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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable 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 23B86C43219 for ; Sat, 4 May 2019 16:08:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E92C42086A for ; Sat, 4 May 2019 16:08:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Qy5UvT9t" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726770AbfEDQIY (ORCPT ); Sat, 4 May 2019 12:08:24 -0400 Received: from mail-pg1-f194.google.com ([209.85.215.194]:44429 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726217AbfEDQIY (ORCPT ); Sat, 4 May 2019 12:08:24 -0400 Received: by mail-pg1-f194.google.com with SMTP id z16so4236371pgv.11; Sat, 04 May 2019 09:08:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=sC4Bm0S6AdzqPJDKFbvFqnZ8jJH7VxxKHL8X8WXctzY=; b=Qy5UvT9tK7aq1yH8lclXhft6+d/JDypXwBKIS31NCEoXBkkwBqtM1qmcroOAdjjzcJ HIcWozT8ShmM+S820CGLhDvYEYIj9LGR4pvCUhZ3MnaMo/fzYhnD3zmXYaE/OH78wgGY w3k1UMPOa62P3EkxJOpRdu7qi2sufU2olhywG5i/IrU3Bp2AoKkNwrjwbiBuqfx/5nTH Z4ASOr4Nb4nZyKKzhIY/IUTYrEsYufbhjIwiUTGx1mUILePaRxU96rrHkSnwwjUAzZTs RPoQIPRCWn2kTh57tIlOhUhYS6LGgjA0aToD2hIgNTUpqbgLfdYcfIVliR+xO2V9062k V8Ug== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=sC4Bm0S6AdzqPJDKFbvFqnZ8jJH7VxxKHL8X8WXctzY=; b=VgG6Q5kE49RvqFCjyiEfuN14bVP7Ma8p5Du2YkgTrmampPbbOmgnBN6Llp2amtJ0Jt ngOGBZOhqpVG6/fdRqCreoQrgMmrhn24j615dbpBBempNigWMSfsuCxluJAfPfpFatBT OCqIhcDf/wUMZRCJQz/XT4vJUbRRFbUGkoPPPOYPxRSbmOx7mcYG/Hjdq1XCgRFhieoS Mqau+pfUm51AQ1bowmWS9t6FYBTVAjX55blNGYUBhJ34brQXkOYIyYWyC0amJt7TLxUm ppcWaPeNe9M5BNKaVyhU+jbusifoyUyxxAltEdqYXoXOqDl44iq1EYRp6mQX5kb00FK+ 78RA== X-Gm-Message-State: APjAAAXDS+0B3/IacieCiZIpEgoupLQkvoqXW2iT/oXUu4vBmql35R9n 1rh3G869ICOfFUeXPsnTvpY= X-Google-Smtp-Source: APXvYqxBQfLA16cLdJkghpXZpM2fYIlOwAM8blNJzY1aoU3igmXWBnATMkuSzRW4vvs5XlcUhLJ6ig== X-Received: by 2002:a63:243:: with SMTP id 64mr19321172pgc.214.1556986103844; Sat, 04 May 2019 09:08:23 -0700 (PDT) Received: from bridge ([119.28.31.106]) by smtp.gmail.com with ESMTPSA id j20sm8706452pfn.84.2019.05.04.09.08.19 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 04 May 2019 09:08:23 -0700 (PDT) Date: Sun, 5 May 2019 00:08:17 +0800 From: Wenbin Zeng To: Al Viro 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: <20190504160817.GA15804@bridge> References: <1556692945-3996-1-git-send-email-wenbinzeng@tencent.com> <1556692945-3996-2-git-send-email-wenbinzeng@tencent.com> <20190502030406.GT23075@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190502030406.GT23075@ZenIV.linux.org.uk> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu, May 02, 2019 at 04:04:06AM +0100, Al Viro wrote: > 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... Hi Al, thank you very much. You are absolutely right. ->evict() should be called before ->put(), i.e.: @@ -49,6 +49,8 @@ static void nsfs_evict(struct inode *inode) struct ns_common *ns = inode->i_private; clear_inode(inode); + if (ns->ops->evict) + ns->ops->evict(ns); ns->ops->put(ns); } Does this look good?