self,
193 unsigned long action, void *hcpu)
194{
195 /*
196 * If a CPU goes away, splice its entries to the current CPU
197 * and trigger a run of the softirq
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 __cpuinitdata 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);
1/*
2 * Functions related to interrupt-poll handling in the block layer. This
3 * is similar to NAPI for network devices.
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/blk-iopoll.h>
13#include <linux/delay.h>
14
15#include "blk.h"
16
17static unsigned int blk_iopoll_budget __read_mostly = 256;
18
19static DEFINE_PER_CPU(struct list_head, blk_cpu_iopoll);
20
21/**
22 * blk_iopoll_sched - Schedule a run of the iopoll handler
23 * @iop: The parent iopoll structure
24 *
25 * Description:
26 * Add this blk_iopoll structure to the pending poll list and trigger the
27 * raise of the blk iopoll softirq. The driver must already have gotten a
28 * successful return from blk_iopoll_sched_prep() before calling this.
29 **/
30void blk_iopoll_sched(struct blk_iopoll *iop)
31{
32 unsigned long flags;
33
34 local_irq_save(flags);
35 list_add_tail(&iop->list, this_cpu_ptr(&blk_cpu_iopoll));
36 __raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ);
37 local_irq_restore(flags);
38}
39EXPORT_SYMBOL(blk_iopoll_sched);
40
41/**
42 * __blk_iopoll_complete - Mark this @iop as un-polled again
43 * @iop: The parent iopoll structure
44 *
45 * Description:
46 * See blk_iopoll_complete(). This function must be called with interrupts
47 * disabled.
48 **/
49void __blk_iopoll_complete(struct blk_iopoll *iop)
50{
51 list_del(&iop->list);
52 smp_mb__before_clear_bit();
53 clear_bit_unlock(IOPOLL_F_SCHED, &iop->state);
54}
55EXPORT_SYMBOL(__blk_iopoll_complete);
56
57/**
58 * blk_iopoll_complete - Mark this @iop as un-polled again
59 * @iop: The parent iopoll structure
60 *
61 * Description:
62 * If a driver consumes less than the assigned budget in its run of the
63 * iopoll handler, it'll end the polled mode by calling this function. The
64 * iopoll handler will not be invoked again before blk_iopoll_sched_prep()
65 * is called.
66 **/
67void blk_iopoll_complete(struct blk_iopoll *iopoll)
68{
69 unsigned long flags;
70
71 local_irq_save(flags);
72 __blk_iopoll_complete(iopoll);
73 local_irq_restore(flags);
74}
75EXPORT_SYMBOL(blk_iopoll_complete);
76
77static void blk_iopoll_softirq(struct softirq_action *h)
78{
79 struct list_head *list = this_cpu_ptr(&blk_cpu_iopoll);
80 int rearm = 0, budget = blk_iopoll_budget;
81 unsigned long start_time = jiffies;
82
83 local_irq_disable();
84
85 while (!list_empty(list)) {
86 struct blk_iopoll *iop;
87 int work, weight;
88
89 /*
90 * If softirq window is exhausted then punt.
91 */
92 if (budget <= 0 || time_after(jiffies, start_time)) {
93 rearm = 1;
94 break;
95 }
96
97 local_irq_enable();
98
99 /* Even though interrupts have been re-enabled, this
100 * access is safe because interrupts can only add new
101 * entries to the tail of this list, and only ->poll()
102 * calls can remove this head entry from the list.
103 */
104 iop = list_entry(list->next, struct blk_iopoll, list);
105
106 weight = iop->weight;
107 work = 0;
108 if (test_bit(IOPOLL_F_SCHED, &iop->state))
109 work = iop->poll(iop, weight);
110
111 budget -= work;
112
113 local_irq_disable();
114
115 /*
116 * Drivers must not modify the iopoll state, if they
117 * consume their assigned weight (or more, some drivers can't
118 * easily just stop processing, they have to complete an
119 * entire mask of commands).In such cases this code
120 * still "owns" the iopoll instance and therefore can
121 * move the instance around on the list at-will.
122 */
123 if (work >= weight) {
124 if (blk_iopoll_disable_pending(iop))
125 __blk_iopoll_complete(iop);
126 else
127 list_move_tail(&iop->list, list);
128 }
129 }
130
131 if (rearm)
132 __raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ);
133
134 local_irq_enable();
135}
136
137/**
138 * blk_iopoll_disable - Disable iopoll on this @iop
139 * @iop: The parent iopoll structure
140 *
141 * Description:
142 * Disable io polling and wait for any pending callbacks to have completed.
143 **/
144void blk_iopoll_disable(struct blk_iopoll *iop)
145{
146 set_bit(IOPOLL_F_DISABLE, &iop->state);
147 while (test_and_set_bit(IOPOLL_F_SCHED, &iop->state))
148 msleep(1);
149 clear_bit(IOPOLL_F_DISABLE, &iop->state);
150}
151EXPORT_SYMBOL(blk_iopoll_disable);
152
153/**
154 * blk_iopoll_enable - Enable iopoll on this @iop
155 * @iop: The parent iopoll structure
156 *
157 * Description:
158 * Enable iopoll on this @iop. Note that the handler run will not be
159 * scheduled, it will only mark it as active.
160 **/
161void blk_iopoll_enable(struct blk_iopoll *iop)
162{
163 BUG_ON(!test_bit(IOPOLL_F_SCHED, &iop->state));
164 smp_mb__before_clear_bit();
165 clear_bit_unlock(IOPOLL_F_SCHED, &iop->state);
166}
167EXPORT_SYMBOL(blk_iopoll_enable);
168
169/**
170 * blk_iopoll_init - Initialize this @iop
171 * @iop: The parent iopoll structure
172 * @weight: The default weight (or command completion budget)
173 * @poll_fn: The handler to invoke
174 *
175 * Description:
176 * Initialize this blk_iopoll structure. Before being actively used, the
177 * driver must call blk_iopoll_enable().
178 **/
179void blk_iopoll_init(struct blk_iopoll *iop, int weight, blk_iopoll_fn *poll_fn)
180{
181 memset(iop, 0, sizeof(*iop));
182 INIT_LIST_HEAD(&iop->list);
183 iop->weight = weight;
184 iop->poll = poll_fn;
185 set_bit(IOPOLL_F_SCHED, &iop->state);
186}
187EXPORT_SYMBOL(blk_iopoll_init);
188
189static int blk_iopoll_cpu_notify(struct notifier_block *self,
190 unsigned long action, void *hcpu)
191{
192 /*
193 * If a CPU goes away, splice its entries to the current CPU
194 * and trigger a run of the softirq
195 */
196 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
197 int cpu = (unsigned long) hcpu;
198
199 local_irq_disable();
200 list_splice_init(&per_cpu(blk_cpu_iopoll, cpu),
201 this_cpu_ptr(&blk_cpu_iopoll));
202 __raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ);
203 local_irq_enable();
204 }
205
206 return NOTIFY_OK;
207}
208
209static struct notifier_block blk_iopoll_cpu_notifier = {
210 .notifier_call = blk_iopoll_cpu_notify,
211};
212
213static __init int blk_iopoll_setup(void)
214{
215 int i;
216
217 for_each_possible_cpu(i)
218 INIT_LIST_HEAD(&per_cpu(blk_cpu_iopoll, i));
219
220 open_softirq(BLOCK_IOPOLL_SOFTIRQ, blk_iopoll_softirq);
221 register_hotcpu_notifier(&blk_iopoll_cpu_notifier);
222 return 0;
223}
224subsys_initcall(blk_iopoll_setup);