netdev - Re: [PATCH v3 2/2] net: io_uring/zcrx: call netdev_queue_get_dma

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Message-ID: <c374df85-23ec-4324-b966-9f2b3a74489a@gmail.com>
Date: Mon, 3 Nov 2025 13:51:19 +0000
From: Pavel Begunkov <asml.silence@...il.com>
To: David Wei <dw@...idwei.uk>, io-uring@...r.kernel.org,
 netdev@...r.kernel.org
Cc: Jens Axboe <axboe@...nel.dk>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>
Subject: Re: [PATCH v3 2/2] net: io_uring/zcrx: call
 netdev_queue_get_dma_dev() under instance lock

On 11/1/25 02:24, David Wei wrote:
> netdev ops must be called under instance lock or rtnl_lock, but
> io_register_zcrx_ifq() isn't doing this for netdev_queue_get_dma_dev().
> Fix this by taking the instance lock using netdev_get_by_index_lock().
> 
> Extended the instance lock section to include attaching a memory
> provider. Could not move io_zcrx_create_area() outside, since the dmabuf
> codepath IORING_ZCRX_AREA_DMABUF requires ifq->dev.

It's probably fine for now, but this nested waiting feels
uncomfortable considering that it could be waiting for other
devices to finish IO via dmabuf fences.

-- 
Pavel Begunkov