x86_64: allocate sparsemem memmap above 4G

On systems with huge amount of physical memory, VFS cache and memory memmap
may eat all available system memory under 4G, then the system may fail to
allocate swiotlb bounce buffer.

There was a fix for this issue in arch/x86_64/mm/numa.c, but that fix dose
not cover sparsemem model.

This patch add fix to sparsemem model by first try to allocate memmap above
4G.

Signed-off-by: Zou Nan hai <nanhai.zou@intel.com>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Andi Kleen <ak@suse.de>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/sparse.c b/mm/sparse.c
index 1302f83..545e4d3 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -209,6 +209,12 @@
 	return 1;
 }
 
+__attribute__((weak))
+void *alloc_bootmem_high_node(pg_data_t *pgdat, unsigned long size)
+{
+	return NULL;
+}
+
 static struct page __init *sparse_early_mem_map_alloc(unsigned long pnum)
 {
 	struct page *map;
@@ -219,6 +225,11 @@
 	if (map)
 		return map;
 
+  	map = alloc_bootmem_high_node(NODE_DATA(nid),
+                       sizeof(struct page) * PAGES_PER_SECTION);
+	if (map)
+		return map;
+
 	map = alloc_bootmem_node(NODE_DATA(nid),
 			sizeof(struct page) * PAGES_PER_SECTION);
 	if (map)