linux-kernel - Re: [PATCH] cfq: Remove useless css reference get

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Message-ID: <4B875A73.2070103@cn.fujitsu.com>
Date:	Fri, 26 Feb 2010 13:21:55 +0800
From:	Gui Jianfeng <guijianfeng@...fujitsu.com>
To:	Jens Axboe <jens.axboe@...cle.com>
CC:	Vivek Goyal <vgoyal@...hat.com>,
	Corrado Zoccolo <czoccolo@...il.com>,
	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Li Zefan <lizf@...fujitsu.com>
Subject: Re: [PATCH] cfq: Remove useless css reference get

Vivek Goyal wrote:
> On Wed, Dec 16, 2009 at 04:38:43PM +0800, Gui Jianfeng wrote:
>> There's no need to take css reference here, for the caller
>> has already called rcu_read_lock() to prevent cgroup from 
>> being removed.
>>
>> Signed-off-by: Gui Jianfeng <guijianfeng@...fujitsu.com>
>> Reviewed-by: Li Zefan <lizf@...fujitsu.com>
> 
> Acked-by: Vivek Goyal <vgoyal@...hat.com>

Hi Jens

Would you pick this patch up?

> 
> Thanks
> Vivek
> 
>> ---
>>  block/blk-cgroup.c  |   14 --------------
>>  block/blk-cgroup.h  |    3 ---
>>  block/cfq-iosched.c |    5 -----
>>  3 files changed, 0 insertions(+), 22 deletions(-)
>>
>> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
>> index 1fa2654..cba28f4 100644
>> --- a/block/blk-cgroup.c
>> +++ b/block/blk-cgroup.c
>> @@ -23,20 +23,6 @@ static LIST_HEAD(blkio_list);
>>  struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
>>  EXPORT_SYMBOL_GPL(blkio_root_cgroup);
>>  
>> -bool blkiocg_css_tryget(struct blkio_cgroup *blkcg)
>> -{
>> -	if (!css_tryget(&blkcg->css))
>> -		return false;
>> -	return true;
>> -}
>> -EXPORT_SYMBOL_GPL(blkiocg_css_tryget);
>> -
>> -void blkiocg_css_put(struct blkio_cgroup *blkcg)
>> -{
>> -	css_put(&blkcg->css);
>> -}
>> -EXPORT_SYMBOL_GPL(blkiocg_css_put);
>> -
>>  struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
>>  {
>>  	return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
>> diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
>> index 4d316df..84bf745 100644
>> --- a/block/blk-cgroup.h
>> +++ b/block/blk-cgroup.h
>> @@ -43,9 +43,6 @@ struct blkio_group {
>>  	unsigned long sectors;
>>  };
>>  
>> -extern bool blkiocg_css_tryget(struct blkio_cgroup *blkcg);
>> -extern void blkiocg_css_put(struct blkio_cgroup *blkcg);
>> -
>>  typedef void (blkio_unlink_group_fn) (void *key, struct blkio_group *blkg);
>>  typedef void (blkio_update_group_weight_fn) (struct blkio_group *blkg,
>>  						unsigned int weight);
>> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
>> index e2f8046..5d6b427 100644
>> --- a/block/cfq-iosched.c
>> +++ b/block/cfq-iosched.c
>> @@ -958,10 +958,6 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
>>  	struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
>>  	unsigned int major, minor;
>>  
>> -	/* Do we need to take this reference */
>> -	if (!blkiocg_css_tryget(blkcg))
>> -		return NULL;;
>> -
>>  	cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
>>  	if (cfqg || !create)
>>  		goto done;
>> @@ -992,7 +988,6 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
>>  	hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
>>  
>>  done:
>> -	blkiocg_css_put(blkcg);
>>  	return cfqg;
>>  }
>>  
>> -- 
>> 1.5.4.rc3
>>
> 
> 
> 

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