Re: [PATCH net-next v1 02/11] net: Add memory provider capabilities

[Jakub Kicinski <kuba@kernel.org>]

On Tue, 10 Nov 2026 11:20:23 +0100 Björn Töpel wrote:
> diff --git a/include/net/page_pool/memory_provider.h b/include/net/page_pool/memory_provider.h
> index bceb5f7740e2..4417e54a0f81 100644
> --- a/include/net/page_pool/memory_provider.h
> +++ b/include/net/page_pool/memory_provider.h
> @@ -19,6 +19,18 @@ struct sk_buff;
>   * Per-provider custom logic must be delegated to memory_provider_ops rather
>   * than handled directly in page_pool core code.
>   */
> +
> +/**
> + * enum mp_caps - memory provider capabilities
> + * @MP_CAP_READABLE: The CPU can access provider memory. It may back header
> + *	page pools, and XDP programs may run on it.

Being readable is the normal state for memory.
We should be marking mps as unreadable, not as readable?

> @@ -1070,6 +1095,9 @@ netmem_ref page_pool_alloc_frag_netmem(struct page_pool *pool,
>  	unsigned int max_size = PAGE_SIZE << pool->p.order;
>  	netmem_ref netmem = pool->frag_page;
>  
> +	if (static_branch_unlikely(&page_pool_mem_providers) &&
> +	    WARN_ON_ONCE(!page_pool_supports_frag(pool)))
> +		return 0;

Shouldn't we return a full page if we can't frag?
Fragmentation breaks up a page into smaller units,
it should be legal to simply return a full page if
fragmentation is not supported for the provider.

>  	if (WARN_ON(size > max_size))
>  		return 0;