linux-kernel - Re: [Xen-devel] [PATCH v3] xen/grant-table: Avoid m2p

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Message-ID: <52E113AE.5060405@citrix.com>
Date:	Thu, 23 Jan 2014 13:05:50 +0000
From:	Zoltan Kiss <zoltan.kiss@...rix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	<ian.campbell@...rix.com>, <wei.liu2@...rix.com>,
	<xen-devel@...ts.xenproject.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <jonathan.davies@...rix.com>
Subject: Re: [Xen-devel] [PATCH v3] xen/grant-table: Avoid m2p_override during
 mapping

On 20/01/14 21:22, Konrad Rzeszutek Wilk wrote:
> Zoltan Kiss <zoltan.kiss@...rix.com> wrote:
>> The grant mapping API does m2p_override unnecessarily: only gntdev
>> needs it,
>> for blkback and future netback patches it just cause a lock contention,
>> as
>> those pages never go to userspace. Therefore this series does the
>> following:
>> - the original functions were renamed to __gnttab_[un]map_refs, with a
>> new
>>   parameter m2p_override
>> - based on m2p_override either they follow the original behaviour, or
>> just set
>>   the private flag and call set_phys_to_machine
>> - gnttab_[un]map_refs are now a wrapper to call __gnttab_[un]map_refs
>> with
>>   m2p_override false
>> - a new function gnttab_[un]map_refs_userspace provides the old
>> behaviour
>
> You don't say anything about the 'return ret' changed to 'return 0'.
>
> Any particular reason for that?

That's the only possible return value there, so it just makes it more 
obvious. I'll add a description about that.

Zoli

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