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Message-Id: <200804071724.51781.rusty@rustcorp.com.au> Date: Mon, 7 Apr 2008 17:24:51 +1000 From: Rusty Russell <rusty@...tcorp.com.au> To: Herbert Xu <herbert@...dor.apana.org.au> Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org, maxk@...lcomm.com Subject: Re: [PATCH RFC 4/5] tun: vringfd xmit support. On Monday 07 April 2008 15:13:44 Herbert Xu wrote: > Rusty Russell <rusty@...tcorp.com.au> wrote: > > +/* We are done with this skb: put it in the used pile. */ > > +static void skb_finished(struct skb_shared_info *sinfo) > > +{ > > + struct skb_shinfo_tun *sht = (void *)(sinfo + 1); > > + > > + /* FIXME: Race prevention */ > > + vring_used_buffer_atomic(sht->tun->outring, sht->id, sht->len); > > + vring_wake(sht->tun->outring); > > + > > + /* Release device. */ > > + dev_put(sht->tun->dev); > > +} > > On second thought, this is not going to work. The network stack > can clone individual pages out of this skb and put it into a new > skb. Therefore whatever scheme we come up with will either need > to be page-based, or add a flag to tell the network stack that it > can't clone those pages. Erk... I'll put in the latter for now. A page-level solution is not really an option: if userspace hands us mmaped pages for example. Thanks, Rusty. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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