linux-kernel - Re: [RFC v8 PATCH 08/20] memory-hotplug: remove /sys/firmware/memmap/X sysfs

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Date:	Wed, 05 Sep 2012 09:41:06 +0800
From:	Wen Congyang <wency@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	x86@...nel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-acpi@...r.kernel.org,
	linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
	linux-ia64@...r.kernel.org, cmetcalf@...era.com,
	sparclinux@...r.kernel.org, rientjes@...gle.com, liuj97@...il.com,
	len.brown@...el.com, benh@...nel.crashing.org, paulus@...ba.org,
	cl@...ux.com, minchan.kim@...il.com,
	kosaki.motohiro@...fujitsu.com, isimatu.yasuaki@...fujitsu.com,
	Christoph Lameter <cl@...ux-foundation.org>
Subject: Re: [RFC v8 PATCH 08/20] memory-hotplug: remove /sys/firmware/memmap/X
 sysfs

At 09/05/2012 07:16 AM, Andrew Morton Wrote:
> On Mon, 03 Sep 2012 13:51:10 +0800
> Wen Congyang <wency@...fujitsu.com> wrote:
> 
>>>> +static void release_firmware_map_entry(struct kobject *kobj)
>>>> +{
>>>> +	struct firmware_map_entry *entry = to_memmap_entry(kobj);
>>>> +	struct page *page;
>>>> +
>>>> +	page = virt_to_page(entry);
>>>> +	if (PageSlab(page) || PageCompound(page))
>>>
>>> That PageCompound() test looks rather odd.  Why is this done?
>>
>> Liu Jiang and Christoph Lameter discussed how to find slab page
>> in this mail:
>> https://lkml.org/lkml/2012/7/6/333.
> 
> Well, please add a code comment to release_firmware_map_entry() which
> fully explains these things.
> 
> I see that Christoph and I agree: "It would be cleaner if memory
> hotplug had an indicator which allocation mechanism was used and would
> use the corresponding free action".  You didn't respond to this
> suggestion when he made it, nor when I made it.  What are your thoughts
> on this?

Hmm, I think it is better to use an indicator which allocation mechanism was
used. I will do it in the next version.

Thanks
Wen Congyang
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