netdev - Re: [bpf-next V5 PATCH 11/15] page_pool: refurbish version of page

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Message-ID: <7c1a98ab-3bc3-d99a-9ad0-456911b5b54c@gmail.com>
Date:   Fri, 23 Mar 2018 06:28:13 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>, netdev@...r.kernel.org,
        BjörnTöpel <bjorn.topel@...el.com>,
        magnus.karlsson@...el.com
Cc:     eugenia@...lanox.com, Jason Wang <jasowang@...hat.com>,
        John Fastabend <john.fastabend@...il.com>,
        Eran Ben Elisha <eranbe@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>, galp@...lanox.com,
        Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Tariq Toukan <tariqt@...lanox.com>
Subject: Re: [bpf-next V5 PATCH 11/15] page_pool: refurbish version of
 page_pool code



On 03/23/2018 05:18 AM, Jesper Dangaard Brouer wrote:

> +
> +	/* Note, below struct compat code was primarily needed when
> +	 * page_pool code lived under MM-tree control, given mmots and
> +	 * net-next trees progress in very different rates.
> +	 *
> +	 * Allow kernel devel trees and driver to progress at different rates
> +	 */
> +	param_copy_sz = PAGE_POOL_PARAMS_SIZE;
> +	memset(&pool->p, 0, param_copy_sz);
> +	if (params->size < param_copy_sz) {
> +		/* Older module calling newer kernel, handled by only
> +		 * copying supplied size, and keep remaining params zero
> +		 */
> +		param_copy_sz = params->size;
> +	} else if (params->size > param_copy_sz) {
> +		/* Newer module calling older kernel. Need to validate
> +		 * no new features were requested.
> +		 */
> +		unsigned char *addr = (unsigned char *)params + param_copy_sz;
> +		unsigned char *end  = (unsigned char *)params + params->size;
> +
> +		for (; addr < end; addr++) {
> +			if (*addr != 0)
> +				return -E2BIG;
> +		}
> +	}

I do not see the need for this part.