linux-kernel - Re: [PATCH] cfq-iosched: Fix a gcc 4.5 warning and put some comments

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Message-ID: <20101022133101.GA7020@redhat.com>
Date:	Fri, 22 Oct 2010 09:31:01 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Jens Axboe <jaxboe@...ionio.com>
Cc:	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Moyer Jeff Moyer <jmoyer@...hat.com>
Subject: Re: [PATCH] cfq-iosched: Fix a gcc 4.5 warning and put some comments

On Fri, Oct 22, 2010 at 09:46:19AM +0200, Jens Axboe wrote:
> On 2010-10-21 20:24, Vivek Goyal wrote:
> > - Andi encountedred following warning with gcc 4.5
> > 
> >   linux/block/cfq-iosched.c: In function ‘cfq_dispatch_requests’:
> >   linux/block/cfq-iosched.c:2156:3: warning: array subscript is above array
> >   bounds
> > 
> > - Warning happens due to following code.
> > 
> >   slice = group_slice * count /
> > 		max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio],
> > 		cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg));
> > 
> >   gcc is complaining about cfqg->busy_queues_avg[] being indexed by CFQ
> >   prio classes (RT, BE and IDLE) while the array size is only 2.
> > 
> > - At run time, we never access cfqg->busy_queues_avg[IDLE] and return from
> >   function before this code hits.
> > 
> > - To fix warning increase the array size though it will remain unused. This
> >   patch also puts some comments to clarify some of the confusions.
> > 
> > - I have taken Jens's patch and modified it a bit.
> > 
> > - Compile tested with gcc 4.4 and boot tested. I don't have gcc 4.5
> >   running, Andi can you please test it with gcc 4.5 to make sure it
> >   worked.
> > 
> > Reported-by: Andi Kleen <ak@...ux.intel.com>
> > Signed-off-by: Vivek Goyal <vgoyal@...hat.com>
> > Signed-off-by: Jens Axboe <axboe@...nel.dk>
> 
> Thanks, I'll put this one in. BTW, you can't just add a signed-off-by
> from me (or anyone else, for that matter), they have to be provided
> explicitly by each individual.

Ok, sorry about that.

So in general, if I happen to pick somebody's patch, modify it and repost
it, how do I reflect the Signed-off-by of original author.

Thanks
Vivek
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