Re: [PATCH v3 11/12] xarray, radix-tree: enable sheaf support for kmem_cache

[Daniel Gomez]

On 2026-02-09 15:38, Andreas Hindborg wrote:
> The rust null block driver plans to rely on preloading xarray nodes from
> the radix_tree_node_cachep kmem_cache.
> 
> Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
> Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx>
> ---
>  lib/radix-tree.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/radix-tree.c b/lib/radix-tree.c
> index 976b9bd02a1b5..1cf0012b15ade 100644
> --- a/lib/radix-tree.c
> +++ b/lib/radix-tree.c
> @@ -1598,10 +1598,16 @@ void __init radix_tree_init(void)
>  	BUILD_BUG_ON(RADIX_TREE_MAX_TAGS + __GFP_BITS_SHIFT > 32);
>  	BUILD_BUG_ON(ROOT_IS_IDR & ~GFP_ZONEMASK);
>  	BUILD_BUG_ON(XA_CHUNK_SIZE > 255);
> -	radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
> -			sizeof(struct radix_tree_node), 0,
> -			SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
> -			radix_tree_node_ctor);
> +
> +	struct kmem_cache_args args = {
> +		.ctor = radix_tree_node_ctor,
> +		.sheaf_capacity = 64,
> +	};

Is the sheaf_capacity matching the number of slots in an XArray node? If so,
this should be bindings::XA_CHUNK_SIZE.