linux-kernel - [PATCH 13/16] blkio: Provide some isolation between groups

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Date:	Thu, 12 Nov 2009 18:32:33 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	linux-kernel@...r.kernel.org, jens.axboe@...cle.com
Cc:	nauman@...gle.com, dpshah@...gle.com, lizf@...fujitsu.com,
	ryov@...inux.co.jp, fernando@....ntt.co.jp, s-uchida@...jp.nec.com,
	taka@...inux.co.jp, guijianfeng@...fujitsu.com, jmoyer@...hat.com,
	balbir@...ux.vnet.ibm.com, righi.andrea@...il.com,
	m-ikeda@...jp.nec.com, vgoyal@...hat.com,
	akpm@...ux-foundation.org, riel@...hat.com,
	kamezawa.hiroyu@...fujitsu.com
Subject: [PATCH 13/16] blkio: Provide some isolation between groups

o Do not allow following three operations across groups for isolation.
	- selection of co-operating queues
	- preemtpions across groups
	- request merging across groups.

Signed-off-by: Vivek Goyal <vgoyal@...hat.com>
---
 block/cfq-iosched.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 24640f1..6081efe 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1432,6 +1432,9 @@ static int cfq_allow_merge(struct request_queue *q, struct request *rq,
 	struct cfq_io_context *cic;
 	struct cfq_queue *cfqq;
 
+	/* Deny merge if bio and rq don't belong to same cfq group */
+	if ((RQ_CFQQ(rq))->cfqg != cfq_get_cfqg(cfqd, 0))
+		return false;
 	/*
 	 * Disallow merge of a sync bio into an async request.
 	 */
@@ -1677,6 +1680,10 @@ static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
 	if (!cfqq)
 		return NULL;
 
+	/* If new queue belongs to different cfq_group, don't choose it */
+	if (cur_cfqq->cfqg != cfqq->cfqg)
+		return NULL;
+
 	/*
 	 * It only makes sense to merge sync queues.
 	 */
@@ -2945,6 +2952,9 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
 	if (!cfqq)
 		return false;
 
+	if (new_cfqq->cfqg != cfqq->cfqg)
+		return false;
+
 	if (cfq_slice_used(cfqq))
 		return true;
 
-- 
1.6.2.5

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