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From: Eric Dumazet <eric.dumazet@gmail.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: Wei Liu <wei.liu2@citrix.com>,
	davem@davemloft.net, Ian Campbell <ian.campbell@citrix.com>,
	Dion Kant <g.w.kant@hunenet.nl>,
	xen-devel@lists.xen.org, netdev@vger.kernel.org,
	stable@vger.kernel.org
Subject: Re: [Xen-devel] [PATCH] xen-netfront: pull on receive skb may need to happen earlier
Date: Mon, 08 Jul 2013 08:22:18 -0700	[thread overview]
Message-ID: <1373296938.4979.111.camel@edumazet-glaptop> (raw)
In-Reply-To: <51DAE6CA02000078000E3566@nat28.tlf.novell.com>

On Mon, 2013-07-08 at 15:20 +0100, Jan Beulich wrote:

> Okay, so with that done (see below) Dion is now seeing the
> WARN_ON_ONCE(delta < len) in skb_try_coalesce() triggering. Of
> course, with it having crashed before, it's hard to tell whether the
> triggering now is an effect of the patch, or just got unmasked by it.

Please note this warning is not the sign of an error.

It can be triggered because network stack (IP + TCP) had to reallocate
skb->head to hold all the headers.

pskb_may_pull() doesn't change skb->truesize, for various reasons, so we
can have a situation where the warning triggers.

For example, it can happen when drivers use a really small skb->head,
like 64 bytes, as its not big enough to hold ethernet+IP+TCP headers.

For example, I did a patch on a wifi driver (iwl3945: better skb
management in rx path) because of this sub optimal skb->head sizing.

  parent reply	other threads:[~2013-07-08 15:22 UTC|newest]

Thread overview: 85+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <8511913.uMAmUdIO30@eistomin.edss.local>
2013-05-17  8:59 ` [Xen-users] kernel 3.9.2 - xen 4.2.2/4.3rc1 => BUG unable to handle kernel paging request netif_poll+0x49c/0xe8 Wei Liu
2013-05-17  9:08   ` Jan Beulich
2013-05-17  9:37   ` Eugene Istomin
2013-05-17  9:40     ` Eugene Istomin
2013-05-17 10:45     ` Jan Beulich
2013-05-17 12:03       ` Eugene Istomin
2013-05-17 12:25         ` Jan Beulich
2013-05-17 12:30           ` Eugene Istomin
2013-05-17 12:36             ` Jan Beulich
2013-05-17 12:52               ` Eugene Istomin
2013-05-17 13:00                 ` Eugene Istomin
2013-05-18 10:06                   ` Eugene Istomin
2013-05-20  6:52                     ` Eugene Istomin
2013-05-20  8:58                       ` Ian Campbell
2013-05-20  9:06                       ` Wei Liu
2013-05-20  9:17                         ` Eugene Istomin
2013-05-20  9:24                           ` Wei Liu
2013-05-21  9:55                   ` Jan Beulich
2013-05-21 11:09                     ` Eugene Istomin
2013-05-21 11:49                       ` Jan Beulich
2013-05-21 16:19                         ` Eugene Istomin
2013-05-31  3:37                           ` Eugene Istomin
2013-05-31  6:19                             ` Jan Beulich
2013-05-31  6:22                               ` Eugene Istomin
2013-05-31  8:20                               ` Wei Liu
2013-05-21 15:28                     ` Wei Liu
2013-05-31 15:47                       ` Wei Liu
2013-05-31 16:00                         ` Jan Beulich
2013-05-31 16:05                           ` Wei Liu
2013-07-04 13:43   ` Dion Kant
2013-07-04 14:18     ` Jan Beulich
2013-07-04 15:01     ` Wei Liu
2013-07-05  9:32       ` [PATCH] xen-netfront: pull on receive skb may need to happen earlier Jan Beulich
2013-07-05 14:53         ` Wei Liu
2013-07-05 14:53         ` Wei Liu
2013-07-07  1:10           ` David Miller
2013-07-07  1:10           ` David Miller
2013-07-08  9:59           ` Jan Beulich
2013-07-08 12:16             ` Dion Kant
2013-07-08 12:41               ` Jan Beulich
2013-07-08 12:41               ` Jan Beulich
2013-07-08 14:20             ` [Xen-devel] " Jan Beulich
2013-07-08 15:22               ` Eric Dumazet
2013-07-08 15:22               ` Eric Dumazet [this message]
2013-07-09  7:47                 ` [Xen-devel] " Jan Beulich
2013-07-09  7:47                 ` Jan Beulich
2013-07-08 15:48               ` [Xen-devel] " Wei Liu
2013-07-09  6:52                 ` Jan Beulich
2013-07-09  6:52                 ` [Xen-devel] " Jan Beulich
2013-07-09 16:51                   ` Wei Liu
2013-07-09 16:51                   ` [Xen-devel] " Wei Liu
2013-07-10  6:58                     ` Jan Beulich
2013-07-10  6:58                     ` [Xen-devel] " Jan Beulich
2013-07-10 10:04                       ` Wei Liu
2013-07-10 10:04                       ` [Xen-devel] " Wei Liu
2013-07-10 10:46                         ` Jan Beulich
2013-07-10 12:50                           ` Ian Campbell
2013-07-10 12:53                             ` Wei Liu
2013-07-10 12:53                             ` Wei Liu
2013-07-10 13:58                             ` Jan Beulich
2013-07-10 13:58                             ` [Xen-devel] " Jan Beulich
2013-07-10 12:50                           ` Ian Campbell
2013-07-10 10:46                         ` Jan Beulich
2013-07-10 13:19                       ` [Xen-devel] " Eric Dumazet
2013-07-10 13:19                       ` Eric Dumazet
2013-07-08 15:48               ` Wei Liu
2013-07-12  8:32               ` [Xen-devel] " Wei Liu
2013-07-12  8:56                 ` Jan Beulich
2013-07-13 11:26                   ` Dion Kant
2013-07-13 11:26                   ` [Xen-devel] " Dion Kant
2013-07-13 20:17                     ` Dion Kant
2013-07-15  6:37                       ` Jan Beulich
2013-07-12  8:56                 ` Jan Beulich
2013-07-12  8:32               ` Wei Liu
2013-07-08 14:20             ` Jan Beulich
2013-07-08  9:59           ` Jan Beulich
2013-07-05  9:32       ` Jan Beulich
2013-07-05  9:36       ` kernel 3.9.2 - xen 4.2.2/4.3rc1 => BUG unable to handle kernel paging request netif_poll+0x49c/0xe8 Jan Beulich
2013-07-05 10:40       ` [Xen-users] " Dion Kant
2013-07-05 10:54         ` Wei Liu
2013-07-05 19:11           ` Dion Kant
2013-07-05 10:56         ` Jan Beulich
2013-07-05 19:46           ` Dion Kant
2013-07-06 13:36             ` Wei Liu
2013-07-08  8:25             ` Jan Beulich

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