[PATCH v4 4/5] mm: make processing of movable_node arch-specific

[Reza Arbab]

Currently, CONFIG_MOVABLE_NODE depends on X86_64. In preparation to
enable it for other arches, we need to factor a detail which is unique
to x86 out of the generic mm code.

Specifically, as documented in kernel-parameters.txt, the use of
"movable_node" should remain restricted to x86:

movable_node    [KNL,X86] Boot-time switch to enable the effects
                of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.

This option tells x86 to find movable nodes identified by the ACPI SRAT.
On other arches, it would have no benefit, only the undesired side
effect of setting bottom-up memblock allocation.

Since #ifdef CONFIG_MOVABLE_NODE will no longer be enough to restrict
this option to x86, move it to an arch-specific compilation unit
instead.

Signed-off-by: Reza Arbab <arbab@xxxxxxxxxxxxxxxxxx>
---
 arch/x86/mm/numa.c  | 35 ++++++++++++++++++++++++++++++++++-
 mm/memory_hotplug.c | 31 -------------------------------
 2 files changed, 34 insertions(+), 32 deletions(-)

diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
index fb68210..e95cab4 100644
--- a/arch/x86/mm/numa.c
+++ b/arch/x86/mm/numa.c
@@ -887,6 +887,38 @@ EXPORT_SYMBOL(cpumask_of_node);
 #endif	/* !CONFIG_DEBUG_PER_CPU_MAPS */
 
 #ifdef CONFIG_MEMORY_HOTPLUG
+
+static int __init cmdline_parse_movable_node(char *p)
+{
+#ifdef CONFIG_MOVABLE_NODE
+	/*
+	 * Memory used by the kernel cannot be hot-removed because Linux
+	 * cannot migrate the kernel pages. When memory hotplug is
+	 * enabled, we should prevent memblock from allocating memory
+	 * for the kernel.
+	 *
+	 * ACPI SRAT records all hotpluggable memory ranges. But before
+	 * SRAT is parsed, we don't know about it.
+	 *
+	 * The kernel image is loaded into memory at very early time. We
+	 * cannot prevent this anyway. So on NUMA system, we set any
+	 * node the kernel resides in as un-hotpluggable.
+	 *
+	 * Since on modern servers, one node could have double-digit
+	 * gigabytes memory, we can assume the memory around the kernel
+	 * image is also un-hotpluggable. So before SRAT is parsed, just
+	 * allocate memory near the kernel image to try the best to keep
+	 * the kernel away from hotpluggable memory.
+	 */
+	memblock_set_bottom_up(true);
+	movable_node_enabled = true;
+#else
+	pr_warn("movable_node option not supported\n");
+#endif
+	return 0;
+}
+early_param("movable_node", cmdline_parse_movable_node);
+
 int memory_add_physaddr_to_nid(u64 start)
 {
 	struct numa_meminfo *mi = &numa_meminfo;
@@ -899,4 +931,5 @@ int memory_add_physaddr_to_nid(u64 start)
 	return nid;
 }
 EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid);
-#endif
+
+#endif /* CONFIG_MEMORY_HOTPLUG */
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 9d29ba0..79c709a 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1738,37 +1738,6 @@ static bool can_offline_normal(struct zone *zone, unsigned long nr_pages)
 }
 #endif /* CONFIG_MOVABLE_NODE */
 
-static int __init cmdline_parse_movable_node(char *p)
-{
-#ifdef CONFIG_MOVABLE_NODE
-	/*
-	 * Memory used by the kernel cannot be hot-removed because Linux
-	 * cannot migrate the kernel pages. When memory hotplug is
-	 * enabled, we should prevent memblock from allocating memory
-	 * for the kernel.
-	 *
-	 * ACPI SRAT records all hotpluggable memory ranges. But before
-	 * SRAT is parsed, we don't know about it.
-	 *
-	 * The kernel image is loaded into memory at very early time. We
-	 * cannot prevent this anyway. So on NUMA system, we set any
-	 * node the kernel resides in as un-hotpluggable.
-	 *
-	 * Since on modern servers, one node could have double-digit
-	 * gigabytes memory, we can assume the memory around the kernel
-	 * image is also un-hotpluggable. So before SRAT is parsed, just
-	 * allocate memory near the kernel image to try the best to keep
-	 * the kernel away from hotpluggable memory.
-	 */
-	memblock_set_bottom_up(true);
-	movable_node_enabled = true;
-#else
-	pr_warn("movable_node option not supported\n");
-#endif
-	return 0;
-}
-early_param("movable_node", cmdline_parse_movable_node);
-
 /* check which state of node_states will be changed when offline memory */
 static void node_states_check_changes_offline(unsigned long nr_pages,
 		struct zone *zone, struct memory_notify *arg)
-- 
1.8.3.1