Re: SLUB ia64 linux-next crash bisected to 756dee75

[Lee Schermerhorn <Lee.Schermerhorn@hp.com>]

On Fri, 2010-01-15 at 14:07 -0600, Christoph Lameter wrote:
> Another stab at the problem:
> 
> We have the following code in init_kmem_cache_nodes()
> 
>   if (slab_state >= UP)
>                 local_node = page_to_nid(virt_to_page(s));
>         else
>                 local_node = 0;
> 
> 
> If the slab bootstrap is complete (UP) (which is the case here) then
> the structure pointing to by s was allocated using kmalloc itself. So
> virt_to_page() works for the typical.
> 
> The changeset results in the use of a statically allocated structure
> after boot is complete. Now page_to_nid(virt_to_page(s)) runs on a
> global data address.
> 
> Could this be problematic for some reasons on IA64?

Dunno.  Alex or I will check and get back to you.

> 
> The following patch makes init_kmem_cache_nodes assume 0
> for statically allocated kmem_cache structures even after
> boot is complete.

I believe that on Alex's platform, the kernel will get loaded into "node
2", the hardware interleaved pseudo-node, because it's located at phys
0..., and has sufficient space.  So, this might not work here.

> 
> Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
> 
> ---
>  mm/slub.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> Index: linux-2.6/mm/slub.c
> ===================================================================
> --- linux-2.6.orig/mm/slub.c	2010-01-15 14:02:54.000000000 -0600
> +++ linux-2.6/mm/slub.c	2010-01-15 14:04:47.000000000 -0600
> @@ -2176,7 +2176,8 @@ static int init_kmem_cache_nodes(struct
>  	int node;
>  	int local_node;
> 
> -	if (slab_state >= UP)
> +	if (slab_state >= UP &&


>  s < kmalloc_caches &&
> +			s > kmalloc_caches + KMALLOC_CACHES)

??? can this ever be so?  for positive KMALLOC_CACHES, I mean...


>  		local_node = page_to_nid(virt_to_page(s));
>  	else
>  		local_node = 0;
> 
> 
> 
> 

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