[IA64] fix show_mem for VIRTUAL_MEM_MAP+FLATMEM

contig.c (FLATMEM) requires the same optimization as in discontig.c for show_mem
when VIRTUAL_MEM_MAP is in use. Otherwise FLATMEM has softlockup timeouts.
This was boot tested for memory configuration: SPARSEMEM,
DISCONTIG+VIRTUAL_MEM_MAP, FLATMEM, FLATMEM+VIRTUAL_MEM_MAP and
FLATMEM+VIRTUAL_MEM_MAP with largest memory gap less than LARGE_GAP by
using boot parameter "mem=".

This was boot tested and "echo m >/proc/sysrq-trigger" output evaluated for
: FLATMEM, FLATMEM+VIRTUAL_MEM_MAP, DISCONTIGMEM+VIRTUAL_MEM_MAP and
SPARSEMEM.

Signed-off-by: Bob Picco <bob.picco@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
diff --git a/arch/ia64/mm/contig.c b/arch/ia64/mm/contig.c
index 8919fed..e004143 100644
--- a/arch/ia64/mm/contig.c
+++ b/arch/ia64/mm/contig.c
@@ -27,6 +27,7 @@
 
 #ifdef CONFIG_VIRTUAL_MEM_MAP
 static unsigned long num_dma_physpages;
+static unsigned long max_gap;
 #endif
 
 /**
@@ -45,9 +46,15 @@
 
 	printk("Free swap:       %6ldkB\n", nr_swap_pages<<(PAGE_SHIFT-10));
 	i = max_mapnr;
-	while (i-- > 0) {
-		if (!pfn_valid(i))
+	for (i = 0; i < max_mapnr; i++) {
+		if (!pfn_valid(i)) {
+#ifdef CONFIG_VIRTUAL_MEM_MAP
+			if (max_gap < LARGE_GAP)
+				continue;
+			i = vmemmap_find_next_valid_pfn(0, i) - 1;
+#endif
 			continue;
+		}
 		total++;
 		if (PageReserved(mem_map+i))
 			reserved++;
@@ -234,7 +241,6 @@
 	unsigned long zones_size[MAX_NR_ZONES];
 #ifdef CONFIG_VIRTUAL_MEM_MAP
 	unsigned long zholes_size[MAX_NR_ZONES];
-	unsigned long max_gap;
 #endif
 
 	/* initialize mem_map[] */
@@ -266,7 +272,6 @@
 		}
 	}
 
-	max_gap = 0;
 	efi_memmap_walk(find_largest_hole, (u64 *)&max_gap);
 	if (max_gap < LARGE_GAP) {
 		vmem_map = (struct page *) 0;