From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: linux-nfs-owner@vger.kernel.org Received: from relay.parallels.com ([195.214.232.42]:39573 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932302Ab2EWLa0 (ORCPT ); Wed, 23 May 2012 07:30:26 -0400 Message-ID: <4FBCCA4F.3020600@parallels.com> Date: Wed, 23 May 2012 15:30:23 +0400 From: Stanislav Kinsbursky MIME-Version: 1.0 To: "Myklebust, Trond" CC: "linux-nfs@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "devel@openvz.org" Subject: Re: [PATCH] NFS: init client before declaration 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> <1337701904.4269.16.camel@lade.trondhjem.org> <4FBBBC4C.5010103@parallels.com> <1337705000.4269.23.camel@lade.trondhjem.org> <1337718771.4269.29.camel@lade.trondhjem.org> In-Reply-To: <1337718771.4269.29.camel@lade.trondhjem.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Sender: linux-nfs-owner@vger.kernel.org List-ID: On 23.05.2012 00:32, Myklebust, Trond wrote: > On Tue, 2012-05-22 at 12:43 -0400, Trond Myklebust wrote: >> On Tue, 2012-05-22 at 20:18 +0400, Stanislav Kinsbursky wrote: >>> We have another problem here. >>> nfs4_init_client() will try to create pipe dentries prior to set of NFS_CS_READY >>> to the client. And dentries will be created since semaphore is dropped and >>> per-net superblock variable is initialized already. >>> But __rpc_pipefs_event() relays on the fact, that no dentries present. >>> Looks like the problem was introduced by me in aad9487c... >>> So maybe we should not call "continue" instead "__rpc_pipefs_event()", when >>> client becomes ready? >>> Looks like this will allow us to handle such races. >> >> Let me rework this patch a bit... > > The following is ugly, but it should be demonstrably correct, and will > ensure that __rpc_pipefs_event() will only be called for fully > initialised nfs_clients... > > 8<--------------------------------------------------------------------- > From 90c3b9fe9faeae32c8f629e8b6cbf5f50bb9b295 Mon Sep 17 00:00:00 2001 > From: Trond Myklebust > Date: Tue, 22 May 2012 16:22:50 -0400 > Subject: [PATCH 1/2] 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 on such a thing. > > The solution is to have the mount notification wait for the > initialisation of each nfs_client to complete, and then to > skip any entries for which the it failed. > > Reported-by: Stanislav Kinsbursky > Signed-off-by: Trond Myklebust > --- > fs/nfs/client.c | 10 ++++++++++ > fs/nfs/idmap.c | 15 +++++++++++++++ > fs/nfs/internal.h | 1 + > 3 files changed, 26 insertions(+), 0 deletions(-) > > diff --git a/fs/nfs/client.c b/fs/nfs/client.c > index 60f7e4e..d3c8553 100644 > --- a/fs/nfs/client.c > +++ b/fs/nfs/client.c > @@ -583,6 +583,16 @@ found_client: > return clp; > } > > +static bool nfs_client_ready(const struct nfs_client *clp) > +{ > + return clp->cl_cons_state<= NFS_CS_READY; > +} > + > +int nfs_wait_client_ready(const struct nfs_client *clp) > +{ > + return wait_event_killable(nfs_client_active_wq, nfs_client_ready(clp)); > +} > + > /* > * Mark a server as ready or failed > */ > diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c > index 3e8edbe..c0753c5 100644 > --- a/fs/nfs/idmap.c > +++ b/fs/nfs/idmap.c > @@ -530,9 +530,24 @@ static struct nfs_client *nfs_get_client_for_event(struct net *net, int event) > struct nfs_net *nn = net_generic(net, nfs_net_id); > struct dentry *cl_dentry; > struct nfs_client *clp; > + int err; > > +restart: > spin_lock(&nn->nfs_client_lock); > list_for_each_entry(clp,&nn->nfs_client_list, cl_share_link) { > + /* Wait for initialisation to finish */ > + if (clp->cl_cons_state> NFS_CS_READY) { > + atomic_inc(&clp->cl_count); > + spin_unlock(&nn->nfs_client_lock); > + err = nfs_wait_client_ready(clp); What about NFSv4.1 ? It's clients NFS_CS_READY status depends on session establishing RPC calls... Which in turn can hung up pipefs mount call... Moreover, looks like pipefs dentries creation have to be synchronized by nfs_client_lock somehow... Otherwise because of races we can get a client without pipe dentry.... > + nfs_put_client(clp); > + if (err) > + return NULL; > + goto restart; > + } > + /* Skip nfs_clients that failed to initialise */ > + if (clp->cl_cons_state< 0) > + continue; > if (clp->rpc_ops !=&nfs_v4_clientops) > continue; > cl_dentry = clp->cl_idmap->idmap_pipe->dentry; > diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h > index b777bda..3ee4040 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(const 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, -- Best regards, Stanislav Kinsbursky