Merge tag 'nfs-rdma-for-4.18-1' of git://git.linux-nfs.org/projects/anna/linux-nfs

NFS-over-RDMA client updates for Linux 4.18

Stable patches:
- xprtrdma: Return -ENOBUFS when no pages are available

New features:
- Add ->alloc_slot() and ->free_slot() functions

Bugfixes and cleanups:
- Add missing SPDX tags to some files
- Try to fail mount quickly if client has no RDMA devices
- Create transport IDs in the correct network namespace
- Fix max_send_wr computation
- Clean up receive tracepoints
- Refactor receive handling
- Remove unused functions

16 files changed, 359 insertions, 355 deletions

diff --git a/include/linux/sunrpc/rpc_rdma.h b/include/linux/sunrpc/rpc_rdma.h
index 8f144db73e38..92d182fd8e3b 100644
--- a/include/linux/sunrpc/rpc_rdma.h
+++ b/include/linux/sunrpc/rpc_rdma.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause */
 /*
  * Copyright (c) 2015-2017 Oracle. All rights reserved.
  * Copyright (c) 2003-2007 Network Appliance, Inc. All rights reserved.
diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index 5fea0fb420df..336fd1a19cca 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -84,7 +84,6 @@ struct rpc_rqst {
 	void (*rq_release_snd_buf)(struct rpc_rqst *); /* release rq_enc_pages */
 	struct list_head	rq_list;
 
-	void			*rq_xprtdata;	/* Per-xprt private data */
 	void			*rq_buffer;	/* Call XDR encode buffer */
 	size_t			rq_callsize;
 	void			*rq_rbuffer;	/* Reply XDR decode buffer */
@@ -127,6 +126,8 @@ struct rpc_xprt_ops {
 	int		(*reserve_xprt)(struct rpc_xprt *xprt, struct rpc_task *task);
 	void		(*release_xprt)(struct rpc_xprt *xprt, struct rpc_task *task);
 	void		(*alloc_slot)(struct rpc_xprt *xprt, struct rpc_task *task);
+	void		(*free_slot)(struct rpc_xprt *xprt,
+				     struct rpc_rqst *req);
 	void		(*rpcbind)(struct rpc_task *task);
 	void		(*set_port)(struct rpc_xprt *xprt, unsigned short port);
 	void		(*connect)(struct rpc_xprt *xprt, struct rpc_task *task);
@@ -324,10 +325,13 @@ struct xprt_class {
 struct rpc_xprt		*xprt_create_transport(struct xprt_create *args);
 void			xprt_connect(struct rpc_task *task);
 void			xprt_reserve(struct rpc_task *task);
+void			xprt_request_init(struct rpc_task *task);
 void			xprt_retry_reserve(struct rpc_task *task);
 int			xprt_reserve_xprt(struct rpc_xprt *xprt, struct rpc_task *task);
 int			xprt_reserve_xprt_cong(struct rpc_xprt *xprt, struct rpc_task *task);
 void			xprt_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task);
+void			xprt_free_slot(struct rpc_xprt *xprt,
+				       struct rpc_rqst *req);
 void			xprt_lock_and_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task);
 bool			xprt_prepare_transmit(struct rpc_task *task);
 void			xprt_transmit(struct rpc_task *task);
diff --git a/include/linux/sunrpc/xprtrdma.h b/include/linux/sunrpc/xprtrdma.h
index 5859563e3c1f..86fc38ff0355 100644
--- a/include/linux/sunrpc/xprtrdma.h
+++ b/include/linux/sunrpc/xprtrdma.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause */
 /*
  * Copyright (c) 2003-2007 Network Appliance, Inc. All rights reserved.
  *
diff --git a/include/trace/events/rpcrdma.h b/include/trace/events/rpcrdma.h
index 50ed3f8bf534..c4494a2b3ecd 100644
--- a/include/trace/events/rpcrdma.h
+++ b/include/trace/events/rpcrdma.h
@@ -528,24 +528,54 @@ TRACE_EVENT(xprtrdma_post_send,
 
 TRACE_EVENT(xprtrdma_post_recv,
 	TP_PROTO(
-		const struct rpcrdma_rep *rep,
+		const struct ib_cqe *cqe
+	),
+
+	TP_ARGS(cqe),
+
+	TP_STRUCT__entry(
+		__field(const void *, cqe)
+	),
+
+	TP_fast_assign(
+		__entry->cqe = cqe;
+	),
+
+	TP_printk("cqe=%p",
+		__entry->cqe
+	)
+);
+
+TRACE_EVENT(xprtrdma_post_recvs,
+	TP_PROTO(
+		const struct rpcrdma_xprt *r_xprt,
+		unsigned int count,
 		int status
 	),
 
-	TP_ARGS(rep, status),
+	TP_ARGS(r_xprt, count, status),
 
 	TP_STRUCT__entry(
-		__field(const void *, rep)
+		__field(const void *, r_xprt)
+		__field(unsigned int, count)
 		__field(int, status)
+		__field(int, posted)
+		__string(addr, rpcrdma_addrstr(r_xprt))
+		__string(port, rpcrdma_portstr(r_xprt))
 	),
 
 	TP_fast_assign(
-		__entry->rep = rep;
+		__entry->r_xprt = r_xprt;
+		__entry->count = count;
 		__entry->status = status;
+		__entry->posted = r_xprt->rx_buf.rb_posted_receives;
+		__assign_str(addr, rpcrdma_addrstr(r_xprt));
+		__assign_str(port, rpcrdma_portstr(r_xprt));
 	),
 
-	TP_printk("rep=%p status=%d",
-		__entry->rep, __entry->status
+	TP_printk("peer=[%s]:%s r_xprt=%p: %u new recvs, %d active (rc %d)",
+		__get_str(addr), __get_str(port), __entry->r_xprt,
+		__entry->count, __entry->posted, __entry->status
 	)
 );
 
@@ -584,28 +614,32 @@ TRACE_EVENT(xprtrdma_wc_send,
 
 TRACE_EVENT(xprtrdma_wc_receive,
 	TP_PROTO(
-		const struct rpcrdma_rep *rep,
 		const struct ib_wc *wc
 	),
 
-	TP_ARGS(rep, wc),
+	TP_ARGS(wc),
 
 	TP_STRUCT__entry(
-		__field(const void *, rep)
-		__field(unsigned int, byte_len)
+		__field(const void *, cqe)
+		__field(u32, byte_len)
 		__field(unsigned int, status)
-		__field(unsigned int, vendor_err)
+		__field(u32, vendor_err)
 	),
 
 	TP_fast_assign(
-		__entry->rep = rep;
-		__entry->byte_len = wc->byte_len;
+		__entry->cqe = wc->wr_cqe;
 		__entry->status = wc->status;
-		__entry->vendor_err = __entry->status ? wc->vendor_err : 0;
+		if (wc->status) {
+			__entry->byte_len = 0;
+			__entry->vendor_err = wc->vendor_err;
+		} else {
+			__entry->byte_len = wc->byte_len;
+			__entry->vendor_err = 0;
+		}
 	),
 
-	TP_printk("rep=%p, %u bytes: %s (%u/0x%x)",
-		__entry->rep, __entry->byte_len,
+	TP_printk("cqe=%p %u bytes: %s (%u/0x%x)",
+		__entry->cqe, __entry->byte_len,
 		rdma_show_wc_status(__entry->status),
 		__entry->status, __entry->vendor_err
 	)
@@ -616,6 +650,7 @@ DEFINE_FRWR_DONE_EVENT(xprtrdma_wc_li);
 DEFINE_FRWR_DONE_EVENT(xprtrdma_wc_li_wake);
 
 DEFINE_MR_EVENT(xprtrdma_localinv);
+DEFINE_MR_EVENT(xprtrdma_dma_map);
 DEFINE_MR_EVENT(xprtrdma_dma_unmap);
 DEFINE_MR_EVENT(xprtrdma_remoteinv);
 DEFINE_MR_EVENT(xprtrdma_recover_mr);
@@ -799,7 +834,6 @@ TRACE_EVENT(xprtrdma_allocate,
 		__field(unsigned int, task_id)
 		__field(unsigned int, client_id)
 		__field(const void *, req)
-		__field(const void *, rep)
 		__field(size_t, callsize)
 		__field(size_t, rcvsize)
 	),
@@ -808,15 +842,13 @@ TRACE_EVENT(xprtrdma_allocate,
 		__entry->task_id = task->tk_pid;
 		__entry->client_id = task->tk_client->cl_clid;
 		__entry->req = req;
-		__entry->rep = req ? req->rl_reply : NULL;
 		__entry->callsize = task->tk_rqstp->rq_callsize;
 		__entry->rcvsize = task->tk_rqstp->rq_rcvsize;
 	),
 
-	TP_printk("task:%u@%u req=%p rep=%p (%zu, %zu)",
+	TP_printk("task:%u@%u req=%p (%zu, %zu)",
 		__entry->task_id, __entry->client_id,
-		__entry->req, __entry->rep,
-		__entry->callsize, __entry->rcvsize
+		__entry->req, __entry->callsize, __entry->rcvsize
 	)
 );
 
@@ -848,8 +880,6 @@ TRACE_EVENT(xprtrdma_rpc_done,
 	)
 );
 
-DEFINE_RXPRT_EVENT(xprtrdma_noreps);
-
 /**
  ** Callback events
  **/
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index c2266f387213..d839c33ae7d9 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -1546,6 +1546,7 @@ call_reserveresult(struct rpc_task *task)
 	task->tk_status = 0;
 	if (status >= 0) {
 		if (task->tk_rqstp) {
+			xprt_request_init(task);
 			task->tk_action = call_refresh;
 			return;
 		}
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 70f005044f06..3c85af058227 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -66,7 +66,7 @@
  * Local functions
  */
 static void	 xprt_init(struct rpc_xprt *xprt, struct net *net);
-static void	xprt_request_init(struct rpc_task *, struct rpc_xprt *);
+static __be32	xprt_alloc_xid(struct rpc_xprt *xprt);
 static void	xprt_connect_status(struct rpc_task *task);
 static int      __xprt_get_cong(struct rpc_xprt *, struct rpc_task *);
 static void     __xprt_put_cong(struct rpc_xprt *, struct rpc_rqst *);
@@ -987,6 +987,8 @@ bool xprt_prepare_transmit(struct rpc_task *task)
 		task->tk_status = -EAGAIN;
 		goto out_unlock;
 	}
+	if (!bc_prealloc(req) && !req->rq_xmit_bytes_sent)
+		req->rq_xid = xprt_alloc_xid(xprt);
 	ret = true;
 out_unlock:
 	spin_unlock_bh(&xprt->transport_lock);
@@ -1163,10 +1165,10 @@ void xprt_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task)
 out_init_req:
 	xprt->stat.max_slots = max_t(unsigned int, xprt->stat.max_slots,
 				     xprt->num_reqs);
+	spin_unlock(&xprt->reserve_lock);
+
 	task->tk_status = 0;
 	task->tk_rqstp = req;
-	xprt_request_init(task, xprt);
-	spin_unlock(&xprt->reserve_lock);
 }
 EXPORT_SYMBOL_GPL(xprt_alloc_slot);
 
@@ -1184,7 +1186,7 @@ void xprt_lock_and_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task)
 }
 EXPORT_SYMBOL_GPL(xprt_lock_and_alloc_slot);
 
-static void xprt_free_slot(struct rpc_xprt *xprt, struct rpc_rqst *req)
+void xprt_free_slot(struct rpc_xprt *xprt, struct rpc_rqst *req)
 {
 	spin_lock(&xprt->reserve_lock);
 	if (!xprt_dynamic_free_slot(xprt, req)) {
@@ -1194,6 +1196,7 @@ static void xprt_free_slot(struct rpc_xprt *xprt, struct rpc_rqst *req)
 	xprt_wake_up_backlog(xprt);
 	spin_unlock(&xprt->reserve_lock);
 }
+EXPORT_SYMBOL_GPL(xprt_free_slot);
 
 static void xprt_free_all_slots(struct rpc_xprt *xprt)
 {
@@ -1303,8 +1306,9 @@ static inline void xprt_init_xid(struct rpc_xprt *xprt)
 	xprt->xid = prandom_u32();
 }
 
-static void xprt_request_init(struct rpc_task *task, struct rpc_xprt *xprt)
+void xprt_request_init(struct rpc_task *task)
 {
+	struct rpc_xprt *xprt = task->tk_xprt;
 	struct rpc_rqst	*req = task->tk_rqstp;
 
 	INIT_LIST_HEAD(&req->rq_list);
@@ -1312,7 +1316,6 @@ static void xprt_request_init(struct rpc_task *task, struct rpc_xprt *xprt)
 	req->rq_task	= task;
 	req->rq_xprt    = xprt;
 	req->rq_buffer  = NULL;
-	req->rq_xid     = xprt_alloc_xid(xprt);
 	req->rq_connect_cookie = xprt->connect_cookie - 1;
 	req->rq_bytes_sent = 0;
 	req->rq_snd_buf.len = 0;
@@ -1373,7 +1376,7 @@ void xprt_release(struct rpc_task *task)
 
 	dprintk("RPC: %5u release request %p\n", task->tk_pid, req);
 	if (likely(!bc_prealloc(req)))
-		xprt_free_slot(xprt, req);
+		xprt->ops->free_slot(xprt, req);
 	else
 		xprt_free_bc_request(req);
 }
diff --git a/net/sunrpc/xprtrdma/backchannel.c b/net/sunrpc/xprtrdma/backchannel.c
index 47ebac949769..c8f1c2b89dad 100644
--- a/net/sunrpc/xprtrdma/backchannel.c
+++ b/net/sunrpc/xprtrdma/backchannel.c
@@ -29,29 +29,41 @@ static void rpcrdma_bc_free_rqst(struct rpcrdma_xprt *r_xprt,
 	spin_unlock(&buf->rb_reqslock);
 
 	rpcrdma_destroy_req(req);
-
-	kfree(rqst);
 }
 
-static int rpcrdma_bc_setup_rqst(struct rpcrdma_xprt *r_xprt,
-				 struct rpc_rqst *rqst)
+static int rpcrdma_bc_setup_reqs(struct rpcrdma_xprt *r_xprt,
+				 unsigned int count)
 {
-	struct rpcrdma_regbuf *rb;
-	struct rpcrdma_req *req;
-	size_t size;
+	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
+	struct rpc_rqst *rqst;
+	unsigned int i;
+
+	for (i = 0; i < (count << 1); i++) {
+		struct rpcrdma_regbuf *rb;
+		struct rpcrdma_req *req;
+		size_t size;
+
+		req = rpcrdma_create_req(r_xprt);
+		if (IS_ERR(req))
+			return PTR_ERR(req);
+		rqst = &req->rl_slot;
+
+		rqst->rq_xprt = 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);
+		spin_lock_bh(&xprt->bc_pa_lock);
+		list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
+		spin_unlock_bh(&xprt->bc_pa_lock);
 
-	req = rpcrdma_create_req(r_xprt);
-	if (IS_ERR(req))
-		return PTR_ERR(req);
-
-	size = r_xprt->rx_data.inline_rsize;
-	rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
-	if (IS_ERR(rb))
-		goto out_fail;
-	req->rl_sendbuf = rb;
-	xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base,
-		     min_t(size_t, size, PAGE_SIZE));
-	rpcrdma_set_xprtdata(rqst, req);
+		size = r_xprt->rx_data.inline_rsize;
+		rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
+		if (IS_ERR(rb))
+			goto out_fail;
+		req->rl_sendbuf = rb;
+		xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base,
+			     min_t(size_t, size, PAGE_SIZE));
+	}
 	return 0;
 
 out_fail:
@@ -59,23 +71,6 @@ out_fail:
 	return -ENOMEM;
 }
 
-/* Allocate and add receive buffers to the rpcrdma_buffer's
- * existing list of rep's. These are released when the
- * transport is destroyed.
- */
-static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
-				 unsigned int count)
-{
-	int rc = 0;
-
-	while (count--) {
-		rc = rpcrdma_create_rep(r_xprt);
-		if (rc)
-			break;
-	}
-	return rc;
-}
-
 /**
  * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
  * @xprt: transport associated with these backchannel resources
@@ -86,9 +81,6 @@ static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
 {
 	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
-	struct rpcrdma_buffer *buffer = &r_xprt->rx_buf;
-	struct rpc_rqst *rqst;
-	unsigned int i;
 	int rc;
 
 	/* The backchannel reply path returns each rpc_rqst to the
@@ -103,35 +95,11 @@ int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
 	if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
 		goto out_err;
 
-	for (i = 0; i < (reqs << 1); i++) {
-		rqst = kzalloc(sizeof(*rqst), GFP_KERNEL);
-		if (!rqst)
-			goto out_free;
-
-		dprintk("RPC:       %s: new rqst %p\n", __func__, rqst);
-
-		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;
-
-		spin_lock_bh(&xprt->bc_pa_lock);
-		list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
-		spin_unlock_bh(&xprt->bc_pa_lock);
-	}
-
-	rc = rpcrdma_bc_setup_reps(r_xprt, reqs);
+	rc = rpcrdma_bc_setup_reqs(r_xprt, reqs);
 	if (rc)
 		goto out_free;
 
-	rc = rpcrdma_ep_post_extra_recv(r_xprt, reqs);
-	if (rc)
-		goto out_free;
-
-	buffer->rb_bc_srv_max_requests = reqs;
+	r_xprt->rx_buf.rb_bc_srv_max_requests = reqs;
 	request_module("svcrdma");
 	trace_xprtrdma_cb_setup(r_xprt, reqs);
 	return 0;
@@ -235,6 +203,7 @@ int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst)
 	if (rc < 0)
 		goto failed_marshal;
 
+	rpcrdma_post_recvs(r_xprt, true);
 	if (rpcrdma_ep_post(&r_xprt->rx_ia, &r_xprt->rx_ep, req))
 		goto drop_connection;
 	return 0;
@@ -275,10 +244,14 @@ void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
  */
 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
 {
+	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 	struct rpc_xprt *xprt = rqst->rq_xprt;
 
 	dprintk("RPC:       %s: freeing rqst %p (req %p)\n",
-		__func__, rqst, rpcr_to_rdmar(rqst));
+		__func__, rqst, req);
+
+	rpcrdma_recv_buffer_put(req->rl_reply);
+	req->rl_reply = NULL;
 
 	spin_lock_bh(&xprt->bc_pa_lock);
 	list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
diff --git a/net/sunrpc/xprtrdma/fmr_ops.c b/net/sunrpc/xprtrdma/fmr_ops.c
index f2f63959fddd..58b472666255 100644
--- a/net/sunrpc/xprtrdma/fmr_ops.c
+++ b/net/sunrpc/xprtrdma/fmr_ops.c
@@ -156,10 +156,32 @@ out_release:
 	fmr_op_release_mr(mr);
 }
 
+/* On success, sets:
+ *	ep->rep_attr.cap.max_send_wr
+ *	ep->rep_attr.cap.max_recv_wr
+ *	cdata->max_requests
+ *	ia->ri_max_segs
+ */
 static int
 fmr_op_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
 	    struct rpcrdma_create_data_internal *cdata)
 {
+	int max_qp_wr;
+
+	max_qp_wr = ia->ri_device->attrs.max_qp_wr;
+	max_qp_wr -= RPCRDMA_BACKWARD_WRS;
+	max_qp_wr -= 1;
+	if (max_qp_wr < RPCRDMA_MIN_SLOT_TABLE)
+		return -ENOMEM;
+	if (cdata->max_requests > max_qp_wr)
+		cdata->max_requests = max_qp_wr;
+	ep->rep_attr.cap.max_send_wr = cdata->max_requests;
+	ep->rep_attr.cap.max_send_wr += RPCRDMA_BACKWARD_WRS;
+	ep->rep_attr.cap.max_send_wr += 1; /* for ib_drain_sq */
+	ep->rep_attr.cap.max_recv_wr = cdata->max_requests;
+	ep->rep_attr.cap.max_recv_wr += RPCRDMA_BACKWARD_WRS;
+	ep->rep_attr.cap.max_recv_wr += 1; /* for ib_drain_rq */
+
 	ia->ri_max_segs = max_t(unsigned int, 1, RPCRDMA_MAX_DATA_SEGS /
 				RPCRDMA_MAX_FMR_SGES);
 	return 0;
@@ -219,6 +241,7 @@ fmr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
 				     mr->mr_sg, i, mr->mr_dir);
 	if (!mr->mr_nents)
 		goto out_dmamap_err;
+	trace_xprtrdma_dma_map(mr);
 
 	for (i = 0, dma_pages = mr->fmr.fm_physaddrs; i < mr->mr_nents; i++)
 		dma_pages[i] = sg_dma_address(&mr->mr_sg[i]);
diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
index c59c5c788db0..d46dc7e6e30a 100644
--- a/net/sunrpc/xprtrdma/frwr_ops.c
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -202,12 +202,22 @@ out_release:
 	frwr_op_release_mr(mr);
 }
 
+/* On success, sets:
+ *	ep->rep_attr.cap.max_send_wr
+ *	ep->rep_attr.cap.max_recv_wr
+ *	cdata->max_requests
+ *	ia->ri_max_segs
+ *
+ * And these FRWR-related fields:
+ *	ia->ri_max_frwr_depth
+ *	ia->ri_mrtype
+ */
 static int
 frwr_op_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
 	     struct rpcrdma_create_data_internal *cdata)
 {
 	struct ib_device_attr *attrs = &ia->ri_device->attrs;
-	int depth, delta;
+	int max_qp_wr, depth, delta;
 
 	ia->ri_mrtype = IB_MR_TYPE_MEM_REG;
 	if (attrs->device_cap_flags & IB_DEVICE_SG_GAPS_REG)
@@ -241,14 +251,26 @@ frwr_op_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
 		} while (delta > 0);
 	}
 
-	ep->rep_attr.cap.max_send_wr *= depth;
-	if (ep->rep_attr.cap.max_send_wr > attrs->max_qp_wr) {
-		cdata->max_requests = attrs->max_qp_wr / depth;
+	max_qp_wr = ia->ri_device->attrs.max_qp_wr;
+	max_qp_wr -= RPCRDMA_BACKWARD_WRS;
+	max_qp_wr -= 1;
+	if (max_qp_wr < RPCRDMA_MIN_SLOT_TABLE)
+		return -ENOMEM;
+	if (cdata->max_requests > max_qp_wr)
+		cdata->max_requests = max_qp_wr;
+	ep->rep_attr.cap.max_send_wr = cdata->max_requests * depth;
+	if (ep->rep_attr.cap.max_send_wr > max_qp_wr) {
+		cdata->max_requests = max_qp_wr / depth;
 		if (!cdata->max_requests)
 			return -EINVAL;
 		ep->rep_attr.cap.max_send_wr = cdata->max_requests *
 					       depth;
 	}
+	ep->rep_attr.cap.max_send_wr += RPCRDMA_BACKWARD_WRS;
+	ep->rep_attr.cap.max_send_wr += 1; /* for ib_drain_sq */
+	ep->rep_attr.cap.max_recv_wr = cdata->max_requests;
+	ep->rep_attr.cap.max_recv_wr += RPCRDMA_BACKWARD_WRS;
+	ep->rep_attr.cap.max_recv_wr += 1; /* for ib_drain_rq */
 
 	ia->ri_max_segs = max_t(unsigned int, 1, RPCRDMA_MAX_DATA_SEGS /
 				ia->ri_max_frwr_depth);
@@ -393,6 +415,7 @@ frwr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
 	mr->mr_nents = ib_dma_map_sg(ia->ri_device, mr->mr_sg, i, mr->mr_dir);
 	if (!mr->mr_nents)
 		goto out_dmamap_err;
+	trace_xprtrdma_dma_map(mr);
 
 	ibmr = frwr->fr_mr;
 	n = ib_map_mr_sg(ibmr, mr->mr_sg, mr->mr_nents, NULL, PAGE_SIZE);
diff --git a/net/sunrpc/xprtrdma/module.c b/net/sunrpc/xprtrdma/module.c
index a762d192372b..f338065121f2 100644
--- a/net/sunrpc/xprtrdma/module.c
+++ b/net/sunrpc/xprtrdma/module.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
 /*
  * Copyright (c) 2015, 2017 Oracle.  All rights reserved.
  */
diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index e8adad33d0bb..1c78516aa6f2 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
 /*
  * Copyright (c) 2014-2017 Oracle.  All rights reserved.
  * Copyright (c) 2003-2007 Network Appliance, Inc. All rights reserved.
@@ -54,14 +55,6 @@
 # define RPCDBG_FACILITY	RPCDBG_TRANS
 #endif
 
-static const char transfertypes[][12] = {
-	"inline",	/* no chunks */
-	"read list",	/* some argument via rdma read */
-	"*read list",	/* entire request via rdma read */
-	"write list",	/* some result via rdma write */
-	"reply chunk"	/* entire reply via rdma write */
-};
-
 /* Returns size of largest RPC-over-RDMA header in a Call message
  *
  * The largest Call header contains a full-size Read list and a
@@ -230,7 +223,7 @@ rpcrdma_convert_iovs(struct rpcrdma_xprt *r_xprt, struct xdr_buf *xdrbuf,
 			 */
 			*ppages = alloc_page(GFP_ATOMIC);
 			if (!*ppages)
-				return -EAGAIN;
+				return -ENOBUFS;
 		}
 		seg->mr_page = *ppages;
 		seg->mr_offset = (char *)page_base;
@@ -365,7 +358,7 @@ rpcrdma_encode_read_list(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
 		seg = r_xprt->rx_ia.ri_ops->ro_map(r_xprt, seg, nsegs,
 						   false, &mr);
 		if (IS_ERR(seg))
-			goto out_maperr;
+			return PTR_ERR(seg);
 		rpcrdma_mr_push(mr, &req->rl_registered);
 
 		if (encode_read_segment(xdr, mr, pos) < 0)
@@ -377,11 +370,6 @@ rpcrdma_encode_read_list(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
 	} while (nsegs);
 
 	return 0;
-
-out_maperr:
-	if (PTR_ERR(seg) == -EAGAIN)
-		xprt_wait_for_buffer_space(rqst->rq_task, NULL);
-	return PTR_ERR(seg);
 }
 
 /* Register and XDR encode the Write list. Supports encoding a list
@@ -428,7 +416,7 @@ rpcrdma_encode_write_list(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
 		seg = r_xprt->rx_ia.ri_ops->ro_map(r_xprt, seg, nsegs,
 						   true, &mr);
 		if (IS_ERR(seg))
-			goto out_maperr;
+			return PTR_ERR(seg);
 		rpcrdma_mr_push(mr, &req->rl_registered);
 
 		if (encode_rdma_segment(xdr, mr) < 0)
@@ -445,11 +433,6 @@ rpcrdma_encode_write_list(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
 	*segcount = cpu_to_be32(nchunks);
 
 	return 0;
-
-out_maperr:
-	if (PTR_ERR(seg) == -EAGAIN)
-		xprt_wait_for_buffer_space(rqst->rq_task, NULL);
-	return PTR_ERR(seg);
 }
 
 /* Register and XDR encode the Reply chunk. Supports encoding an array
@@ -491,7 +474,7 @@ rpcrdma_encode_reply_chunk(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
 		seg = r_xprt->rx_ia.ri_ops->ro_map(r_xprt, seg, nsegs,
 						   true, &mr);
 		if (IS_ERR(seg))
-			goto out_maperr;
+			return PTR_ERR(seg);
 		rpcrdma_mr_push(mr, &req->rl_registered);
 
 		if (encode_rdma_segment(xdr, mr) < 0)
@@ -508,11 +491,6 @@ rpcrdma_encode_reply_chunk(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
 	*segcount = cpu_to_be32(nchunks);
 
 	return 0;
-
-out_maperr:
-	if (PTR_ERR(seg) == -EAGAIN)
-		xprt_wait_for_buffer_space(rqst->rq_task, NULL);
-	return PTR_ERR(seg);
 }
 
 /**
@@ -709,7 +687,7 @@ rpcrdma_prepare_send_sges(struct rpcrdma_xprt *r_xprt,
 {
 	req->rl_sendctx = rpcrdma_sendctx_get_locked(&r_xprt->rx_buf);
 	if (!req->rl_sendctx)
-		return -ENOBUFS;
+		return -EAGAIN;
 	req->rl_sendctx->sc_wr.num_sge = 0;
 	req->rl_sendctx->sc_unmap_count = 0;
 	req->rl_sendctx->sc_req = req;
@@ -883,7 +861,15 @@ rpcrdma_marshal_req(struct rpcrdma_xprt *r_xprt, struct rpc_rqst *rqst)
 	return 0;
 
 out_err:
-	r_xprt->rx_stats.failed_marshal_count++;
+	switch (ret) {
+	case -EAGAIN:
+		xprt_wait_for_buffer_space(rqst->rq_task, NULL);
+		break;
+	case -ENOBUFS:
+		break;
+	default:
+		r_xprt->rx_stats.failed_marshal_count++;
+	}
 	return ret;
 }
 
@@ -1026,8 +1012,6 @@ rpcrdma_is_bcall(struct rpcrdma_xprt *r_xprt, struct rpcrdma_rep *rep)
 
 out_short:
 	pr_warn("RPC/RDMA short backward direction call\n");
-	if (rpcrdma_ep_post_recv(&r_xprt->rx_ia, rep))
-		xprt_disconnect_done(&r_xprt->rx_xprt);
 	return true;
 }
 #else	/* CONFIG_SUNRPC_BACKCHANNEL */
@@ -1333,13 +1317,14 @@ void rpcrdma_reply_handler(struct rpcrdma_rep *rep)
 	u32 credits;
 	__be32 *p;
 
+	--buf->rb_posted_receives;
+
 	if (rep->rr_hdrbuf.head[0].iov_len == 0)
 		goto out_badstatus;
 
+	/* Fixed transport header fields */
 	xdr_init_decode(&rep->rr_stream, &rep->rr_hdrbuf,
 			rep->rr_hdrbuf.head[0].iov_base);
-
-	/* Fixed transport header fields */
 	p = xdr_inline_decode(&rep->rr_stream, 4 * sizeof(*p));
 	if (unlikely(!p))
 		goto out_shortreply;
@@ -1378,17 +1363,10 @@ void rpcrdma_reply_handler(struct rpcrdma_rep *rep)
 
 	trace_xprtrdma_reply(rqst->rq_task, rep, req, credits);
 
+	rpcrdma_post_recvs(r_xprt, false);
 	queue_work(rpcrdma_receive_wq, &rep->rr_work);
 	return;
 
-out_badstatus:
-	rpcrdma_recv_buffer_put(rep);
-	if (r_xprt->rx_ep.rep_connected == 1) {
-		r_xprt->rx_ep.rep_connected = -EIO;
-		rpcrdma_conn_func(&r_xprt->rx_ep);
-	}
-	return;
-
 out_badversion:
 	trace_xprtrdma_reply_vers(rep);
 	goto repost;
@@ -1408,7 +1386,7 @@ out_shortreply:
  * receive buffer before returning.
  */
 repost:
-	r_xprt->rx_stats.bad_reply_count++;
-	if (rpcrdma_ep_post_recv(&r_xprt->rx_ia, rep))
-		rpcrdma_recv_buffer_put(rep);
+	rpcrdma_post_recvs(r_xprt, false);
+out_badstatus:
+	rpcrdma_recv_buffer_put(rep);
 }
diff --git a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
index a73632ca9048..1035516d54e2 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
@@ -273,6 +273,7 @@ static const struct rpc_xprt_ops xprt_rdma_bc_procs = {
 	.reserve_xprt		= xprt_reserve_xprt_cong,
 	.release_xprt		= xprt_release_xprt_cong,
 	.alloc_slot		= xprt_alloc_slot,
+	.free_slot		= xprt_free_slot,
 	.release_request	= xprt_release_rqst_cong,
 	.buf_alloc		= xprt_rdma_bc_allocate,
 	.buf_free		= xprt_rdma_bc_free,
diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
index cc1aad325496..0c775f05123c 100644
--- a/net/sunrpc/xprtrdma/transport.c
+++ b/net/sunrpc/xprtrdma/transport.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
 /*
  * Copyright (c) 2014-2017 Oracle.  All rights reserved.
  * Copyright (c) 2003-2007 Network Appliance, Inc. All rights reserved.
@@ -330,9 +331,7 @@ xprt_setup_rdma(struct xprt_create *args)
 		return ERR_PTR(-EBADF);
 	}
 
-	xprt = xprt_alloc(args->net, sizeof(struct rpcrdma_xprt),
-			xprt_rdma_slot_table_entries,
-			xprt_rdma_slot_table_entries);
+	xprt = xprt_alloc(args->net, sizeof(struct rpcrdma_xprt), 0, 0);
 	if (xprt == NULL) {
 		dprintk("RPC:       %s: couldn't allocate rpcrdma_xprt\n",
 			__func__);
@@ -364,7 +363,7 @@ xprt_setup_rdma(struct xprt_create *args)
 		xprt_set_bound(xprt);
 	xprt_rdma_format_addresses(xprt, sap);
 
-	cdata.max_requests = xprt->max_reqs;
+	cdata.max_requests = xprt_rdma_slot_table_entries;
 
 	cdata.rsize = RPCRDMA_MAX_SEGS * PAGE_SIZE; /* RDMA write max */
 	cdata.wsize = RPCRDMA_MAX_SEGS * PAGE_SIZE; /* RDMA read max */
@@ -537,6 +536,47 @@ xprt_rdma_connect(struct rpc_xprt *xprt, struct rpc_task *task)
 	}
 }
 
+/**
+ * xprt_rdma_alloc_slot - allocate an rpc_rqst
+ * @xprt: controlling RPC transport
+ * @task: RPC task requesting a fresh rpc_rqst
+ *
+ * tk_status values:
+ *	%0 if task->tk_rqstp points to a fresh rpc_rqst
+ *	%-EAGAIN if no rpc_rqst is available; queued on backlog
+ */
+static void
+xprt_rdma_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task)
+{
+	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
+	struct rpcrdma_req *req;
+
+	req = rpcrdma_buffer_get(&r_xprt->rx_buf);
+	if (!req)
+		goto out_sleep;
+	task->tk_rqstp = &req->rl_slot;
+	task->tk_status = 0;
+	return;
+
+out_sleep:
+	rpc_sleep_on(&xprt->backlog, task, NULL);
+	task->tk_status = -EAGAIN;
+}
+
+/**
+ * xprt_rdma_free_slot - release an rpc_rqst
+ * @xprt: controlling RPC transport
+ * @rqst: rpc_rqst to release
+ *
+ */
+static void
+xprt_rdma_free_slot(struct rpc_xprt *xprt, struct rpc_rqst *rqst)
+{
+	memset(rqst, 0, sizeof(*rqst));
+	rpcrdma_buffer_put(rpcr_to_rdmar(rqst));
+	rpc_wake_up_next(&xprt->backlog);
+}
+
 static bool
 rpcrdma_get_sendbuf(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
 		    size_t size, gfp_t flags)
@@ -607,13 +647,9 @@ xprt_rdma_allocate(struct rpc_task *task)
 {
 	struct rpc_rqst *rqst = task->tk_rqstp;
 	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
-	struct rpcrdma_req *req;
+	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 	gfp_t flags;
 
-	req = rpcrdma_buffer_get(&r_xprt->rx_buf);
-	if (req == NULL)
-		goto out_get;
-
 	flags = RPCRDMA_DEF_GFP;
 	if (RPC_IS_SWAPPER(task))
 		flags = __GFP_MEMALLOC | GFP_NOWAIT | __GFP_NOWARN;
@@ -623,15 +659,12 @@ xprt_rdma_allocate(struct rpc_task *task)
 	if (!rpcrdma_get_recvbuf(r_xprt, req, rqst->rq_rcvsize, flags))
 		goto out_fail;
 
-	rpcrdma_set_xprtdata(rqst, req);
 	rqst->rq_buffer = req->rl_sendbuf->rg_base;
 	rqst->rq_rbuffer = req->rl_recvbuf->rg_base;
 	trace_xprtrdma_allocate(task, req);
 	return 0;
 
 out_fail:
-	rpcrdma_buffer_put(req);
-out_get:
 	trace_xprtrdma_allocate(task, NULL);
 	return -ENOMEM;
 }
@@ -652,7 +685,6 @@ xprt_rdma_free(struct rpc_task *task)
 	if (test_bit(RPCRDMA_REQ_F_PENDING, &req->rl_flags))
 		rpcrdma_release_rqst(r_xprt, req);
 	trace_xprtrdma_rpc_done(task, req);
-	rpcrdma_buffer_put(req);
 }
 
 /**
@@ -690,9 +722,6 @@ xprt_rdma_send_request(struct rpc_task *task)
 	if (rc < 0)
 		goto failed_marshal;
 
-	if (req->rl_reply == NULL) 		/* e.g. reconnection */
-		rpcrdma_recv_buffer_get(req);
-
 	/* Must suppress retransmit to maintain credits */
 	if (rqst->rq_connect_cookie == xprt->connect_cookie)
 		goto drop_connection;
@@ -779,7 +808,8 @@ xprt_rdma_disable_swap(struct rpc_xprt *xprt)
 static const struct rpc_xprt_ops xprt_rdma_procs = {
 	.reserve_xprt		= xprt_reserve_xprt_cong,
 	.release_xprt		= xprt_release_xprt_cong, /* sunrpc/xprt.c */
-	.alloc_slot		= xprt_alloc_slot,
+	.alloc_slot		= xprt_rdma_alloc_slot,
+	.free_slot		= xp