1 files changed, 175 insertions, 0 deletions

diff --git a/block/blk-softirq.c b/block/blk-softirq.c
new file mode 100644
index 000000000000..e660d26ca656
--- /dev/null
+++ b/block/blk-softirq.c
@@ -0,0 +1,175 @@
+/*
+ * Functions related to softirq rq completions
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/bio.h>
+#include <linux/blkdev.h>
+#include <linux/interrupt.h>
+#include <linux/cpu.h>
+
+#include "blk.h"
+
+static DEFINE_PER_CPU(struct list_head, blk_cpu_done);
+
+/*
+ * Softirq action handler - move entries to local list and loop over them
+ * while passing them to the queue registered handler.
+ */
+static void blk_done_softirq(struct softirq_action *h)
+{
+        struct list_head *cpu_list, local_list;
+
+        local_irq_disable();
+        cpu_list = &__get_cpu_var(blk_cpu_done);
+        list_replace_init(cpu_list, &local_list);
+        local_irq_enable();
+
+        while (!list_empty(&local_list)) {
+                struct request *rq;
+
+                rq = list_entry(local_list.next, struct request, csd.list);
+                list_del_init(&rq->csd.list);
+                rq->q->softirq_done_fn(rq);
+        }
+}
+
+#if defined(CONFIG_SMP) && defined(CONFIG_USE_GENERIC_SMP_HELPERS)
+static void trigger_softirq(void *data)
+{
+        struct request *rq = data;
+        unsigned long flags;
+        struct list_head *list;
+
+        local_irq_save(flags);
+        list = &__get_cpu_var(blk_cpu_done);
+        list_add_tail(&rq->csd.list, list);
+
+        if (list->next == &rq->csd.list)
+                raise_softirq_irqoff(BLOCK_SOFTIRQ);
+
+        local_irq_restore(flags);
+}
+
+/*
+ * Setup and invoke a run of 'trigger_softirq' on the given cpu.
+ */
+static int raise_blk_irq(int cpu, struct request *rq)
+{
+        if (cpu_online(cpu)) {
+                struct call_single_data *data = &rq->csd;
+
+                data->func = trigger_softirq;
+                data->info = rq;
+                data->flags = 0;
+
+                __smp_call_function_single(cpu, data);
+                return 0;
+        }
+
+        return 1;
+}
+#else /* CONFIG_SMP && CONFIG_USE_GENERIC_SMP_HELPERS */
+static int raise_blk_irq(int cpu, struct request *rq)
+{
+        return 1;
+}
+#endif
+
+static int __cpuinit blk_cpu_notify(struct notifier_block *self,
+                                    unsigned long action, void *hcpu)
+{
+        /*
+         * If a CPU goes away, splice its entries to the current CPU
+         * and trigger a run of the softirq
+         */
+        if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
+                int cpu = (unsigned long) hcpu;
+
+                local_irq_disable();
+                list_splice_init(&per_cpu(blk_cpu_done, cpu),
+                                 &__get_cpu_var(blk_cpu_done));
+                raise_softirq_irqoff(BLOCK_SOFTIRQ);
+                local_irq_enable();
+        }
+
+        return NOTIFY_OK;
+}
+
+static struct notifier_block __cpuinitdata blk_cpu_notifier = {
+        .notifier_call  = blk_cpu_notify,
+};
+
+void __blk_complete_request(struct request *req)
+{
+        struct request_queue *q = req->q;
+        unsigned long flags;
+        int ccpu, cpu, group_cpu;
+
+        BUG_ON(!q->softirq_done_fn);
+
+        local_irq_save(flags);
+        cpu = smp_processor_id();
+        group_cpu = blk_cpu_to_group(cpu);
+
+        /*
+         * Select completion CPU
+         */
+        if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) && req->cpu != -1)
+                ccpu = req->cpu;
+        else
+                ccpu = cpu;
+
+        if (ccpu == cpu || ccpu == group_cpu) {
+                struct list_head *list;
+do_local:
+                list = &__get_cpu_var(blk_cpu_done);
+                list_add_tail(&req->csd.list, list);
+
+                /*
+                 * if the list only contains our just added request,
+                 * signal a raise of the softirq. If there are already
+                 * entries there, someone already raised the irq but it
+                 * hasn't run yet.
+                 */
+                if (list->next == &req->csd.list)
+                        raise_softirq_irqoff(BLOCK_SOFTIRQ);
+        } else if (raise_blk_irq(ccpu, req))
+                goto do_local;
+
+        local_irq_restore(flags);
+}
+
+/**
+ * blk_complete_request - end I/O on a request
+ * @req:      the request being processed
+ *
+ * Description:
+ *     Ends all I/O on a request. It does not handle partial completions,
+ *     unless the driver actually implements this in its completion callback
+ *     through requeueing. The actual completion happens out-of-order,
+ *     through a softirq handler. The user must have registered a completion
+ *     callback through blk_queue_softirq_done().
+ **/
+void blk_complete_request(struct request *req)
+{
+        if (unlikely(blk_should_fake_timeout(req->q)))
+                return;
+        if (!blk_mark_rq_complete(req))
+                __blk_complete_request(req);
+}
+EXPORT_SYMBOL(blk_complete_request);
+
+__init int blk_softirq_init(void)
+{
+        int i;
+
+        for_each_possible_cpu(i)
+                INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
+
+        open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
+        register_hotcpu_notifier(&blk_cpu_notifier);
+        return 0;
+}
+subsys_initcall(blk_softirq_init);