mm/memory_hotplug: add __add_memory_driver_managed() with online_type arg

Existing callers of add_memory_driver_managed cannot select the preferred
online type (ZONE_NORMAL vs ZONE_MOVABLE), requiring it to hot-add memory
as offline blocks, and then follow up by onlining each memory block
individually.

Most drivers prefer the system default, but the CXL driver wants to plumb
a preferred policy through the dax kmem driver.

Refactor APIs to add a new interface which allows the dax kmem module to
select a preferred policy.

Overriding the configured auto-online policy is only safe for known
in-tree modules, where we know the override reflects a different,
user-requested policy.  We do not want arbitrary out-of-tree drivers
silently overriding the system-wide onlining policy, so restrict the new
interface to the kmem module using EXPORT_SYMBOL_FOR_MODULES() rather than
a plain EXPORT_SYMBOL_GPL().  Other in-tree modules (e.g.  cxl_core) can
be added to the allowed list as the need arises.

Refactor add_memory_driver_managed, extract __add_memory_driver_managed
- Add proper kernel-doc for add_memory_driver_managed while refactoring
- New helper accepts an explicit online_type.
- New helper validates online_type is between OFFLINE and ONLINE_MOVABLE

Refactor: add_memory_resource, extract __add_memory_resource
- new helper accepts an explicit online_type

Original APIs now explicitly pass the system-default to new helpers.

No functional change for existing users.

Link: https://lore.kernel.org/20260712154505.3564379-6-gourry@gourry.net
Signed-off-by: Gregory Price <gourry@gourry.net>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Dan Williams <djbw@kernel.org>
Cc: Alison Schofield <alison.schofield@intel.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 5240aa28bc90..d69b273ed304 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -295,6 +295,9 @@ extern int __add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags);
 extern int add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags);
 extern int add_memory_resource(int nid, struct resource *resource,
 			       mhp_t mhp_flags);
+int __add_memory_driver_managed(int nid, u64 start, u64 size,
+				const char *resource_name, mhp_t mhp_flags,
+				enum mmop online_type);
 extern int add_memory_driver_managed(int nid, u64 start, u64 size,
 				     const char *resource_name,
 				     mhp_t mhp_flags);