linux-kernel - Re: [v4,net-next,13/15] net: fec: add fec_alloc_rxq_buffers

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Message-ID: <20260126161830.58ba78b3@kernel.org>
Date: Mon, 26 Jan 2026 16:18:30 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Wei Fang <wei.fang@....com>
Cc: "john.fastabend@...il.com" <john.fastabend@...il.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Shenwei Wang
 <shenwei.wang@....com>, "daniel@...earbox.net" <daniel@...earbox.net>,
 Frank Li <frank.li@....com>, "netdev@...r.kernel.org"
 <netdev@...r.kernel.org>, Clark Wang <xiaoning.wang@....com>,
 "ast@...nel.org" <ast@...nel.org>, "sdf@...ichev.me" <sdf@...ichev.me>,
 "imx@...ts.linux.dev" <imx@...ts.linux.dev>, "davem@...emloft.net"
 <davem@...emloft.net>, "edumazet@...gle.com" <edumazet@...gle.com>,
 "hawk@...nel.org" <hawk@...nel.org>, "bpf@...r.kernel.org"
 <bpf@...r.kernel.org>, "pabeni@...hat.com" <pabeni@...hat.com>,
 "andrew+netdev@...n.ch" <andrew+netdev@...n.ch>
Subject: Re: [v4,net-next,13/15] net: fec: add fec_alloc_rxq_buffers_pp() to
 allocate buffers from page pool

On Mon, 26 Jan 2026 02:37:01 +0000 Wei Fang wrote:
> > > +	if (is_run) {
> > > +		err = fec_enet_alloc_buffers(ndev);
> > > +		if (err) {
> > > +			netdev_err(ndev, "Failed to alloc buffers\n");
> > > +			goto err_alloc_buffers;
> > > +		}
> > > +
> > > +		fec_restart(ndev);
> > > +		napi_enable(&fep->napi);
> > > +		netif_tx_start_all_queues(ndev);
> > > +	}
> > > +
> > > +	return 0;
> > > +
> > > +err_alloc_buffers:
> > > +	if (enable) {
> > > +		xsk_pool_dma_unmap(pool, 0);
> > > +		rxq->xsk_pool = NULL;
> > > +		txq->xsk_pool = NULL;
> > > +	}
> > > +
> > > +	return err;  
> > 
> > Similarly, the err_alloc_buffers path cleans up the XSK pool state but
> > does not restore NAPI/TX or restart the device when is_run was true.
> > Does this leave the device in the same non-functional state?
> >   
> 
> The current driver does not support allocating the buffers first and then
> replacing the old buffers, so calling fec_enet_alloc_buffers() again in the
> err_alloc_buffers path may still fail and potentially make the device
> unusable. I will think about how to change this situation. Thanks.

Yes, a lot of older drivers don't. We make people improve things
whenever they try to add major features 🤷️ BTW I'm quite impressed
that AI pointed this out.