mm/memory_hotplug: introduce add_pages

There are new users of memory hotplug emerging. Some of them require
different subset of arch_add_memory. There are some which only require
allocation of struct pages without mapping those pages to the kernel
address space. We currently have __add_pages for that purpose. But this
is rather lowlevel and not very suitable for the code outside of the
memory hotplug. E.g. x86_64 wants to update max_pfn which should be
done by the caller. Introduce add_pages() which should care about those
details if they are needed. Each architecture should define its
implementation and select CONFIG_ARCH_HAS_ADD_PAGES. All others use
the currently existing __add_pages.

Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>

3 files changed, 30 insertions, 7 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f00fa5176f72..5f3d0ace25b9 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2264,6 +2264,10 @@ source "kernel/livepatch/Kconfig"
 
 endmenu
 
+config ARCH_HAS_ADD_PAGES
+	def_bool y
+	depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
+
 config ARCH_ENABLE_MEMORY_HOTPLUG
 	def_bool y
 	depends on X86_64 || (X86_32 && HIGHMEM)
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 73329300192b..a8a9972d6b71 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -671,7 +671,7 @@ void __init paging_init(void)
  * After memory hotplug the variables max_pfn, max_low_pfn and high_memory need
  * updating.
  */
-static void  update_end_of_memory_vars(u64 start, u64 size)
+static void update_end_of_memory_vars(u64 start, u64 size)
 {
 	unsigned long end_pfn = PFN_UP(start + size);
 
@@ -682,22 +682,30 @@ static void  update_end_of_memory_vars(u64 start, u64 size)
 	}
 }
 
-int arch_add_memory(int nid, u64 start, u64 size, bool want_memblock)
+int add_pages(int nid, unsigned long start_pfn,
+	      unsigned long nr_pages, bool want_memblock)
 {
-	unsigned long start_pfn = start >> PAGE_SHIFT;
-	unsigned long nr_pages = size >> PAGE_SHIFT;
 	int ret;
 
-	init_memory_mapping(start, start + size);
-
 	ret = __add_pages(nid, start_pfn, nr_pages, want_memblock);
 	WARN_ON_ONCE(ret);
 
 	/* update max_pfn, max_low_pfn and high_memory */
-	update_end_of_memory_vars(start, size);
+	update_end_of_memory_vars(start_pfn << PAGE_SHIFT,
+				  nr_pages << PAGE_SHIFT);
 
 	return ret;
 }
+
+int arch_add_memory(int nid, u64 start, u64 size, bool want_memblock)
+{
+	unsigned long start_pfn = start >> PAGE_SHIFT;
+	unsigned long nr_pages = size >> PAGE_SHIFT;
+
+	init_memory_mapping(start, start + size);
+
+	return add_pages(nid, start_pfn, nr_pages, want_memblock);
+}
 EXPORT_SYMBOL_GPL(arch_add_memory);
 
 #define PAGE_INUSE 0xFD
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index c8a5056a5ae0..0c19c38b7f20 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -133,6 +133,17 @@ extern int __remove_pages(struct zone *zone, unsigned long start_pfn,
 extern int __add_pages(int nid, unsigned long start_pfn,
 	unsigned long nr_pages, bool want_memblock);
 
+#ifndef CONFIG_ARCH_HAS_ADD_PAGES
+static inline int add_pages(int nid, unsigned long start_pfn,
+			    unsigned long nr_pages, bool want_memblock)
+{
+	return __add_pages(nid, start_pfn, nr_pages, want_memblock);
+}
+#else /* ARCH_HAS_ADD_PAGES */
+int add_pages(int nid, unsigned long start_pfn,
+	      unsigned long nr_pages, bool want_memblock);
+#endif /* ARCH_HAS_ADD_PAGES */
+
 #ifdef CONFIG_NUMA
 extern int memory_add_physaddr_to_nid(u64 start);
 #else