Bug#582281: Upstream fix

[Peter Oberparleiter <oberpar@linux.vnet.ibm.com>]

Hello Stephen,

On 03.08.2010 21:43, Stephen Powell wrote:
> On Tue, 20 Jul 2010 09:55:58 -0400 (EDT), Peter Oberparleiter wrote:
> > A fix for this problem has been accepted for inclusion into 2.6.35-rc5. See:
> >
> > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=cffab6bc5511cd6f67a60bf16b62de4267b68c4c
>
> Hello, Peter.  I finally got a chance to take a look at this today.
> I can't apply the patch as written to my 2.6.32 source code due to changes
> between 2.6.32 and 2.6.35 that will cause the patch to not apply.
> However, I did look at the patch.  While I confess to being a complete
> novice in the C language, the patch doesn't look quite right to me.
> Consider the following excerpt from the patch:
>
> +       if ((info->cu_type == 0x6310&&  info->dev_type == 0x9336) ||
> +           (info->cu_type == 0x3880&&  info->dev_type == 0x3370))
> +               labelsect = info->label_block;
> +       else
> +               labelsect = info->label_block * (blocksize>>  9);
>
> This is unexpected.  I expected that last line to be
>
> +               labelsect = info->label_block * (blocksize/512)

Note that >> is the "shift right" operator in C and that shifting an 
integer 9 positions to the right is the same as a division by 512. I 
used the >> operator for consistency with the remaining function.

> My concern is not for FBA DASD.  I expect your code to execute correctly
> for FBA DASD.  My concern is that it will break for CKD DASD.  Are you
> sure that this is correct?  Did you test the fix for CKD DASD as well
> as FBA DASD?

I tested the code successfully for both FBA and CKD DASD.


Regards,
  Peter

--
Peter Oberparleiter
Linux on System z Development
IBM Deutschland Research & Development GmbH
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