linux-kernel - Re: [PATCH] sparsemem vmemmap: initialize memmap.

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Date:	Fri, 9 May 2008 13:34:34 +0200
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Andy Whitcroft <apw@...dowen.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <clameter@....com>,
	Gerald Schaefer <gerald.schaefer@...ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] sparsemem vmemmap: initialize memmap.

> > Index: linux-2.6/mm/sparse-vmemmap.c
> > ===================================================================
> > --- linux-2.6.orig/mm/sparse-vmemmap.c
> > +++ linux-2.6/mm/sparse-vmemmap.c
> > @@ -154,6 +154,6 @@ struct page * __meminit sparse_mem_map_p
> >  	int error = vmemmap_populate(map, PAGES_PER_SECTION, nid);
> >  	if (error)
> >  		return NULL;
> > -
> > +	memset(map, 0, PAGES_PER_SECTION * sizeof(struct page));
> >  	return map;
> >  }
> 
> The normal expectation is that all allocations are made using
> vmemmap_alloc_block() which allocates from the appropriate place.  Once
> the buddy is up and available it uses:
> 
> 	struct page *page = alloc_pages_node(node,
> 			GFP_KERNEL | __GFP_ZERO, get_order(size));
> 
> to get the memory so it should all be zero'd.  So I would expect all
> existing users to be covered by that?  Can you not simply use __GFP_ZERO
> for your allocations or use vmemmap_alloc_block() ?

Ah, I didn't notice the __GFP_ZERO. So it's just an s390 bug. Will
move the memset to our code instead.
Thanks!
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