linux-kernel - [PATCH] block: Make rq_affinity = 1 work as expected.

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Message-Id: <1312519150-3261-1-git-send-email-tm@tao.ma>
Date:	Fri,  5 Aug 2011 12:39:10 +0800
From:	Tao Ma <tm@....ma>
To:	linux-kernel@...r.kernel.org
Cc:	Christoph Hellwig <hch@...radead.org>,
	Roland Dreier <roland@...estorage.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Jens Axboe <jaxboe@...ionio.com>
Subject: [PATCH] block: Make rq_affinity = 1 work as expected.

From: Tao Ma <boyu.mt@...bao.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@...radead.org>
Cc: Roland Dreier <roland@...estorage.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Jens Axboe <jaxboe@...ionio.com>
Signed-off-by: Tao Ma <boyu.mt@...bao.com>
---
 block/blk-softirq.c |    8 +++-----
 1 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index 475fab8..487addc 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);
-- 
1.6.3.3.334.g916e1.dirty

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