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From: Leon Romanovsky <leon@kernel•org>
To: Haiyang Zhang <haiyangz@microsoft•com>
Cc: linux-hyperv@vger•kernel.org, netdev@vger•kernel.org,
	decui@microsoft•com, kys@microsoft•com, paulros@microsoft•com,
	olaf@aepfle•de, vkuznets@redhat•com, davem@davemloft•net,
	wei.liu@kernel•org, edumazet@google•com, kuba@kernel•org,
	pabeni@redhat•com, longli@microsoft•com,
	ssengar@linux•microsoft.com, linux-kernel@vger•kernel.org
Subject: Re: [PATCH net-next] net: mana: Add support for jumbo frame
Date: Mon, 20 Mar 2023 09:42:02 +0200	[thread overview]
Message-ID: <20230320074202.GH36557@unreal> (raw)
In-Reply-To: <1679261264-26375-1-git-send-email-haiyangz@microsoft.com>

On Sun, Mar 19, 2023 at 02:27:44PM -0700, Haiyang Zhang wrote:
> During probe, get the hardware allowed max MTU by querying the device
> configuration. Users can select MTU up to the device limit. Also,
> when XDP is in use, we currently limit the buffer size to one page.
> 
> Updated RX data path to allocate and use RX queue DMA buffers with
> proper size based on the MTU setting.
> 
> Signed-off-by: Haiyang Zhang <haiyangz@microsoft•com>
> ---
>  .../net/ethernet/microsoft/mana/mana_bpf.c    |  22 +-
>  drivers/net/ethernet/microsoft/mana/mana_en.c | 229 ++++++++++++------
>  include/net/mana/gdma.h                       |   4 +
>  include/net/mana/mana.h                       |  18 +-
>  4 files changed, 183 insertions(+), 90 deletions(-)

<...>

> +static int mana_change_mtu(struct net_device *ndev, int new_mtu)
> +{
> +	unsigned int old_mtu = ndev->mtu;
> +	int err, err2;
> +
> +	err = mana_detach(ndev, false);
> +	if (err) {
> +		netdev_err(ndev, "mana_detach failed: %d\n", err);
> +		return err;
> +	}
> +
> +	ndev->mtu = new_mtu;
> +
> +	err = mana_attach(ndev);
> +	if (!err)
> +		return 0;
> +
> +	netdev_err(ndev, "mana_attach failed: %d\n", err);
> +
> +	/* Try to roll it back to the old configuration. */
> +	ndev->mtu = old_mtu;
> +	err2 = mana_attach(ndev);

I second to Francois and agree with him that it is very questionable.
If mana_attach() failed for first try, you should bail out and not
retry with some hope that it will pass.

Thanks

> +	if (err2)
> +		netdev_err(ndev, "mana re-attach failed: %d\n", err2);
> +
> +	return err;

next prev parent reply	other threads:[~2023-03-20  7:42 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-19 21:27 [PATCH net-next] net: mana: Add support for jumbo frame Haiyang Zhang
2023-03-19 22:46 ` Francois Romieu
2023-03-20  1:47   ` Haiyang Zhang
2023-03-20 11:33     ` Francois Romieu
2023-03-20 15:13       ` Haiyang Zhang
2023-03-20  7:42 ` Leon Romanovsky [this message]
2023-03-20 15:14   ` Haiyang Zhang
2023-03-20  9:42 ` Yunsheng Lin
2023-03-20 15:21   ` Haiyang Zhang

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