[PATCH v1 01/18] sunrpc: Advertise maximum backchannel payload size

Chuck Lever
2016-04-11T20:10:16Z

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-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
---
fs/nfs/nfs4proc.c | 10 ++++++----
include/linux/sunrpc/clnt.h | 1 +
include/linux/sunrpc/xprt.h | 1 +
net/sunrpc/clnt.c | 17 +++++++++++++++++
net/sunrpc/xprtrdma/backchannel.c | 16 ++++++++++++++++
net/sunrpc/xprtrdma/transport.c | 1 +
net/sunrpc/xprtrdma/xprt_rdma.h | 1 +
net/sunrpc/xprtsock.c | 6 ++++++
8 files changed, 49 insertions(+), 4 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 327b8c3..01bef06 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -7351,9 +7351,11 @@ int nfs4_proc_get_lease_time(struct nfs_client *clp, struct nfs_fsinfo *fsinfo)
* always set csa_cachethis to FALSE because the current implementation
* of the back channel DRC only supports caching the CB_SEQUENCE operation.
*/
-static void nfs4_init_channel_attrs(struct nfs41_create_session_args *args)
+static void nfs4_init_channel_attrs(struct nfs41_create_session_args *args,
+ struct rpc_clnt *clnt)
{
unsigned int max_rqst_sz, max_resp_sz;
+ unsigned int max_bc_payload = rpc_max_bc_payload(clnt);

max_rqst_sz = NFS_MAX_FILE_IO_SIZE + nfs41_maxwrite_overhead;
max_resp_sz = NFS_MAX_FILE_IO_SIZE + nfs41_maxread_overhead;
@@ -7371,8 +7373,8 @@ static void nfs4_init_channel_attrs(struct nfs41_create_session_args *args)
args->fc_attrs.max_ops, args->fc_attrs.max_reqs);

/* Back channel attributes */
- args->bc_attrs.max_rqst_sz = PAGE_SIZE;
- args->bc_attrs.max_resp_sz = PAGE_SIZE;
+ args->bc_attrs.max_rqst_sz = max_bc_payload;
+ args->bc_attrs.max_resp_sz = max_bc_payload;
args->bc_attrs.max_resp_sz_cached = 0;
args->bc_attrs.max_ops = NFS4_MAX_BACK_CHANNEL_OPS;
args->bc_attrs.max_reqs = NFS41_BC_MAX_CALLBACKS;
@@ -7476,7 +7478,7 @@ static int _nfs4_proc_create_session(struct nfs_client *clp,
};
int status;

- nfs4_init_channel_attrs(&args);
+ nfs4_init_channel_attrs(&args, clp->cl_rpcclient);
args.flags = (SESSION4_PERSIST | SESSION4_BACK_CHAN);

status = rpc_call_sync(session->clp->cl_rpcclient, &msg, RPC_TASK_TIMEOUT);
diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
index 9a7ddba..19c659d 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/include/linux/sunrpc/clnt.h
@@ -176,6 +176,7 @@ void rpc_setbufsize(struct rpc_clnt *, unsigned int, unsigned int);
int rpc_protocol(struct rpc_clnt *);
struct net * rpc_net_ns(struct rpc_clnt *);
size_t rpc_max_payload(struct rpc_clnt *);
+size_t rpc_max_bc_payload(struct rpc_clnt *);
unsigned long rpc_get_timeout(struct rpc_clnt *clnt);
void rpc_force_rebind(struct rpc_clnt *);
size_t rpc_peeraddr(struct rpc_clnt *, struct sockaddr *, size_t);
diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index fb0d212..5aa3834 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -142,6 +142,7 @@ struct rpc_xprt_ops {
int (*bc_setup)(struct rpc_xprt *xprt,
unsigned int min_reqs);
int (*bc_up)(struct svc_serv *serv, struct net *net);
+ size_t (*bc_maxpayload)(struct rpc_xprt *xprt);
void (*bc_free_rqst)(struct rpc_rqst *rqst);
void (*bc_destroy)(struct rpc_xprt *xprt,
unsigned int max_reqs);
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 @@ size_t rpc_max_payload(struct rpc_clnt *clnt)
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 @@ int xprt_rdma_bc_up(struct svc_serv *serv, struct net *net)
}

/**
+ * 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 @@ static struct rpc_xprt_ops xprt_rdma_procs = {
#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 @@ void xprt_rdma_cleanup(void);
#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 @@ static int xs_tcp_bc_up(struct svc_serv *serv, struct net *net)
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 @@ static struct rpc_xprt_ops xs_tcp_ops = {
#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

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