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

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Date:	Fri, 7 Sep 2012 22:32:16 +0000
From:	"Myklebust, Trond" <Trond.Myklebust@...app.com>
To:	Jeff Layton <jlayton@...hat.com>
CC:	Stanislav Kinsbursky <skinsbursky@...allels.com>,
	"bfields@...ldses.org" <bfields@...ldses.org>,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...nvz.org" <devel@...nvz.org>
Subject: Re: [PATCH v2] SUNRPC: check current nsproxy before set of node
 name on client creation

On Mon, 2012-08-13 at 08:10 -0400, Jeff Layton wrote:
> On Mon, 13 Aug 2012 15:37:31 +0400
> Stanislav Kinsbursky <skinsbursky@...allels.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@...allels.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@...r.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> Acked-by: Jeff Layton <jlayton@...hat.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@...app.com
www.netapp.com