SUNRPC: Fix backchannel latency metrics

mainline inclusion
from mainline-v5.5-rc1
commit 8729aaba
category: bugfix
bugzilla: 51810
CVE: NA

-------------------------------------------------

I noticed that for callback requests, the reported backlog latency
is always zero, and the rtt value is crazy big. The problem was that
rqst->rq_xtime is never set for backchannel requests.

Fixes: 78215759 ("SUNRPC: Make RTT measurement more ... ")
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>
Signed-off-by: NLu Wei <luwei32@huawei.com>
Reviewed-by: NYue Haibing <yuehaibing@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

net/sunrpc/xprtrdma/svc_rdma_backchannel.c

@@ -198,6 +198,7 @@ rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst)
 	pr_info("%s: %*ph\n", __func__, 64, rqst->rq_buffer);
 #endif
 
+	rqst->rq_xtime = ktime_get();
 	rc = svc_rdma_bc_sendto(rdma, rqst, ctxt);
 	if (rc) {
 		svc_rdma_send_ctxt_put(rdma, ctxt);

net/sunrpc/xprtsock.c

@@ -2698,6 +2698,9 @@ static int bc_sendto(struct rpc_rqst *req)
 
 	tailoff = (unsigned long)xbufp->tail[0].iov_base & ~PAGE_MASK;
 	headoff = (unsigned long)xbufp->head[0].iov_base & ~PAGE_MASK;
+
+	req->rq_xtime = ktime_get();
+
 	len = svc_send_common(sock, xbufp,
 			      virt_to_page(xbufp->head[0].iov_base), headoff,
 			      xbufp->tail[0].iov_base, tailoff);
@@ -2719,7 +2722,6 @@ static int bc_send_request(struct rpc_task *task)
 	struct svc_xprt	*xprt;
 	int len;
 
-	dprintk("sending request with xid: %08x\n", ntohl(req->rq_xid));
 	/*
 	 * Get the server socket associated with this callback xprt
 	 */