RPC-over-RDMA Version One transports have a limit on how large
a backward direction RPC (backchannel) message can be. Ensure
that the NFSv4.x CREATE_SESSION operation advertises the
correct value to servers.
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
This patch makes the client advertise the maximum size of a
backchannel RPC message, which is 996 bytes with the current RDMA
transport implementation.
I wanted to propose this patch for v4.6, but it breaks
Linux-to-Linux NFSv4.1 over RDMA. When attempting a mount, the Linux
client reports this in its log:
NFS: state manager: lease expired failed on NFSv4 server klimt-ib with error 525
NFS: nfs4_discover_server_trunking unhandled error -512. Exiting with error EIO
Then the mount command hangs (interruptibly).
On the Linux server, CREATE_SESSION calls check_backchannel_attrs()
which checks the maxreq_sz and maxresp_sz on the backchannel and
returns NFS4ERR_TOOSMALL because it wants maxreq_sz to be larger
than 1044 bytes.
[ The client could do a better job of recovering, perhaps. Should it
fall back to NFSv4.0 if vers= was not specified, and otherwise
have mount exit with an error code? ]
We have:
#define NFSD_CB_MAX_REQ_SZ ((NFS4_enc_cb_recall_sz + \
RPC_MAX_HEADER_WITH_AUTH) * sizeof(__be32))
NFS4_enc_cb_recall_sz is 51 and RPC_MAX_HEADER_WITH_AUTH is 210.
The comment in check_backchannel_attrs() says:
/*
* These RPC_MAX_HEADER macros are overkill, especially since we
* don't even do gss on the backchannel yet. But this is still
* less than 1k. Tighten up this estimate in the unlikely event
* it turns out to be a problem for some client:
*/
It seems that "still less than 1k" is not strictly true.
To address this, a new minimum could be chosen that assumes that
RPC_AUTH_GSS is not going to be used for now.
Thoughts?
fs/nfs/nfs4proc.c | 10 ++++++----
include/linux/sunrpc/clnt.h | 1 +
include/linux/sunrpc/xprt.h | 1 +
net/sunrpc/clnt.c | 15 +++++++++++++++
net/sunrpc/xprtrdma/transport.c | 1 +
net/sunrpc/xprtsock.c | 4 ++++
6 files changed, 28 insertions(+), 4 deletions(-)
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 4bfc33a..a0e2cda 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -7295,9 +7295,11 @@ 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;
@@ -7315,8 +7317,8 @@ 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 = 1;
@@ -7420,7 +7422,7 @@ 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 131032f..1cad92e 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/include/linux/sunrpc/clnt.h
@@ -175,6 +175,7 @@ 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 69ef5b3..d32c319 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -179,6 +179,7 @@ struct rpc_xprt {
size_t max_payload; /* largest RPC payload size,
in bytes */
+ size_t max_bc_payload; /* max bytes per bc payload */
unsigned int tsh_size; /* size of transport specific
header */
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index b7f2104..ac3dbde 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -1335,6 +1335,21 @@ 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)
+{
+ size_t ret;
+
+ rcu_read_lock();
+ ret = rcu_dereference(clnt->cl_xprt)->max_bc_payload;
+ 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/transport.c b/net/sunrpc/xprtrdma/transport.c
index b1b009f..06fe152 100644
--- a/net/sunrpc/xprtrdma/transport.c
+++ b/net/sunrpc/xprtrdma/transport.c
@@ -402,6 +402,7 @@ xprt_setup_rdma(struct xprt_create *args)
xprt->max_payload <<= PAGE_SHIFT;
dprintk("RPC: %s: transport data payload maximum: %zu bytes\n",
__func__, xprt->max_payload);
+ xprt->max_bc_payload = cdata.inline_rsize - RPCRDMA_HDRLEN_MIN;
if (!try_module_get(THIS_MODULE))
goto out4;
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index fde2138..910e192 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -2781,6 +2781,7 @@ static struct rpc_xprt *xs_setup_local(struct xprt_create *args)
xprt->prot = 0;
xprt->tsh_size = sizeof(rpc_fraghdr) / sizeof(u32);
xprt->max_payload = RPC_MAX_FRAGMENT_SIZE;
+ xprt->max_bc_payload = PAGE_SIZE;
xprt->bind_timeout = XS_BIND_TO;
xprt->reestablish_timeout = XS_TCP_INIT_REEST_TO;
@@ -2852,6 +2853,7 @@ static struct rpc_xprt *xs_setup_udp(struct xprt_create *args)
xprt->tsh_size = 0;
/* XXX: header size can vary due to auth type, IPv6, etc. */
xprt->max_payload = (1U << 16) - (MAX_HEADER << 3);
+ xprt->max_bc_payload = PAGE_SIZE;
xprt->bind_timeout = XS_BIND_TO;
xprt->reestablish_timeout = XS_UDP_REEST_TO;
@@ -2931,6 +2933,7 @@ static struct rpc_xprt *xs_setup_tcp(struct xprt_create *args)
xprt->prot = IPPROTO_TCP;
xprt->tsh_size = sizeof(rpc_fraghdr) / sizeof(u32);
xprt->max_payload = RPC_MAX_FRAGMENT_SIZE;
+ xprt->max_bc_payload = PAGE_SIZE;
xprt->bind_timeout = XS_BIND_TO;
xprt->reestablish_timeout = XS_TCP_INIT_REEST_TO;
@@ -3000,6 +3003,7 @@ static struct rpc_xprt *xs_setup_bc_tcp(struct xprt_create *args)
xprt->prot = IPPROTO_TCP;
xprt->tsh_size = sizeof(rpc_fraghdr) / sizeof(u32);
xprt->max_payload = RPC_MAX_FRAGMENT_SIZE;
+ xprt->max_bc_payload = PAGE_SIZE;
xprt->timeout = &xs_tcp_default_timeout;
/* backchannel */
--
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