linux-kernel - Re: [PATCH] blkio: Fix a crash during rq stats update

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Message-ID: <20100421145514.GT27497@kernel.dk>
Date:	Wed, 21 Apr 2010 16:55:14 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Divyesh Shah <dpshah@...gle.com>,
	Nauman Rafique <nauman@...gle.com>,
	Gui Jianfeng <guijianfeng@...fujitsu.com>
Subject: Re: [PATCH] blkio: Fix a crash during rq stats update

On Wed, Apr 21 2010, Vivek Goyal wrote:
> @@ -1001,6 +1002,10 @@ static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
>  	return cfqg;
>  }
>  
> +static inline void cfq_get_cfqg_ref(struct cfq_group *cfqg) {
> +	atomic_inc(&cfqg->ref);
> +}

Would be nicer as

static inline void cfq_ref_get_cfqg(struct cfq_group *cfqg)
{
	atomic_inc(&cfqg->ref);
        return cfqg;
}

...

static inline void cfq_ref_get_cfqg(struct cfq_group *cfqg)
{
        return NULL;
}

...

> @@ -3560,6 +3570,9 @@ new_queue:
>  
>  	rq->elevator_private = cic;
>  	rq->elevator_private2 = cfqq;
> +	rq->elevator_private3 = cfqq->cfqg;
> +	/* rq reference on cfqg */
> +	cfq_get_cfqg_ref(RQ_CFQG(rq));
>  	return 0;

rq->elevator_private3 = cfq_ref_get_cfqg(...);

-- 
Jens Axboe

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