netdev - Re: [PATCH 5/5] skbuff: skb_segment: orphan frags before copying

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Message-ID: <20140310221223.GA15839@gondor.apana.org.au>
Date:	Tue, 11 Mar 2014 06:12:23 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	linux-kernel@...r.kernel.org, jbenc@...hat.com,
	David Miller <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Daniel Borkmann <dborkman@...hat.com>,
	Simon Horman <horms@...ge.net.au>,
	Paul Durrant <Paul.Durrant@...rix.com>,
	Thomas Graf <tgraf@...g.ch>, Miklos Szeredi <mszeredi@...e.cz>,
	=?UTF-8?q?Peter=20Pan=28=E6=BD=98=E5=8D=AB=E5=B9=B3=29?= <panweiping3@...il.com>,
	netdev@...r.kernel.org
Subject: Re: [PATCH 5/5] skbuff: skb_segment: orphan frags before copying

On Tue, Mar 11, 2014 at 12:07:17AM +0200, Michael S. Tsirkin wrote:
> 
> Once one skb completes the callback is invoked and userspace
> reuses this buffer for something else.
> At that point it's too late to do the copy.

OK, would it be possible to delay the callback until all generated
skbs are completed?

> > IOW if we pass along SKBTX_SHARED_FRAG will it work?
> 
> I don't see how would SKBTX_SHARED_FRAG help with this at all.
> That only works for pages gifted to kernel by e.g. vmsplice
> that aren't reused by userspace.

Sorry cut-n-paste error, I meant SKBTX_DEV_ZEROCOPY.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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