linux-kernel - Re: [PATCH] memory hotadd fixes [4/5] avoid check in acpi

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Message-Id: <1154650396.5925.49.camel@keithlap>
Date:	Thu, 03 Aug 2006 17:13:16 -0700
From:	keith mannthey <kmannth@...ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	lhms-devel <lhms-devel@...ts.sourceforge.net>,
	"y-goto@...fujitsu.com" <y-goto@...fujitsu.com>,
	Andrew Morton <akpm@...l.org>
Subject: Re: [PATCH] memory hotadd fixes [4/5] avoid check in acpi

On Thu, 2006-08-03 at 12:36 +0900, KAMEZAWA Hiroyuki wrote:
> add_memory() does all necessary check to avoid collision.
> then, acpi layer doesn't have to check region by itself.
> 
> (*) pfn_valid() just returns page struct is valid or not. It returns 0
>     if a section has been already added even is ioresource is not added.
>     ioresource collision check in mm/memory_hotplug.c can do more precise
>     collistion check.
>     added enabled bit check just for sanity check..
> 
> Signed-Off-By: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

> -		start_pfn = info->start_addr >> PAGE_SHIFT;
> -		end_pfn = (info->start_addr + info->length - 1) >> PAGE_SHIFT;
> -
> -		if (pfn_valid(start_pfn) || pfn_valid(end_pfn)) {

This check needs to go somewhare in the add path.  I am thinking of a
validate_add_memory_area call in add_memory (that can also be flexable
to enable the reserve check of (this memory area in add_nodes).  

  It is a useful protection for the sparsemem add path. I would rather
the kernel be able to stand up to odd acpi namespaces or other
mechanisms of invoking add_memory. 

Thanks,
  Keith 

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