Re: [RFC PATCH 5 3/7] nfsd - use service thread if not executing in init namespace

["J. Bruce Fields" <bfields@fieldses.org>]

On Tue, Mar 31, 2015 at 11:14:58AM +0800, Ian Kent wrote:
> From: Ian Kent <ikent@redhat.com>
> 
> If nfsd is running within a container the client tracking operations
> should run within their originating container also. To do that get a
> token to a service thread created within the container environment
> for usermode helper calls.
> 
> Signed-off-by: Ian Kent <ikent@redhat.com>
> Cc: Benjamin Coddington <bcodding@redhat.com>
> Cc: Al Viro <viro@ZenIV.linux.org.uk>
> Cc: J. Bruce Fields <bfields@fieldses.org>
> Cc: David Howells <dhowells@redhat.com>
> Cc: Trond Myklebust <trond.myklebust@primarydata.com>
> Cc: Oleg Nesterov <onestero@redhat.com>
> Cc: Eric W. Biederman <ebiederm@xmission.com>
> Cc: Jeff Layton <jeff.layton@primarydata.com>
> ---
>  fs/nfsd/netns.h       |    3 +++
>  fs/nfsd/nfs4recover.c |   48 +++++++++++++++++++++++++++++++-----------------
>  fs/nfsd/nfsctl.c      |    6 ++++++
>  3 files changed, 40 insertions(+), 17 deletions(-)
> 
> diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
> index ea6749a..099a3c5 100644
> --- a/fs/nfsd/netns.h
> +++ b/fs/nfsd/netns.h
> @@ -112,6 +112,9 @@ struct nfsd_net {
>  	u32 clientid_counter;
>  
>  	struct svc_serv *nfsd_serv;
> +
> +	/* Namespace token */
> +	int umh_token;
>  };
>  
>  /* Simple check to find out if a given net was properly initialized */
> diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
> index 1c307f0..2547edb 100644
> --- a/fs/nfsd/nfs4recover.c
> +++ b/fs/nfsd/nfs4recover.c
> @@ -1184,7 +1184,8 @@ nfsd4_cltrack_grace_start(time_t grace_start)
>  }
>  
>  static int
> -nfsd4_umh_cltrack_upcall(char *cmd, char *arg, char *env0, char *env1)
> +nfsd4_umh_cltrack_upcall(char *cmd, char *arg,
> +			 char *env0, char *env1, int token)
>  {
>  	char *envp[3];
>  	char *argv[4];
> @@ -1209,7 +1210,11 @@ nfsd4_umh_cltrack_upcall(char *cmd, char *arg, char *env0, char *env1)
>  	argv[2] = arg;
>  	argv[3] = NULL;
>  
> -	ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_PROC);
> +	if (token > 0)
> +		ret = call_usermodehelper_service(argv[0], argv, envp,
> +						  token, UMH_WAIT_PROC);
> +	else
> +		ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_PROC);

Do we really need to handle the init_net case specially, or could we
just let it create a workqueue in that case as well?

--b.

>  	/*
>  	 * Disable the upcall mechanism if we're getting an ENOENT or EACCES
>  	 * error. The admin can re-enable it on the fly by using sysfs
> @@ -1252,14 +1257,8 @@ nfsd4_umh_cltrack_init(struct net *net)
>  	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
>  	char *grace_start = nfsd4_cltrack_grace_start(nn->boot_time);
>  
> -	/* XXX: The usermode helper s not working in container yet. */
> -	if (net != &init_net) {
> -		WARN(1, KERN_ERR "NFSD: attempt to initialize umh client "
> -			"tracking in a container!\n");
> -		return -EINVAL;
> -	}
> -
> -	ret = nfsd4_umh_cltrack_upcall("init", NULL, grace_start, NULL);
> +	ret = nfsd4_umh_cltrack_upcall("init", NULL,
> +					grace_start, NULL, nn->umh_token);
>  	kfree(grace_start);
>  	return ret;
>  }
> @@ -1285,6 +1284,7 @@ nfsd4_umh_cltrack_create(struct nfs4_client *clp)
>  {
>  	char *hexid, *has_session, *grace_start;
>  	struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
> +	int ret;
>  
>  	/*
>  	 * With v4.0 clients, there's little difference in outcome between a
> @@ -1312,7 +1312,10 @@ nfsd4_umh_cltrack_create(struct nfs4_client *clp)
>  	grace_start = nfsd4_cltrack_grace_start(nn->boot_time);
>  
>  	nfsd4_cltrack_upcall_lock(clp);
> -	if (!nfsd4_umh_cltrack_upcall("create", hexid, has_session, grace_start))
> +	ret = nfsd4_umh_cltrack_upcall("create",
> +				       hexid, has_session, grace_start,
> +				       nn->umh_token);
> +	if (!ret)
>  		set_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
>  	nfsd4_cltrack_upcall_unlock(clp);
>  
> @@ -1324,7 +1327,9 @@ nfsd4_umh_cltrack_create(struct nfs4_client *clp)
>  static void
>  nfsd4_umh_cltrack_remove(struct nfs4_client *clp)
>  {
> +	struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
>  	char *hexid;
> +	int ret;
>  
>  	if (!test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags))
>  		return;
> @@ -1336,9 +1341,13 @@ nfsd4_umh_cltrack_remove(struct nfs4_client *clp)
>  	}
>  
>  	nfsd4_cltrack_upcall_lock(clp);
> -	if (test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags) &&
> -	    nfsd4_umh_cltrack_upcall("remove", hexid, NULL, NULL) == 0)
> -		clear_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
> +	if (test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags)) {
> +		ret = nfsd4_umh_cltrack_upcall("remove",
> +					       hexid, NULL, NULL,
> +					       nn->umh_token);
> +		if (ret == 0)
> +			clear_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
> +	}
>  	nfsd4_cltrack_upcall_unlock(clp);
>  
>  	kfree(hexid);
> @@ -1347,8 +1356,9 @@ nfsd4_umh_cltrack_remove(struct nfs4_client *clp)
>  static int
>  nfsd4_umh_cltrack_check(struct nfs4_client *clp)
>  {
> -	int ret;
> +	struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
>  	char *hexid, *has_session, *legacy;
> +	int ret;
>  
>  	if (test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags))
>  		return 0;
> @@ -1366,7 +1376,9 @@ nfsd4_umh_cltrack_check(struct nfs4_client *clp)
>  	if (test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags)) {
>  		ret = 0;
>  	} else {
> -		ret = nfsd4_umh_cltrack_upcall("check", hexid, has_session, legacy);
> +		ret = nfsd4_umh_cltrack_upcall("check", hexid,
> +					       has_session, legacy,
> +					       nn->umh_token);
>  		if (ret == 0)
>  			set_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
>  	}
> @@ -1386,7 +1398,9 @@ nfsd4_umh_cltrack_grace_done(struct nfsd_net *nn)
>  
>  	sprintf(timestr, "%ld", nn->boot_time);
>  	legacy = nfsd4_cltrack_legacy_topdir();
> -	nfsd4_umh_cltrack_upcall("gracedone", timestr, legacy, NULL);
> +	nfsd4_umh_cltrack_upcall("gracedone",
> +				 timestr, legacy, NULL,
> +				 nn->umh_token);
>  	kfree(legacy);
>  }
>  
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index aa47d75..f5ae092 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -1224,6 +1224,8 @@ static __net_init int nfsd_init_net(struct net *net)
>  		goto out_idmap_error;
>  	nn->nfsd4_lease = 90;	/* default lease time */
>  	nn->nfsd4_grace = 90;
> +	if (net != &init_net)
> +		nn->umh_token = umh_wq_get_token(nn->umh_token, "knfsd");
>  	return 0;
>  
>  out_idmap_error:
> @@ -1234,6 +1236,10 @@ out_export_error:
>  
>  static __net_exit void nfsd_exit_net(struct net *net)
>  {
> +	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
> +
> +	umh_wq_put_token(nn->umh_token);
> +	nn->umh_token = 0;
>  	nfsd_idmap_shutdown(net);
>  	nfsd_export_shutdown(net);
>  }