[RFC][PATCH 3/4] sunrpc: Improve UTS namespace workaround

Chuck Lever chuck.lever at oracle.com
Tue Jan 6 08:02:01 PST 2009


Matt-

Thanks for pursuing a permanent fix for this.

On Jan 5, 2009, at Jan 5, 2009, 8:13 PM, Matt Helsley wrote:

> We can improve upon a workaround applied in commit
> 63ffc23d307c9534c732edd87895e37b223004a3 ( http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=63ffc23d307c9534c732edd87895e37b223004a3 
>  )
>
> The original problem was:
>
> "On a system with nfs mounts, if a task unshares its mount namespace,
> a oops can occur when the system is rebooted if the task is the last
> to unreference the nfs mount. It will try to create a rpc request
> using utsname() which has been invalidated by free_nsproxy()."
>
> Cedric worked around this by always using the initial uts namespace  
> for RPC.
> Critically this workaround meant that RPC clients in uts namespaces  
> can never
> report the changed nodename when utilizing RPC.
>
> Fix that by storing the nodename in the NFS server structure (part  
> of the NFS
> super block) and, when an RPC client is operating on behalf of NFS,  
> reporting
> that nodename. This solves the problem for NFS clients but leaves  
> any other
> RPC users out in the cold.
>
> Rather than caching the nodename in the client structure RPC should  
> obtain the
> nodename from RPC callers. It would then be up to those services  
> making RPC
> calls to cache the nodename for as long as necessary -- somewhat  
> like this patch
> does with NFS.

Instead of having the RPC client call the consumer back, why can't you  
pass the nodename as an argument to each RPC call; say, via the  
rpc_message structure?

> NOTE: Part of Cedric's workaround -- use of the initial uts  
> namespace -- is
> still necessary because non-NFS RPC callers still rely on the  
> nodename cached
> with the RPC client struct.

In the long run I think it would be more useful to spell out where  
each consumer gets its nodename value, rather than having a convenient  
default value.  A default would encourage exposing nodenames  
inappropriately due to sloppy coding and incorrect assumptions (on the  
developer's part) about a complex API.

Where would NFSv4 callbacks get a nodename, for example?  And what  
about rpcbind requests?

> Thoughts?


More comments below.

> Signed-off-by: Matt Helsley <matthltc at us.ibm.com>
> Cc: Cedric Le Goater <clg at fr.ibm.com>
> Cc: Linux Kernel Mailing List <linux-kernel at vger.kernel.org>
> Cc: linux-nfs at vger.kernel.org
> Cc: Trond Myklebust <trond.myklebust at fys.uio.no>
> Cc: Chuck Lever <chuck.lever at oracle.com>
> Cc: Eric W. Biederman <ebiederm at xmission.com>
> Cc: Linux Containers <containers at lists.osdl.org>
>
> ---
> fs/lockd/clntproc.c         |   16 +++++++++++++---
> fs/nfs/client.c             |    6 ++++++
> fs/nfs/super.c              |    6 ++++++
> include/linux/nfs_fs.h      |    2 ++
> include/linux/nfs_fs_sb.h   |    3 +++
> include/linux/sunrpc/clnt.h |    2 ++
> net/sunrpc/auth_unix.c      |   13 ++++++++++++-
> 7 files changed, 44 insertions(+), 4 deletions(-)
>
> Index: linux-2.6.28/include/linux/sunrpc/clnt.h
> ===================================================================
> --- linux-2.6.28.orig/include/linux/sunrpc/clnt.h
> +++ linux-2.6.28/include/linux/sunrpc/clnt.h
> @@ -19,6 +19,7 @@
> #include <asm/signal.h>
>
> struct rpc_inode;
> +struct nfs_server;
>
> /*
>  * The high-level client handle
> @@ -50,6 +51,7 @@ struct rpc_clnt {
>
> 	int			cl_nodelen;	/* nodename length */
> 	char 			cl_nodename[UNX_MAXNODENAME];
> +	struct nfs_server	*cl_nfs_server;

This is a layering violation...  I would rather avoid introducing new  
strong data structure dependencies on one of RPC's consumers.

> 	char			cl_pathname[30];/* Path in rpc_pipe_fs */
> 	struct vfsmount *	cl_vfsmnt;
> 	struct dentry *		cl_dentry;	/* inode */
> Index: linux-2.6.28/net/sunrpc/auth_unix.c
> ===================================================================
> --- linux-2.6.28.orig/net/sunrpc/auth_unix.c
> +++ linux-2.6.28/net/sunrpc/auth_unix.c
> @@ -12,6 +12,13 @@
> #include <linux/sunrpc/clnt.h>
> #include <linux/sunrpc/auth.h>
>
> +#include <linux/nfs.h>
> +#include <linux/nfs2.h>
> +#include <linux/nfs3.h>
> +#include <linux/nfs4.h>
> +#include <linux/nfs_xdr.h>
> +#include <linux/nfs_fs_sb.h>
> +
> #define NFS_NGROUPS	16
>
> struct unx_cred {
> @@ -151,7 +158,11 @@ unx_marshal(struct rpc_task *task, __be3
> 	/*
> 	 * Copy the UTS nodename captured when the client was created.
> 	 */
> -	p = xdr_encode_array(p, clnt->cl_nodename, clnt->cl_nodelen);
> +	if (clnt->cl_nfs_server)
> +		p = xdr_encode_array(p, clnt->cl_nfs_server->nodename,
> +				     clnt->cl_nfs_server->nodelen);
> +	else
> +		p = xdr_encode_array(p, clnt->cl_nodename, clnt->cl_nodelen);
>
> 	*p++ = htonl((u32) cred->uc_uid);
> 	*p++ = htonl((u32) cred->uc_gid);
> Index: linux-2.6.28/include/linux/nfs_fs_sb.h
> ===================================================================
> --- linux-2.6.28.orig/include/linux/nfs_fs_sb.h
> +++ linux-2.6.28/include/linux/nfs_fs_sb.h
> @@ -126,6 +126,9 @@ struct nfs_server {
> 	u32			mountd_version;
> 	unsigned short		mountd_port;
> 	unsigned short		mountd_protocol;
> +
> +	int			nodelen;	/* nodename length */
> +	char 			nodename[UNX_MAXNODENAME];
> };
>
> /* Server capabilities */
> Index: linux-2.6.28/fs/nfs/super.c
> ===================================================================
> --- linux-2.6.28.orig/fs/nfs/super.c
> +++ linux-2.6.28/fs/nfs/super.c
> @@ -51,6 +51,7 @@
> #include <linux/nfs_xdr.h>
> #include <linux/magic.h>
> #include <linux/parser.h>
> +#include <linux/utsname.h>
>
> #include <asm/system.h>
> #include <asm/uaccess.h>
> @@ -1830,6 +1831,11 @@ static void nfs_fill_super(struct super_
> 		sb->s_time_gran = 1;
> 	}
>
> +	server->nodelen = strlen(utsname()->nodename);
> +	if (server->nodelen > UNX_MAXNODENAME)
> +		server->nodelen = UNX_MAXNODENAME;
> +	memcpy(server->nodename, utsname()->nodename, server->nodelen);
> +
> 	sb->s_op = &nfs_sops;
>  	nfs_initialise_sb(sb);
> }
> Index: linux-2.6.28/fs/nfs/client.c
> ===================================================================
> --- linux-2.6.28.orig/fs/nfs/client.c
> +++ linux-2.6.28/fs/nfs/client.c
> @@ -25,10 +25,12 @@
> #include <linux/sunrpc/metrics.h>
> #include <linux/sunrpc/xprtsock.h>
> #include <linux/sunrpc/xprtrdma.h>
> +#include <linux/sunrpc/svc.h>
> #include <linux/nfs_fs.h>
> #include <linux/nfs_mount.h>
> #include <linux/nfs4_mount.h>
> #include <linux/lockd/bind.h>
> +#include <linux/lockd/lockd.h>
> #include <linux/seq_file.h>
> #include <linux/mount.h>
> #include <linux/nfs_idmap.h>
> @@ -47,6 +49,7 @@
> #include "internal.h"
>
> #define NFSDBG_FACILITY		NFSDBG_CLIENT
> +#define NLMDBG_FACILITY		NLMDBG_CLIENT
>
> static DEFINE_SPINLOCK(nfs_client_lock);
> static LIST_HEAD(nfs_client_list);
> @@ -555,6 +558,7 @@ static void nfs_init_server_aclclient(st
>
> 	/* No errors! Assume that Sun nfsacls are supported */
> 	server->caps |= NFS_CAP_ACLS;
> +	server->client_acl->cl_nfs_server = server;
> 	return;
>
> out_noacl:
> @@ -673,6 +677,7 @@ static int nfs_init_server(struct nfs_se
> 		goto error;
>
> 	server->nfs_client = clp;
> + 	clp->cl_rpcclient->cl_nfs_server = server;
>
> 	/* Initialise the client representation from the mount data */
> 	server->flags = data->flags;
> @@ -1035,6 +1040,7 @@ static int nfs4_set_client(struct nfs_se
> 		goto error_put;
>
> 	server->nfs_client = clp;
> +	clp->cl_rpcclient->cl_nfs_server = server;
> 	dprintk("<-- nfs4_set_client() = 0 [new %p]\n", clp);
> 	return 0;
>
> Index: linux-2.6.28/fs/lockd/clntproc.c
> ===================================================================
> --- linux-2.6.28.orig/fs/lockd/clntproc.c
> +++ linux-2.6.28/fs/lockd/clntproc.c
> @@ -10,8 +10,8 @@
> #include <linux/types.h>
> #include <linux/errno.h>
> #include <linux/fs.h>
> +#include <linux/mount.h>
> #include <linux/nfs_fs.h>
> -#include <linux/utsname.h>
> #include <linux/freezer.h>
> #include <linux/sunrpc/clnt.h>
> #include <linux/sunrpc/svc.h>
> @@ -118,6 +118,11 @@ static struct nlm_lockowner *nlm_find_lo
> 	return res;
> }
>
> +struct nfs_server *fl_nfs_server(struct file_lock *fl)
> +{
> +	return NFS_SB(fl->fl_file->f_path.mnt->mnt_sb);
> +}
> +
> /*
>  * Initialize arguments for TEST/LOCK/UNLOCK/CANCEL calls
>  */
> @@ -125,15 +130,18 @@ static void nlmclnt_setlockargs(struct n
> {
> 	struct nlm_args	*argp = &req->a_args;
> 	struct nlm_lock	*lock = &argp->lock;
> +	char *nodename;
>
> 	nlmclnt_next_cookie(&argp->cookie);
> 	argp->state   = nsm_local_state;
> 	memcpy(&lock->fh, NFS_FH(fl->fl_file->f_path.dentry->d_inode),  
> sizeof(struct nfs_fh));
> -	lock->caller  = utsname()->nodename;
> +
> +	nodename = fl_nfs_server(fl)->nodename;
> +	lock->caller  = nodename;
> 	lock->oh.data = req->a_owner;
> 	lock->oh.len  = snprintf(req->a_owner, sizeof(req->a_owner), "%u@%s",
> 				(unsigned int)fl->fl_u.nfs_fl.owner->pid,
> -				utsname()->nodename);
> +				nodename);
> 	lock->svid = fl->fl_u.nfs_fl.owner->pid;
> 	lock->fl.fl_start = fl->fl_start;
> 	lock->fl.fl_end = fl->fl_end;
> @@ -272,6 +280,7 @@ nlmclnt_call(struct rpc_cred *cred, stru
> 		/* If we have no RPC client yet, create one. */
> 		if ((clnt = nlm_bind_host(host)) == NULL)
> 			return -ENOLCK;
> +		clnt->cl_nfs_server = fl_nfs_server(&argp->lock.fl);
> 		msg.rpc_proc = &clnt->cl_procinfo[proc];
>
> 		/* Perform the RPC call. If an error occurs, try again */
> @@ -344,6 +353,7 @@ static struct rpc_task *__nlm_async_call
> 	clnt = nlm_bind_host(host);
> 	if (clnt == NULL)
> 		goto out_err;
> +	clnt->cl_nfs_server = fl_nfs_server(&req->a_args.lock.fl);

This change takes care of fixing NFS client locking requests, but the  
NFS server also makes lockd callbacks to the client.  You won't have  
an nfs_server handle on the NFS server side.

Generally, you ought to pass just the nodename where needed, not a  
pointer to the nfs_server.

> 	msg->rpc_proc = &clnt->cl_procinfo[proc];
> 	task_setup_data.rpc_client = clnt;
>
> Index: linux-2.6.28/include/linux/nfs_fs.h
> ===================================================================
> --- linux-2.6.28.orig/include/linux/nfs_fs.h
> +++ linux-2.6.28/include/linux/nfs_fs.h
> @@ -262,6 +262,8 @@ static inline __u64 NFS_FILEID(const str
> 	return NFS_I(inode)->fileid;
> }
>
> +struct nfs_server *fl_nfs_server(struct file_lock *fl);
> +
> static inline void set_nfs_fileid(struct inode *inode, __u64 fileid)
> {
> 	NFS_I(inode)->fileid = fileid;
>
> -- 

--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com


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