linux-kernel - Re: [patch 2/5] sparse-vmemmap: specify vmemmap population range in bytes

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Date:	Wed, 20 Mar 2013 14:43:41 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	hannes@...xchg.org
Cc:	x86@...nel.org, akpm@...ux-foundation.org, ben@...adent.org.uk,
	linux-mm@...ck.org, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 2/5] sparse-vmemmap: specify vmemmap population range
 in bytes

From: Johannes Weiner <hannes@...xchg.org>
Date: Wed, 20 Mar 2013 14:03:29 -0400

> The sparse code, when asking the architecture to populate the vmemmap,
> specifies the section range as a starting page and a number of pages.
> 
> This is an awkward interface, because none of the arch-specific code
> actually thinks of the range in terms of 'struct page' units and
> always translates it to bytes first.
> 
> In addition, later patches mix huge page and regular page backing for
> the vmemmap.  For this, they need to call vmemmap_populate_basepages()
> on sub-section ranges with PAGE_SIZE and PMD_SIZE in mind.  But these
> are not necessarily multiples of the 'struct page' size and so this
> unit is too coarse.
> 
> Just translate the section range into bytes once in the generic sparse
> code, then pass byte ranges down the stack.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Boot tested on sparc64:

Acked-by: David S. Miller <davem@...emloft.net>
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