linux-kernel - Re: [patch] block layer: kmemcheck fixes

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Message-ID: <alpine.LFD.1.00.0802070940230.2883@woody.linux-foundation.org>
Date:	Thu, 7 Feb 2008 09:42:56 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Jens Axboe <jens.axboe@...cle.com>, linux-kernel@...r.kernel.org,
	Alan.Brunelle@...com, arjan@...ux.intel.com, dgc@....com,
	npiggin@...e.de, Andrew Morton <akpm@...ux-foundation.org>,
	Vegard Nossum <vegard.nossum@...il.com>,
	Pekka Enberg <penberg@...il.com>
Subject: Re: [patch] block layer: kmemcheck fixes



On Thu, 7 Feb 2008, Ingo Molnar wrote:
>  	INIT_HLIST_NODE(&rq->hash);
>  	RB_CLEAR_NODE(&rq->rb_node);
> -	rq->ioprio = 0;
> -	rq->buffer = NULL;
> -	rq->ref_count = 1;
> -	rq->q = q;
> -	rq->special = NULL;
> -	rq->data_len = 0;
> -	rq->data = NULL;
> -	rq->nr_phys_segments = 0;
> -	rq->sense = NULL;
> -	rq->end_io = NULL;
> -	rq->end_io_data = NULL;
> -	rq->completion_data = NULL;
> -	rq->next_rq = NULL;
> +	rq->completion_data		= NULL;
> +	/* rq->elevator_private			*/
> +	/* rq->elevator_private2		*/
> +	/* rq->rq_disk				*/
> +	/* rq->start_time			*/
> +	rq->nr_phys_segments		= 0;
> +	/* rq->nr_hw_segments			*/
> +	rq->ioprio			= 0;
> +	rq->special			= NULL;
> +	rq->buffer			= NULL;
...

Can we please just stop doing these one-by-one assignments, and just do 
something like

	memset(rq, 0, sizeof(*rq));
	rq->q = q;
	rq->ref_count = 1;
	INIT_HLIST_NODE(&rq->hash);
	RB_CLEAR_NODE(&rq->rb_node);

instead?

The memset() is likely faster and smaller than one-by-one assignments 
anyway, even if the one-by-ones can avoid initializing some field or there 
ends up being a double initialization..

			Linus
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