Subject: [PATCH] x86, mm: put memory block size probing back

commit bdee237c0343 ("x86: mm: Use 2GB memory block size on large-memory x86-64 systems")
let system with more than 64GiB ram just use 2G as memory block
size without probing.

found one system: has memory map like:
[0x00000000-0x60000000)
[0x100000000-0x20a0000000)

We should use 0x20000000 in this case. So can not assume system with big
memory have 2g tail anymore.

So revert it to put probing back.

Fixes: bdee237c0343 ("x86: mm: Use 2GB memory block size on large-memory x86-64 systems")
Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 arch/x86/mm/init_64.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

Index: linux-2.6/arch/x86/mm/init_64.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/init_64.c
+++ linux-2.6/arch/x86/mm/init_64.c
@@ -52,6 +52,7 @@
 #include <asm/numa.h>
 #include <asm/cacheflush.h>
 #include <asm/init.h>
+#include <asm/uv/uv.h>
 #include <asm/setup.h>
 
 #include "mm_internal.h"
@@ -1204,10 +1205,12 @@ static unsigned long probe_memory_block_
 	/* start from 2g */
 	unsigned long bz = 1UL<<31;
 
-	if (totalram_pages >= (64ULL << (30 - PAGE_SHIFT))) {
-		pr_info("Using 2GB memory block size for large-memory system\n");
+#ifdef CONFIG_X86_UV
+	if (is_uv_system()) {
+		printk(KERN_INFO "UV: memory block size 2GB\n");
 		return 2UL * 1024 * 1024 * 1024;
 	}
+#endif
 
 	/* less than 64g installed */
 	if ((max_pfn << PAGE_SHIFT) < (16UL << 32))