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

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
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 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
RPC_TASK_SOFTCONN.

Suggested-by: default avatarTrond Myklebust <trondmy@hammerspace.com>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
Cc: <stable@vger.kernel.org> # v4.20+
parent 43e33924

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);

}



/*