linux-kernel - [PATCH] cfq-iosched: don't check cfqg in choose_service

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Message-ID: <4D070F7C.3060503@cn.fujitsu.com>
Date:	Tue, 14 Dec 2010 14:32:28 +0800
From:	Gui Jianfeng <guijianfeng@...fujitsu.com>
To:	Jens Axboe <axboe@...nel.dk>, Vivek Goyal <vgoyal@...hat.com>
CC:	linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: [PATCH] cfq-iosched: don't check cfqg in choose_service_tree()

When cfq_choose_cfqg() is called in select_queue(), there must be at least one
backlogged CFQ queue waiting for dispatching, hence there must be at least one
backlogged CFQ group on service tree. So we never call choose_service_tree()
with cfqg == NULL.

Signed-off-by: Gui Jianfeng <guijianfeng@...fujitsu.com>
---
 block/cfq-iosched.c |    6 ------
 1 files changed, 0 insertions(+), 6 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 9b186fd..c19d015 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -2103,12 +2103,6 @@ static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
 	unsigned group_slice;
 	enum wl_prio_t original_prio = cfqd->serving_prio;
 
-	if (!cfqg) {
-		cfqd->serving_prio = IDLE_WORKLOAD;
-		cfqd->workload_expires = jiffies + 1;
-		return;
-	}
-
 	/* Choose next priority. RT > BE > IDLE */
 	if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
 		cfqd->serving_prio = RT_WORKLOAD;
-- 
1.6.5.2


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