Subject: Re: [net-next PATCH 5/9] fib_trie: Add tnode struct as a container for fields not needed in key_vector

From: Sergei Shtylyov <[email-masked]>
Date: Fri, 06 Mar 2015 16:17:11 +0300

Hello.

On 3/6/2015 1:51 AM, Alexander Duyck wrote:

> This change pulls the fields not explicitly needed in the key_vector and
> placed them in the new tnode structure.  By doing this we will eventually
> be able to reduce the key_vector down to 16 bytes on 64 bit systems, and
> 12 bytes on 32 bit systems.

> Signed-off-by: Alexander Duyck <[email-masked]>
> ---
>   net/ipv4/fib_trie.c |   72 ++++++++++++++++++++++++++++-----------------------
>   1 file changed, 39 insertions(+), 33 deletions(-)
>
> diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
> index f06c92e..5e1c469 100644
> --- a/net/ipv4/fib_trie.c
> +++ b/net/ipv4/fib_trie.c
[...]
> @@ -316,48 +320,50 @@ static inline void empty_child_dec(struct key_vector *n)
>
>   static struct key_vector *leaf_new(t_key key, struct fib_alias *fa)
>   {
[...]
> +	struct tnode *kv = kmem_cache_alloc(trie_leaf_kmem, GFP_KERNEL);
> +	struct key_vector *l = kv->kv;
> +
> +	if (!kv)

    You dereference 'kv' before this check.

[...]
>   static struct key_vector *tnode_new(t_key key, int pos, int bits)
>   {
> -	struct key_vector *tn = tnode_alloc(bits);
> +	struct tnode *tnode = tnode_alloc(bits);
>   	unsigned int shift = pos + bits;
> +	struct key_vector *tn = tnode->kv;
>
>   	/* verify bits and pos their msb bits clear and values are valid */
>   	BUG_ON(!bits || (shift > KEYLENGTH));
>
[...]
> +	pr_debug("AT %p s=%zu %zu\n", tnode, TNODE_SIZE(0),
>   		 sizeof(struct key_vector *) << bits);
> +
> +	if (!tnode)

    Likewise with 'tnode'.

[...]

WBR, Sergei