linux-kernel - Re: [PATCH 08/18] io-controller: idle for sometime on sync queue before expiring it

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Date:	Tue, 09 Jun 2009 15:56:38 +0800
From:	Gui Jianfeng <guijianfeng@...fujitsu.com>
To:	Vivek Goyal <vgoyal@...hat.com>
CC:	nauman@...gle.com, dpshah@...gle.com, lizf@...fujitsu.com,
	mikew@...gle.com, fchecconi@...il.com, paolo.valente@...more.it,
	jens.axboe@...cle.com, ryov@...inux.co.jp, fernando@....ntt.co.jp,
	s-uchida@...jp.nec.com, taka@...inux.co.jp, jmoyer@...hat.com,
	dhaval@...ux.vnet.ibm.com, balbir@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, righi.andrea@...il.com,
	agk@...hat.com, dm-devel@...hat.com, snitzer@...hat.com,
	m-ikeda@...jp.nec.com, akpm@...ux-foundation.org
Subject: Re: [PATCH 08/18] io-controller: idle for sometime on sync queue
 before expiring it

Vivek Goyal wrote:
...
> +ssize_t elv_fairness_store(struct request_queue *q, const char *name,
> +			  size_t count)
> +{
> +	struct elv_fq_data *efqd;
> +	unsigned int data;
> +	unsigned long flags;
> +
> +	char *p = (char *)name;
> +
> +	data = simple_strtoul(p, &p, 10);
> +
> +	if (data < 0)
> +		data = 0;
> +	else if (data > INT_MAX)
> +		data = INT_MAX;

  Hi Vivek,

  data might overflow on 64 bit systems. In addition, since "fairness" is nothing 
  more than a switch, just let it be.

Signed-off-by: Gui Jianfeng <guijianfeng@...fujitsu.com>
---
 block/elevator-fq.c |   10 +++++-----
 block/elevator-fq.h |    2 +-
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index 655162b..42d4279 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -2605,7 +2605,7 @@ static inline int is_root_group_ioq(struct request_queue *q,
 ssize_t elv_fairness_show(struct request_queue *q, char *name)
 {
 	struct elv_fq_data *efqd;
-	unsigned int data;
+	unsigned long data;
 	unsigned long flags;
 
 	spin_lock_irqsave(q->queue_lock, flags);
@@ -2619,17 +2619,17 @@ ssize_t elv_fairness_store(struct request_queue *q, const char *name,
 			  size_t count)
 {
 	struct elv_fq_data *efqd;
-	unsigned int data;
+	unsigned long data;
 	unsigned long flags;
 
 	char *p = (char *)name;
 
 	data = simple_strtoul(p, &p, 10);
 
-	if (data < 0)
+	if (!data)
 		data = 0;
-	else if (data > INT_MAX)
-		data = INT_MAX;
+	else
+		data = 1;
 
 	spin_lock_irqsave(q->queue_lock, flags);
 	efqd = &q->elevator->efqd;
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index b2bb11a..4fe843a 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -359,7 +359,7 @@ struct elv_fq_data {
 	 * throughput and focus more on providing fairness for sync
 	 * queues.
 	 */
-	int fairness;
+	unsigned long fairness;
 };
 
 extern int elv_slice_idle;
-- 
1.5.4.rc3


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