From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail.candelatech.com ([208.74.158.172]:38495 "EHLO ns3.lanforge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755122Ab3AWSPT (ORCPT ); Wed, 23 Jan 2013 13:15:19 -0500 Message-ID: <510028A7.1080902@candelatech.com> Date: Wed, 23 Jan 2013 10:15:03 -0800 From: Ben Greear MIME-Version: 1.0 To: Eric Dumazet CC: netdev , "linux-nfs@vger.kernel.org" Subject: Re: 3.7.3+: Bad paging request in ip_rcv_finish while running NFS traffic. References: <50FDADF4.3060601@candelatech.com> <50FDDE35.7070806@candelatech.com> <1358829606.3464.3151.camel@edumazet-glaptop> <50FE2A57.3040804@candelatech.com> <50FEC796.5090404@candelatech.com> <1358875020.3464.4006.camel@edumazet-glaptop> <1358875607.3464.4020.camel@edumazet-glaptop> <50FF102F.2050008@candelatech.com> <50FF4BC9.1060206@candelatech.com> <1358921493.12374.737.camel@edumazet-glaptop> <50FF8DEC.9070901@candelatech.com> <1358948110.12374.748.camel@edumazet-glaptop> In-Reply-To: <1358948110.12374.748.camel@edumazet-glaptop> Content-Type: text/plain; charset=UTF-8; format=flowed Sender: linux-nfs-owner@vger.kernel.org List-ID: On 01/23/2013 05:35 AM, Eric Dumazet wrote: > On Tue, 2013-01-22 at 23:14 -0800, Ben Greear wrote: > >> How are the non-ref-counted dst objects used safely? Any chance >> that tearing down the IP protocol on a device (or deleting a device) >> could delete a dst that is referenced by an skb (and thus crashes as >> I see)? > > There is probably a bug. Normally it should be RCU protected. I'm building net-next, and will do some testing on it later today if all goes well. In the meantime, a few questions about RCU. If the non-ref-counted dst is protected by RCU, does that mean that from the time we acquire the pointer (ie, set it in the skb), to the time we clear the pointer from the skb, we must be under RCU read lock? If so, that means that ip_rcv_finish must be called under RCU read lock, etc? Btw, this seems non related to NFS, so I'm dropping them from CC after this email unless I hear a request otherwise. Thanks, Ben -- Ben Greear Candela Technologies Inc http://www.candelatech.com