linux-kernel - Re: [PATCH] mm: Fix memory hotplug oops from ZONE

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Message-Id: <20070720162152.25c929bf.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Fri, 20 Jul 2007 16:21:52 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Paul Mundt <lethal@...ux-sh.org>
Cc:	Mel Gorman <mel@....ul.ie>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: Fix memory hotplug oops from ZONE_MOVABLE changes.

On Fri, 20 Jul 2007 15:03:42 +0900
Paul Mundt <lethal@...ux-sh.org> wrote:

> zone_movable_pfn is presently marked as __initdata and referenced
> from adjust_zone_range_for_zone_movable(), which in turn is
> referenced by zone_spanned_pages_in_node(). Both of these are
> __meminit annotated. When memory hotplug is enabled, this will oops
> on a hot-add, due to zone_movable_pfn having been freed.
> 
> __meminitdata annotation gives the desired behaviour.
> 
> This will only impact platforms that enable both memory hotplug
> and ARCH_POPULATES_NODE_MAP.
> 
> Signed-off-by: Paul Mundt <lethal@...ux-sh.org>
> 
Thank you for catching.
It seems that this route will called at node-hotplug.
We tested node hotplug with our machine but haven't seen this.

The reason is maybe...
==
Currently, our firmware shows *to-be-added* nodes in SRAT at boot and
ia64 creates empty node against possible node. So, when we add node,
pgdat is already allocated and free_area_init_core() is not called at hotplug.
==
We need to use dummy firmware to test this route, sorry.

just thinking of:
I'm now considering to post patches for "specifies a zone which all hotaddes pages are
added to, MOVABLE, NORMAL, DMA..."If we do that, we may be able to avoid calling 
adjust_zone_range_for_zone_movable() (which touches this __meminit data) at hot-add.

Thanks,
-Kame

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