linux-kernel - Re: [PATCH] ide: ide_port_wait

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Message-Id: <20111013.132527.2221791090526837668.davem@davemloft.net>
Date:	Thu, 13 Oct 2011 13:25:27 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	bzolnier@...il.com
Cc:	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ide: ide_port_wait_ready() fix

From: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
Date: Thu, 13 Oct 2011 12:41:04 +0200

> David Miller wrote:
> 
>> From: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
>> Date: Wed, 12 Oct 2011 16:59:55 +0200
>> 
>> > David Miller wrote:
>> > 
>> >> From: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
>> >> Date: Tue, 11 Oct 2011 19:13:18 +0200
>> >> 
>> >> > From: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
>> >> > Subject: [PATCH] ide: ide_port_wait_ready() fix
>> >> > 
>> >> > Fix for commit a20b2a4 ("ide: skip probe if there are no devices on
>> >> > the port (v2)").  We must check for slave device before failing.
>> >> > 
>> >> > Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
>> >> 
>> >> This will mishandle the case where there is no slave in the device
>> >> list.
>> > 
>> > I don't see it:
>> > 
>> > @ -598,7 +598,7 @@ static int ide_port_wait_ready(ide_hwif_
>> >  {
>> >  	const struct ide_tp_ops *tp_ops = hwif->tp_ops;
>> >  	ide_drive_t *drive;
>> > -	int i, rc;
>> > +	int i, rc, prev_rc = 0;
>> >  
>> >  	printk(KERN_DEBUG "Probing IDE interface %s...\n", hwif->name);
>> >  
>> > @@ -623,8 +623,10 @@ static int ide_port_wait_ready(ide_hwif_
>> >  			tp_ops->write_devctl(hwif, ATA_DEVCTL_OBS);
>> >  			mdelay(2);
>> >  			rc = ide_wait_not_busy(hwif, 35000);
>> > -			if (rc)
>> > +			if (prev_rc && rc)
>> >  				goto out;
>> > +			prev_rc = rc;
>> > +			rc = 0;
>> >  		} else
>> >  			printk(KERN_DEBUG "%s: ide_wait_not_busy() skipped\n",
>> >  					  drive->name);
>> > 
>> > If there is no slave device but there is a master device the code falls-through
>> > and returns a success.
>> 
>> That's not what we want, if there is only a master device and no slave device
>> in the list this loop is iterating over we want to return the error code
>> in "rc", not zero.
> 
> No, we want to return zero (success) since at least once device was found
> (otherwise we fail probe on some esoteric setups returning -ENODEV from
> ide_wait_not_busy() for master device).
> 
> This is how this function worked before commit a20b2a4 if you want something
> else okay but it needs to work with aforementioned setups.

You unconditionally assign "prev_rc = rc" and set "rc = 0" so if we only run
the loop once, we return zero.

And we do this even if that one device gave a non-zero return value.

That's not what we want.
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