From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Ricardo Leitner Subject: [PATCH v2 0/2] Avoid link dependency of dlm on sctp module Date: Tue, 14 Jul 2015 14:13:23 -0300 Message-ID: Cc: Neil Horman , Vlad Yasevich , linux-sctp@vger.kernel.org To: netdev@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:49827 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751885AbbGNRN4 (ORCPT ); Tue, 14 Jul 2015 13:13:56 -0400 Sender: netdev-owner@vger.kernel.org List-ID: Hi, I'm trying to remove a direct dependency of dlm module on sctp one. Currently dlm code is calling sctp_do_peeloff() directly and this call only is causing the load of sctp module together with dlm. For that, we have basically 3 options: - Doing a module split on dlm - which I'm avoiding because it was already split and was merged (more info on patch2 changelog) - and the sctp code on it is rather small if compared with sctp module itself - Using some other infra that gets indirectly activated, like getsockopt() - It was like this before, but the exposed sockopt created a file descriptor for the new socket and that create some serious issues. More info on 2f2d76cc3e93 ("dlm: Do not allocate a fd for peeloff") - Doing something like ipv6_stub (which is used by vxlan) or similar - but I don't feel that's a good way out here, it doesn't feel right. So I'm approaching this by going with 2nd option again but this time also creating a new sockopt that is only accessible for kernel users of this protocol, so that we are safe to directly return a struct socket * via getsockopt() results. "Kernel users" are identified by sockets that don't have a file descriptor attached to it, as only kernel users are allowed to do that and, if original socket has a file descriptor, one should just use the original option. I kept __user marker on sctp_getsockopt_peeloff_kernel() prototype and its helpers just to avoid issues with static checkers. I tried minimizing the code duplication while adding the new option, but it's just better to add a whole new function to handle it. As the sockopt arguments are different, the only thing in common between both call handlers is the call to sctp_do_peeloff(). All rest would have to have checks around it. RFC->v1, from Neil: - For identifying kernel users, switched from segment_eq() to fd check - Reused original option to avoid code duplication v1->v2, from David: - Back to new sockopt implementation, to avoid changing sockopt arg format. Marcelo Ricardo Leitner (2): sctp: add new getsockopt option SCTP_SOCKOPT_PEELOFF_KERNEL dlm: avoid using sctp_do_peeloff directly fs/dlm/lowcomms.c | 17 ++++++++--------- include/uapi/linux/sctp.h | 12 ++++++++++++ net/sctp/socket.c | 37 +++++++++++++++++++++++++++++++++++++ 3 files changed, 57 insertions(+), 9 deletions(-) -- 2.4.1