Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1404 insertions, 0 deletions

diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
new file mode 100644
index 000000000..7f9d8365c
--- /dev/null
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -0,0 +1,1404 @@
+// 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.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the BSD-type
+ * license below:
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *      Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *
+ *      Redistributions in binary form must reproduce the above
+ *      copyright notice, this list of conditions and the following
+ *      disclaimer in the documentation and/or other materials provided
+ *      with the distribution.
+ *
+ *      Neither the name of the Network Appliance, Inc. nor the names of
+ *      its contributors may be used to endorse or promote products
+ *      derived from this software without specific prior written
+ *      permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/*
+ * rpc_rdma.c
+ *
+ * This file contains the guts of the RPC RDMA protocol, and
+ * does marshaling/unmarshaling, etc. It is also where interfacing
+ * to the Linux RPC framework lives.
+ */
+
+#include <linux/highmem.h>
+
+#include <linux/sunrpc/svc_rdma.h>
+
+#include "xprt_rdma.h"
+#include <trace/events/rpcrdma.h>
+
+#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
+# define RPCDBG_FACILITY	RPCDBG_TRANS
+#endif
+
+/* Returns size of largest RPC-over-RDMA header in a Call message
+ *
+ * The largest Call header contains a full-size Read list and a
+ * minimal Reply chunk.
+ */
+static unsigned int rpcrdma_max_call_header_size(unsigned int maxsegs)
+{
+	unsigned int size;
+
+	/* Fixed header fields and list discriminators */
+	size = RPCRDMA_HDRLEN_MIN;
+
+	/* Maximum Read list size */
+	maxsegs += 2;	/* segment for head and tail buffers */
+	size += maxsegs * rpcrdma_readchunk_maxsz * sizeof(__be32);
+
+	/* Minimal Read chunk size */
+	size += sizeof(__be32);	/* segment count */
+	size += rpcrdma_segment_maxsz * sizeof(__be32);
+	size += sizeof(__be32);	/* list discriminator */
+
+	dprintk("RPC:       %s: max call header size = %u\n",
+		__func__, size);
+	return size;
+}
+
+/* Returns size of largest RPC-over-RDMA header in a Reply message
+ *
+ * There is only one Write list or one Reply chunk per Reply
+ * message.  The larger list is the Write list.
+ */
+static unsigned int rpcrdma_max_reply_header_size(unsigned int maxsegs)
+{
+	unsigned int size;
+
+	/* Fixed header fields and list discriminators */
+	size = RPCRDMA_HDRLEN_MIN;
+
+	/* Maximum Write list size */
+	maxsegs += 2;	/* segment for head and tail buffers */
+	size += sizeof(__be32);		/* segment count */
+	size += maxsegs * rpcrdma_segment_maxsz * sizeof(__be32);
+	size += sizeof(__be32);	/* list discriminator */
+
+	dprintk("RPC:       %s: max reply header size = %u\n",
+		__func__, size);
+	return size;
+}
+
+void rpcrdma_set_max_header_sizes(struct rpcrdma_xprt *r_xprt)
+{
+	struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
+	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
+	unsigned int maxsegs = ia->ri_max_segs;
+
+	ia->ri_max_inline_write = cdata->inline_wsize -
+				  rpcrdma_max_call_header_size(maxsegs);
+	ia->ri_max_inline_read = cdata->inline_rsize -
+				 rpcrdma_max_reply_header_size(maxsegs);
+}
+
+/* The client can send a request inline as long as the RPCRDMA header
+ * plus the RPC call fit under the transport's inline limit. If the
+ * combined call message size exceeds that limit, the client must use
+ * a Read chunk for this operation.
+ *
+ * A Read chunk is also required if sending the RPC call inline would
+ * exceed this device's max_sge limit.
+ */
+static bool rpcrdma_args_inline(struct rpcrdma_xprt *r_xprt,
+				struct rpc_rqst *rqst)
+{
+	struct xdr_buf *xdr = &rqst->rq_snd_buf;
+	unsigned int count, remaining, offset;
+
+	if (xdr->len > r_xprt->rx_ia.ri_max_inline_write)
+		return false;
+
+	if (xdr->page_len) {
+		remaining = xdr->page_len;
+		offset = offset_in_page(xdr->page_base);
+		count = RPCRDMA_MIN_SEND_SGES;
+		while (remaining) {
+			remaining -= min_t(unsigned int,
+					   PAGE_SIZE - offset, remaining);
+			offset = 0;
+			if (++count > r_xprt->rx_ia.ri_max_send_sges)
+				return false;
+		}
+	}
+
+	return true;
+}
+
+/* The client can't know how large the actual reply will be. Thus it
+ * plans for the largest possible reply for that particular ULP
+ * operation. If the maximum combined reply message size exceeds that
+ * limit, the client must provide a write list or a reply chunk for
+ * this request.
+ */
+static bool rpcrdma_results_inline(struct rpcrdma_xprt *r_xprt,
+				   struct rpc_rqst *rqst)
+{
+	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
+
+	return rqst->rq_rcv_buf.buflen <= ia->ri_max_inline_read;
+}
+
+/* Split @vec on page boundaries into SGEs. FMR registers pages, not
+ * a byte range. Other modes coalesce these SGEs into a single MR
+ * when they can.
+ *
+ * Returns pointer to next available SGE, and bumps the total number
+ * of SGEs consumed.
+ */
+static struct rpcrdma_mr_seg *
+rpcrdma_convert_kvec(struct kvec *vec, struct rpcrdma_mr_seg *seg,
+		     unsigned int *n)
+{
+	u32 remaining, page_offset;
+	char *base;
+
+	base = vec->iov_base;
+	page_offset = offset_in_page(base);
+	remaining = vec->iov_len;
+	while (remaining) {
+		seg->mr_page = NULL;
+		seg->mr_offset = base;
+		seg->mr_len = min_t(u32, PAGE_SIZE - page_offset, remaining);
+		remaining -= seg->mr_len;
+		base += seg->mr_len;
+		++seg;
+		++(*n);
+		page_offset = 0;
+	}
+	return seg;
+}
+
+/* Convert @xdrbuf into SGEs no larger than a page each. As they
+ * are registered, these SGEs are then coalesced into RDMA segments
+ * when the selected memreg mode supports it.
+ *
+ * Returns positive number of SGEs consumed, or a negative errno.
+ */
+
+static int
+rpcrdma_convert_iovs(struct rpcrdma_xprt *r_xprt, struct xdr_buf *xdrbuf,
+		     unsigned int pos, enum rpcrdma_chunktype type,
+		     struct rpcrdma_mr_seg *seg)
+{
+	unsigned long page_base;
+	unsigned int len, n;
+	struct page **ppages;
+
+	n = 0;
+	if (pos == 0)
+		seg = rpcrdma_convert_kvec(&xdrbuf->head[0], seg, &n);
+
+	len = xdrbuf->page_len;
+	ppages = xdrbuf->pages + (xdrbuf->page_base >> PAGE_SHIFT);
+	page_base = offset_in_page(xdrbuf->page_base);
+	while (len) {
+		if (unlikely(!*ppages)) {
+			/* XXX: Certain upper layer operations do
+			 *	not provide receive buffer pages.
+			 */
+			*ppages = alloc_page(GFP_ATOMIC);
+			if (!*ppages)
+				return -ENOBUFS;
+		}
+		seg->mr_page = *ppages;
+		seg->mr_offset = (char *)page_base;
+		seg->mr_len = min_t(u32, PAGE_SIZE - page_base, len);
+		len -= seg->mr_len;
+		++ppages;
+		++seg;
+		++n;
+		page_base = 0;
+	}
+
+	/* When encoding a Read chunk, the tail iovec contains an
+	 * XDR pad and may be omitted.
+	 */
+	if (type == rpcrdma_readch && r_xprt->rx_ia.ri_implicit_roundup)
+		goto out;
+
+	/* When encoding a Write chunk, some servers need to see an
+	 * extra segment for non-XDR-aligned Write chunks. The upper
+	 * layer provides space in the tail iovec that may be used
+	 * for this purpose.
+	 */
+	if (type == rpcrdma_writech && r_xprt->rx_ia.ri_implicit_roundup)
+		goto out;
+
+	if (xdrbuf->tail[0].iov_len)
+		seg = rpcrdma_convert_kvec(&xdrbuf->tail[0], seg, &n);
+
+out:
+	if (unlikely(n > RPCRDMA_MAX_SEGS))
+		return -EIO;
+	return n;
+}
+
+static inline int
+encode_item_present(struct xdr_stream *xdr)
+{
+	__be32 *p;
+
+	p = xdr_reserve_space(xdr, sizeof(*p));
+	if (unlikely(!p))
+		return -EMSGSIZE;
+
+	*p = xdr_one;
+	return 0;
+}
+
+static inline int
+encode_item_not_present(struct xdr_stream *xdr)
+{
+	__be32 *p;
+
+	p = xdr_reserve_space(xdr, sizeof(*p));
+	if (unlikely(!p))
+		return -EMSGSIZE;
+
+	*p = xdr_zero;
+	return 0;
+}
+
+static void
+xdr_encode_rdma_segment(__be32 *iptr, struct rpcrdma_mr *mr)
+{
+	*iptr++ = cpu_to_be32(mr->mr_handle);
+	*iptr++ = cpu_to_be32(mr->mr_length);
+	xdr_encode_hyper(iptr, mr->mr_offset);
+}
+
+static int
+encode_rdma_segment(struct xdr_stream *xdr, struct rpcrdma_mr *mr)
+{
+	__be32 *p;
+
+	p = xdr_reserve_space(xdr, 4 * sizeof(*p));
+	if (unlikely(!p))
+		return -EMSGSIZE;
+
+	xdr_encode_rdma_segment(p, mr);
+	return 0;
+}
+
+static int
+encode_read_segment(struct xdr_stream *xdr, struct rpcrdma_mr *mr,
+		    u32 position)
+{
+	__be32 *p;
+
+	p = xdr_reserve_space(xdr, 6 * sizeof(*p));
+	if (unlikely(!p))
+		return -EMSGSIZE;
+
+	*p++ = xdr_one;			/* Item present */
+	*p++ = cpu_to_be32(position);
+	xdr_encode_rdma_segment(p, mr);
+	return 0;
+}
+
+/* Register and XDR encode the Read list. Supports encoding a list of read
+ * segments that belong to a single read chunk.
+ *
+ * Encoding key for single-list chunks (HLOO = Handle32 Length32 Offset64):
+ *
+ *  Read chunklist (a linked list):
+ *   N elements, position P (same P for all chunks of same arg!):
+ *    1 - PHLOO - 1 - PHLOO - ... - 1 - PHLOO - 0
+ *
+ * Returns zero on success, or a negative errno if a failure occurred.
+ * @xdr is advanced to the next position in the stream.
+ *
+ * Only a single @pos value is currently supported.
+ */
+static noinline int
+rpcrdma_encode_read_list(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
+			 struct rpc_rqst *rqst, enum rpcrdma_chunktype rtype)
+{
+	struct xdr_stream *xdr = &req->rl_stream;
+	struct rpcrdma_mr_seg *seg;
+	struct rpcrdma_mr *mr;
+	unsigned int pos;
+	int nsegs;
+
+	pos = rqst->rq_snd_buf.head[0].iov_len;
+	if (rtype == rpcrdma_areadch)
+		pos = 0;
+	seg = req->rl_segments;
+	nsegs = rpcrdma_convert_iovs(r_xprt, &rqst->rq_snd_buf, pos,
+				     rtype, seg);
+	if (nsegs < 0)
+		return nsegs;
+
+	do {
+		seg = r_xprt->rx_ia.ri_ops->ro_map(r_xprt, seg, nsegs,
+						   false, &mr);
+		if (IS_ERR(seg))
+			return PTR_ERR(seg);
+		rpcrdma_mr_push(mr, &req->rl_registered);
+
+		if (encode_read_segment(xdr, mr, pos) < 0)
+			return -EMSGSIZE;
+
+		trace_xprtrdma_read_chunk(rqst->rq_task, pos, mr, nsegs);
+		r_xprt->rx_stats.read_chunk_count++;
+		nsegs -= mr->mr_nents;
+	} while (nsegs);
+
+	return 0;
+}
+
+/* Register and XDR encode the Write list. Supports encoding a list
+ * containing one array of plain segments that belong to a single
+ * write chunk.
+ *
+ * Encoding key for single-list chunks (HLOO = Handle32 Length32 Offset64):
+ *
+ *  Write chunklist (a list of (one) counted array):
+ *   N elements:
+ *    1 - N - HLOO - HLOO - ... - HLOO - 0
+ *
+ * Returns zero on success, or a negative errno if a failure occurred.
+ * @xdr is advanced to the next position in the stream.
+ *
+ * Only a single Write chunk is currently supported.
+ */
+static noinline int
+rpcrdma_encode_write_list(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
+			  struct rpc_rqst *rqst, enum rpcrdma_chunktype wtype)
+{
+	struct xdr_stream *xdr = &req->rl_stream;
+	struct rpcrdma_mr_seg *seg;
+	struct rpcrdma_mr *mr;
+	int nsegs, nchunks;
+	__be32 *segcount;
+
+	seg = req->rl_segments;
+	nsegs = rpcrdma_convert_iovs(r_xprt, &rqst->rq_rcv_buf,
+				     rqst->rq_rcv_buf.head[0].iov_len,
+				     wtype, seg);
+	if (nsegs < 0)
+		return nsegs;
+
+	if (encode_item_present(xdr) < 0)
+		return -EMSGSIZE;
+	segcount = xdr_reserve_space(xdr, sizeof(*segcount));
+	if (unlikely(!segcount))
+		return -EMSGSIZE;
+	/* Actual value encoded below */
+
+	nchunks = 0;
+	do {
+		seg = r_xprt->rx_ia.ri_ops->ro_map(r_xprt, seg, nsegs,
+						   true, &mr);
+		if (IS_ERR(seg))
+			return PTR_ERR(seg);
+		rpcrdma_mr_push(mr, &req->rl_registered);
+
+		if (encode_rdma_segment(xdr, mr) < 0)
+			return -EMSGSIZE;
+
+		trace_xprtrdma_write_chunk(rqst->rq_task, mr, nsegs);
+		r_xprt->rx_stats.write_chunk_count++;
+		r_xprt->rx_stats.total_rdma_request += mr->mr_length;
+		nchunks++;
+		nsegs -= mr->mr_nents;
+	} while (nsegs);
+
+	/* Update count of segments in this Write chunk */
+	*segcount = cpu_to_be32(nchunks);
+
+	return 0;
+}
+
+/* Register and XDR encode the Reply chunk. Supports encoding an array
+ * of plain segments that belong to a single write (reply) chunk.
+ *
+ * Encoding key for single-list chunks (HLOO = Handle32 Length32 Offset64):
+ *
+ *  Reply chunk (a counted array):
+ *   N elements:
+ *    1 - N - HLOO - HLOO - ... - HLOO
+ *
+ * Returns zero on success, or a negative errno if a failure occurred.
+ * @xdr is advanced to the next position in the stream.
+ */
+static noinline int
+rpcrdma_encode_reply_chunk(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
+			   struct rpc_rqst *rqst, enum rpcrdma_chunktype wtype)
+{
+	struct xdr_stream *xdr = &req->rl_stream;
+	struct rpcrdma_mr_seg *seg;
+	struct rpcrdma_mr *mr;
+	int nsegs, nchunks;
+	__be32 *segcount;
+
+	seg = req->rl_segments;
+	nsegs = rpcrdma_convert_iovs(r_xprt, &rqst->rq_rcv_buf, 0, wtype, seg);
+	if (nsegs < 0)
+		return nsegs;
+
+	if (encode_item_present(xdr) < 0)
+		return -EMSGSIZE;
+	segcount = xdr_reserve_space(xdr, sizeof(*segcount));
+	if (unlikely(!segcount))
+		return -EMSGSIZE;
+	/* Actual value encoded below */
+
+	nchunks = 0;
+	do {
+		seg = r_xprt->rx_ia.ri_ops->ro_map(r_xprt, seg, nsegs,
+						   true, &mr);
+		if (IS_ERR(seg))
+			return PTR_ERR(seg);
+		rpcrdma_mr_push(mr, &req->rl_registered);
+
+		if (encode_rdma_segment(xdr, mr) < 0)
+			return -EMSGSIZE;
+
+		trace_xprtrdma_reply_chunk(rqst->rq_task, mr, nsegs);
+		r_xprt->rx_stats.reply_chunk_count++;
+		r_xprt->rx_stats.total_rdma_request += mr->mr_length;
+		nchunks++;
+		nsegs -= mr->mr_nents;
+	} while (nsegs);
+
+	/* Update count of segments in the Reply chunk */
+	*segcount = cpu_to_be32(nchunks);
+
+	return 0;
+}
+
+/**
+ * rpcrdma_unmap_sendctx - DMA-unmap Send buffers
+ * @sc: sendctx containing SGEs to unmap
+ *
+ */
+void
+rpcrdma_unmap_sendctx(struct rpcrdma_sendctx *sc)
+{
+	struct rpcrdma_ia *ia = &sc->sc_xprt->rx_ia;
+	struct ib_sge *sge;
+	unsigned int count;
+
+	/* The first two SGEs contain the transport header and
+	 * the inline buffer. These are always left mapped so
+	 * they can be cheaply re-used.
+	 */
+	sge = &sc->sc_sges[2];
+	for (count = sc->sc_unmap_count; count; ++sge, --count)
+		ib_dma_unmap_page(ia->ri_device,
+				  sge->addr, sge->length, DMA_TO_DEVICE);
+
+	if (test_and_clear_bit(RPCRDMA_REQ_F_TX_RESOURCES, &sc->sc_req->rl_flags)) {
+		smp_mb__after_atomic();
+		wake_up_bit(&sc->sc_req->rl_flags, RPCRDMA_REQ_F_TX_RESOURCES);
+	}
+}
+
+/* Prepare an SGE for the RPC-over-RDMA transport header.
+ */
+static bool
+rpcrdma_prepare_hdr_sge(struct rpcrdma_ia *ia, struct rpcrdma_req *req,
+			u32 len)
+{
+	struct rpcrdma_sendctx *sc = req->rl_sendctx;
+	struct rpcrdma_regbuf *rb = req->rl_rdmabuf;
+	struct ib_sge *sge = sc->sc_sges;
+
+	if (!rpcrdma_dma_map_regbuf(ia, rb))
+		goto out_regbuf;
+	sge->addr = rdmab_addr(rb);
+	sge->length = len;
+	sge->lkey = rdmab_lkey(rb);
+
+	ib_dma_sync_single_for_device(rdmab_device(rb), sge->addr,
+				      sge->length, DMA_TO_DEVICE);
+	sc->sc_wr.num_sge++;
+	return true;
+
+out_regbuf:
+	pr_err("rpcrdma: failed to DMA map a Send buffer\n");
+	return false;
+}
+
+/* Prepare the Send SGEs. The head and tail iovec, and each entry
+ * in the page list, gets its own SGE.
+ */
+static bool
+rpcrdma_prepare_msg_sges(struct rpcrdma_ia *ia, struct rpcrdma_req *req,
+			 struct xdr_buf *xdr, enum rpcrdma_chunktype rtype)
+{
+	struct rpcrdma_sendctx *sc = req->rl_sendctx;
+	unsigned int sge_no, page_base, len, remaining;
+	struct rpcrdma_regbuf *rb = req->rl_sendbuf;
+	struct ib_device *device = ia->ri_device;
+	struct ib_sge *sge = sc->sc_sges;
+	u32 lkey = ia->ri_pd->local_dma_lkey;
+	struct page *page, **ppages;
+
+	/* The head iovec is straightforward, as it is already
+	 * DMA-mapped. Sync the content that has changed.
+	 */
+	if (!rpcrdma_dma_map_regbuf(ia, rb))
+		goto out_regbuf;
+	sge_no = 1;
+	sge[sge_no].addr = rdmab_addr(rb);
+	sge[sge_no].length = xdr->head[0].iov_len;
+	sge[sge_no].lkey = rdmab_lkey(rb);
+	ib_dma_sync_single_for_device(rdmab_device(rb), sge[sge_no].addr,
+				      sge[sge_no].length, DMA_TO_DEVICE);
+
+	/* If there is a Read chunk, the page list is being handled
+	 * via explicit RDMA, and thus is skipped here. However, the
+	 * tail iovec may include an XDR pad for the page list, as
+	 * well as additional content, and may not reside in the
+	 * same page as the head iovec.
+	 */
+	if (rtype == rpcrdma_readch) {
+		len = xdr->tail[0].iov_len;
+
+		/* Do not include the tail if it is only an XDR pad */
+		if (len < 4)
+			goto out;
+
+		page = virt_to_page(xdr->tail[0].iov_base);
+		page_base = offset_in_page(xdr->tail[0].iov_base);
+
+		/* If the content in the page list is an odd length,
+		 * xdr_write_pages() has added a pad at the beginning
+		 * of the tail iovec. Force the tail's non-pad content
+		 * to land at the next XDR position in the Send message.
+		 */
+		page_base += len & 3;
+		len -= len & 3;
+		goto map_tail;
+	}
+
+	/* If there is a page list present, temporarily DMA map
+	 * and prepare an SGE for each page to be sent.
+	 */
+	if (xdr->page_len) {
+		ppages = xdr->pages + (xdr->page_base >> PAGE_SHIFT);
+		page_base = offset_in_page(xdr->page_base);
+		remaining = xdr->page_len;
+		while (remaining) {
+			sge_no++;
+			if (sge_no > RPCRDMA_MAX_SEND_SGES - 2)
+				goto out_mapping_overflow;
+
+			len = min_t(u32, PAGE_SIZE - page_base, remaining);
+			sge[sge_no].addr = ib_dma_map_page(device, *ppages,
+							   page_base, len,
+							   DMA_TO_DEVICE);
+			if (ib_dma_mapping_error(device, sge[sge_no].addr))
+				goto out_mapping_err;
+			sge[sge_no].length = len;
+			sge[sge_no].lkey = lkey;
+
+			sc->sc_unmap_count++;
+			ppages++;
+			remaining -= len;
+			page_base = 0;
+		}
+	}
+
+	/* The tail iovec is not always constructed in the same
+	 * page where the head iovec resides (see, for example,
+	 * gss_wrap_req_priv). To neatly accommodate that case,
+	 * DMA map it separately.
+	 */
+	if (xdr->tail[0].iov_len) {
+		page = virt_to_page(xdr->tail[0].iov_base);
+		page_base = offset_in_page(xdr->tail[0].iov_base);
+		len = xdr->tail[0].iov_len;
+
+map_tail:
+		sge_no++;
+		sge[sge_no].addr = ib_dma_map_page(device, page,
+						   page_base, len,
+						   DMA_TO_DEVICE);
+		if (ib_dma_mapping_error(device, sge[sge_no].addr))
+			goto out_mapping_err;
+		sge[sge_no].length = len;
+		sge[sge_no].lkey = lkey;
+		sc->sc_unmap_count++;
+	}
+
+out:
+	sc->sc_wr.num_sge += sge_no;
+	if (sc->sc_unmap_count)
+		__set_bit(RPCRDMA_REQ_F_TX_RESOURCES, &req->rl_flags);
+	return true;
+
+out_regbuf:
+	pr_err("rpcrdma: failed to DMA map a Send buffer\n");
+	return false;
+
+out_mapping_overflow:
+	rpcrdma_unmap_sendctx(sc);
+	pr_err("rpcrdma: too many Send SGEs (%u)\n", sge_no);
+	return false;
+
+out_mapping_err:
+	rpcrdma_unmap_sendctx(sc);
+	pr_err("rpcrdma: Send mapping error\n");
+	return false;
+}
+
+/**
+ * rpcrdma_prepare_send_sges - Construct SGEs for a Send WR
+ * @r_xprt: controlling transport
+ * @req: context of RPC Call being marshalled
+ * @hdrlen: size of transport header, in bytes
+ * @xdr: xdr_buf containing RPC Call
+ * @rtype: chunk type being encoded
+ *
+ * Returns 0 on success; otherwise a negative errno is returned.
+ */
+int
+rpcrdma_prepare_send_sges(struct rpcrdma_xprt *r_xprt,
+			  struct rpcrdma_req *req, u32 hdrlen,
+			  struct xdr_buf *xdr, enum rpcrdma_chunktype rtype)
+{
+	req->rl_sendctx = rpcrdma_sendctx_get_locked(&r_xprt->rx_buf);
+	if (!req->rl_sendctx)
+		return -EAGAIN;
+	req->rl_sendctx->sc_wr.num_sge = 0;
+	req->rl_sendctx->sc_unmap_count = 0;
+	req->rl_sendctx->sc_req = req;
+	__clear_bit(RPCRDMA_REQ_F_TX_RESOURCES, &req->rl_flags);
+
+	if (!rpcrdma_prepare_hdr_sge(&r_xprt->rx_ia, req, hdrlen))
+		return -EIO;
+
+	if (rtype != rpcrdma_areadch)
+		if (!rpcrdma_prepare_msg_sges(&r_xprt->rx_ia, req, xdr, rtype))
+			return -EIO;
+
+	return 0;
+}
+
+/**
+ * rpcrdma_marshal_req - Marshal and send one RPC request
+ * @r_xprt: controlling transport
+ * @rqst: RPC request to be marshaled
+ *
+ * For the RPC in "rqst", this function:
+ *  - Chooses the transfer mode (eg., RDMA_MSG or RDMA_NOMSG)
+ *  - Registers Read, Write, and Reply chunks
+ *  - Constructs the transport header
+ *  - Posts a Send WR to send the transport header and request
+ *
+ * Returns:
+ *	%0 if the RPC was sent successfully,
+ *	%-ENOTCONN if the connection was lost,
+ *	%-EAGAIN if the caller should call again with the same arguments,
+ *	%-ENOBUFS if the caller should call again after a delay,
+ *	%-EMSGSIZE if the transport header is too small,
+ *	%-EIO if a permanent problem occurred while marshaling.
+ */
+int
+rpcrdma_marshal_req(struct rpcrdma_xprt *r_xprt, struct rpc_rqst *rqst)
+{
+	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
+	struct xdr_stream *xdr = &req->rl_stream;
+	enum rpcrdma_chunktype rtype, wtype;
+	bool ddp_allowed;
+	__be32 *p;
+	int ret;
+
+	rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
+	xdr_init_encode(xdr, &req->rl_hdrbuf,
+			req->rl_rdmabuf->rg_base);
+
+	/* Fixed header fields */
+	ret = -EMSGSIZE;
+	p = xdr_reserve_space(xdr, 4 * sizeof(*p));
+	if (!p)
+		goto out_err;
+	*p++ = rqst->rq_xid;
+	*p++ = rpcrdma_version;
+	*p++ = cpu_to_be32(r_xprt->rx_buf.rb_max_requests);
+
+	/* When the ULP employs a GSS flavor that guarantees integrity
+	 * or privacy, direct data placement of individual data items
+	 * is not allowed.
+	 */
+	ddp_allowed = !(rqst->rq_cred->cr_auth->au_flags &
+						RPCAUTH_AUTH_DATATOUCH);
+
+	/*
+	 * Chunks needed for results?
+	 *
+	 * o If the expected result is under the inline threshold, all ops
+	 *   return as inline.
+	 * o Large read ops return data as write chunk(s), header as
+	 *   inline.
+	 * o Large non-read ops return as a single reply chunk.
+	 */
+	if (rpcrdma_results_inline(r_xprt, rqst))
+		wtype = rpcrdma_noch;
+	else if (ddp_allowed && rqst->rq_rcv_buf.flags & XDRBUF_READ)
+		wtype = rpcrdma_writech;
+	else
+		wtype = rpcrdma_replych;
+
+	/*
+	 * Chunks needed for arguments?
+	 *
+	 * o If the total request is under the inline threshold, all ops
+	 *   are sent as inline.
+	 * o Large write ops transmit data as read chunk(s), header as
+	 *   inline.
+	 * o Large non-write ops are sent with the entire message as a
+	 *   single read chunk (protocol 0-position special case).
+	 *
+	 * This assumes that the upper layer does not present a request
+	 * that both has a data payload, and whose non-data arguments
+	 * by themselves are larger than the inline threshold.
+	 */
+	if (rpcrdma_args_inline(r_xprt, rqst)) {
+		*p++ = rdma_msg;
+		rtype = rpcrdma_noch;
+	} else if (ddp_allowed && rqst->rq_snd_buf.flags & XDRBUF_WRITE) {
+		*p++ = rdma_msg;
+		rtype = rpcrdma_readch;
+	} else {
+		r_xprt->rx_stats.nomsg_call_count++;
+		*p++ = rdma_nomsg;
+		rtype = rpcrdma_areadch;
+	}
+
+	/* If this is a retransmit, discard previously registered
+	 * chunks. Very likely the connection has been replaced,
+	 * so these registrations are invalid and unusable.
+	 */
+	while (unlikely(!list_empty(&req->rl_registered))) {
+		struct rpcrdma_mr *mr;
+
+		mr = rpcrdma_mr_pop(&req->rl_registered);
+		rpcrdma_mr_defer_recovery(mr);
+	}
+
+	/* This implementation supports the following combinations
+	 * of chunk lists in one RPC-over-RDMA Call message:
+	 *
+	 *   - Read list
+	 *   - Write list
+	 *   - Reply chunk
+	 *   - Read list + Reply chunk
+	 *
+	 * It might not yet support the following combinations:
+	 *
+	 *   - Read list + Write list
+	 *
+	 * It does not support the following combinations:
+	 *
+	 *   - Write list + Reply chunk
+	 *   - Read list + Write list + Reply chunk
+	 *
+	 * This implementation supports only a single chunk in each
+	 * Read or Write list. Thus for example the client cannot
+	 * send a Call message with a Position Zero Read chunk and a
+	 * regular Read chunk at the same time.
+	 */
+	if (rtype != rpcrdma_noch) {
+		ret = rpcrdma_encode_read_list(r_xprt, req, rqst, rtype);
+		if (ret)
+			goto out_err;
+	}
+	ret = encode_item_not_present(xdr);
+	if (ret)
+		goto out_err;
+
+	if (wtype == rpcrdma_writech) {
+		ret = rpcrdma_encode_write_list(r_xprt, req, rqst, wtype);
+		if (ret)
+			goto out_err;
+	}
+	ret = encode_item_not_present(xdr);
+	if (ret)
+		goto out_err;
+
+	if (wtype != rpcrdma_replych)
+		ret = encode_item_not_present(xdr);
+	else
+		ret = rpcrdma_encode_reply_chunk(r_xprt, req, rqst, wtype);
+	if (ret)
+		goto out_err;
+
+	trace_xprtrdma_marshal(rqst, xdr_stream_pos(xdr), rtype, wtype);
+
+	ret = rpcrdma_prepare_send_sges(r_xprt, req, xdr_stream_pos(xdr),
+					&rqst->rq_snd_buf, rtype);
+	if (ret)
+		goto out_err;
+	return 0;
+
+out_err:
+	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;
+}
+
+/**
+ * rpcrdma_inline_fixup - Scatter inline received data into rqst's iovecs
+ * @rqst: controlling RPC request
+ * @srcp: points to RPC message payload in receive buffer
+ * @copy_len: remaining length of receive buffer content
+ * @pad: Write chunk pad bytes needed (zero for pure inline)
+ *
+ * The upper layer has set the maximum number of bytes it can
+ * receive in each component of rq_rcv_buf. These values are set in
+ * the head.iov_len, page_len, tail.iov_len, and buflen fields.
+ *
+ * Unlike the TCP equivalent (xdr_partial_copy_from_skb), in
+ * many cases this function simply updates iov_base pointers in
+ * rq_rcv_buf to point directly to the received reply data, to
+ * avoid copying reply data.
+ *
+ * Returns the count of bytes which had to be memcopied.
+ */
+static unsigned long
+rpcrdma_inline_fixup(struct rpc_rqst *rqst, char *srcp, int copy_len, int pad)
+{
+	unsigned long fixup_copy_count;
+	int i, npages, curlen;
+	char *destp;
+	struct page **ppages;
+	int page_base;
+
+	/* The head iovec is redirected to the RPC reply message
+	 * in the receive buffer, to avoid a memcopy.
+	 */
+	rqst->rq_rcv_buf.head[0].iov_base = srcp;
+	rqst->rq_private_buf.head[0].iov_base = srcp;
+
+	/* The contents of the receive buffer that follow
+	 * head.iov_len bytes are copied into the page list.
+	 */
+	curlen = rqst->rq_rcv_buf.head[0].iov_len;
+	if (curlen > copy_len)
+		curlen = copy_len;
+	trace_xprtrdma_fixup(rqst, copy_len, curlen);
+	srcp += curlen;
+	copy_len -= curlen;
+
+	ppages = rqst->rq_rcv_buf.pages +
+		(rqst->rq_rcv_buf.page_base >> PAGE_SHIFT);
+	page_base = offset_in_page(rqst->rq_rcv_buf.page_base);
+	fixup_copy_count = 0;
+	if (copy_len && rqst->rq_rcv_buf.page_len) {
+		int pagelist_len;
+
+		pagelist_len = rqst->rq_rcv_buf.page_len;
+		if (pagelist_len > copy_len)
+			pagelist_len = copy_len;
+		npages = PAGE_ALIGN(page_base + pagelist_len) >> PAGE_SHIFT;
+		for (i = 0; i < npages; i++) {
+			curlen = PAGE_SIZE - page_base;
+			if (curlen > pagelist_len)
+				curlen = pagelist_len;
+
+			trace_xprtrdma_fixup_pg(rqst, i, srcp,
+						copy_len, curlen);
+			destp = kmap_atomic(ppages[i]);
+			memcpy(destp + page_base, srcp, curlen);
+			flush_dcache_page(ppages[i]);
+			kunmap_atomic(destp);
+			srcp += curlen;
+			copy_len -= curlen;
+			fixup_copy_count += curlen;
+			pagelist_len -= curlen;
+			if (!pagelist_len)
+				break;
+			page_base = 0;
+		}
+
+		/* Implicit padding for the last segment in a Write
+		 * chunk is inserted inline at the front of the tail
+		 * iovec. The upper layer ignores the content of
+		 * the pad. Simply ensure inline content in the tail
+		 * that follows the Write chunk is properly aligned.
+		 */
+		if (pad)
+			srcp -= pad;
+	}
+
+	/* The tail iovec is redirected to the remaining data
+	 * in the receive buffer, to avoid a memcopy.
+	 */
+	if (copy_len || pad) {
+		rqst->rq_rcv_buf.tail[0].iov_base = srcp;
+		rqst->rq_private_buf.tail[0].iov_base = srcp;
+	}
+
+	return fixup_copy_count;
+}
+
+/* By convention, backchannel calls arrive via rdma_msg type
+ * messages, and never populate the chunk lists. This makes
+ * the RPC/RDMA header small and fixed in size, so it is
+ * straightforward to check the RPC header's direction field.
+ */
+static bool
+rpcrdma_is_bcall(struct rpcrdma_xprt *r_xprt, struct rpcrdma_rep *rep)
+#if defined(CONFIG_SUNRPC_BACKCHANNEL)
+{
+	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
+	struct xdr_stream *xdr = &rep->rr_stream;
+	__be32 *p;
+
+	if (rep->rr_proc != rdma_msg)
+		return false;
+
+	/* Peek at stream contents without advancing. */
+	p = xdr_inline_decode(xdr, 0);
+
+	/* Chunk lists */
+	if (*p++ != xdr_zero)
+		return false;
+	if (*p++ != xdr_zero)
+		return false;
+	if (*p++ != xdr_zero)
+		return false;
+
+	/* RPC header */
+	if (*p++ != rep->rr_xid)
+		return false;
+	if (*p != cpu_to_be32(RPC_CALL))
+		return false;
+
+	/* No bc service. */
+	if (xprt->bc_serv == NULL)
+		return false;
+
+	/* Now that we are sure this is a backchannel call,
+	 * advance to the RPC header.
+	 */
+	p = xdr_inline_decode(xdr, 3 * sizeof(*p));
+	if (unlikely(!p))
+		goto out_short;
+
+	rpcrdma_bc_receive_call(r_xprt, rep);
+	return true;
+
+out_short:
+	pr_warn("RPC/RDMA short backward direction call\n");
+	return true;
+}
+#else	/* CONFIG_SUNRPC_BACKCHANNEL */
+{
+	return false;
+}
+#endif	/* CONFIG_SUNRPC_BACKCHANNEL */
+
+static int decode_rdma_segment(struct xdr_stream *xdr, u32 *length)
+{
+	u32 handle;
+	u64 offset;
+	__be32 *p;
+
+	p = xdr_inline_decode(xdr, 4 * sizeof(*p));
+	if (unlikely(!p))
+		return -EIO;
+
+	handle = be32_to_cpup(p++);
+	*length = be32_to_cpup(p++);
+	xdr_decode_hyper(p, &offset);
+
+	trace_xprtrdma_decode_seg(handle, *length, offset);
+	return 0;
+}
+
+static int decode_write_chunk(struct xdr_stream *xdr, u32 *length)
+{
+	u32 segcount, seglength;
+	__be32 *p;
+
+	p = xdr_inline_decode(xdr, sizeof(*p));
+	if (unlikely(!p))
+		return -EIO;
+
+	*length = 0;
+	segcount = be32_to_cpup(p);
+	while (segcount--) {
+		if (decode_rdma_segment(xdr, &seglength))
+			return -EIO;
+		*length += seglength;
+	}
+
+	return 0;
+}
+
+/* In RPC-over-RDMA Version One replies, a Read list is never
+ * expected. This decoder is a stub that returns an error if
+ * a Read list is present.
+ */
+static int decode_read_list(struct xdr_stream *xdr)
+{
+	__be32 *p;
+
+	p = xdr_inline_decode(xdr, sizeof(*p));
+	if (unlikely(!p))
+		return -EIO;
+	if (unlikely(*p != xdr_zero))
+		return -EIO;
+	return 0;
+}
+
+/* Supports only one Write chunk in the Write list
+ */
+static int decode_write_list(struct xdr_stream *xdr, u32 *length)
+{
+	u32 chunklen;
+	bool first;
+	__be32 *p;
+
+	*length = 0;
+	first = true;
+	do {
+		p = xdr_inline_decode(xdr, sizeof(*p));
+		if (unlikely(!p))
+			return -EIO;
+		if (*p == xdr_zero)
+			break;
+		if (!first)
+			return -EIO;
+
+		if (decode_write_chunk(xdr, &chunklen))
+			return -EIO;
+		*length += chunklen;
+		first = false;
+	} while (true);
+	return 0;
+}
+
+static int decode_reply_chunk(struct xdr_stream *xdr, u32 *length)
+{
+	__be32 *p;
+
+	p = xdr_inline_decode(xdr, sizeof(*p));
+	if (unlikely(!p))
+		return -EIO;
+
+	*length = 0;
+	if (*p != xdr_zero)
+		if (decode_write_chunk(xdr, length))
+			return -EIO;
+	return 0;
+}
+
+static int
+rpcrdma_decode_msg(struct rpcrdma_xprt *r_xprt, struct rpcrdma_rep *rep,
+		   struct rpc_rqst *rqst)
+{
+	struct xdr_stream *xdr = &rep->rr_stream;
+	u32 writelist, replychunk, rpclen;
+	char *base;
+
+	/* Decode the chunk lists */
+	if (decode_read_list(xdr))
+		return -EIO;
+	if (decode_write_list(xdr, &writelist))
+		return -EIO;
+	if (decode_reply_chunk(xdr, &replychunk))
+		return -EIO;
+
+	/* RDMA_MSG sanity checks */
+	if (unlikely(replychunk))
+		return -EIO;
+
+	/* Build the RPC reply's Payload stream in rqst->rq_rcv_buf */
+	base = (char *)xdr_inline_decode(xdr, 0);
+	rpclen = xdr_stream_remaining(xdr);
+	r_xprt->rx_stats.fixup_copy_count +=
+		rpcrdma_inline_fixup(rqst, base, rpclen, writelist & 3);
+
+	r_xprt->rx_stats.total_rdma_reply += writelist;
+	return rpclen + xdr_align_size(writelist);
+}
+
+static noinline int
+rpcrdma_decode_nomsg(struct rpcrdma_xprt *r_xprt, struct rpcrdma_rep *rep)
+{
+	struct xdr_stream *xdr = &rep->rr_stream;
+	u32 writelist, replychunk;
+
+	/* Decode the chunk lists */
+	if (decode_read_list(xdr))
+		return -EIO;
+	if (decode_write_list(xdr, &writelist))
+		return -EIO;
+	if (decode_reply_chunk(xdr, &replychunk))
+		return -EIO;
+
+	/* RDMA_NOMSG sanity checks */
+	if (unlikely(writelist))
+		return -EIO;
+	if (unlikely(!replychunk))
+		return -EIO;
+
+	/* Reply chunk buffer already is the reply vector */
+	r_xprt->rx_stats.total_rdma_reply += replychunk;
+	return replychunk;
+}
+
+static noinline int
+rpcrdma_decode_error(struct rpcrdma_xprt *r_xprt, struct rpcrdma_rep *rep,
+		     struct rpc_rqst *rqst)
+{
+	struct xdr_stream *xdr = &rep->rr_stream;
+	__be32 *p;
+
+	p = xdr_inline_decode(xdr, sizeof(*p));
+	if (unlikely(!p))
+		return -EIO;
+
+	switch (*p) {
+	case err_vers:
+		p = xdr_inline_decode(xdr, 2 * sizeof(*p));
+		if (!p)
+			break;
+		dprintk("RPC: %5u: %s: server reports version error (%u-%u)\n",
+			rqst->rq_task->tk_pid, __func__,
+			be32_to_cpup(p), be32_to_cpu(*(p + 1)));
+		break;
+	case err_chunk:
+		dprintk("RPC: %5u: %s: server reports header decoding error\n",
+			rqst->rq_task->tk_pid, __func__);
+		break;
+	default:
+		dprintk("RPC: %5u: %s: server reports unrecognized error %d\n",
+			rqst->rq_task->tk_pid, __func__, be32_to_cpup(p));
+	}
+
+	r_xprt->rx_stats.bad_reply_count++;
+	return -EREMOTEIO;
+}
+
+/* Perform XID lookup, reconstruction of the RPC reply, and
+ * RPC completion while holding the transport lock to ensure
+ * the rep, rqst, and rq_task pointers remain stable.
+ */
+void rpcrdma_complete_rqst(struct rpcrdma_rep *rep)
+{
+	struct rpcrdma_xprt *r_xprt = rep->rr_rxprt;
+	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
+	struct rpc_rqst *rqst = rep->rr_rqst;
+	unsigned long cwnd;
+	int status;
+
+	xprt->reestablish_timeout = 0;
+
+	switch (rep->rr_proc) {
+	case rdma_msg:
+		status = rpcrdma_decode_msg(r_xprt, rep, rqst);
+		break;
+	case rdma_nomsg:
+		status = rpcrdma_decode_nomsg(r_xprt, rep);
+		break;
+	case rdma_error:
+		status = rpcrdma_decode_error(r_xprt, rep, rqst);
+		break;
+	default:
+		status = -EIO;
+	}
+	if (status < 0)
+		goto out_badheader;
+
+out:
+	spin_lock(&xprt->recv_lock);
+	cwnd = xprt->cwnd;
+	xprt->cwnd = r_xprt->rx_buf.rb_credits << RPC_CWNDSHIFT;
+	if (xprt->cwnd > cwnd)
+		xprt_release_rqst_cong(rqst->rq_task);
+
+	xprt_complete_rqst(rqst->rq_task, status);
+	xprt_unpin_rqst(rqst);
+	spin_unlock(&xprt->recv_lock);
+	return;
+
+/* If the incoming reply terminated a pending RPC, the next
+ * RPC call will post a replacement receive buffer as it is
+ * being marshaled.
+ */
+out_badheader:
+	trace_xprtrdma_reply_hdr(rep);
+	r_xprt->rx_stats.bad_reply_count++;
+	status = -EIO;
+	goto out;
+}
+
+void rpcrdma_release_rqst(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
+{
+	/* Invalidate and unmap the data payloads before waking
+	 * the waiting application. This guarantees the memory
+	 * regions are properly fenced from the server before the
+	 * application accesses the data. It also ensures proper
+	 * send flow control: waking the next RPC waits until this
+	 * RPC has relinquished all its Send Queue entries.
+	 */
+	if (!list_empty(&req->rl_registered))
+		r_xprt->rx_ia.ri_ops->ro_unmap_sync(r_xprt,
+						    &req->rl_registered);
+
+	/* Ensure that any DMA mapped pages associated with
+	 * the Send of the RPC Call have been unmapped before
+	 * allowing the RPC to complete. This protects argument
+	 * memory not controlled by the RPC client from being
+	 * re-used before we're done with it.
+	 */
+	if (test_bit(RPCRDMA_REQ_F_TX_RESOURCES, &req->rl_flags)) {
+		r_xprt->rx_stats.reply_waits_for_send++;
+		out_of_line_wait_on_bit(&req->rl_flags,
+					RPCRDMA_REQ_F_TX_RESOURCES,
+					bit_wait,
+					TASK_UNINTERRUPTIBLE);
+	}
+}
+
+/* Reply handling runs in the poll worker thread. Anything that
+ * might wait is deferred to a separate workqueue.
+ */
+void rpcrdma_deferred_completion(struct work_struct *work)
+{
+	struct rpcrdma_rep *rep =
+			container_of(work, struct rpcrdma_rep, rr_work);
+	struct rpcrdma_req *req = rpcr_to_rdmar(rep->rr_rqst);
+	struct rpcrdma_xprt *r_xprt = rep->rr_rxprt;
+
+	trace_xprtrdma_defer_cmp(rep);
+	if (rep->rr_wc_flags & IB_WC_WITH_INVALIDATE)
+		r_xprt->rx_ia.ri_ops->ro_reminv(rep, &req->rl_registered);
+	rpcrdma_release_rqst(r_xprt, req);
+	rpcrdma_complete_rqst(rep);
+}
+
+/* Process received RPC/RDMA messages.
+ *
+ * Errors must result in the RPC task either being awakened, or
+ * allowed to timeout, to discover the errors at that time.
+ */
+void rpcrdma_reply_handler(struct rpcrdma_rep *rep)
+{
+	struct rpcrdma_xprt *r_xprt = rep->rr_rxprt;
+	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
+	struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
+	struct rpcrdma_req *req;
+	struct rpc_rqst *rqst;
+	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);
+	p = xdr_inline_decode(&rep->rr_stream, 4 * sizeof(*p));
+	if (unlikely(!p))
+		goto out_shortreply;
+	rep->rr_xid = *p++;
+	rep->rr_vers = *p++;
+	credits = be32_to_cpu(*p++);
+	rep->rr_proc = *p++;
+
+	if (rep->rr_vers != rpcrdma_version)
+		goto out_badversion;
+
+	if (rpcrdma_is_bcall(r_xprt, rep))
+		return;
+
+	/* Match incoming rpcrdma_rep to an rpcrdma_req to
+	 * get context for handling any incoming chunks.
+	 */
+	spin_lock(&xprt->recv_lock);
+	rqst = xprt_lookup_rqst(xprt, rep->rr_xid);
+	if (!rqst)
+		goto out_norqst;
+	xprt_pin_rqst(rqst);
+
+	if (credits == 0)
+		credits = 1;	/* don't deadlock */
+	else if (credits > buf->rb_max_requests)
+		credits = buf->rb_max_requests;
+	buf->rb_credits = credits;
+
+	spin_unlock(&xprt->recv_lock);
+
+	req = rpcr_to_rdmar(rqst);
+	if (req->rl_reply) {
+		trace_xprtrdma_leaked_rep(rqst, req->rl_reply);
+		rpcrdma_recv_buffer_put(req->rl_reply);
+	}
+	req->rl_reply = rep;
+	rep->rr_rqst = rqst;
+	clear_bit(RPCRDMA_REQ_F_PENDING, &req->rl_flags);
+
+	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_badversion:
+	trace_xprtrdma_reply_vers(rep);
+	goto repost;
+
+/* The RPC transaction has already been terminated, or the header
+ * is corrupt.
+ */
+out_norqst:
+	spin_unlock(&xprt->recv_lock);
+	trace_xprtrdma_reply_rqst(rep);
+	goto repost;
+
+out_shortreply:
+	trace_xprtrdma_reply_short(rep);
+
+/* If no pending RPC transaction was matched, post a replacement
+ * receive buffer before returning.
+ */
+repost:
+	rpcrdma_post_recvs(r_xprt, false);
+out_badstatus:
+	rpcrdma_recv_buffer_put(rep);
+}