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Date: Fri, 18 Jan 2008 13:43:45 -0800 (PST)
From: Christoph Lameter <clameter@sgi.com>
To: Mel Gorman <mel@csn.ul.ie>
Subject: Re: crash in kmem_cache_init
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Cc: linuxppc-dev@ozlabs.org, Olaf Hering <olaf@aepfle.de>,
	Pekka Enberg <penberg@cs.helsinki.fi>,
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On Fri, 18 Jan 2008, Mel Gorman wrote:

> static void check_for_regular_memory(pg_data_t *pgdat)
> {
> #ifdef CONFIG_HIGHMEM
>         enum zone_type zone_type;
> 
>         for (zone_type = 0; zone_type <= ZONE_NORMAL; zone_type++) {
>                 struct zone *zone = &pgdat->node_zones[zone_type];
>                 if (zone->present_pages)
>                         node_set_state(zone_to_nid(zone), N_NORMAL_MEMORY);
>         }
> #endif
> }
> 
> i.e. go through the other zones and if any of them have memory, set
> N_NORMAL_MEMORY. But... it only does this on CONFIG_HIGHMEM which on
> PPC64 is not going to be set so N_NORMAL_MEMORY never gets set on
> POWER.... That sounds bad.

Argh. We may need to do a

node_set_state(zone_to_nid(zone), N_NORMAL_MEMORY) in the !HIGHMEM case.

> and one of them is in kmem_cache_init(). That seems very significant.
> Christoph, can you think of possibilities of where N_NORMAL_MEMORY not
> being set would cause trouble for slab?

Yes. That results in the per node structures not being created and thus l3 
== NULL. Explains our failures.