linux-kernel - Re: [PATCH]drivers/ata/libata-eh.c:1509 unneeded memset()

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Message-Id: <1262964519.3025.614.camel@mulgrave.site>
Date:	Fri, 08 Jan 2010 09:28:39 -0600
From:	James Bottomley <James.Bottomley@...e.de>
To:	Jeff Garzik <jgarzik@...ox.com>
Cc:	René Bolldorf <xsecute@...glemail.com>,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-scsi <linux-scsi@...r.kernel.org>
Subject: Re: [PATCH]drivers/ata/libata-eh.c:1509 unneeded memset()

On Thu, 2010-01-07 at 14:15 -0500, Jeff Garzik wrote:
> On 12/30/2009 05:59 PM, René Bolldorf wrote:
> > We don't need this ;-).
> >
> > Best regards René Bolldorf & a happy new year in advance.
> >
> > --- ./drivers/ata/libata-eh.c 2009-12-30 23:44:05.578988545 +0100
> > +++ ./drivers/ata/libata-eh.c 2009-12-30 23:45:06.991987607 +0100
> > @@ -1505,9 +1505,6 @@ static unsigned int atapi_eh_request_sen
> >
> > DPRINTK("ATAPI request sense\n");
> >
> > - /* FIXME: is this needed? */
> > - memset(sense_buf, 0, SCSI_SENSE_BUFFERSIZE);
> 
> I need a little bit more detail than an unqualified statement...  Did 
> you audit all paths leading to this code point?

There are two code paths coming into here.  One directly from the scsi
sense buffer:

		if (!(qc->ap->pflags & ATA_PFLAG_FROZEN)) {
			tmp = atapi_eh_request_sense(qc->dev,
						qc->scsicmd->sense_buffer,
						qc->result_tf.feature >> 4);

Which is fine because SCSI zeros the sense buffer.

But one also here:

		u8 *sense_buffer = dev->link->ap->sector_buf;
		[...]
		err_mask = atapi_eh_request_sense(dev, sense_buffer, sense_key);

Which doesn't look OK because it looks like the sector_buf isn't cleared
(and it is reused).

James


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