linux-kernel - Re: [Xen-devel] [PATCH 3/3 v2] xen/xenbus: Improve failure processing code for __xenbus_switch

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Date:	Tue, 23 Sep 2014 09:56:17 +0800
From:	Chen Gang <gang.chen.5i5j@...il.com>
To:	David Vrabel <david.vrabel@...rix.com>
CC:	konrad.wilk@...cle.com, boris.ostrovsky@...cle.com,
	stefano.stabellini@...citrix.com, mukesh.rathor@...cle.com,
	xen-devel@...ts.xenproject.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH 3/3 v2] xen/xenbus: Improve failure processing
 code for __xenbus_switch_state()

On 9/23/14 0:01, David Vrabel wrote:
> On 22/09/14 16:51, Chen Gang wrote:
>> On 09/22/2014 11:04 PM, David Vrabel wrote:
>>> On 18/09/14 15:01, Chen Gang wrote:
>>>> When failure occurs, need return failure code instead of 0, or some of
>>>> indirect upper callers may misunderstand.
>>>>
>>>> e.g. in "block/xen-blkback/xenbus.c":
>>>>
>>>>     connect() -> xenbus_switch_state() -> __xenbus_switch_state().
>>>
>>> Can you make xenbus_switch_state() void?  The callers don't need to do
>>> any error handling.
>>>
>>
>> After "grep rn xenbus_switch_state *" under "drivers/", it is not one
>> place to check the return value of xenbus_switch_state(), and also it
>> is export to outside for individual modules.
>>
>> So we need change many subsystems for it, and also need face the rick
>> for incompatible with the old individual modules which source code are
>> not in upstream.
> 
> Having to update 9 callers doesn't seem like much work.
> 

OK, thanks, and I guess, we need not care about the individual modules
which source code are not in upstream.

>> And are you sure the caller need not notice about it, when it really
>> fails? (for me, I guess they need notice about it)
> 
> Yes.  xenbus_switch_state() already signals the fatal error to the
> toolstack with xenbus_dev_fatal().
> 

OK, what you said sound reasonable to me, I shall send patch v3 for it
within this week (do not consider about the individual modules which
source code are not in upstream).


Thanks.
-- 
Chen Gang

Open, share, and attitude like air, water, and life which God blessed
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