linux-kernel - Re: [PATCH 3/9] s390: Replace weird use of PTR

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Date:	Mon, 17 Jun 2013 07:03:10 +0200
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	linux-kernel@...r.kernel.org,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [PATCH 3/9] s390: Replace weird use of PTR_RET.

On Sun, Jun 16, 2013 at 02:12:42PM +0930, Rusty Russell wrote:
> Saves repeating "(void __force *)__uptr" but it's less clear.  Using
> the output of PTR_RET() to determine the error rather than just
> testing IS_ERR() is odd.

Ok, if it's confusing I won't mind if it gets changed. I intended to
keep the code as short as possible, but.. ;)

> For example, I *assume* __gptr_to_uptr() never returns NULL?  Because
> the __ret would be 0 for the old code.  The new version is clearer, IMHO:
> it would try to get_user() on that address.

__gptr_to_uptr() could return 0 and it's not an error case. In that case
it should indeed try a to get_user() on that address.

> If you hate this variant, I can just s/PTR_RET/PTR_ERR_OR_ZERO/ instead.

Your patch is fine.

> Cc: Heiko Carstens <heiko.carstens@...ibm.com>
> Cc: Christian Borntraeger <borntraeger@...ibm.com>
> Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
> Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
> ---
>  arch/s390/kvm/gaccess.h | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)

Acked-by: Heiko Carstens <heiko.carstens@...ibm.com>

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