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Date: Wed, 15 Jan 2025 19:12:17 -0800
From: Jakub Kicinski <kuba@kernel.org>
To: Pavel Begunkov <asml.silence@gmail.com>
Cc: David Wei <dw@davidwei.uk>, io-uring@vger.kernel.org,
 netdev@vger.kernel.org, Jens Axboe <axboe@kernel.dk>, Paolo Abeni
 <pabeni@redhat.com>, "David S. Miller" <davem@davemloft.net>, Eric Dumazet
 <edumazet@google.com>, Jesper Dangaard Brouer <hawk@kernel.org>, David
 Ahern <dsahern@kernel.org>, Mina Almasry <almasrymina@google.com>,
 Stanislav Fomichev <stfomichev@gmail.com>, Joe Damato <jdamato@fastly.com>,
 Pedro Tammela <pctammela@mojatatu.com>
Subject: Re: [PATCH net-next v10 14/22] io_uring/zcrx: grab a net device
Message-ID: <20250115191217.5ab89aa3@kernel.org>
In-Reply-To: <bb19ef4d-6871-4ae9-b478-34dd2efcb361@gmail.com>
References: <20250108220644.3528845-1-dw@davidwei.uk>
	<20250108220644.3528845-15-dw@davidwei.uk>
	<20250115170644.57409b2f@kernel.org>
	<bb19ef4d-6871-4ae9-b478-34dd2efcb361@gmail.com>
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On Thu, 16 Jan 2025 02:33:06 +0000 Pavel Begunkov wrote:
> On 1/16/25 01:06, Jakub Kicinski wrote:
> > On Wed,  8 Jan 2025 14:06:35 -0800 David Wei wrote:  
> >> From: Pavel Begunkov <asml.silence@gmail.com>
> >>
> >> Zerocopy receive needs a net device to bind to its rx queue and dma map
> >> buffers. As a preparation to following patches, resolve a net device
> >> from the if_idx parameter with no functional changes otherwise.  
> > 
> > How do you know if someone unregisters this netdevice?
> > The unregister process waits for all the refs to be released,
> > for *ekhm* historic reasons. Normally ref holders subscribe
> > to netdev events and kill their dependent objects. Perhaps
> > it is somewhere else/later in the series...  
> 
> Ok, I can pin the struct device long term instead and kill
> netdev in the uninstall callback off
> unregister_netdevice_many_notify(), if that works with you.

I think that would work. You mean the "underlying" device, right,
netdev->dev.parent ? Like page_pool itself does. SG.