linux-kernel - Re: [PATCH 05/18] io-controller: Common hierarchical fair queuing code in elevaotor layer

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Date:	Fri, 8 May 2009 23:09:37 +0200
From:	Andrea Righi <righi.andrea@...il.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,
	guijianfeng@...fujitsu.com, jmoyer@...hat.com,
	dhaval@...ux.vnet.ibm.com, balbir@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, agk@...hat.com,
	dm-devel@...hat.com, snitzer@...hat.com, m-ikeda@...jp.nec.com,
	akpm@...ux-foundation.org
Subject: Re: [PATCH 05/18] io-controller: Common hierarchical fair queuing
	code in elevaotor layer

On Tue, May 05, 2009 at 03:58:32PM -0400, Vivek Goyal wrote:
> +#define STORE_FUNCTION(__VAR, __MIN, __MAX)				\
> +static int io_cgroup_##__VAR##_write(struct cgroup *cgroup,		\
> +					struct cftype *cftype,		\
> +					u64 val)			\
> +{									\
> +	struct io_cgroup *iocg;					\
> +	struct io_group *iog;						\
> +	struct hlist_node *n;						\
> +									\
> +	if (val < (__MIN) || val > (__MAX))				\
> +		return -EINVAL;						\
> +									\
> +	if (!cgroup_lock_live_group(cgroup))				\
> +		return -ENODEV;						\
> +									\
> +	iocg = cgroup_to_io_cgroup(cgroup);				\
> +									\
> +	spin_lock_irq(&iocg->lock);					\
> +	iocg->__VAR = (unsigned long)val;				\
> +	hlist_for_each_entry(iog, n, &iocg->group_data, group_node) {	\
> +		iog->entity.new_##__VAR = (unsigned long)val;		\
> +		smp_wmb();						\
> +		iog->entity.ioprio_changed = 1;				\
> +	}								\
> +	spin_unlock_irq(&iocg->lock);					\
> +									\
> +	cgroup_unlock();						\
> +									\
> +	return 0;							\
> +}
> +
> +STORE_FUNCTION(weight, 0, WEIGHT_MAX);

A small fix: io.weight should be strictly greater than 0 if we don't
want to automatically trigger the BUG_ON(entity->weight == 0) in
bfq_calc_finish().

Signed-off-by: Andrea Righi <righi.andrea@...il.com>
---
 block/elevator-fq.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index 9500619..de25f44 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -1136,7 +1136,7 @@ static int io_cgroup_##__VAR##_write(struct cgroup *cgroup,		\
 	return 0;							\
 }
 
-STORE_FUNCTION(weight, 0, WEIGHT_MAX);
+STORE_FUNCTION(weight, 1, WEIGHT_MAX);
 STORE_FUNCTION(ioprio_class, IOPRIO_CLASS_RT, IOPRIO_CLASS_IDLE);
 #undef STORE_FUNCTION
 
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