Re: [PATCH v2] SUNRPC: check current nsproxy before set of node name on client creation

Myklebust, Trond
2012-09-07T22:32:41Z

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On Mon, 2012-08-13 at 08:10 -0400, Jeff Layton wrote:
> On Mon, 13 Aug 2012 15:37:31 +0400
> Stanislav Kinsbursky <skinsbursky@parallels.com> wrote:
>
> > v2:
> > 1) rpc_clnt_set_nodename() prototype updated.
> > 2) fixed errors in comment.
> >
> > When child reaper exits, it can destroy mount namespace it belongs to, and if
> > there are NFS mounts inside, then it will try to umount them. But in this
> > point current->nsproxy is set to NULL and all namespaces will be destroyed one
> > by one. I.e. we can't dereference current->nsproxy to obtain uts namespace.
> >
> > Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
> > ---
> > net/sunrpc/clnt.c | 16 +++++++++++++---
> > 1 files changed, 13 insertions(+), 3 deletions(-)
> >
> > diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
> > index 9a9676e..8fbcbc8 100644
> > --- a/net/sunrpc/clnt.c
> > +++ b/net/sunrpc/clnt.c
> > @@ -277,8 +277,18 @@ void rpc_clients_notifier_unregister(void)
> > return rpc_pipefs_notifier_unregister(&rpc_clients_block);
> > }
> >
> > -static void rpc_clnt_set_nodename(struct rpc_clnt *clnt, const char *nodename)
> > +static void rpc_clnt_set_nodename(struct rpc_clnt *clnt)
> > {
> > + const char *nodename;
> > +
> > + /*
> > + * We have to protect against dying child reaper, which has released
> > + * its nsproxy already and is trying to destroy mount namespace.
> > + */
> > + if (current->nsproxy == NULL)
> > + return;
> > +
> > + nodename = utsname()->nodename;
> > clnt->cl_nodelen = strlen(nodename);
> > if (clnt->cl_nodelen > UNX_MAXNODENAME)
> > clnt->cl_nodelen = UNX_MAXNODENAME;
> > @@ -365,7 +375,7 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, stru
> > }
> >
> > /* save the nodename */
> > - rpc_clnt_set_nodename(clnt, utsname()->nodename);
> > + rpc_clnt_set_nodename(clnt);
> > rpc_register_client(clnt);
> > return clnt;
> >
> > @@ -524,7 +534,7 @@ rpc_clone_client(struct rpc_clnt *clnt)
> > err = rpc_setup_pipedir(new, clnt->cl_program->pipe_dir_name);
> > if (err != 0)
> > goto out_no_path;
> > - rpc_clnt_set_nodename(new, utsname()->nodename);
> > + rpc_clnt_set_nodename(new);
> > if (new->cl_auth)
> > atomic_inc(&new->cl_auth->au_count);
> > atomic_inc(&clnt->cl_count);
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
>
> Acked-by: Jeff Layton <jlayton@redhat.com>

OK, colour me confused (again). Why should a umount trigger an
rpc_create() or rpc_clone_client()?

--
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com

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