linux-kernel - Re: [PATCH] af_key: suppress a warning for 64k pages.

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Message-Id: <20071030.210846.215166155.davem@davemloft.net>
Date:	Tue, 30 Oct 2007 21:08:46 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	sfr@...b.auug.org.au
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] af_key: suppress a warning for 64k pages.

From: Stephen Rothwell <sfr@...b.auug.org.au>
Date: Wed, 31 Oct 2007 14:59:54 +1100

> On PowerPC allmodconfig build we get this:
> 
> net/key/af_key.c:400: warning: comparison is always false due to limited range of data type
> 
> Signed-off-by: Stephen Rothwell <sfr@...b.auug.org.au>
...
>  
> +	/* sadb_x_ctx_len is uint16_t */
> +#if PAGE_SIZE < (1 << 16)
>  	if (sec_ctx->sadb_x_ctx_len > PAGE_SIZE)
>  		return -EINVAL;
> +#endif
>  
>  	len = pfkey_sec_ctx_len(sec_ctx);
>  

I'm not so sure ifdef'ing things up all over the place is the way to
solve this.  It makes the code ultra ugly.

I think we should retain the check, but modify it so that GCC knows we
understand that it's OK if it is always false.  Perhaps a simple (u32)
cast on the left branch of the comparison is sufficient?
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