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From: Eric Dumazet <eric.dumazet@gmail.com>
To: Alexander Duyck <alexander.duyck@gmail.com>
Cc: "Alexander Duyck" <alexander.h.duyck@intel.com>,
	"David Miller" <davem@davemloft.net>,
	netdev <netdev@vger.kernel.org>,
	"Neal Cardwell" <ncardwell@google.com>,
	"Tom Herbert" <therbert@google.com>,
	"Jeff Kirsher" <jeffrey.t.kirsher@intel.com>,
	"Michael Chan" <mchan@broadcom.com>,
	"Matt Carlson" <mcarlson@broadcom.com>,
	"Herbert Xu" <herbert@gondor.apana.org.au>,
	"Ben Hutchings" <bhutchings@solarflare.com>,
	"Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>,
	"Maciej Żenczykowski" <maze@google.com>
Subject: Re: [PATCH net-next] net: take care of cloned skbs in tcp_try_coalesce()
Date: Thu, 03 May 2012 05:14:29 +0200	[thread overview]
Message-ID: <1336014869.22133.821.camel@edumazet-glaptop> (raw)
In-Reply-To: <4FA1F4C3.8000804@gmail.com>

On Wed, 2012-05-02 at 20:00 -0700, Alexander Duyck wrote:

> This is exactly my point.  The way your current code works the check in 
> pskb_expand_head will not detect the header is cloned.
> 
> So for example lets say you have one of your skbs that goes through and 
> is merged.
> 
> 1.  You start with a cloned skb.  dataref = 2, head_frag page count = 1;
> 2.  You go through tcp_try_coalesce.  dataref = 2, head_frag page count = 2;
> 3.  You call __kfree_skb on the skb.  dataref = 1, head_frag page count = 2;


If page count was incremented in 2., this is because we stole the head.

But we could not stole the head since dataref = 2

So try to find a real example, based on current state, not on the first
patch I sent, since we made progress since this time.

Thanks

  reply	other threads:[~2012-05-03  3:14 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-27 10:37 [PATCH 3/4 net-next] net: make GRO aware of skb->head_frag Eric Dumazet
2012-04-30 17:54 ` Eric Dumazet
2012-04-30 18:10 ` [PATCH 3/4 v2 " Eric Dumazet
2012-04-30 23:36   ` Alexander Duyck
2012-05-01  1:27     ` Eric Dumazet
2012-05-01  5:33       ` Alexander Duyck
2012-05-01  6:39         ` Eric Dumazet
2012-05-01 16:17           ` Alexander Duyck
2012-05-01 17:04             ` Eric Dumazet
2012-05-01 19:45               ` Alexander Duyck
2012-05-02  2:45                 ` Eric Dumazet
2012-05-02  8:24                 ` Eric Dumazet
2012-05-02 16:16                   ` Alexander Duyck
2012-05-02 16:19                     ` Eric Dumazet
2012-05-02 16:27                       ` Eric Dumazet
2012-05-02 17:04                         ` Alexander Duyck
2012-05-02 17:02                       ` Alexander Duyck
2012-05-02 17:16                   ` Rick Jones
2012-05-01 22:58               ` Alexander Duyck
2012-05-01 23:10                 ` Alexander Duyck
2012-05-02  2:47                   ` Eric Dumazet
2012-05-02  3:54                     ` Eric Dumazet
2012-05-02  8:13                     ` [PATCH net-next] net: take care of cloned skbs in tcp_try_coalesce() Eric Dumazet
2012-05-02 15:52                       ` Alexander Duyck
2012-05-02 16:12                         ` Eric Dumazet
2012-05-02 16:27                           ` Alexander Duyck
2012-05-02 16:46                             ` Eric Dumazet
2012-05-02 17:55                               ` [PATCH v2 " Eric Dumazet
2012-05-02 19:58                                 ` [PATCH net-next] net: implement tcp coalescing in tcp_queue_rcv() Eric Dumazet
2012-05-02 20:11                                   ` Joe Perches
2012-05-02 20:23                                     ` Eric Dumazet
2012-05-02 20:34                                       ` Joe Perches
2012-05-03  0:32                                       ` David Miller
2012-05-03  1:11                                   ` David Miller
2012-05-03  2:14                                     ` Eric Dumazet
2012-05-03  2:21                                       ` David Miller
2012-05-03  1:11                                 ` [PATCH v2 net-next] net: take care of cloned skbs in tcp_try_coalesce() David Miller
2012-05-02 18:05                               ` [PATCH " Alexander Duyck
2012-05-02 18:15                                 ` Eric Dumazet
2012-05-02 20:55                                   ` Alexander Duyck
2012-05-03  1:52                                     ` Eric Dumazet
2012-05-03  3:00                                       ` Alexander Duyck
2012-05-03  3:14                                         ` Eric Dumazet [this message]
2012-05-03  3:28                                           ` Alexander Duyck
2012-05-01  1:48   ` [PATCH 3/4 v2 net-next] net: make GRO aware of skb->head_frag David Miller

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