[PATCH V2] memory-hotplug: revert register_page_bootmem_info_node() to empty when platform related code is not implemented

[Lin Feng <linfeng@cn.fujitsu.com>]

Memory-hotplug codes for x86_64 have been implemented by patchset:
https://lkml.org/lkml/2013/1/9/124
While other platforms haven't been completely implemented yet.

If we enable both CONFIG_MEMORY_HOTPLUG_SPARSE and CONFIG_SPARSEMEM_VMEMMAP,
register_page_bootmem_info_node() may be buggy, which is a hotplug generic
function but falling back to call platform related function
register_page_bootmem_memmap().

Other platforms such as powerpc it's not implemented, so on such platforms,
revert them to empty as they were before.

It's implemented by adding a new Kconfig option named
CONFIG_HAVE_BOOTMEM_INFO_NODE, which will be automatically selected by
supported archs(currently only on x86_64).

Reported-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Lin Feng <linfeng@cn.fujitsu.com>
---
ChangeLog v1->v2:
- Add a Kconfig option named HAVE_BOOTMEM_INFO_NODE suggested by Michal, which
  will be automatically selected by supported archs(currently only on x86_64).
---
 mm/Kconfig          |    8 ++++++++
 mm/memory_hotplug.c |    7 +++++++
 2 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/mm/Kconfig b/mm/Kconfig
index 278e3ab..f8c5799 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -162,10 +162,18 @@ config MOVABLE_NODE
 	  Say Y here if you want to hotplug a whole node.
 	  Say N here if you want kernel to use memory on all nodes evenly.
 
+#
+# Only be set on architectures that have completely implemented memory hotplug
+# feature. If you are not sure, don't touch it.
+#
+config HAVE_BOOTMEM_INFO_NODE
+	def_bool n
+
 # eventually, we can have this option just 'select SPARSEMEM'
 config MEMORY_HOTPLUG
 	bool "Allow for memory hot-add"
 	select MEMORY_ISOLATION
+	select HAVE_BOOTMEM_INFO_NODE if X86_64
 	depends on SPARSEMEM || X86_64_ACPI_NUMA
 	depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG
 	depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 8aa2b56..ef7a5c8 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -189,6 +189,7 @@ static void register_page_bootmem_info_section(unsigned long start_pfn)
 }
 #endif
 
+#ifdef CONFIG_HAVE_BOOTMEM_INFO_NODE
 void register_page_bootmem_info_node(struct pglist_data *pgdat)
 {
 	unsigned long i, pfn, end_pfn, nr_pages;
@@ -230,6 +231,12 @@ void register_page_bootmem_info_node(struct pglist_data *pgdat)
 			register_page_bootmem_info_section(pfn);
 	}
 }
+#else
+void register_page_bootmem_info_node(struct pglist_data *pgdat)
+{
+	/* TODO */
+}
+#endif
 
 static void grow_zone_span(struct zone *zone, unsigned long start_pfn,
 			   unsigned long end_pfn)
-- 
1.7.1

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