linux-kernel - RE: [PATCH net-next] net: fec: implement TSO descriptor cleanup

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Message-ID:
 <PAXPR04MB8510E1BAD3FDB59268138682881B2@PAXPR04MB8510.eurprd04.prod.outlook.com>
Date: Fri, 17 Jan 2025 02:47:33 +0000
From: Wei Fang <wei.fang@....com>
To: Dheeraj Reddy Jonnalagadda <dheeraj.linuxdev@...il.com>, Shenwei Wang
	<shenwei.wang@....com>, Clark Wang <xiaoning.wang@....com>
CC: "andrew+netdev@...n.ch" <andrew+netdev@...n.ch>, "davem@...emloft.net"
	<davem@...emloft.net>, "edumazet@...gle.com" <edumazet@...gle.com>,
	"kuba@...nel.org" <kuba@...nel.org>, "pabeni@...hat.com" <pabeni@...hat.com>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net-next] net: fec: implement TSO descriptor cleanup

> Implement the TODO in fec_enet_txq_submit_tso() error path to properly
> release buffer descriptors that were allocated during a failed TSO
> operation. This prevents descriptor leaks when TSO operations fail
> partway through.
> 
> The cleanup iterates from the starting descriptor to where the error
> occurred, resetting the status and buffer address fields of each
> descriptor.
> 
> Signed-off-by: Dheeraj Reddy Jonnalagadda <dheeraj.linuxdev@...il.com>
> ---
>  drivers/net/ethernet/freescale/fec_main.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/freescale/fec_main.c
> b/drivers/net/ethernet/freescale/fec_main.c
> index b2daed55bf6c..eff065010c9e 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -913,7 +913,18 @@ static int fec_enet_txq_submit_tso(struct
> fec_enet_priv_tx_q *txq,
>  	return 0;
> 
>  err_release:
> -	/* TODO: Release all used data descriptors for TSO */
> +	/* Release all used data descriptors for TSO */
> +	struct bufdesc *tmp_bdp = txq->bd.cur;
> +
> +	while (tmp_bdp != bdp) {
> +		tmp_bdp->cbd_sc = 0;
> +		tmp_bdp->cbd_bufaddr = 0;
> +		tmp_bdp->cbd_datlen = 0;
> +		tmp_bdp = fec_enet_get_nextdesc(tmp_bdp, &txq->bd);
> +	}

There is still some cleanup to do.
1. If bufdesc_ex is used, we also need to clear it, such as ebdp->cbd_esc.
2. The data buffers have been mapped in fec_enet_txq_put_data_tso(),
I think we need to unmap them in the error path. But do not unmap
the TSO header buff, which is a DMA memory. Actually it is not necessary
for fec_enet_txq_put_hdr_tso() to call dma_map_single(). If you are
interested, you can add a separate patch to remove dma_map_single()
in fec_enet_txq_put_hdr_tso().

> +
> +	dev_kfree_skb_any(skb);
> +
>  	return ret;
>  }
> 
> --
> 2.34.1