Re: [PATCH_V4 1/9] SUNRPC new transport for the NFSv4.1 shared back channel

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

On Fri, Dec 17, 2010 at 01:20:02PM -0500, andros@netapp.com wrote:
> From: Andy Adamson <andros@netapp.com>
> 
> Create a new transport for the shared back channel.l Move the current sock
> create and destroy routines into the new transport ops.
> 
> Reference the back channel transport across message processing (recv/send).
> 
> Signed-off-by: Andy Adamson <andros@netapp.com>
> ---
>  include/linux/sunrpc/svcsock.h |    1 +
>  net/sunrpc/svc.c               |   18 +++---
>  net/sunrpc/svcsock.c           |  122 +++++++++++++++++++++++++++++++++-------
>  3 files changed, 112 insertions(+), 29 deletions(-)
> 
> diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h
> index 1b353a7..3a45a80 100644
> --- a/include/linux/sunrpc/svcsock.h
> +++ b/include/linux/sunrpc/svcsock.h
> @@ -45,6 +45,7 @@ int		svc_sock_names(struct svc_serv *serv, char *buf,
>  int		svc_addsock(struct svc_serv *serv, const int fd,
>  					char *name_return, const size_t len);
>  void		svc_init_xprt_sock(void);
> +void		svc_init_bc_xprt_sock(void);
>  void		svc_cleanup_xprt_sock(void);
>  struct svc_xprt *svc_sock_create(struct svc_serv *serv, int prot);
>  void		svc_sock_destroy(struct svc_xprt *);
> diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
> index 6359c42..3520cb3 100644
> --- a/net/sunrpc/svc.c
> +++ b/net/sunrpc/svc.c
> @@ -488,10 +488,6 @@ svc_destroy(struct svc_serv *serv)
>  	if (svc_serv_is_pooled(serv))
>  		svc_pool_map_put();
>  
> -#if defined(CONFIG_NFS_V4_1)
> -	svc_sock_destroy(serv->bc_xprt);
> -#endif /* CONFIG_NFS_V4_1 */
> -
>  	svc_unregister(serv);
>  	kfree(serv->sv_pools);
>  	kfree(serv);
> @@ -1264,7 +1260,7 @@ bc_svc_process(struct svc_serv *serv, struct rpc_rqst *req,
>  {
>  	struct kvec	*argv = &rqstp->rq_arg.head[0];
>  	struct kvec	*resv = &rqstp->rq_res.head[0];
> -	int 		error;
> +	int		ret;
>  
>  	/* Build the svc_rqst used by the common processing routine */
>  	rqstp->rq_xprt = serv->bc_xprt;
> @@ -1292,12 +1288,16 @@ bc_svc_process(struct svc_serv *serv, struct rpc_rqst *req,
>  	svc_getu32(argv);	/* XID */
>  	svc_getnl(argv);	/* CALLDIR */
>  
> -	error = svc_process_common(rqstp, argv, resv);
> -	if (error <= 0)
> -		return error;
> +	/* Hold a reference to the back channel socket across the call */
> +	svc_xprt_get(serv->bc_xprt);

Either we already have a reference, in which case this is unnecessary,
or we don't, in which case this is risky.

The nfs client code knows when it wants to create and destroy the
backchannel, so I think all you want is to create the svc_xprt when you
create the backchannel and then put it once when you bring it down.

--b.

> +	ret = svc_process_common(rqstp, argv, resv);
> +	if (ret <= 0)
> +		return ret;
>  
>  	memcpy(&req->rq_snd_buf, &rqstp->rq_res, sizeof(req->rq_snd_buf));
> -	return bc_send(req);
> +	ret = bc_send(req);
> +	svc_xprt_put(serv->bc_xprt);
> +	return ret;
>  }
>  EXPORT_SYMBOL(bc_svc_process);
>  #endif /* CONFIG_NFS_V4_1 */
> diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> index 07919e1..5875551 100644
> --- a/net/sunrpc/svcsock.c
> +++ b/net/sunrpc/svcsock.c
> @@ -66,6 +66,13 @@ static void		svc_sock_free(struct svc_xprt *);
>  static struct svc_xprt *svc_create_socket(struct svc_serv *, int,
>  					  struct net *, struct sockaddr *,
>  					  int, int);
> +#if defined(CONFIG_NFS_V4_1)
> +static struct svc_xprt *svc_bc_create_socket(struct svc_serv *, int,
> +					     struct net *, struct sockaddr *,
> +					     int, int);
> +static void svc_bc_sock_free(struct svc_xprt *xprt);
> +#endif /* CONFIG_NFS_V4_1 */
> +
>  #ifdef CONFIG_DEBUG_LOCK_ALLOC
>  static struct lock_class_key svc_key[2];
>  static struct lock_class_key svc_slock_key[2];
> @@ -1184,6 +1191,79 @@ static struct svc_xprt *svc_tcp_create(struct svc_serv *serv,
>  	return svc_create_socket(serv, IPPROTO_TCP, net, sa, salen, flags);
>  }
>  
> +#if defined(CONFIG_NFS_V4_1)
> +static struct svc_xprt *svc_bc_create_socket(struct svc_serv *, int,
> +					     struct net *, struct sockaddr *,
> +					     int, int);
> +static void svc_bc_sock_free(struct svc_xprt *xprt);
> +
> +static struct svc_xprt *svc_bc_tcp_create(struct svc_serv *serv,
> +				       struct net *net,
> +				       struct sockaddr *sa, int salen,
> +				       int flags)
> +{
> +	return svc_bc_create_socket(serv, IPPROTO_TCP, net, sa, salen, flags);
> +}
> +
> +static void svc_bc_tcp_sock_detach(struct svc_xprt *xprt)
> +{
> +}
> +
> +/* These bc ops are never called. The shared fore channel is used instead */
> +static int svc_bc_tcp_recvfrom(struct svc_rqst *rqstp)
> +{
> +	return 0;
> +}
> +
> +static int svc_bc_tcp_sendto(struct svc_rqst *rqstp)
> +{
> +	return 0;
> +}
> +
> +static void svc_bc_tcp_prep_reply_hdr(struct svc_rqst *rqstp)
> +{
> +}
> +
> +static void svc_bc_release_skb(struct svc_rqst *rqstp)
> +{
> +}
> +
> +static int svc_bc_tcp_has_wspace(struct svc_xprt *xprt)
> +{
> +	return 0;
> +}
> +
> +static struct svc_xprt *svc_bc_tcp_accept(struct svc_xprt *xprt)
> +{
> +	return NULL;
> +}
> +
> +static struct svc_xprt_ops svc_tcp_bc_ops = {
> +	.xpo_create = svc_bc_tcp_create,
> +	.xpo_recvfrom = svc_bc_tcp_recvfrom,
> +	.xpo_sendto = svc_bc_tcp_sendto,
> +	.xpo_release_rqst = svc_bc_release_skb,
> +	.xpo_detach = svc_bc_tcp_sock_detach,
> +	.xpo_free = svc_bc_sock_free,
> +	.xpo_prep_reply_hdr = svc_bc_tcp_prep_reply_hdr,
> +	.xpo_has_wspace = svc_bc_tcp_has_wspace,
> +	.xpo_accept = svc_bc_tcp_accept,
> +};
> +
> +static struct svc_xprt_class svc_tcp_bc_class = {
> +	.xcl_name = "tcp-bc",
> +	.xcl_owner = THIS_MODULE,
> +	.xcl_ops = &svc_tcp_bc_ops,
> +	.xcl_max_payload = RPCSVC_MAXPAYLOAD_TCP,
> +};
> +
> +void svc_init_bc_xprt_sock(void)
> +{
> +	svc_reg_xprt_class(&svc_tcp_bc_class);
> +}
> +EXPORT_SYMBOL_GPL(svc_init_bc_xprt_sock);
> +#endif /* CONFIG_NFS_V4_1 */
> +
>  static struct svc_xprt_ops svc_tcp_ops = {
>  	.xpo_create = svc_tcp_create,
>  	.xpo_recvfrom = svc_tcp_recvfrom,
> @@ -1509,41 +1589,43 @@ static void svc_sock_free(struct svc_xprt *xprt)
>  	kfree(svsk);
>  }
>  
> +#if defined(CONFIG_NFS_V4_1)
>  /*
> - * Create a svc_xprt.
> - *
> - * For internal use only (e.g. nfsv4.1 backchannel).
> - * Callers should typically use the xpo_create() method.
> + * Create a back channel svc_xprt which shares the fore channel socket.
>   */
> -struct svc_xprt *svc_sock_create(struct svc_serv *serv, int prot)
> +static struct svc_xprt *svc_bc_create_socket(struct svc_serv *serv,
> +					     int protocol,
> +					     struct net *net,
> +					     struct sockaddr *sin, int len,
> +					     int flags)
>  {
>  	struct svc_sock *svsk;
> -	struct svc_xprt *xprt = NULL;
> +	struct svc_xprt *xprt;
> +
> +	if (protocol != IPPROTO_TCP) {
> +		printk(KERN_WARNING "svc: only and TCP sockets"
> +			" supported on shared back channel\n");
> +		return ERR_PTR(-EINVAL);
> +	}
>  
> -	dprintk("svc: %s\n", __func__);
>  	svsk = kzalloc(sizeof(*svsk), GFP_KERNEL);
>  	if (!svsk)
> -		goto out;
> +		return ERR_PTR(-ENOMEM);
>  
>  	xprt = &svsk->sk_xprt;
> -	if (prot == IPPROTO_TCP)
> -		svc_xprt_init(&svc_tcp_class, xprt, serv);
> -	else if (prot == IPPROTO_UDP)
> -		svc_xprt_init(&svc_udp_class, xprt, serv);
> -	else
> -		BUG();
> -out:
> -	dprintk("svc: %s return %p\n", __func__, xprt);
> +	svc_xprt_init(&svc_tcp_bc_class, xprt, serv);
> +
> +	serv->bc_xprt = xprt;
> +
>  	return xprt;
>  }
> -EXPORT_SYMBOL_GPL(svc_sock_create);
>  
>  /*
> - * Destroy a svc_sock.
> + * Free a back channel svc_sock.
>   */
> -void svc_sock_destroy(struct svc_xprt *xprt)
> +static void svc_bc_sock_free(struct svc_xprt *xprt)
>  {
>  	if (xprt)
>  		kfree(container_of(xprt, struct svc_sock, sk_xprt));
>  }
> -EXPORT_SYMBOL_GPL(svc_sock_destroy);
> +#endif /* CONFIG_NFS_V4_1 */
> -- 
> 1.6.6
>