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

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Date:	Thu, 03 Aug 2006 11:28:44 -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>
> 
> 
>  drivers/acpi/acpi_memhotplug.c |    9 +--------
>  1 files changed, 1 insertion(+), 8 deletions(-)
> 
> Index: linux-2.6.18-rc3/drivers/acpi/acpi_memhotplug.c
> ===================================================================
> --- linux-2.6.18-rc3.orig/drivers/acpi/acpi_memhotplug.c	2006-08-01 16:11:47.000000000 +0900
> +++ linux-2.6.18-rc3/drivers/acpi/acpi_memhotplug.c	2006-08-02 14:12:45.000000000 +0900
> @@ -230,17 +230,10 @@
>  	 * (i.e. memory-hot-remove function)
>  	 */
>  	list_for_each_entry(info, &mem_device->res_list, list) {
> -		u64 start_pfn, end_pfn;
> -
> -		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)) {
> -			/* already enabled. try next area */
> +		if (info->enabled) { /* just sanity check...*/
>  			num_enabled++;
>  			continue;
>  		}

This check needs to go.  pfn_valid is a sparsemem specific check. Sanity
checking should be done it the the add_memory code. 

I will test and let you know. This is going to expose some baddness I
see already with my RESERVE path work. (Extra add_memory calls from this
driver during boot....)


Thanks,
keith mannthey <kmannth@...ibm.com>
Linux Technology Center IBM

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