Re: [PATCH] populated_map: fix !NUMA case, remove comment

[Nishanth Aravamudan <nacc@us.ibm.com>]

On 12.06.2007 [12:58:16 -0700], Christoph Lameter wrote:
> On Tue, 12 Jun 2007, Christoph Lameter wrote:
> 
> > Uhhh... Right there is another special case. The recently 
> > introduces zonelist swizzle makes the DMA zone come last and if a 
> > node had only a DMA zone then it may become swizzled to the end of 
> > the zonelist.
> 
> Maybe we can ignore that case for now:
> 
> 
> Fix GFP_THISNODE behavior for memoryless nodes
> 
> GFP_THISNODE checks that the zone selected is within the pgdat (node) of the
> first zone of a nodelist. That only works if the node has memory. A
> memoryless node will have its first node on another pgdat (node).
> 
> GFP_THISNODE currently will return simply memory on the first pgdat.
> Thus it is returning memory on other nodes. GFP_THISNODE should fail
> if there is no local memory on a node.
> 
> So we add a check to verify that the node specified has memory in
> alloc_pages_node(). If the node has no memory then return NULL.
> 
> The case of alloc_pages(GFP_THISNODE) is not changed. alloc_pages() (with no memory
> policies in effect)
> 
> Signed-off-by: Christoph Lameter <clameter@sgi.com>
> Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
> 
> Index: linux-2.6.22-rc4-mm2/include/linux/gfp.h
> ===================================================================
> --- linux-2.6.22-rc4-mm2.orig/include/linux/gfp.h	2007-06-12 12:33:37.000000000 -0700
> +++ linux-2.6.22-rc4-mm2/include/linux/gfp.h	2007-06-12 12:38:37.000000000 -0700
> @@ -175,6 +175,13 @@ static inline struct page *alloc_pages_n
>  	if (nid < 0)
>  		nid = numa_node_id();
> 
> +	/*
> +	 * Check for the special case that GFP_THISNODE is used on a
> +	 * memoryless node
> +	 */
> +	if ((gfp_mask & __GFP_THISNODE) && !node_memory(nid))
> +		return NULL;
> +

Yep, this seems to be the right thing to do, and was in my rolled-up
patch.

Thanks,
Nish

-- 
Nishanth Aravamudan <nacc@us.ibm.com>
IBM Linux Technology Center

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