Message-ID: <4D08899F.4050502@akana.de>
Date: Wed, 15 Dec 2010 10:25:51 +0100
From: Ingo Korb <ingo@akana.de>
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To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
CC: linux-mm@kvack.org, akpm@linux-foundation.org, mel@csn.ul.ie,
        cl@linux-foundation.org, yinghai@kernel.org, andi.kleen@intel.com,
        linux-kernel@vger.kernel.org
Subject: Re: PROBLEM: __offline_isolated_pages may offline too many pages
References: <4D0786D3.7070007@akana.de> <20101215092134.e2c8849f.kamezawa.hiroyu@jp.fujitsu.com>
In-Reply-To: <20101215092134.e2c8849f.kamezawa.hiroyu@jp.fujitsu.com>
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On 15.12.2010 01:21, KAMEZAWA Hiroyuki wrote:

> It's designed for offline memory section>  MAX_ORDER. pageblock_nr_pages
> is tend to be smaller than that.
>
> Do you see the problem with _exsisting_ user interface of memory hotplug ?
> I think we have no control other than memory section.

The existing, exported interface (remove_memory() - the check itself is 
in offline_pages()) only checks if both start and end of the 
to-be-removed block are aligned to pageblock_nr_pages. As you noted the 
actual size and alignment requirements in __offline_isolated_pages can 
be larger that that, so I think the checks in offline_pages() should be 
changed (if 1<<MAX_ORDER is always >= pageblock_nr_pages) or extended 
(if there can be any relation between the two).

-ik
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