Re: [PATCH v2 3/3] mm/hwpoison: fix return value of madvise_hwpoison

[Wanpeng Li <liwanp@linux.vnet.ibm.com>]

Hi Chen,
On Tue, Aug 27, 2013 at 03:37:01AM -0400, Chen Gong wrote:
>On Mon, Aug 26, 2013 at 11:41:36PM -0400, Naoya Horiguchi wrote:
>> Date: Mon, 26 Aug 2013 23:41:36 -0400
>> From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
>> To: Wanpeng Li <liwanp@linux.vnet.ibm.com>
>> Cc: Andrew Morton <akpm@linux-foundation.org>, Andi Kleen
>>  <andi@firstfloor.org>, Fengguang Wu <fengguang.wu@intel.com>, Tony Luck
>>  <tony.luck@intel.com>, gong.chen@linux.intel.com, linux-mm@kvack.org,
>>  linux-kernel@vger.kernel.org
>> Subject: Re: [PATCH v2 3/3] mm/hwpoison: fix return value of
>>  madvise_hwpoison
>> User-Agent: Mutt 1.5.21 (2010-09-15)
>> 
>> On Tue, Aug 27, 2013 at 11:38:27AM +0800, Wanpeng Li wrote:
>> > Hi Naoya,
>> > On Mon, Aug 26, 2013 at 11:28:16PM -0400, Naoya Horiguchi wrote:
>> > >On Tue, Aug 27, 2013 at 10:39:31AM +0800, Wanpeng Li wrote:
>> > >> The return value outside for loop is always zero which means madvise_hwpoison 
>> > >> return success, however, this is not truth for soft_offline_page w/ failure
>> > >> return value.
>> > >
>> > >I don't understand what you want to do for what reason. Could you clarify
>> > >those?
>> > 
>> > int ret is defined in two place in madvise_hwpoison. One is out of for
>> > loop and its value is always zero(zero means success for madvise), the 
>> > other one is in for loop. The soft_offline_page function maybe return 
>> > -EBUSY and break, however, the ret out of for loop is return which means 
>> > madvise_hwpoison success. 
>> 
>> Oh, I see. Thanks.
>> 
>I don't think such change is a good idea. The original code is obviously
>easy to confuse people. Why not removing redundant local variable?
>

I think the trick here is get_user_pages_fast will return the number of
pages pinned. It is always 1 in madvise_hwpoison, the return value of
memory_failure is ignored. Therefore we still need to reset ret to 0
before return madvise_hwpoison.

Regards,
Wanpeng Li

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