On Fri, Dec 17, 2010 at 1:40 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
> On Fri, Dec 17, 2010 at 01:20:02PM -0500, andros@xxxxxxxxxx wrote:
>> From: Andy Adamson <andros@xxxxxxxxxx>
>>
>> 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@xxxxxxxxxx>
>> ---
>> 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.
This is done so that when svc_xprt_put is called due to an svc_drop
(svc_xprt_release, svc_xprt_put) it is not freed. It's not risky
because AFAICS it's the way the rpc server code is intended to work.
Note that svc_recv calls svc_xprt_get, and svc_send calls svc_xprt_put
for the same reason.
> 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.
Correct, and without the references in bc_svc_process, svc_drop == freeing.
-->Andy
>
> --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
>>
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