linux-kernel - Re: [PATCH] Re: cciss: warning: right shift count >= width of type

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Message-Id: <1186950769.3400.34.camel@localhost.localdomain>
Date:	Sun, 12 Aug 2007 15:32:49 -0500
From:	James Bottomley <James.Bottomley@...elEye.com>
To:	Al Viro <viro@....linux.org.uk>
Cc:	Rene Herman <rene.herman@...il.com>,
	Jesper Juhl <jesper.juhl@...il.com>,
	linux-scsi@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Mike.miller@...com
Subject: Re: [PATCH] Re: cciss: warning: right shift count >= width of type

On Sun, 2007-08-12 at 07:58 +0100, Al Viro wrote:
> On Sun, Aug 12, 2007 at 03:21:57AM +0200, Rene Herman wrote:
> > @@ -2609,13 +2609,13 @@ static void do_cciss_request(request_queue_t *q)
> >  		} else {
> >  			c->Request.CDBLen = 16;
> >  			c->Request.CDB[1]= 0;
> > -			c->Request.CDB[2]= (start_blk >> 56) & 0xff;	//MSB
> > -			c->Request.CDB[3]= (start_blk >> 48) & 0xff;
> > -			c->Request.CDB[4]= (start_blk >> 40) & 0xff;
> > -			c->Request.CDB[5]= (start_blk >> 32) & 0xff;
> > -			c->Request.CDB[6]= (start_blk >> 24) & 0xff;
> > -			c->Request.CDB[7]= (start_blk >> 16) & 0xff;
> > -			c->Request.CDB[8]= (start_blk >>  8) & 0xff;
> > +			c->Request.CDB[2]= ((u64)start_blk >> 56) & 0xff;	//MSB
> > +			c->Request.CDB[3]= ((u64)start_blk >> 48) & 0xff;
> > +			c->Request.CDB[4]= ((u64)start_blk >> 40) & 0xff;
> > +			c->Request.CDB[5]= ((u64)start_blk >> 32) & 0xff;
> > +			c->Request.CDB[6]= ((u64)start_blk >> 24) & 0xff;
> > +			c->Request.CDB[7]= ((u64)start_blk >> 16) & 0xff;
> > +			c->Request.CDB[8]= ((u64)start_blk >>  8) & 0xff;
> 
> 	put_unaligned(cpu_to_be64(start_blk), &c->Request.CDB[2]);
> 
> which is what's happening here anyway.

Well ... this was debated a while ago ad nauseam:

http://marc.info/?t=117699555300010

The main objection to what you propose is that it forces the u64
coercion even in the 32 bit start_blk case.  The preferred solution as a
result of that debate was simply to us a macro Andrew introduced:

upper_32_bits()

Which will silently replace zero in the non LBD case.  I actually
thought this had already been done.

James


James


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