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
  12 #include "blk.h"
  13
  14 static 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  */
  20 static 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)
  39 static 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  */
  58 static 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 */
  74 static int raise_blk_irq(int cpu, struct request *rq)
  75 {
  76         return 1;
  77 }
  78 #endif
  79
  80 static 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
 100 static struct notifier_block __cpuinitdata blk_cpu_notifier = {
 101         .notifier_call  = blk_cpu_notify,
 102 };
 103
 104 void __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;
 126 do_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  **/
 155 void 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 }
 162 EXPORT_SYMBOL(blk_complete_request);
 163
 164 static __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 }
 175 subsys_initcall(blk_softirq_init);