linux-kernel - Re: [PATCH v3] tcp: splice as many packets as possible at once

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Message-ID: <20090127075418.GB4197@ff.dom.local>
Date:	Tue, 27 Jan 2009 07:54:18 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	David Miller <davem@...emloft.net>, zbr@...emap.net, w@....eu,
	dada1@...mosbay.com, ben@...s.com, mingo@...e.hu,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	jens.axboe@...cle.com
Subject: Re: [PATCH v3] tcp: splice as many packets as possible at once

On Tue, Jan 27, 2009 at 06:11:30PM +1100, Herbert Xu wrote:
> David Miller <davem@...emloft.net> wrote:
> > From: Jarek Poplawski <jarkao2@...il.com>
> > Date: Thu, 22 Jan 2009 09:04:42 +0000
> > 
> >> It seems this sk_sndmsg_page usage (refcounting) isn't consistent.
> >> I used here tcp_sndmsg() way, but I think I'll go back to this question
> >> soon.
> > 
> > Indeed, it is something to look into, as well as locking.
> > 
> > I'll try to find some time for this, thanks Jarek.
> 
> After a quick look it seems to be OK to me.  The code in the patch
> is called from tcp_splice_read, which holds the socket lock.  So as
> long as the patch uses the usual TCP convention it should work.

Yes, but ip_append_data() (and skb_append_datato_frags() for
NETIF_F_UFO only, so currently not a problem), uses this differently,
and these pages in sk->sk_sndmsg_page could leak or be used after
kfree. (I didn't track locking in these other places).

Thanks,
Jarek P.
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