netdev - Re: [PATCH] net: Initialize entire flowi struct

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Message-ID: <alpine.LFD.2.00.1109031004500.1492@ja.ssi.bg>
Date:	Sat, 3 Sep 2011 10:27:34 +0300 (EEST)
From:	Julian Anastasov <ja@....bg>
To:	"Ward, David - 0663 - MITLL" <david.ward@...mit.edu>
cc:	David Miller <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: Initialize entire flowi struct


	Hello,

On Thu, 1 Sep 2011, Ward, David - 0663 - MITLL wrote:

> > 	Not sure if adding size as parameter to flow_hash_code
> > is better approach. May be flow_cache_lookup needs to
> > determine size from family that can be used for flow_hash_code,
> > flow_key_compare and the memcpy(&fle->key, key, sizeof(*key))
> > after fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC).
> 
> Makes sense to me.  However should we just replace flow_key_compare with
> memcmp then, since the assumptions about constant size and alignment will no
> longer apply?  Or should there be a separate flow_key_compare function for
> each family, and have all of the flowi* structures become
> __attribute__((__aligned__(BITS_PER_LONG/8))) ?

	I don't know this code well but I guess memcmp is
not preferred. IMHO, as the callers provide per-family
structures and we do not want to change that, these
structures must be aligned to long type as required by
flow_compare_t and jhash2 (at least u32) usage. The second
option is to use memcmp and jhash instead of jhash2 to
avoid such alignment but I guess other developers will
oppose it. More opinions are needed here.

Regards

--
Julian Anastasov <ja@....bg>
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