sunrpc: Advertise maximum backchannel payload size
RPC-over-RDMA transports have a limit on how large a backward
direction (backchannel) RPC message can be. Ensure that the NFSv4.x
CREATE_SESSION operation advertises this limit to servers.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 7e0c9bf..06b4df9 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -1414,6 +1414,23 @@
EXPORT_SYMBOL_GPL(rpc_max_payload);
/**
+ * rpc_max_bc_payload - Get maximum backchannel payload size, in bytes
+ * @clnt: RPC client to query
+ */
+size_t rpc_max_bc_payload(struct rpc_clnt *clnt)
+{
+ struct rpc_xprt *xprt;
+ size_t ret;
+
+ rcu_read_lock();
+ xprt = rcu_dereference(clnt->cl_xprt);
+ ret = xprt->ops->bc_maxpayload(xprt);
+ rcu_read_unlock();
+ return ret;
+}
+EXPORT_SYMBOL_GPL(rpc_max_bc_payload);
+
+/**
* rpc_get_timeout - Get timeout for transport in units of HZ
* @clnt: RPC client to query
*/
diff --git a/net/sunrpc/xprtrdma/backchannel.c b/net/sunrpc/xprtrdma/backchannel.c
index 2dcd764..87762d9 100644
--- a/net/sunrpc/xprtrdma/backchannel.c
+++ b/net/sunrpc/xprtrdma/backchannel.c
@@ -192,6 +192,22 @@
}
/**
+ * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
+ * @xprt: transport
+ *
+ * Returns maximum size, in bytes, of a backchannel message
+ */
+size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
+{
+ struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
+ struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
+ size_t maxmsg;
+
+ maxmsg = min_t(unsigned int, cdata->inline_rsize, cdata->inline_wsize);
+ return maxmsg - RPCRDMA_HDRLEN_MIN;
+}
+
+/**
* rpcrdma_bc_marshal_reply - Send backwards direction reply
* @rqst: buffer containing RPC reply data
*
diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
index b1b009f..9954342 100644
--- a/net/sunrpc/xprtrdma/transport.c
+++ b/net/sunrpc/xprtrdma/transport.c
@@ -707,6 +707,7 @@
#if defined(CONFIG_SUNRPC_BACKCHANNEL)
.bc_setup = xprt_rdma_bc_setup,
.bc_up = xprt_rdma_bc_up,
+ .bc_maxpayload = xprt_rdma_bc_maxpayload,
.bc_free_rqst = xprt_rdma_bc_free_rqst,
.bc_destroy = xprt_rdma_bc_destroy,
#endif
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index 2ebc743..7723e5f 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -534,6 +534,7 @@
#if defined(CONFIG_SUNRPC_BACKCHANNEL)
int xprt_rdma_bc_setup(struct rpc_xprt *, unsigned int);
int xprt_rdma_bc_up(struct svc_serv *, struct net *);
+size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *);
int rpcrdma_bc_post_recv(struct rpcrdma_xprt *, unsigned int);
void rpcrdma_bc_receive_call(struct rpcrdma_xprt *, struct rpcrdma_rep *);
int rpcrdma_bc_marshal_reply(struct rpc_rqst *);
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 65e7595..f1faf6b 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -1365,6 +1365,11 @@
return ret;
return 0;
}
+
+static size_t xs_tcp_bc_maxpayload(struct rpc_xprt *xprt)
+{
+ return PAGE_SIZE;
+}
#else
static inline int _xs_tcp_read_data(struct rpc_xprt *xprt,
struct xdr_skb_reader *desc)
@@ -2660,6 +2665,7 @@
#ifdef CONFIG_SUNRPC_BACKCHANNEL
.bc_setup = xprt_setup_bc,
.bc_up = xs_tcp_bc_up,
+ .bc_maxpayload = xs_tcp_bc_maxpayload,
.bc_free_rqst = xprt_free_bc_rqst,
.bc_destroy = xprt_destroy_bc,
#endif