[PATCH] block: Make rq_affinity = 1 work as expected

Jan Kara
2014-10-10T14:24:12Z

From: Tao Ma <boyu.mt@taobao.com>

Commit 5757a6d76c introduced a new rq_affinity = 2 so as to make
the request completed in the __make_request cpu. But it makes the
old rq_affinity = 1 not work any more. The root cause is that
if the 'cpu' and 'req->cpu' is in the same group and cpu != req->cpu,
ccpu will be the same as group_cpu, so the completion will be
excuted in the 'cpu' not 'group_cpu'.

This patch fix problem by simpling removing group_cpu and the codes
are more explicit now. If ccpu == cpu, we complete in cpu, otherwise
we raise_blk_irq to ccpu.

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Roland Dreier <roland@purestorage.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Reviewed-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
---
block/blk-softirq.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index 475fab809a80..487addc85bb5 100644
--- a/block/blk-softirq.c
+++ b/block/blk-softirq.c
@@ -103,7 +103,7 @@ static struct notifier_block __cpuinitdata blk_cpu_notifier = {

void __blk_complete_request(struct request *req)
{
- int ccpu, cpu, group_cpu = NR_CPUS;
+ int ccpu, cpu;
struct request_queue *q = req->q;
unsigned long flags;

@@ -117,14 +117,12 @@ void __blk_complete_request(struct request *req)
*/
if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) && req->cpu != -1) {
ccpu = req->cpu;
- if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags)) {
+ 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 (ccpu == cpu || ccpu == group_cpu) {
+ if (ccpu == cpu) {
struct list_head *list;
do_local:
list = &__get_cpu_var(blk_cpu_done);