Re: [PATCH 03/12] kho: add a struct for radix callbacks

[Mike Rapoport <rppt@kernel.org>]

On Wed, Apr 29, 2026 at 03:39:05PM +0200, Pratyush Yadav wrote:
> From: "Pratyush Yadav (Google)" <pratyush@kernel.org>
> 
> A future commit will add more callbacks for the KHO radix tree. Add a
> struct for collecting the callbacks.
> 
> Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
> ---
>  include/linux/kho_radix_tree.h     | 15 ++++++++++++---
>  kernel/liveupdate/kexec_handover.c | 29 ++++++++++++++++-------------
>  2 files changed, 28 insertions(+), 16 deletions(-)
> 
> diff --git a/include/linux/kho_radix_tree.h b/include/linux/kho_radix_tree.h
> index f368f3b9f923..030da6399d28 100644
> --- a/include/linux/kho_radix_tree.h
> +++ b/include/linux/kho_radix_tree.h
> @@ -34,14 +34,23 @@ struct kho_radix_tree {
>  	struct mutex lock; /* protects the tree's structure and root pointer */
>  };
>  
> -typedef int (*kho_radix_tree_walk_callback_t)(unsigned long key);
> +/**
> + * struct kho_radix_walk_cb - Callbacks for KHO radix tree walk.
> + * @key:      Called on each present key in the radix tree.
> + *
> + * For each callback, a return value of 0 continues the walk and a non-zero
> + * return value is directly returned to the caller.
> + */
> +struct kho_radix_walk_cb {
> +	int (*key)(unsigned long key);
> +};
>  
>  #ifdef CONFIG_KEXEC_HANDOVER
>  
>  int kho_radix_add_key(struct kho_radix_tree *tree, unsigned long key);
>  void kho_radix_del_key(struct kho_radix_tree *tree, unsigned long key);
>  int kho_radix_walk_tree(struct kho_radix_tree *tree,
> -			kho_radix_tree_walk_callback_t cb);
> +			const struct kho_radix_walk_cb *cb);
>  
>  #else  /* #ifdef CONFIG_KEXEC_HANDOVER */
>  
> @@ -54,7 +63,7 @@ static inline void kho_radix_del_key(struct kho_radix_tree *tree,
>  				     unsigned long key) { }
>  
>  static inline int kho_radix_walk_tree(struct kho_radix_tree *tree,
> -				      kho_radix_tree_walk_callback_t cb)
> +				      const struct kho_radix_walk_cb *cb)
>  {
>  	return -EOPNOTSUPP;
>  }
> diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
> index 5758dc6fab5d..4a5d1b47799c 100644
> --- a/kernel/liveupdate/kexec_handover.c
> +++ b/kernel/liveupdate/kexec_handover.c
> @@ -266,16 +266,18 @@ void kho_radix_del_key(struct kho_radix_tree *tree, unsigned long key)
>  }
>  EXPORT_SYMBOL_GPL(kho_radix_del_key);
>  
> -static int kho_radix_walk_leaf(struct kho_radix_leaf *leaf,
> -			       unsigned long key,
> -			       kho_radix_tree_walk_callback_t cb)
> +static int kho_radix_walk_leaf(struct kho_radix_leaf *leaf, unsigned long key,
> +			       const struct kho_radix_walk_cb *cb)
>  {
>  	unsigned long *bitmap = (unsigned long *)leaf;
>  	unsigned int i;
>  	int err;
>  
> +	if (!cb->key)
> +		return 0;
> +
>  	for_each_set_bit(i, bitmap, PAGE_SIZE * BITS_PER_BYTE) {
> -		err = cb(key | i);
> +		err = cb->key(key | i);

key(key) reads weird :)
Can't say I have a good name, maybe key_action()?

>  		if (err)
>  			return err;
>  	}

-- 
Sincerely yours,
Mike.