Re: [PATCH net] net: page_pool: allow enabling recycling late, fix false positive warning

[Stanislav Fomichev <stfomichev@gmail.com>]

On 08/01, Jakub Kicinski wrote:
> On Fri, 1 Aug 2025 13:55:09 -0700 Stanislav Fomichev wrote:
> > > +static void bnxt_enable_rx_page_pool(struct bnxt_rx_ring_info *rxr)
> > > +{
> > > +	page_pool_enable_direct_recycling(rxr->head_pool, &rxr->bnapi->napi);
> > > +	page_pool_enable_direct_recycling(rxr->page_pool, &rxr->bnapi->napi);  
> > 
> > We do bnxt_separate_head_pool check for the disable_direct_recycling
> > of head_pool. Is it safe to skip the check here because we always allocate two
> > pps from queue_mgmt callbacks? (not clear for me from a quick glance at
> > bnxt_alloc_rx_page_pool)
> 
> It's safe (I hope) because the helper is duplicate-call-friendly:
> 
> +void page_pool_enable_direct_recycling(struct page_pool *pool,
> +				       struct napi_struct *napi)
> +{
> +	if (READ_ONCE(pool->p.napi) == napi)   <<< right here
> +		return;
> +	WARN_ON_ONCE(!napi || pool->p.napi);
> +
> +	mutex_lock(&page_pools_lock);
> +	WRITE_ONCE(pool->p.napi, napi);
> +	mutex_unlock(&page_pools_lock);
> +}
> 
> We already have a refcount in page pool, I'm planning to add
> page_pool_get() in net-next and remove the
> 
> 	if (bnxt_separate_head_pool)
> 
> before page_pool_destroy(), too.

Ah, I see, I missed that fact that page_pool and head_pool point to the
same address when we don't have separate pools. Makes sense, thanks!