netdev - Re: [PATCH v8 06/11] net/mlx4_en: add page recycle to prepare rx ring for tx support

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Date:	Tue, 12 Jul 2016 14:18:32 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	bblanco@...mgrid.com
Cc:	netdev@...r.kernel.org, jhs@...atatu.com,
	saeedm@....mellanox.co.il, kafai@...com, brouer@...hat.com,
	as754m@....com, alexei.starovoitov@...il.com, gerlitz.or@...il.com,
	john.fastabend@...il.com, hannes@...essinduktion.org,
	tgraf@...g.ch, tom@...bertland.com, daniel@...earbox.net
Subject: Re: [PATCH v8 06/11] net/mlx4_en: add page recycle to prepare rx
 ring for tx support

From: Brenden Blanco <bblanco@...mgrid.com>
Date: Tue, 12 Jul 2016 00:51:29 -0700

> +	mlx4_en_free_resources(priv);
> +
>  	old_prog = xchg(&priv->prog, prog);
>  	if (old_prog)
>  		bpf_prog_put(old_prog);
>  
> -	return 0;
> +	err = mlx4_en_alloc_resources(priv);
> +	if (err) {
> +		en_err(priv, "Failed reallocating port resources\n");
> +		goto out;
> +	}
> +	if (port_up) {
> +		err = mlx4_en_start_port(dev);
> +		if (err)
> +			en_err(priv, "Failed starting port\n");

A failed configuration operation should _NEVER_ leave the interface in
an inoperative state like these error paths do.

You must instead preallocate the necessary resources, and only change
the chip's configuration and commit to the new settings once you have
successfully allocated those resources.