svcrdma: Fix leak of svc_rdma_recv_ctxt objects

Utilize the xpo_release_rqst transport method to ensure that each
rqstp's svc_rdma_recv_ctxt object is released even when the server
cannot return a Reply for that rqstp.

Without this fix, each RPC whose Reply cannot be sent leaks one
svc_rdma_recv_ctxt. This is a 2.5KB structure, a 4KB DMA-mapped
Receive buffer, and any pages that might be part of the Reply
message.

The leak is infrequent unless the network fabric is unreliable or
Kerberos is in use, as GSS sequence window overruns, which result
in connection loss, are more common on fast transports.

Fixes: 3a88092e ("svcrdma: Preserve Receive buffer until svc_rdma_sendto")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

include/linux/sunrpc/svc_rdma.h

@@ -170,6 +170,7 @@ extern bool svc_rdma_post_recvs(struct svcxprt_rdma *rdma);
 extern void svc_rdma_recv_ctxt_put(struct svcxprt_rdma *rdma,
 				   struct svc_rdma_recv_ctxt *ctxt);
 extern void svc_rdma_flush_recv_queues(struct svcxprt_rdma *rdma);
+extern void svc_rdma_release_rqst(struct svc_rqst *rqstp);
 extern int svc_rdma_recvfrom(struct svc_rqst *);
 
 /* svc_rdma_rw.c */

net/sunrpc/svc_xprt.c

@@ -908,9 +908,6 @@ int svc_send(struct svc_rqst *rqstp)
 	if (!xprt)
 		goto out;
 
-	/* release the receive skb before sending the reply */
-	xprt->xpt_ops->xpo_release_rqst(rqstp);
-
 	/* calculate over-all length */
 	xb = &rqstp->rq_res;
 	xb->len = xb->head[0].iov_len +

net/sunrpc/svcsock.c

@@ -527,6 +527,8 @@ static int svc_udp_sendto(struct svc_rqst *rqstp)
 	unsigned int uninitialized_var(sent);
 	int err;
 
+	svc_release_udp_skb(rqstp);
+
 	svc_set_cmsg_data(rqstp, cmh);
 
 	err = xprt_sock_sendmsg(svsk->sk_sock, &msg, xdr, 0, 0, &sent);
@@ -1076,6 +1078,8 @@ static int svc_tcp_sendto(struct svc_rqst *rqstp)
 	unsigned int uninitialized_var(sent);
 	int err;
 
+	svc_release_skb(rqstp);
+
 	err = xprt_sock_sendmsg(svsk->sk_sock, &msg, xdr, 0, marker, &sent);
 	xdr_free_bvec(xdr);
 	if (err < 0 || sent != (xdr->len + sizeof(marker)))

net/sunrpc/xprtrdma/svc_rdma_recvfrom.c

@@ -223,6 +223,26 @@ void svc_rdma_recv_ctxt_put(struct svcxprt_rdma *rdma,
 		svc_rdma_recv_ctxt_destroy(rdma, ctxt);
 }
 
+/**
+ * svc_rdma_release_rqst - Release transport-specific per-rqst resources
+ * @rqstp: svc_rqst being released
+ *
+ * Ensure that the recv_ctxt is released whether or not a Reply
+ * was sent. For example, the client could close the connection,
+ * or svc_process could drop an RPC, before the Reply is sent.
+ */
+void svc_rdma_release_rqst(struct svc_rqst *rqstp)
+{
+	struct svc_rdma_recv_ctxt *ctxt = rqstp->rq_xprt_ctxt;
+	struct svc_xprt *xprt = rqstp->rq_xprt;
+	struct svcxprt_rdma *rdma =
+		container_of(xprt, struct svcxprt_rdma, sc_xprt);
+
+	rqstp->rq_xprt_ctxt = NULL;
+	if (ctxt)
+		svc_rdma_recv_ctxt_put(rdma, ctxt);
+}
+
 static int __svc_rdma_post_recv(struct svcxprt_rdma *rdma,
 				struct svc_rdma_recv_ctxt *ctxt)
 {
@@ -820,6 +840,8 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
 	__be32 *p;
 	int ret;
 
+	rqstp->rq_xprt_ctxt = NULL;
+
 	spin_lock(&rdma_xprt->sc_rq_dto_lock);
 	ctxt = svc_rdma_next_recv_ctxt(&rdma_xprt->sc_read_complete_q);
 	if (ctxt) {

net/sunrpc/xprtrdma/svc_rdma_sendto.c

@@ -926,12 +926,7 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
 	ret = svc_rdma_send_reply_msg(rdma, sctxt, rctxt, rqstp);
 	if (ret < 0)
 		goto err1;
-	ret = 0;
-
-out:
-	rqstp->rq_xprt_ctxt = NULL;
-	svc_rdma_recv_ctxt_put(rdma, rctxt);
-	return ret;
+	return 0;
 
  err2:
 	if (ret != -E2BIG && ret != -EINVAL)
@@ -940,16 +935,14 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
 	ret = svc_rdma_send_error_msg(rdma, sctxt, rqstp);
 	if (ret < 0)
 		goto err1;
-	ret = 0;
-	goto out;
+	return 0;
 
  err1:
 	svc_rdma_send_ctxt_put(rdma, sctxt);
  err0:
 	trace_svcrdma_send_failed(rqstp, ret);
 	set_bit(XPT_CLOSE, &xprt->xpt_flags);
-	ret = -ENOTCONN;
-	goto out;
+	return -ENOTCONN;
 }
 
 /**

net/sunrpc/xprtrdma/svc_rdma_transport.c

@@ -71,7 +71,6 @@ static struct svc_xprt *svc_rdma_create(struct svc_serv *serv,
 					struct sockaddr *sa, int salen,
 					int flags);
 static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt);
-static void svc_rdma_release_rqst(struct svc_rqst *);
 static void svc_rdma_detach(struct svc_xprt *xprt);
 static void svc_rdma_free(struct svc_xprt *xprt);
 static int svc_rdma_has_wspace(struct svc_xprt *xprt);
@@ -552,10 +551,6 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt)
 	return NULL;
 }
 
-static void svc_rdma_release_rqst(struct svc_rqst *rqstp)
-{
-}
-
 /*
  * When connected, an svc_xprt has at least two references:
  *