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

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Message-Id: <1154656472.5925.71.camel@keithlap>
Date:	Thu, 03 Aug 2006 18:54:32 -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, andrew <akpm@...l.org>
Subject: Re: [PATCH] memory hotadd fixes [4/5] avoid check in acpi

On Fri, 2006-08-04 at 09:44 +0900, KAMEZAWA Hiroyuki wrote:
> 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 ?
  Yea.  I am working a a full patch set for but my sparsemem and reserve
add-based paths.  It creates a valid_memory_add_range call at the start
of add_memory. I should be posting the set in the next few hours.

> 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. 
Hmm... I thought memory add areas needed to be section aligned for the arch?

  What protecting is there for calling add_memory on an already present
memory range?  


Thanks,
  Keith 


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