linux-kernel - Re: [PATCH 07/20] io-controller: Export disk time used and nr sectors dipatched through cgroups

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Date:	Tue, 23 Jun 2009 10:38:56 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Gui Jianfeng <guijianfeng@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, dm-devel@...hat.com,
	jens.axboe@...cle.com, nauman@...gle.com, dpshah@...gle.com,
	lizf@...fujitsu.com, mikew@...gle.com, fchecconi@...il.com,
	paolo.valente@...more.it, 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, righi.andrea@...il.com,
	m-ikeda@...jp.nec.com, jbaron@...hat.com, agk@...hat.com,
	snitzer@...hat.com, akpm@...ux-foundation.org, peterz@...radead.org
Subject: Re: [PATCH 07/20] io-controller: Export disk time used and nr
	sectors dipatched through cgroups

On Tue, Jun 23, 2009 at 08:10:54PM +0800, Gui Jianfeng wrote:
> Vivek Goyal wrote:
> ...
> > +
> > +static int io_cgroup_disk_sectors_read(struct cgroup *cgroup,
> > +				struct cftype *cftype, struct seq_file *m)
> > +{
> > +	struct io_cgroup *iocg;
> > +	struct io_group *iog;
> > +	struct hlist_node *n;
> > +
> > +	if (!cgroup_lock_live_group(cgroup))
> > +		return -ENODEV;
> > +
> > +	iocg = cgroup_to_io_cgroup(cgroup);
> > +
> > +	spin_lock_irq(&iocg->lock);
> 
> It's better to make use of rcu_read_lock instead since it's
> a read action.
> 

Thanks Gui. Queued for next posting.

Vivek

> Signed-off-by: Gui Jianfeng <guijianfeng@...fujitsu.com>
> ---
>  block/elevator-fq.c |   12 ++++++------
>  1 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/block/elevator-fq.c b/block/elevator-fq.c
> index 2ad40eb..d779282 100644
> --- a/block/elevator-fq.c
> +++ b/block/elevator-fq.c
> @@ -1418,7 +1418,7 @@ static int io_cgroup_disk_time_read(struct cgroup *cgroup,
>  
>  	iocg = cgroup_to_io_cgroup(cgroup);
>  
> -	spin_lock_irq(&iocg->lock);
> +	rcu_read_lock();
>  	hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
>  		/*
>  		 * There might be groups which are not functional and
> @@ -1430,7 +1430,7 @@ static int io_cgroup_disk_time_read(struct cgroup *cgroup,
>  					iog->entity.total_service);
>  		}
>  	}
> -	spin_unlock_irq(&iocg->lock);
> +	rcu_read_unlock();
>  	cgroup_unlock();
>  
>  	return 0;
> @@ -1448,7 +1448,7 @@ static int io_cgroup_disk_sectors_read(struct cgroup *cgroup,
>  
>  	iocg = cgroup_to_io_cgroup(cgroup);
>  
> -	spin_lock_irq(&iocg->lock);
> +	rcu_read_lock();
>  	hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
>  		/*
>  		 * There might be groups which are not functional and
> @@ -1460,7 +1460,7 @@ static int io_cgroup_disk_sectors_read(struct cgroup *cgroup,
>  					iog->entity.total_sector_service);
>  		}
>  	}
> -	spin_unlock_irq(&iocg->lock);
> +	rcu_read_unlock();
>  	cgroup_unlock();
>  
>  	return 0;
> @@ -1478,7 +1478,7 @@ static int io_cgroup_disk_queue_read(struct cgroup *cgroup,
>  		return -ENODEV;
>  
>  	iocg = cgroup_to_io_cgroup(cgroup);
> -	spin_lock_irq(&iocg->lock);
> +	rcu_read_lock();
>  	/* Loop through all the io groups and print statistics */
>  	hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
>  		/*
> @@ -1491,7 +1491,7 @@ static int io_cgroup_disk_queue_read(struct cgroup *cgroup,
>  					iog->queue_duration);
>  		}
>  	}
> -	spin_unlock_irq(&iocg->lock);
> +	rcu_read_unlock();
>  	cgroup_unlock();
>  
>  	return 0;
> -- 
> 1.5.4.rc3
> 
> 
> 
> > +	hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
> > +		/*
> > +		 * There might be groups which are not functional and
> > +		 * waiting to be reclaimed upon cgoup deletion.
> > +		 */
> > +		if (iog->key) {
> > +			seq_printf(m, "%u %u %lu\n", MAJOR(iog->dev),
> > +					MINOR(iog->dev),
> > +					iog->entity.total_sector_service);
> > +		}
> > +	}
> > +	spin_unlock_irq(&iocg->lock);
> > +	cgroup_unlock();
> > +
> > +	return 0;
> > +}
> > +
> >
--
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