Re: [ RESEND PATCH v3] Memory-Hotplug: Fix the bug on interface/dev/mem for 64-bit kernel

From: Wu Fengguang
Date: Thu Jan 14 2010 - 08:58:16 EST


On Tue, Jan 12, 2010 at 05:04:33PM +0900, KAMEZAWA Hiroyuki wrote:

> 3 points...
> 1. I think this patch cannot be compiled in archs other than x86. Right ?
> IOW, please add static inline dummy...

Good catch!

> 2. pgdat->[start,end], totalram_pages etc...are updated at memory hotplug.
> Please place the hook nearby them.

arch/x86/mm/init_64.c:arch_add_memory() updates max_pfn_mapped, in
this sense it's equally OK to update max_pfn/max_low_pfn etc before
the call to arch_add_memory() ;)

> 3. I recommend you yo use memory hotplug notifier.
> If it's allowed, it will be cleaner.

Hmm, notifier is for _outsider_ subsystems. It smells a bit
overkill to do notifier _inside_ the hotplug code.

> It seems there are no strict ordering to update parameters this patch touches.

I tend to agree. That said, it does help keep our mind straight if we do it
in some logical order: max_pfn => max_pfn_mapped => totalram_pages etc.

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