netdev - Re: [RFC V4 PATCH] rtnetlink: Compute and store minimum ifinfo dump size

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Message-Id: <20110518.180913.273729651812642114.davem@davemloft.net>
Date:	Wed, 18 May 2011 18:09:13 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	gregory.v.rose@...el.com
Cc:	netdev@...r.kernel.org, bhutchings@...arflare.com,
	eric.dumazet@...il.com
Subject: Re: [RFC V4 PATCH] rtnetlink: Compute and store minimum ifinfo
 dump size

From: Greg Rose <gregory.v.rose@...el.com>
Date: Wed, 18 May 2011 08:54:11 -0700

> The message size allocated for rtnl info dumps was limited to a single
> page.  This is not enough for additional interface info available with
> devices that support SR-IOV.  Calculate the amount of data required so
> the dump can allocate enough data to satisfy the request.
> 
> V2 added the calcit function to the rtnl_register calls so that
> dump functions could get the minimum dump allocation size if they
> needed to.
> 
> V3 leverages the fact that the netdev register function ends up
> calling if_nlmsg_size.  We collect the minimum dump allocation size
> there and keep it in a module static variable so that the calcit
> function doesn't have to search for the device on every info dump.
> 
> V4 fixes the title.
> 
> Signed-off-by: Greg Rose <gregory.v.rose@...el.com>

This only works if someone does a plain GETLINK request on the largest
space requiring device before the dump request happens.

Otherwise the value used by the calcit function won't be properly
prepared yet.
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