From: Chuck Lever <chuck.lever@oracle.com>
Date: Thu, 14 Dec 2017 20:57:39 -0500
Subject: xprtrdma: Don't clear RPC_BC_PA_IN_USE on pre-allocated rpc_rqst's
Patch-mainline: v4.16-rc1
Git-commit: 30b5416bf0fd3bfef55543343ad1e85d32e32de4
References: bsc#1103992 FATE#326009

No need for the overhead of atomically setting and clearing this bit
flag for every use of a pre-allocated backchannel rpc_rqst. These
are a distinct pool of rpc_rqsts that are used only for callback
operations, so it is safe to simply leave the bit set.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/sunrpc/xprtrdma/backchannel.c |    7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

--- a/net/sunrpc/xprtrdma/backchannel.c
+++ b/net/sunrpc/xprtrdma/backchannel.c
@@ -119,6 +119,7 @@ int xprt_rdma_bc_setup(struct rpc_xprt *
 		rqst->rq_xprt = &r_xprt->rx_xprt;
 		INIT_LIST_HEAD(&rqst->rq_list);
 		INIT_LIST_HEAD(&rqst->rq_bc_list);
+		__set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
 
 		if (rpcrdma_bc_setup_rqst(r_xprt, rqst))
 			goto out_free;
@@ -283,11 +284,6 @@ void xprt_rdma_bc_free_rqst(struct rpc_r
 	dprintk("RPC:       %s: freeing rqst %p (req %p)\n",
 		__func__, rqst, rpcr_to_rdmar(rqst));
 
-	smp_mb__before_atomic();
-	WARN_ON_ONCE(!test_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state));
-	clear_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
-	smp_mb__after_atomic();
-
 	spin_lock_bh(&xprt->bc_pa_lock);
 	list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
 	spin_unlock_bh(&xprt->bc_pa_lock);
@@ -342,7 +338,6 @@ void rpcrdma_bc_receive_call(struct rpcr
 	rqst->rq_xid = *p;
 
 	rqst->rq_private_buf.len = size;
-	set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
 
 	buf = &rqst->rq_rcv_buf;
 	memset(buf, 0, sizeof(*buf));