linux-kernel - Re: [PATCH net-next] net: mana: Improve mana_set

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Message-ID: <d73d45af-e76e-4e87-8df1-0ed71e823abc@engleder-embedded.com>
Date: Thu, 29 Aug 2024 21:54:18 +0200
From: Gerhard Engleder <gerhard@...leder-embedded.com>
To: Shradha Gupta <shradhagupta@...ux.microsoft.com>,
 linux-hyperv@...r.kernel.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org
Cc: "K. Y. Srinivasan" <kys@...rosoft.com>,
 Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>,
 Dexuan Cui <decui@...rosoft.com>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Long Li <longli@...rosoft.com>,
 Simon Horman <horms@...nel.org>, Konstantin Taranov
 <kotaranov@...rosoft.com>,
 Souradeep Chakrabarti <schakrabarti@...ux.microsoft.com>,
 Erick Archer <erick.archer@...look.com>,
 Pavan Chebbi <pavan.chebbi@...adcom.com>, Ahmed Zaki <ahmed.zaki@...el.com>,
 Colin Ian King <colin.i.king@...il.com>,
 Shradha Gupta <shradhagupta@...rosoft.com>
Subject: Re: [PATCH net-next] net: mana: Improve mana_set_channels() for low
 mem conditions

On 29.08.24 16:16, Shradha Gupta wrote:
> The mana_set_channels() function requires detaching the mana
> driver and reattaching it with changed channel values.
> During this operation if the system is low on memory, the reattach
> might fail, causing the network device being down.
> To avoid this we pre-allocate buffers at the beginning of set operation,
> to prevent complete network loss
> 
> Signed-off-by: Shradha Gupta <shradhagupta@...ux.microsoft.com>
> ---
>   .../ethernet/microsoft/mana/mana_ethtool.c    | 28 +++++++++++--------
>   1 file changed, 16 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/ethernet/microsoft/mana/mana_ethtool.c b/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
> index d6a35fbda447..5077493fdfde 100644
> --- a/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
> +++ b/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
> @@ -345,27 +345,31 @@ static int mana_set_channels(struct net_device *ndev,
>   	struct mana_port_context *apc = netdev_priv(ndev);
>   	unsigned int new_count = channels->combined_count;
>   	unsigned int old_count = apc->num_queues;
> -	int err, err2;
> +	int err;
> +
> +	apc->num_queues = new_count;
> +	err = mana_pre_alloc_rxbufs(apc, ndev->mtu);
> +	apc->num_queues = old_count;

Are you sure that temporary changing num_queues has no side effects on
other num_queues users like mana_chn_setxdp()?

Gerhard