[patch 2/2] enables booting a NUMA system where some nodes have no memory

[Christian Krafft <krafft@de.ibm.com>]

When booting a NUMA system with nodes that have no memory (eg by limiting memory),
bootmem_alloc_core tried to find pages in an uninitialized bootmem_map.
This caused a null pointer access.
This fix adds a check, so that NULL is returned.
That will enable the caller (bootmem_alloc_nopanic)
to alloc memory on other without a panic.

Signed-off-by: Christian Krafft <krafft@de.ibm.com>

Index: linux/mm/bootmem.c
===================================================================
--- linux.orig/mm/bootmem.c
+++ linux/mm/bootmem.c
@@ -196,6 +196,10 @@ __alloc_bootmem_core(struct bootmem_data
 	if (limit && bdata->node_boot_start >= limit)
 		return NULL;
 
+	/* on nodes without memory - bootmem_map is NULL */
+	if(!bdata->node_bootmem_map)
+		return NULL;
+
 	end_pfn = bdata->node_low_pfn;
 	limit = PFN_DOWN(limit);
 	if (limit && end_pfn > limit)