From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 93021C43219 for ; Thu, 2 May 2019 03:05:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5A7222086C for ; Thu, 2 May 2019 03:05:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726197AbfEBDFU (ORCPT ); Wed, 1 May 2019 23:05:20 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:44140 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726183AbfEBDFU (ORCPT ); Wed, 1 May 2019 23:05:20 -0400 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92 #3 (Red Hat Linux)) id 1hM210-0001NK-Lx; Thu, 02 May 2019 03:04:06 +0000 Date: Thu, 2 May 2019 04:04:06 +0100 From: Al Viro To: Wenbin Zeng Cc: davem@davemloft.net, bfields@fieldses.org, jlayton@kernel.org, trond.myklebust@hammerspace.com, anna.schumaker@netapp.com, wenbinzeng@tencent.com, dsahern@gmail.com, nicolas.dichtel@6wind.com, willy@infradead.org, edumazet@google.com, jakub.kicinski@netronome.com, tyhicks@canonical.com, chuck.lever@oracle.com, neilb@suse.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-nfs@vger.kernel.org Subject: Re: [PATCH 1/3] nsfs: add evict callback into struct proc_ns_operations Message-ID: <20190502030406.GT23075@ZenIV.linux.org.uk> References: <1556692945-3996-1-git-send-email-wenbinzeng@tencent.com> <1556692945-3996-2-git-send-email-wenbinzeng@tencent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1556692945-3996-2-git-send-email-wenbinzeng@tencent.com> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Wed, May 01, 2019 at 02:42:23PM +0800, Wenbin Zeng wrote: > The newly added evict callback shall be called by nsfs_evict(). Currently > only put() callback is called in nsfs_evict(), it is not able to release > all netns refcount, for example, a rpc client holds two netns refcounts, > these refcounts are supposed to be released when the rpc client is freed, > but the code to free rpc client is normally triggered by put() callback > only when netns refcount gets to 0, specifically: > refcount=0 -> cleanup_net() -> ops_exit_list -> free rpc client > But netns refcount will never get to 0 before rpc client gets freed, to > break the deadlock, the code to free rpc client can be put into the newly > added evict callback. > > Signed-off-by: Wenbin Zeng > --- > fs/nsfs.c | 2 ++ > include/linux/proc_ns.h | 1 + > 2 files changed, 3 insertions(+) > > diff --git a/fs/nsfs.c b/fs/nsfs.c > index 60702d6..5939b12 100644 > --- a/fs/nsfs.c > +++ b/fs/nsfs.c > @@ -49,6 +49,8 @@ static void nsfs_evict(struct inode *inode) > struct ns_common *ns = inode->i_private; > clear_inode(inode); > ns->ops->put(ns); > + if (ns->ops->evict) > + ns->ops->evict(ns); What's to guarantee that ns will not be freed by ->put()? Confused...