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

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Message-ID: <20080207175544.GL15220@kernel.dk>
Date:	Thu, 7 Feb 2008 18:55:45 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...e.hu>, 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, Feb 07 2008, Linus Torvalds wrote:
> 
> 
> 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..

I completely agree, the fidgeting with single members quickly loses
appeal. Ingo, I'll merge and integrate your fixes before leaving, I'll
be here all day tomorrow as well.

-- 
Jens Axboe

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