block: split softirq handling into blk-softirq.c

[~andy/linux] / block / blk-softirq.c

diff --git a/block/blk-softirq.c b/block/blk-softirq.c
new file mode 100644 (file)
index 0000000..9e1c43b
--- /dev/null
+++ b/block/blk-softirq.c
@@ -0,0 +1,103 @@
+/*
+ * 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);
+
+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 blk_cpu_notifier __cpuinitdata = {
+       .notifier_call  = blk_cpu_notify,
+};
+
+/*
+ * splice the completion data to a local structure and hand off to
+ * process_completion_queue() to complete the requests
+ */
+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, donelist);
+               list_del_init(&rq->donelist);
+               rq->q->softirq_done_fn(rq);
+       }
+}
+
+/**
+ * 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)
+{
+       struct list_head *cpu_list;
+       unsigned long flags;
+
+       BUG_ON(!req->q->softirq_done_fn);
+
+       local_irq_save(flags);
+
+       cpu_list = &__get_cpu_var(blk_cpu_done);
+       list_add_tail(&req->donelist, cpu_list);
+       raise_softirq_irqoff(BLOCK_SOFTIRQ);
+
+       local_irq_restore(flags);
+}
+EXPORT_SYMBOL(blk_complete_request);
+
+int __init 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);