netdev - Re: [PATCH v3 2/2] sctp: optimize the sctp_sysctl_net

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Date:	Wed, 12 Feb 2014 06:53:44 -0500
From:	Neil Horman <nhorman@...driver.com>
To:	Wang Weidong <wangweidong1@...wei.com>
Cc:	davem@...emloft.net, vyasevich@...il.com, dborkman@...hat.com,
	sergei.shtylyov@...entembedded.com, netdev@...r.kernel.org
Subject: Re: [PATCH v3 2/2] sctp: optimize the sctp_sysctl_net_register

On Wed, Feb 12, 2014 at 09:44:44AM +0800, Wang Weidong wrote:
> Here, when the net is init_net, we needn't to kmemdup the ctl_table
> again. So add a check for net. Also we can save some memory.
> 
> Signed-off-by: Wang Weidong <wangweidong1@...wei.com>
> ---
>  net/sctp/sysctl.c | 17 ++++++++++-------
>  1 file changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
> index d354de5..35c8923 100644
> --- a/net/sctp/sysctl.c
> +++ b/net/sctp/sysctl.c
> @@ -402,15 +402,18 @@ static int proc_sctp_do_rto_max(struct ctl_table *ctl, int write,
>  
>  int sctp_sysctl_net_register(struct net *net)
>  {
> -	struct ctl_table *table;
> -	int i;
> +	struct ctl_table *table = sctp_net_table;
> +
> +	if (!net_eq(net, &init_net)) {
> +		int i;
>  
> -	table = kmemdup(sctp_net_table, sizeof(sctp_net_table), GFP_KERNEL);
> -	if (!table)
> -		return -ENOMEM;
> +		table = kmemdup(sctp_net_table, sizeof(sctp_net_table), GFP_KERNEL);
> +		if (!table)
> +			return -ENOMEM;
>  
> -	for (i = 0; table[i].data; i++)
> -		table[i].data += (char *)(&net->sctp) - (char *)&init_net.sctp;
> +		for (i = 0; table[i].data; i++)
> +			table[i].data += (char *)(&net->sctp) - (char *)&init_net.sctp;
> +	}
>  
In the first version of this patch you complained about a lockdep issue.  Did
you figure out what that was, and if it related to these changes?

Neil

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