Re: [PATCH v4 4/9] mm/memory_hotplug: add __add_memory_driver_managed() with online_type arg

["David Hildenbrand (Arm)" <david@kernel.org>]

On 6/5/26 23:19, Gregory Price wrote:
> 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.
> 
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Acked-by: David Hildenbrand (Arm) <david@kernel.org>
> Signed-off-by: Gregory Price <gourry@gourry.net>
> ---
>  include/linux/memory_hotplug.h |  3 ++
>  mm/memory_hotplug.c            | 61 +++++++++++++++++++++++++++++-----
>  2 files changed, 56 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index f059025f8f8b..d3edeb80aadb 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -294,6 +294,9 @@ 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);

We prefer two-tab indent on second parameter line while touching code / adding
new code.

Same applies to the other instances below.


Apart from that (still) LGTM.

-- 
Cheers,

David