linux-kernel - RE: [patch v1, kernel version 3.2.1] rtnetlink workaround around the skb buff size issue

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Date:	Tue, 7 Feb 2012 18:26:32 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	"Rose, Gregory V" <gregory.v.rose@...el.com>
CC:	David Miller <davem@...emloft.net>,
	"steweg@...t.sk" <steweg@...t.sk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [patch v1, kernel version 3.2.1] rtnetlink workaround around
 the skb buff size issue

On Tue, 2012-02-07 at 00:13 +0000, Rose, Gregory V wrote:
> > -----Original Message-----
> > From: Ben Hutchings [mailto:bhutchings@...arflare.com]
> > Sent: Monday, February 06, 2012 3:51 PM
> > To: Rose, Gregory V
> > Cc: David Miller; steweg@...t.sk; linux-kernel@...r.kernel.org;
> > netdev@...r.kernel.org
> > Subject: RE: [patch v1, kernel version 3.2.1] rtnetlink workaround around
> > the skb buff size issue
> > 
> > On Mon, 2012-02-06 at 04:41 +0000, Rose, Gregory V wrote:
> > [...]
> > > > This is not how we're going to fix this.  I already stated the desired
> > > > way to fix this, which is to make the existing dump request have a way
> > > > for the requestor to enable extended parts of the device dump.
> > > >
> > > > This is just like netlink diag socket dumps, where the dump request
> > > > specifies what the user wants to see.
> > > >
> > > > In this case we'd add a netlink attribute to the dump request which
> > > > is just a u32 bitmask or similar.
> > > >
> > > > The Intel engineer who added the VF dump support said he would work on
> > > > this fix so why don't you just wait patiently for him to do the work?
> > >
> > > The patch below is what I've got so far.  Right now the bit mask array
> > > is global so if you enable display of VF (n) on one interface it will
> > > enable display of the same VF on other interfaces.  I intend to move
> > > the bit mask array into the net_device structure so we can set the
> > > display mask for each interface independently.
> > 
> > I don't think this can work.  Using an application that requests VF
> > information and uses large buffers (e.g. the updated 'ip') will break
> > another application that doesn't (e.g. current Network Manager), won't
> > it?
> 
> It's my understanding that the problem isn't with the application
> buffer size but with the kernel buffer size, which is limited to a
> page.
[...]

Then it's no wonder you're going about this the wrong way.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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