Commit 6221f1d9 authored by Chuck Lever's avatar Chuck Lever

SUNRPC: Fix backchannel RPC soft lockups

Currently, after the forward channel connection goes away,
backchannel operations are causing soft lockups on the server
because call_transmit_status's SOFTCONN logic ignores ENOTCONN.
Such backchannel Calls are aggressively retried until the client

Backchannel Calls should use RPC_TASK_NOCONNECT rather than
RPC_TASK_SOFTCONN. If there is no forward connection, the server is
not capable of establishing a connection back to the client, thus
that backchannel request should fail before the server attempts to
send it. Commit 58255a4e ("NFSD: NFSv4 callback client should
use RPC_TASK_SOFTCONN") was merged several years before
RPC_TASK_NOCONNECT was available.

Because setup_callback_client() explicitly sets NOPING, the NFSv4.0
callback connection depends on the first callback RPC to initiate
a connection to the client. Thus NFSv4.0 needs to continue to use
Suggested-by: default avatarTrond Myklebust <>
Signed-off-by: default avatarChuck Lever <>
Cc: <> # v4.20+
parent 43e33924
......@@ -1312,6 +1312,7 @@ nfsd4_run_cb_work(struct work_struct *work)
container_of(work, struct nfsd4_callback, cb_work);
struct nfs4_client *clp = cb->cb_clp;
struct rpc_clnt *clnt;
int flags;
if (cb->cb_need_restart) {
cb->cb_need_restart = false;
......@@ -1340,7 +1341,8 @@ nfsd4_run_cb_work(struct work_struct *work)
cb->cb_msg.rpc_cred = clp->cl_cb_cred;
rpc_call_async(clnt, &cb->cb_msg, RPC_TASK_SOFT | RPC_TASK_SOFTCONN,
flags = clp->cl_minorversion ? RPC_TASK_NOCONNECT : RPC_TASK_SOFTCONN;
rpc_call_async(clnt, &cb->cb_msg, RPC_TASK_SOFT | flags,
cb->cb_ops ? &nfsd4_cb_ops : &nfsd4_cb_probe_ops, cb);
......@@ -1040,6 +1040,8 @@ static void svc_delete_xprt(struct svc_xprt *xprt)
dprintk("svc: svc_delete_xprt(%p)\n", xprt);
if (xprt->xpt_bc_xprt)
......@@ -244,6 +244,8 @@ static void
xprt_rdma_bc_close(struct rpc_xprt *xprt)
dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);
xprt->cwnd = RPC_CWNDSHIFT;
......@@ -2584,6 +2584,7 @@ static int bc_send_request(struct rpc_rqst *req)
static void bc_close(struct rpc_xprt *xprt)
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