netdev - Re: [PATCH net-next v2 3/3] net: stmmac: Introducing support for Page Pool

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Message-ID: <20190704173758.6d985aa3@carbon>
Date:   Thu, 4 Jul 2019 17:37:58 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Jose Abreu <Jose.Abreu@...opsys.com>
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        "David S . Miller" <davem@...emloft.net>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Arnd Bergmann <arnd@...db.de>, brouer@...hat.com
Subject: Re: [PATCH net-next v2 3/3] net: stmmac: Introducing support for
 Page Pool

On Thu,  4 Jul 2019 17:04:14 +0200
Jose Abreu <Jose.Abreu@...opsys.com> wrote:

> @@ -1498,8 +1480,9 @@ static void free_dma_rx_desc_resources(struct stmmac_priv *priv)
>  					  sizeof(struct dma_extended_desc),
>  					  rx_q->dma_erx, rx_q->dma_rx_phy);
>  
> -		kfree(rx_q->rx_skbuff_dma);
> -		kfree(rx_q->rx_skbuff);
> +		kfree(rx_q->buf_pool);
> +		if (rx_q->page_pool && page_pool_request_shutdown(rx_q->page_pool))
> +			page_pool_free(rx_q->page_pool);
>  	}
>  }

This code is okay, but I would likely write it as:

  if (rx_q->page_pool) {
	page_pool_request_shutdown(rx_q->page_pool));
	page_pool_free(rx_q->page_pool);
  }

Because (as you noticed) page_pool_free() have some API misuse checks,
that will get triggered, and thus provide a warning of you forget to
update this when driver evolves.

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer