netdev - Re: [PATCH net v1] net: io_uring/zcrx: call netdev_queue_get_dma

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Message-ID: <20251028153820.414b3956@kernel.org>
Date: Tue, 28 Oct 2025 15:38:20 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: David Wei <dw@...idwei.uk>
Cc: io-uring@...r.kernel.org, netdev@...r.kernel.org, Jens Axboe
 <axboe@...nel.dk>, Pavel Begunkov <asml.silence@...il.com>, "David S.
 Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo
 Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>
Subject: Re: [PATCH net v1] net: io_uring/zcrx: call
 netdev_queue_get_dma_dev() under instance lock

On Tue, 28 Oct 2025 14:26:39 -0700 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.
> 
> Opted to do this by hand instead of netdev_get_by_index_lock(), which is
> an older helper that doesn't take netdev tracker.

Fixes tag missing.

netdev_get_by_index_lock() + netdev_hold() would be a better choice indeed.
Just a reference doesn't hold off device shutdown.

Is there a chance to reorder the io_zcrx_create_area() call, keep
holding the lock and call __net_mp_open_rxq() ?