Re: [RFC PATCH 2/12] memory-hogplug : check memory offline in offline_pages

[Yasuaki Ishimatsu]

Hi Kosaki-san,

2012/06/28 14:27, KOSAKI Motohiro wrote:
> On Thu, Jun 28, 2012 at 1:06 AM, Yasuaki Ishimatsu
> <isimatu.yasuaki@xxxxxxxxxxxxxx> wrote:
> > Hi Wen,
> >
> > 2012/06/27 17:49, Wen Congyang wrote:
> > > At 06/27/2012 01:44 PM, Yasuaki Ishimatsu Wrote:
> > > > When offline_pages() is called to offlined memory, the function fails since
> > > > all memory has been offlined. In this case, the function should succeed.
> > > > The patch adds the check function into offline_pages().
> > >
> > > You miss such case: some pages are online, while some pages are offline.
> > > offline_pages() will fail too in such case.
> >
> > You are right. But current code fails, when the function is called to offline
> > memory. In this case, the function should succeed. So the patch confirms
> > whether the memory was offlined or not. And if memory has already been
> > offlined, offline_pages return 0.
>
> Can you please explain why the caller can't check it? I hope to avoid
> an ignorance
> as far as we can.

Of course, caller side can check it. But there is a possibility that
offline_pages() is called by many functions. So I do not think that it
is good that all functions which call offline_pages() check it.

Thanks,
Yasuaki Ishimatsu

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