ARM: Fix sparsemem with SPARSEMEM_EXTREME enabled

When SPARSEMEM_EXTREME is enabled, memory_present() wants to use bootmem
to allocate data structures.  However, we call memory_present() after
declaring memory to bootmem, but before we've reserved areas.

This leads to sparsemem data structures being overwritten later in the
kernel's initialization (when slab initializes.)

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/init.c

@@ -273,7 +273,6 @@ static void __init bootmem_init_node(int node, struct meminfo *mi,
 		struct membank *bank = &mi->bank[i];
 		if (!bank->highmem)
 			free_bootmem_node(pgdat, bank_phys_start(bank), bank_phys_size(bank));
-		memory_present(node, bank_pfn_start(bank), bank_pfn_end(bank));
 	}
 
 	/*
@@ -370,6 +369,19 @@ int pfn_valid(unsigned long pfn)
 	return 0;
 }
 EXPORT_SYMBOL(pfn_valid);
+
+static void arm_memory_present(struct meminfo *mi, int node)
+{
+}
+#else
+static void arm_memory_present(struct meminfo *mi, int node)
+{
+	int i;
+	for_each_nodebank(i, mi, node) {
+		struct membank *bank = &mi->bank[i];
+		memory_present(node, bank_pfn_start(bank), bank_pfn_end(bank));
+	}
+}
 #endif
 
 static int __init meminfo_cmp(const void *_a, const void *_b)
@@ -427,6 +439,12 @@ void __init bootmem_init(void)
 		 */
 		if (node == initrd_node)
 			bootmem_reserve_initrd(node);
+
+		/*
+		 * Sparsemem tries to allocate bootmem in memory_present(),
+		 * so must be done after the fixed reservations
+		 */
+		arm_memory_present(mi, node);
 	}
 
 	/*