x86-64, NUMA: Remove %NULL @nodeids handling from compute_hash_shift()

numa_emulation() called compute_hash_shift() with %NULL @nodeids which
meant identity mapping between index and nodeid.  Make
numa_emulation() build identity array and drop %NULL @nodeids handling
from populate_memnodemap() and thus from compute_hash_shift().  This
is to prepare for transition to using memblks instead.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Shaohui Zheng <shaohui.zheng@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/mm/numa_64.c

@@ -63,12 +63,7 @@ static int __init populate_memnodemap(const struct bootnode *nodes,
 		do {
 			if (memnodemap[addr >> shift] != NUMA_NO_NODE)
 				return -1;
-
-			if (!nodeids)
-				memnodemap[addr >> shift] = i;
-			else
 			memnodemap[addr >> shift] = nodeids[i];
-
 			addr += (1UL << shift);
 		} while (addr < end);
 		res = 1;
@@ -706,6 +701,7 @@ static int __init split_nodes_size_interleave(u64 addr, u64 max_addr, u64 size)
 static int __init numa_emulation(unsigned long start_pfn,
 			unsigned long last_pfn, int acpi, int amd)
 {
+	static int nodeid[NR_NODE_MEMBLKS] __initdata;
 	u64 addr = start_pfn << PAGE_SHIFT;
 	u64 max_addr = last_pfn << PAGE_SHIFT;
 	int num_nodes;
@@ -730,7 +726,11 @@ static int __init numa_emulation(unsigned long start_pfn,
 
 	if (num_nodes < 0)
 		return num_nodes;
-	memnode_shift = compute_hash_shift(nodes, num_nodes, NULL);
+
+	for (i = 0; i < ARRAY_SIZE(nodeid); i++)
+		nodeid[i] = i;
+
+	memnode_shift = compute_hash_shift(nodes, num_nodes, nodeid);
 	if (memnode_shift < 0) {
 		memnode_shift = 0;
 		printk(KERN_ERR "No NUMA hash function found.  NUMA emulation "