netdev - Re: [PATCH net 4/8] i40e: Fix XDP program unloading while removing the driver

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Message-ID: <20240605122957.6b961023@kernel.org>
Date: Wed, 5 Jun 2024 12:29:57 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Michal Kubiak <michal.kubiak@...el.com>
Cc: Jacob Keller <jacob.e.keller@...el.com>, David Miller
 <davem@...emloft.net>, netdev <netdev@...r.kernel.org>, Wojciech Drewek
 <wojciech.drewek@...el.com>, George Kuruvinakunnel
 <george.kuruvinakunnel@...el.com>, Maciej Fijalkowski
 <maciej.fijalkowski@...el.com>
Subject: Re: [PATCH net 4/8] i40e: Fix XDP program unloading while removing
 the driver

On Wed, 5 Jun 2024 17:00:02 +0200 Michal Kubiak wrote:
> I am afraid checking for NULL won't be enough here.
> Normally, when ndo_bpf is called from the user space application, that
> callback can be called with NULL too (when the user just wants to unload
> the XDP program). In such a case, apart from calling bpf_prog_put(), we
> have to rebuild our internal data structures (queues, pointers, counters
> etc.) to restore the i40e driver working back in normal mode (with no
> XDP program).

Apologizes for asking a question which can be answered by studying 
the code longer, but why do you need to rebuild internal data
structures for a device which is *down*. Unregistering or not.