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Date: Wed, 13 Aug 2025 16:48:47 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Dipayaan Roy <dipayanroy@linux.microsoft.com>
Cc: horms@kernel.org, kys@microsoft.com, haiyangz@microsoft.com,
 wei.liu@kernel.org, decui@microsoft.com, andrew+netdev@lunn.ch,
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 linux-hyperv@vger.kernel.org, linux-rdma@vger.kernel.org,
 bpf@vger.kernel.org, linux-kernel@vger.kernel.org, dipayanroy@microsoft.com
Subject: Re: [PATCH net-next v4] net: mana: Use page pool fragments for RX
 buffers instead of full pages to improve memory efficiency.
Message-ID: <20250813164847.62ade421@kernel.org>
In-Reply-To: <20250811222919.GA25951@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
References: <20250811222919.GA25951@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
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On Mon, 11 Aug 2025 15:29:19 -0700 Dipayaan Roy wrote:
> -	if (apc->port_is_up)
> +	if (apc->port_is_up) {
> +		/* Re-create rxq's after xdp prog was loaded or unloaded.
> +		 * Ex: re create rxq's to switch from full pages to smaller
> +		 * size page fragments when xdp prog is unloaded and
> +		 * vice-versa.
> +		 */
> +
> +		/* Pre-allocate buffers to prevent failure in mana_attach */
> +		err = mana_pre_alloc_rxbufs(apc, ndev->mtu, apc->num_queues);
> +		if (err) {
> +			NL_SET_ERR_MSG_MOD
> +			    (extack,
> +			    "XDP: Insufficient memory for tx/rx re-config");

This weird line breaking is not necessary, checkpatch understands that
string can go over line limit:

			NL_SET_ERR_MSG_MOD(extack,
					   "XDP: Insufficient memory for tx/rx re-config");

> +			return err;

I think you already replaced the bpf program at this point? 
So the allocation should happen earlier. On failure changes
to the driver state should be undone.
-- 
pw-bot: cr