nvmap: page pools: replace background allocator with background zeroer
[linux-3.10.git] / block / blk-softirq.c
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
15 static 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  */
21 static 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 = &__get_cpu_var(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, csd.list);
34                 list_del_init(&rq->csd.list);
35                 rq->q->softirq_done_fn(rq);
36         }
37 }
38
39 #ifdef CONFIG_SMP
40 static 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 = &__get_cpu_var(blk_cpu_done);
48         list_add_tail(&rq->csd.list, list);
49
50         if (list->next == &rq->csd.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  */
59 static 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(cpu, data, 0);
69                 return 0;
70         }
71
72         return 1;
73 }
74 #else /* CONFIG_SMP */
75 static int raise_blk_irq(int cpu, struct request *rq)
76 {
77         return 1;
78 }
79 #endif
80
81 static int __cpuinit blk_cpu_notify(struct notifier_block *self,
82                                     unsigned long action, 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                                  &__get_cpu_var(blk_cpu_done));
94                 raise_softirq_irqoff(BLOCK_SOFTIRQ);
95                 local_irq_enable();
96         }
97
98         return NOTIFY_OK;
99 }
100
101 static struct notifier_block __cpuinitdata blk_cpu_notifier = {
102         .notifier_call  = blk_cpu_notify,
103 };
104
105 void __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;
137 do_local:
138                 list = &__get_cpu_var(blk_cpu_done);
139                 list_add_tail(&req->csd.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->csd.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  **/
166 void 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 }
173 EXPORT_SYMBOL(blk_complete_request);
174
175 static __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 }
186 subsys_initcall(blk_softirq_init);