memblock: Allow memblock_init to be called early

The Xen setup code needs to call memblock_x86_reserve_range() very early,
so allow it to initialize the memblock subsystem before doing so. The
second memblock_init() is ignored.

Signed-off-by: Jeremy Fitzhardinge <[e-mail]>
Cc: Yinghai Lu <[e-mail]>
Cc: Benjamin Herrenschmidt <[e-mail]>
LKML-Reference: <[e-mail]>
Signed-off-by: H. Peter Anvin <[e-mail]>

arch/x86/xen/enlighten.c

···
 #include <linux/console.h>
 #include <linux/pci.h>
 #include <linux/gfp.h>
+#include <linux/memblock.h>
 
 #include <xen/xen.h>
 #include <xen/interface/xen.h>
···
 
 	local_irq_disable();
 	early_boot_irqs_off();
+
+	memblock_init();
 
 	xen_raw_console_write("mapping kernel into physical memory\n");
 	pgd = xen_setup_kernel_pagetable(pgd, xen_start_info->nr_pages);

mm/memblock.c

···
 
 void __init memblock_init(void)
 {
+	static int init_done __initdata = 0;
+
+	if (init_done)
+		return;
+	init_done = 1;
+
 	/* Hookup the initial arrays */
 	memblock.memory.regions	= memblock_memory_init_regions;
 	memblock.memory.max		= INIT_MEMBLOCK_REGIONS;