SUNRPC: Fix backchannel RPC soft lockups (6221f1d9) · Commits · 戴 / test

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 reconnects. 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 ("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 RPC_TASK_SOFTCONN. Suggested-by:

Trond Myklebust <trondmy@hammerspace.com> Signed-off-by:

Chuck Lever <chuck.lever@oracle.com> Cc: <stable@vger.kernel.org> # v4.20+

fs/nfsd/nfs4callback.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -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);
		}

net/sunrpc/svc_xprt.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -1040,6 +1040,8 @@ static void svc_delete_xprt(struct svc_xprt *xprt)

		dprintk("svc: svc_delete_xprt(%p)\n", xprt);
		xprt->xpt_ops->xpo_detach(xprt);
		if (xprt->xpt_bc_xprt)
		xprt->xpt_bc_xprt->ops->close(xprt->xpt_bc_xprt);

		spin_lock_bh(&serv->sv_lock);
		list_del_init(&xprt->xpt_list);

net/sunrpc/xprtrdma/svc_rdma_backchannel.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -244,6 +244,8 @@ static void
		xprt_rdma_bc_close(struct rpc_xprt *xprt)
		{
		dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);

		xprt_disconnect_done(xprt);
		xprt->cwnd = RPC_CWNDSHIFT;
		}

net/sunrpc/xprtsock.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -2584,6 +2584,7 @@ static int bc_send_request(struct rpc_rqst *req)

		static void bc_close(struct rpc_xprt *xprt)
		{
		xprt_disconnect_done(xprt);
		}

		/*

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