linux-kernel - Re: [PATCH net-next v9 8/8] mt76: use netmem descriptor and APIs for page pool

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Message-ID: <a21b340d-6d0f-4d39-906e-e983564605ed@gmail.com>
Date: Sat, 12 Jul 2025 15:22:17 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: Byungchul Park <byungchul@...com>, willy@...radead.org,
 netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 kernel_team@...ynix.com, kuba@...nel.org, almasrymina@...gle.com,
 ilias.apalodimas@...aro.org, harry.yoo@...cle.com, hawk@...nel.org,
 akpm@...ux-foundation.org, davem@...emloft.net, john.fastabend@...il.com,
 andrew+netdev@...n.ch, toke@...hat.com, tariqt@...dia.com,
 edumazet@...gle.com, pabeni@...hat.com, saeedm@...dia.com, leon@...nel.org,
 ast@...nel.org, daniel@...earbox.net, david@...hat.com,
 lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com, vbabka@...e.cz,
 rppt@...nel.org, surenb@...gle.com, mhocko@...e.com, horms@...nel.org,
 linux-rdma@...r.kernel.org, bpf@...r.kernel.org, vishal.moola@...il.com,
 hannes@...xchg.org, ziy@...dia.com, jackmanb@...gle.com
Subject: Re: [PATCH net-next v9 8/8] mt76: use netmem descriptor and APIs for
 page pool

On 7/10/25 09:28, Byungchul Park wrote:
> To simplify struct page, the effort to separate its own descriptor from
> struct page is required and the work for page pool is on going.
> 
> Use netmem descriptor and APIs for page pool in mt76 code.
> 
> Signed-off-by: Byungchul Park <byungchul@...com>
> Reviewed-by: Mina Almasry <almasrymina@...gle.com>
> ---
...>   static inline void mt76_set_tx_blocked(struct mt76_dev *dev, bool blocked)
> diff --git a/drivers/net/wireless/mediatek/mt76/sdio_txrx.c b/drivers/net/wireless/mediatek/mt76/sdio_txrx.c
> index 0a927a7313a6..b1d89b6f663d 100644
> --- a/drivers/net/wireless/mediatek/mt76/sdio_txrx.c
> +++ b/drivers/net/wireless/mediatek/mt76/sdio_txrx.c
> @@ -68,14 +68,14 @@ mt76s_build_rx_skb(void *data, int data_len, int buf_len)
>   
>   	skb_put_data(skb, data, len);
>   	if (data_len > len) {
> -		struct page *page;
> +		netmem_ref netmem;
>   
>   		data += len;
> -		page = virt_to_head_page(data);
> -		skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
> -				page, data - page_address(page),
> -				data_len - len, buf_len);
> -		get_page(page);
> +		netmem = virt_to_head_netmem(data);
> +		skb_add_rx_frag_netmem(skb, skb_shinfo(skb)->nr_frags,
> +				       netmem, data - netmem_address(netmem),
> +				       data_len - len, buf_len);
> +		get_netmem(netmem);
>   	}
>   
>   	return skb;
> @@ -88,7 +88,7 @@ mt76s_rx_run_queue(struct mt76_dev *dev, enum mt76_rxq_id qid,
>   	struct mt76_queue *q = &dev->q_rx[qid];
>   	struct mt76_sdio *sdio = &dev->sdio;
>   	int len = 0, err, i;
> -	struct page *page;
> +	netmem_ref netmem;
>   	u8 *buf, *end;
>   
>   	for (i = 0; i < intr->rx.num[qid]; i++)
> @@ -100,11 +100,11 @@ mt76s_rx_run_queue(struct mt76_dev *dev, enum mt76_rxq_id qid,
>   	if (len > sdio->func->cur_blksize)
>   		len = roundup(len, sdio->func->cur_blksize);
>   
> -	page = __dev_alloc_pages(GFP_KERNEL, get_order(len));
> -	if (!page)
> +	netmem = page_to_netmem(__dev_alloc_pages(GFP_KERNEL, get_order(len)));
> +	if (!netmem)
>   		return -ENOMEM;
>   
> -	buf = page_address(page);
> +	buf = netmem_address(netmem);

We shouldn't just blindly convert everything to netmem just for the purpose
of creating a type casting hell. It's allocating a page, and continues to
use it as a page, e.g. netmem_address() will fail otherwise. So just leave
it to be a page, and convert it to netmem and the very last moment when
the api expects a netmem. There are likely many chunks like that.

>   
>   	sdio_claim_host(sdio->func);
>   	err = sdio_readsb(sdio->func, buf, MCR_WRDR(qid), len);
> @@ -112,7 +112,7 @@ mt76s_rx_run_queue(struct mt76_dev *dev, enum mt76_rxq_id qid,
>   
>   	if (err < 0) {
>   		dev_err(dev->dev, "sdio read data failed:%d\n", err);
> -		put_page(page);
> +		put_netmem(netmem);
>   		return err;
>   	}
>   
> @@ -140,7 +140,7 @@ mt76s_rx_run_queue(struct mt76_dev *dev, enum mt76_rxq_id qid,
>   		}
>   		buf += round_up(len + 4, 4);
>   	}
> -	put_page(page);
> +	put_netmem(netmem);
>   
>   	spin_lock_bh(&q->lock);
>   	q->head = (q->head + i) % q->ndesc;
-- 
Pavel Begunkov