Merge branch 'btrfs-3.0' into for-linus

[firefly-linux-kernel-4.4.55.git] / block / blk-softirq.c

diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index ee9c21602228e0dcb1b6ab8adf6909dae4adc2fd..58340d0cb23a82d40edf95b77874a5781d49bcdb 100644 (file)
--- a/block/blk-softirq.c
+++ b/block/blk-softirq.c
@@ -103,24 +103,35 @@ static struct notifier_block __cpuinitdata blk_cpu_notifier = {
 
 void __blk_complete_request(struct request *req)
 {
+       int ccpu, cpu, group_cpu = NR_CPUS;
        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)
+       if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) && req->cpu != -1) {
                ccpu = req->cpu;
-       else
+               if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags)) {
+                       ccpu = blk_cpu_to_group(ccpu);
+                       group_cpu = blk_cpu_to_group(cpu);
+               }
+       } else
                ccpu = cpu;
 
+       /*
+        * If current CPU and requested CPU are in the same group, running
+        * softirq in current CPU. One might concern this is just like
+        * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is
+        * running in interrupt handler, and currently I/O controller doesn't
+        * support multiple interrupts, so current CPU is unique actually. This
+        * avoids IPI sending from current CPU to the first CPU of a group.
+        */
        if (ccpu == cpu || ccpu == group_cpu) {
                struct list_head *list;
 do_local: