From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759799Ab2EVPvs (ORCPT ); Tue, 22 May 2012 11:51:48 -0400 Received: from mx2.netapp.com ([216.240.18.37]:45606 "EHLO mx2.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759735Ab2EVPvp (ORCPT ); Tue, 22 May 2012 11:51:45 -0400 X-IronPort-AV: E=Sophos;i="4.75,639,1330934400"; d="scan'208";a="649453305" From: "Myklebust, Trond" To: Stanislav Kinsbursky CC: "linux-nfs@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "devel@openvz.org" Subject: Re: [PATCH] NFS: init client before declaration Thread-Topic: [PATCH] NFS: init client before declaration Thread-Index: AQHNOBgchN+45TnxmEuX3jdeWgHLc5bWU9EAgAAIiACAAAgtgIAABjUA Date: Tue, 22 May 2012 15:51:44 +0000 Message-ID: <1337701904.4269.16.camel@lade.trondhjem.org> References: <20120522124018.338.20817.stgit@localhost.localdomain> <1337696984.4269.4.camel@lade.trondhjem.org> <1337698816.4269.15.camel@lade.trondhjem.org> <4FBBB0DB.6050708@parallels.com> In-Reply-To: <4FBBB0DB.6050708@parallels.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.104.60.115] Content-Type: text/plain; charset="utf-8" Content-ID: <2DFACEB47BBF6A49ACB46BA75F530DD7@tahoe.netapp.com> MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by nfs id q4MFpsB9018269 On Tue, 2012-05-22 at 19:29 +0400, Stanislav Kinsbursky wrote: > On 22.05.2012 19:00, Myklebust, Trond wrote: > > On Tue, 2012-05-22 at 10:29 -0400, Trond Myklebust wrote: > >> On Tue, 2012-05-22 at 16:40 +0400, Stanislav Kinsbursky wrote: > >>> Client have to be initialized prior to adding it to per-net clients list, > >>> because otherwise there are races, shown below: > >>> > >>> CPU#0 CPU#1 > >>> _____ _____ > >>> > >>> nfs_get_client > >>> nfs_alloc_client > >>> list_add(..., nfs_client_list) > >>> rpc_fill_super > >>> rpc_pipefs_event > >>> nfs_get_client_for_event > >>> __rpc_pipefs_event > >>> (clp->cl_rpcclient is uninitialized) > >>> BUG() > >>> init_client > >>> clp->cl_rpcclient = ... > >>> > >> > >> Why not simply change nfs_get_client_for_event() so that it doesn't > >> touch nfs_clients that have clp->cl_cons_state!=NFS_CS_READY? > >> > >> That should ensure that it doesn't touch nfs_clients that failed to > >> initialise and/or are still in the process of being initialised. > > > > ...actually, come to think of it. Why not just add a helper function > > "bool nfs_client_active(const struct nfs_client *clp)" to > > fs/nfs/client.c that does a call to > > wait_event_killable(nfs_client_active_wq, clp->cl_cons_state< NFS_CS_INITING); > > and checks the resulting value of clp->cl_cons_state? > > > > Sorry, but I don't understand the idea... > Where are you proposing to call this function? > In __rpc_pipefs_event() prior to dentries creatios? See below: 8<---------------------------------------------------------------------------------- >>From f5b90df6381a20395d9f88a199e9e52f44267457 Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Tue, 22 May 2012 11:49:55 -0400 Subject: [PATCH] NFSv4: Fix a race in the net namespace mount notification Since the struct nfs_client gets added to the global nfs_client_list before it is initialised, it is possible that rpc_pipefs_event can end up trying to create idmapper entries for such a thing. The solution is to have the mount notification wait for the nfs_client initialisation to complete. Reported-by: Stanislav Kinsbursky Signed-off-by: Trond Myklebust --- fs/nfs/client.c | 14 ++++++++++++++ fs/nfs/idmap.c | 3 ++- fs/nfs/internal.h | 1 + 3 files changed, 17 insertions(+), 1 deletions(-) diff --git a/fs/nfs/client.c b/fs/nfs/client.c index 60f7e4e..3fa44ef 100644 --- a/fs/nfs/client.c +++ b/fs/nfs/client.c @@ -592,6 +592,20 @@ void nfs_mark_client_ready(struct nfs_client *clp, int state) wake_up_all(&nfs_client_active_wq); } +static bool nfs_client_ready(struct nfs_client *clp) +{ + return clp->cl_cons_state <= NFS_CS_READY; +} + +int nfs_wait_client_ready(struct nfs_client *clp) +{ + if (wait_event_killable(nfs_client_active_wq, nfs_client_ready(clp)) < 0) + return -ERESTARTSYS; + if (clp->cl_cons_state < 0) + return clp->cl_cons_state; + return 0; +} + /* * With sessions, the client is not marked ready until after a * successful EXCHANGE_ID and CREATE_SESSION. diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c index 3e8edbe..67962c8 100644 --- a/fs/nfs/idmap.c +++ b/fs/nfs/idmap.c @@ -558,7 +558,8 @@ static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event, return 0; while ((clp = nfs_get_client_for_event(sb->s_fs_info, event))) { - error = __rpc_pipefs_event(clp, event, sb); + if (nfs_wait_client_ready(clp) == 0) + error = __rpc_pipefs_event(clp, event, sb); nfs_put_client(clp); if (error) break; diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h index b777bda..3be00a0 100644 --- a/fs/nfs/internal.h +++ b/fs/nfs/internal.h @@ -168,6 +168,7 @@ extern struct nfs_server *nfs_clone_server(struct nfs_server *, struct nfs_fattr *, rpc_authflavor_t); extern void nfs_mark_client_ready(struct nfs_client *clp, int state); +extern int nfs_wait_client_ready(struct nfs_client *clp); extern int nfs4_check_client_ready(struct nfs_client *clp); extern struct nfs_client *nfs4_set_ds_client(struct nfs_client* mds_clp, const struct sockaddr *ds_addr, -- 1.7.7.6 -- Trond Myklebust Linux NFS client maintainer NetApp Trond.Myklebust@netapp.com www.netapp.com {.n++%ݶw{.n+{G{ayʇڙ,jfhz_(階ݢj"mG?&~iOzv^m ?I