IA64: SPARSEMEM_VMEMMAP 16K page size support

Equip IA64 sparsemem with a virtual memmap.  This is similar to the existing
CONFIG_VIRTUAL_MEM_MAP functionality for DISCONTIGMEM.  It uses a PAGE_SIZE
mapping.

This is provided as a minimally intrusive solution.  We split the 128TB
VMALLOC area into two 64TB areas and use one for the virtual memmap.

This should replace CONFIG_VIRTUAL_MEM_MAP long term.

[apw@shadowen.org: convert to new helper based initialisation]
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NAndy Whitcroft <apw@shadowen.org>
Acked-by: NMel Gorman <mel@csn.ul.ie>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/ia64/Kconfig

@@ -348,6 +348,7 @@ config ARCH_FLATMEM_ENABLE
 config ARCH_SPARSEMEM_ENABLE
 	def_bool y
 	depends on ARCH_DISCONTIGMEM_ENABLE
+	select SPARSEMEM_VMEMMAP_ENABLE
 
 config ARCH_DISCONTIGMEM_DEFAULT
 	def_bool y if (IA64_SGI_SN2 || IA64_GENERIC || IA64_HP_ZX1 || IA64_HP_ZX1_SWIOTLB)

arch/ia64/mm/discontig.c

@@ -715,3 +715,11 @@ void arch_refresh_nodedata(int update_node, pg_data_t *update_pgdat)
 	scatter_node_data();
 }
 #endif
+
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+int __meminit vmemmap_populate(struct page *start_page,
+						unsigned long size, int node)
+{
+	return vmemmap_populate_basepages(start_page, size, node);
+}
+#endif

include/asm-ia64/pgtable.h

@@ -236,8 +236,14 @@ ia64_phys_addr_valid (unsigned long addr)
 # define VMALLOC_END		vmalloc_end
   extern unsigned long vmalloc_end;
 #else
+#if defined(CONFIG_SPARSEMEM) && defined(CONFIG_SPARSEMEM_VMEMMAP)
+/* SPARSEMEM_VMEMMAP uses half of vmalloc... */
+# define VMALLOC_END		(RGN_BASE(RGN_GATE) + (1UL << (4*PAGE_SHIFT - 10)))
+# define vmemmap		((struct page *)VMALLOC_END)
+#else
 # define VMALLOC_END		(RGN_BASE(RGN_GATE) + (1UL << (4*PAGE_SHIFT - 9)))
 #endif
+#endif
 
 /* fs/proc/kcore.c */
 #define	kc_vaddr_to_offset(v) ((v) - RGN_BASE(RGN_GATE))