netdev - Re: [PATCH 2/2] net: Handle different key sizes between address families in flow cache

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Message-ID: <CAHXqBF+eF_zYAFPZv0hWUvDHv5YMHuFAR3-iB8MEZz2G7vCUyA@mail.gmail.com>
Date:	Sun, 4 Sep 2011 17:34:19 +0200
From:	Michał Mirosław <mirqus@...il.com>
To:	David Ward <david.ward@...mit.edu>
Cc:	netdev@...r.kernel.org, Julian Anastasov <ja@....bg>
Subject: Re: [PATCH 2/2] net: Handle different key sizes between address
 families in flow cache

2011/9/4 David Ward <david.ward@...mit.edu>:
> With the conversion of struct flowi to a union of AF-specific structs, some
> operations on the flow cache need to account for the exact size of the key.
[...]
> --- a/include/net/flow.h
> +++ b/include/net/flow.h
[...]
> +typedef unsigned long flow_compare_t;
> +
> +static inline size_t flowi_size(u16 family)
> +{
> +       switch (family) {
> +       case AF_INET:
> +               BUILD_BUG_ON(sizeof(struct flowi4) % sizeof(flow_compare_t));
> +               return sizeof(struct flowi4);
> +       case AF_INET6:
> +               BUILD_BUG_ON(sizeof(struct flowi6) % sizeof(flow_compare_t));
> +               return sizeof(struct flowi6);
> +       case AF_DECnet:
> +               BUILD_BUG_ON(sizeof(struct flowidn) % sizeof(flow_compare_t));
> +               return sizeof(struct flowidn);
> +       }
> +       return 0;
> +}

Since most called user (flow_key_compare) uses returned value didided
by sizeof(flow_compare_t), you could just return divided value here
and save some shift operations by it.

Best Regards,
Michał Mirosław
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