sunrpc: centralise most calls to svc_xprt_received

svc_xprt_received must be called when ->xpo_recvfrom has finished
receiving a message, so that the XPT_BUSY flag will be cleared and
if necessary, requeued for further work.

This call is currently made in each ->xpo_recvfrom function, often
from multiple different points.  In each case it is the earliest point
on a particular path where it is known that the protection provided by
XPT_BUSY is no longer needed.

However there are (still) some error paths which do not call
svc_xprt_received, and requiring each ->xpo_recvfrom to make the call
does not encourage robustness.

So: move the svc_xprt_received call to be made just after the
call to ->xpo_recvfrom(), and move it of the various ->xpo_recvfrom
methods.

This means that it may not be called at the earliest possible instant,
but this is unlikely to be a measurable performance issue.

Note that there are still other calls to svc_xprt_received as it is
also needed when an xprt is newly created.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

net/sunrpc/svc_xprt.c

@@ -743,8 +743,10 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
 		if (rqstp->rq_deferred) {
 			svc_xprt_received(xprt);
 			len = svc_deferred_recv(rqstp);
-		} else
+		} else {
 			len = xprt->xpt_ops->xpo_recvfrom(rqstp);
+			svc_xprt_received(xprt);
+		}
 		dprintk("svc: got len=%d\n", len);
 	}
 

net/sunrpc/svcsock.c

@@ -547,7 +547,6 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
 			dprintk("svc: recvfrom returned error %d\n", -err);
 			set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
 		}
-		svc_xprt_received(&svsk->sk_xprt);
 		return -EAGAIN;
 	}
 	len = svc_addr_len(svc_addr(rqstp));
@@ -562,11 +561,6 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
 	svsk->sk_sk->sk_stamp = skb->tstamp;
 	set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags); /* there may be more data... */
 
-	/*
-	 * Maybe more packets - kick another thread ASAP.
-	 */
-	svc_xprt_received(&svsk->sk_xprt);
-
 	len  = skb->len - sizeof(struct udphdr);
 	rqstp->rq_arg.len = len;
 
@@ -917,7 +911,6 @@ static int svc_tcp_recv_record(struct svc_sock *svsk, struct svc_rqst *rqstp)
 		if (len < want) {
 			dprintk("svc: short recvfrom while reading record "
 				"length (%d of %d)\n", len, want);
-			svc_xprt_received(&svsk->sk_xprt);
 			goto err_again; /* record header not complete */
 		}
 
@@ -953,7 +946,6 @@ static int svc_tcp_recv_record(struct svc_sock *svsk, struct svc_rqst *rqstp)
 	if (len < svsk->sk_reclen) {
 		dprintk("svc: incomplete TCP record (%d of %d)\n",
 			len, svsk->sk_reclen);
-		svc_xprt_received(&svsk->sk_xprt);
 		goto err_again;	/* record not complete */
 	}
 	len = svsk->sk_reclen;
@@ -961,14 +953,11 @@ static int svc_tcp_recv_record(struct svc_sock *svsk, struct svc_rqst *rqstp)
 
 	return len;
  error:
-	if (len == -EAGAIN) {
+	if (len == -EAGAIN)
 		dprintk("RPC: TCP recv_record got EAGAIN\n");
-		svc_xprt_received(&svsk->sk_xprt);
-	}
 	return len;
  err_delete:
 	set_bit(XPT_CLOSE, &svsk->sk_xprt.xpt_flags);
-	svc_xprt_received(&svsk->sk_xprt);
  err_again:
 	return -EAGAIN;
 }
@@ -1110,7 +1099,6 @@ static int svc_tcp_recvfrom(struct svc_rqst *rqstp)
 	svsk->sk_tcplen = 0;
 
 	svc_xprt_copy_addrs(rqstp, &svsk->sk_xprt);
-	svc_xprt_received(&svsk->sk_xprt);
 	if (serv->sv_stats)
 		serv->sv_stats->nettcpcnt++;
 
@@ -1119,7 +1107,6 @@ static int svc_tcp_recvfrom(struct svc_rqst *rqstp)
 err_again:
 	if (len == -EAGAIN) {
 		dprintk("RPC: TCP recvfrom got EAGAIN\n");
-		svc_xprt_received(&svsk->sk_xprt);
 		return len;
 	}
 error:

net/sunrpc/xprtrdma/svc_rdma_recvfrom.c

@@ -566,7 +566,6 @@ static int rdma_read_complete(struct svc_rqst *rqstp,
 		ret, rqstp->rq_arg.len,	rqstp->rq_arg.head[0].iov_base,
 		rqstp->rq_arg.head[0].iov_len);
 
-	svc_xprt_received(rqstp->rq_xprt);
 	return ret;
 }
 
@@ -665,7 +664,6 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
 		rqstp->rq_arg.head[0].iov_len);
 	rqstp->rq_prot = IPPROTO_MAX;
 	svc_xprt_copy_addrs(rqstp, xprt);
-	svc_xprt_received(xprt);
 	return ret;
 
  close_out:
@@ -678,6 +676,5 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
 	 */
 	set_bit(XPT_CLOSE, &xprt->xpt_flags);
 defer:
-	svc_xprt_received(xprt);
 	return 0;
 }