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

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Message-Id: <20060804094443.c6f09de6.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Fri, 4 Aug 2006 09:44:43 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	kmannth@...ibm.com
Cc:	linux-kernel@...r.kernel.org, lhms-devel@...ts.sourceforge.net,
	y-goto@...fujitsu.com, akpm@...l.org
Subject: Re: [PATCH] memory hotadd fixes [4/5] avoid check in acpi

On Thu, 03 Aug 2006 17:13:16 -0700
keith mannthey <kmannth@...ibm.com> wrote:

> 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. 
> 
Hmm..Okay. I'll try some check patch today. please review it.
Maybe moving ioresouce collision check in early stage of add_memory() is good ?

Note:
I remove pfn_valid() here because pfn_valid() just says section exists or
not. When adding seveal small memory chunks in one section, Only the  first
small chunk can be added. 

Thanks,
-Kame


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