Bug fix in slab.c:alloc_arraycache

["Chen, Kenneth W" <kenneth.w.chen@intel.com>]

Kmem_cache_alloc_node is not capable of handling a null cachep
pointer as its input argument.

If I try to increase a slab limit by echoing a very large number
into /proc/slabinfo, kernel will panic from alloc_arraycache()
because Kmem_find_general_cachep() can actually return a NULL
pointer if the size argument is sufficiently large.

Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>


--- linux-2.6.11/mm/slab.c	Mon Oct 18 14:55:43 2004
+++ linux-2.6.11.ken/mm/slab.c	Tue Mar  1 19:14:07 2005
@@ -643,8 +645,10 @@
 	struct array_cache *nc = NULL;

 	if (cpu != -1) {
-		nc = kmem_cache_alloc_node(kmem_find_general_cachep(memsize,
-					GFP_KERNEL), cpu_to_node(cpu));
+		kmem_cache_t * cachep;
+		cachep = kmem_find_general_cachep(memsize, GFP_KERNEL);
+		if (cachep)
+			nc = kmem_cache_alloc_node(cachep, cpu_to_node(cpu));
 	}
 	if (!nc)
 		nc = kmalloc(memsize, GFP_KERNEL);