Re: [PATCH 01/12] kho: generalize radix tree APIs

[Mike Rapoport <rppt@kernel.org>]

On Wed, Apr 29, 2026 at 03:39:03PM +0200, Pratyush Yadav wrote:
> From: "Pratyush Yadav (Google)" <pratyush@kernel.org>
> 
> The KHO radix tree is a data structure that can track the presence or
> absence of an arbitrary key, with nothing inherently tied to KHO memory
> preservation tracking. This was one of the design goals of the radix
> tree. This was done to enable it to be re-used by other users of KHO.
> 
> Despite that, the radix tree APIs are very closely tied to KHO memory
> preservation tracking. Adding a key is done by kho_radix_add_page(),
> which encodes it as a page tracking operation and takes in PFN and
> order. kho_radix_del_page() does the same. These functions encode the
> key internally that goes into the radix tree. kho_radix_walk_tree() does
> the same by baking the PFN and order into the callback arguments.
> 
> Generalize the APIs by taking the key directly and doing the encoding at
> the callers. Rename the functions to kho_radix_add_key() and
> kho_radix_del_key(). In practice, this removes a line each from the
> functions and moves the encoding function call to the callers.
> Similarly, update kho_radix_tree_walk_callback_t to take the key
> directly.
> 
> To keep the naming convention clearer, rename
> kho_radix_{encode,decode}_key() to kho_{encode,decode}_radix_key().
> 
> Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
> ---
>  include/linux/kho_radix_tree.h     | 18 +++----
>  kernel/liveupdate/kexec_handover.c | 76 ++++++++++++++----------------
>  2 files changed, 42 insertions(+), 52 deletions(-)
> 
> diff --git a/include/linux/kho_radix_tree.h b/include/linux/kho_radix_tree.h
> index 84e918b96e53..f368f3b9f923 100644
> --- a/include/linux/kho_radix_tree.h
> +++ b/include/linux/kho_radix_tree.h
> @@ -85,7 +85,7 @@ static struct kho_out kho_out = {
>  };
>  
>  /**
> - * kho_radix_encode_key - Encodes a physical address and order into a radix key.
> + * kho_encode_radix_key - Encodes a physical address and order into a radix key.

Let's keep kho_radix_ prefix for namespasing please.
This is the common practice these days.

>   * @phys: The physical address of the page.
>   * @order: The order of the page.
>   *

...

> @@ -144,24 +144,21 @@ static unsigned long kho_radix_get_table_index(unsigned long key,
>  }
>  
>  /**
> - * kho_radix_add_page - Marks a page as preserved in the radix tree.
> + * kho_radix_add_key - Add a key to the radix tree.
>   * @tree: The KHO radix tree.
> - * @pfn: The page frame number of the page to preserve.
> - * @order: The order of the page.
> + * @key: The key to add.
>   *
> - * This function traverses the radix tree based on the key derived from @pfn
> - * and @order. It sets the corresponding bit in the leaf bitmap to mark the
> - * page for preservation. If intermediate nodes do not exist along the path,
> - * they are allocated and added to the tree.
> + * This function traverses the radix tree based on the key provided. It sets the

Nit:                                                     @key here and in
the comments below.

> + * corresponding bit in the leaf bitmap to mark the key as present. If
> + * intermediate nodes do not exist along the path, they are allocated and added
> + * to the tree.
>   *
>   * Return: 0 on success, or a negative error code on failure.
>   */

-- 
Sincerely yours,
Mike.