Re: [PATCH nf-next 1/1] netfilter: nf_tables: Refine the codes to eliminate useless condition checks in nf_tables_api.c

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Wed, Jan 11, 2017 at 09:32:15AM +0800, fgao@ikuai8.com wrote:
> From: Gao Feng <fgao@ikuai8.com>
> 
> The return value of nf_tables_table_lookup is valid pointer or one
> pointer error. There are two cases totally.
> case1: IS_ERR(table) is true, it would return the error or reset the
> table as NULL, it is unnecessary to perform the latter check
> "table != NULL".
> case2: IS_ERR(obj) is false, the table is one valid pointer. It is also
> unnecessary to perform that check.
> The nf_tables_newset and nf_tables_newobj have same logic codes.
> 
> In summary, we could move the block of condition check "table != NULL"
> in the else block to eliminate the original condition checks.
> 
> Signed-off-by: Gao Feng <fgao@ikuai8.com>
> ---
>  net/netfilter/nf_tables_api.c | 12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)
> 
> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> index a019a87..3d7267f 100644
> --- a/net/netfilter/nf_tables_api.c
> +++ b/net/netfilter/nf_tables_api.c
> @@ -697,9 +697,7 @@ static int nf_tables_newtable(struct net *net, struct sock *nlsk,
>  		if (PTR_ERR(table) != -ENOENT)
>  			return PTR_ERR(table);
>  		table = NULL;

We follow up with table = NULL down the code, I think this breaks.

> -	}
> -
> -	if (table != NULL) {
> +	} else {
>  		if (nlh->nlmsg_flags & NLM_F_EXCL)
>  			return -EEXIST;
>  		if (nlh->nlmsg_flags & NLM_F_REPLACE)