Initial import

1 files changed, 672 insertions, 0 deletions

diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
new file mode 100644
index 000000000..f9f13a32d
--- /dev/null
+++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
@@ -0,0 +1,672 @@
+/*
+ * Copyright (c) 2014 Open Grid Computing, Inc. All rights reserved.
+ * Copyright (c) 2005-2006 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.
+ *
+ * Author: Tom Tucker <tom@opengridcomputing.com>
+ */
+
+#include <linux/sunrpc/debug.h>
+#include <linux/sunrpc/rpc_rdma.h>
+#include <linux/spinlock.h>
+#include <asm/unaligned.h>
+#include <rdma/ib_verbs.h>
+#include <rdma/rdma_cm.h>
+#include <linux/sunrpc/svc_rdma.h>
+
+#define RPCDBG_FACILITY	RPCDBG_SVCXPRT
+
+/*
+ * Replace the pages in the rq_argpages array with the pages from the SGE in
+ * the RDMA_RECV completion. The SGL should contain full pages up until the
+ * last one.
+ */
+static void rdma_build_arg_xdr(struct svc_rqst *rqstp,
+			       struct svc_rdma_op_ctxt *ctxt,
+			       u32 byte_count)
+{
+	struct rpcrdma_msg *rmsgp;
+	struct page *page;
+	u32 bc;
+	int sge_no;
+
+	/* Swap the page in the SGE with the page in argpages */
+	page = ctxt->pages[0];
+	put_page(rqstp->rq_pages[0]);
+	rqstp->rq_pages[0] = page;
+
+	/* Set up the XDR head */
+	rqstp->rq_arg.head[0].iov_base = page_address(page);
+	rqstp->rq_arg.head[0].iov_len =
+		min_t(size_t, byte_count, ctxt->sge[0].length);
+	rqstp->rq_arg.len = byte_count;
+	rqstp->rq_arg.buflen = byte_count;
+
+	/* Compute bytes past head in the SGL */
+	bc = byte_count - rqstp->rq_arg.head[0].iov_len;
+
+	/* If data remains, store it in the pagelist */
+	rqstp->rq_arg.page_len = bc;
+	rqstp->rq_arg.page_base = 0;
+
+	/* RDMA_NOMSG: RDMA READ data should land just after RDMA RECV data */
+	rmsgp = (struct rpcrdma_msg *)rqstp->rq_arg.head[0].iov_base;
+	if (be32_to_cpu(rmsgp->rm_type) == RDMA_NOMSG)
+		rqstp->rq_arg.pages = &rqstp->rq_pages[0];
+	else
+		rqstp->rq_arg.pages = &rqstp->rq_pages[1];
+
+	sge_no = 1;
+	while (bc && sge_no < ctxt->count) {
+		page = ctxt->pages[sge_no];
+		put_page(rqstp->rq_pages[sge_no]);
+		rqstp->rq_pages[sge_no] = page;
+		bc -= min_t(u32, bc, ctxt->sge[sge_no].length);
+		rqstp->rq_arg.buflen += ctxt->sge[sge_no].length;
+		sge_no++;
+	}
+	rqstp->rq_respages = &rqstp->rq_pages[sge_no];
+	rqstp->rq_next_page = rqstp->rq_respages + 1;
+
+	/* If not all pages were used from the SGL, free the remaining ones */
+	bc = sge_no;
+	while (sge_no < ctxt->count) {
+		page = ctxt->pages[sge_no++];
+		put_page(page);
+	}
+	ctxt->count = bc;
+
+	/* Set up tail */
+	rqstp->rq_arg.tail[0].iov_base = NULL;
+	rqstp->rq_arg.tail[0].iov_len = 0;
+}
+
+static int rdma_read_max_sge(struct svcxprt_rdma *xprt, int sge_count)
+{
+	if (rdma_node_get_transport(xprt->sc_cm_id->device->node_type) ==
+	     RDMA_TRANSPORT_IWARP)
+		return 1;
+	else
+		return min_t(int, sge_count, xprt->sc_max_sge);
+}
+
+/* Issue an RDMA_READ using the local lkey to map the data sink */
+int rdma_read_chunk_lcl(struct svcxprt_rdma *xprt,
+			struct svc_rqst *rqstp,
+			struct svc_rdma_op_ctxt *head,
+			int *page_no,
+			u32 *page_offset,
+			u32 rs_handle,
+			u32 rs_length,
+			u64 rs_offset,
+			bool last)
+{
+	struct ib_send_wr read_wr;
+	int pages_needed = PAGE_ALIGN(*page_offset + rs_length) >> PAGE_SHIFT;
+	struct svc_rdma_op_ctxt *ctxt = svc_rdma_get_context(xprt);
+	int ret, read, pno;
+	u32 pg_off = *page_offset;
+	u32 pg_no = *page_no;
+
+	ctxt->direction = DMA_FROM_DEVICE;
+	ctxt->read_hdr = head;
+	pages_needed =
+		min_t(int, pages_needed, rdma_read_max_sge(xprt, pages_needed));
+	read = min_t(int, pages_needed << PAGE_SHIFT, rs_length);
+
+	for (pno = 0; pno < pages_needed; pno++) {
+		int len = min_t(int, rs_length, PAGE_SIZE - pg_off);
+
+		head->arg.pages[pg_no] = rqstp->rq_arg.pages[pg_no];
+		head->arg.page_len += len;
+		head->arg.len += len;
+		if (!pg_off)
+			head->count++;
+		rqstp->rq_respages = &rqstp->rq_arg.pages[pg_no+1];
+		rqstp->rq_next_page = rqstp->rq_respages + 1;
+		ctxt->sge[pno].addr =
+			ib_dma_map_page(xprt->sc_cm_id->device,
+					head->arg.pages[pg_no], pg_off,
+					PAGE_SIZE - pg_off,
+					DMA_FROM_DEVICE);
+		ret = ib_dma_mapping_error(xprt->sc_cm_id->device,
+					   ctxt->sge[pno].addr);
+		if (ret)
+			goto err;
+		atomic_inc(&xprt->sc_dma_used);
+
+		/* The lkey here is either a local dma lkey or a dma_mr lkey */
+		ctxt->sge[pno].lkey = xprt->sc_dma_lkey;
+		ctxt->sge[pno].length = len;
+		ctxt->count++;
+
+		/* adjust offset and wrap to next page if needed */
+		pg_off += len;
+		if (pg_off == PAGE_SIZE) {
+			pg_off = 0;
+			pg_no++;
+		}
+		rs_length -= len;
+	}
+
+	if (last && rs_length == 0)
+		set_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags);
+	else
+		clear_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags);
+
+	memset(&read_wr, 0, sizeof(read_wr));
+	read_wr.wr_id = (unsigned long)ctxt;
+	read_wr.opcode = IB_WR_RDMA_READ;
+	ctxt->wr_op = read_wr.opcode;
+	read_wr.send_flags = IB_SEND_SIGNALED;
+	read_wr.wr.rdma.rkey = rs_handle;
+	read_wr.wr.rdma.remote_addr = rs_offset;
+	read_wr.sg_list = ctxt->sge;
+	read_wr.num_sge = pages_needed;
+
+	ret = svc_rdma_send(xprt, &read_wr);
+	if (ret) {
+		pr_err("svcrdma: Error %d posting RDMA_READ\n", ret);
+		set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
+		goto err;
+	}
+
+	/* return current location in page array */
+	*page_no = pg_no;
+	*page_offset = pg_off;
+	ret = read;
+	atomic_inc(&rdma_stat_read);
+	return ret;
+ err:
+	svc_rdma_unmap_dma(ctxt);
+	svc_rdma_put_context(ctxt, 0);
+	return ret;
+}
+
+/* Issue an RDMA_READ using an FRMR to map the data sink */
+int rdma_read_chunk_frmr(struct svcxprt_rdma *xprt,
+			 struct svc_rqst *rqstp,
+			 struct svc_rdma_op_ctxt *head,
+			 int *page_no,
+			 u32 *page_offset,
+			 u32 rs_handle,
+			 u32 rs_length,
+			 u64 rs_offset,
+			 bool last)
+{
+	struct ib_send_wr read_wr;
+	struct ib_send_wr inv_wr;
+	struct ib_send_wr fastreg_wr;
+	u8 key;
+	int pages_needed = PAGE_ALIGN(*page_offset + rs_length) >> PAGE_SHIFT;
+	struct svc_rdma_op_ctxt *ctxt = svc_rdma_get_context(xprt);
+	struct svc_rdma_fastreg_mr *frmr = svc_rdma_get_frmr(xprt);
+	int ret, read, pno;
+	u32 pg_off = *page_offset;
+	u32 pg_no = *page_no;
+
+	if (IS_ERR(frmr))
+		return -ENOMEM;
+
+	ctxt->direction = DMA_FROM_DEVICE;
+	ctxt->frmr = frmr;
+	pages_needed = min_t(int, pages_needed, xprt->sc_frmr_pg_list_len);
+	read = min_t(int, pages_needed << PAGE_SHIFT, rs_length);
+
+	frmr->kva = page_address(rqstp->rq_arg.pages[pg_no]);
+	frmr->direction = DMA_FROM_DEVICE;
+	frmr->access_flags = (IB_ACCESS_LOCAL_WRITE|IB_ACCESS_REMOTE_WRITE);
+	frmr->map_len = pages_needed << PAGE_SHIFT;
+	frmr->page_list_len = pages_needed;
+
+	for (pno = 0; pno < pages_needed; pno++) {
+		int len = min_t(int, rs_length, PAGE_SIZE - pg_off);
+
+		head->arg.pages[pg_no] = rqstp->rq_arg.pages[pg_no];
+		head->arg.page_len += len;
+		head->arg.len += len;
+		if (!pg_off)
+			head->count++;
+		rqstp->rq_respages = &rqstp->rq_arg.pages[pg_no+1];
+		rqstp->rq_next_page = rqstp->rq_respages + 1;
+		frmr->page_list->page_list[pno] =
+			ib_dma_map_page(xprt->sc_cm_id->device,
+					head->arg.pages[pg_no], 0,
+					PAGE_SIZE, DMA_FROM_DEVICE);
+		ret = ib_dma_mapping_error(xprt->sc_cm_id->device,
+					   frmr->page_list->page_list[pno]);
+		if (ret)
+			goto err;
+		atomic_inc(&xprt->sc_dma_used);
+
+		/* adjust offset and wrap to next page if needed */
+		pg_off += len;
+		if (pg_off == PAGE_SIZE) {
+			pg_off = 0;
+			pg_no++;
+		}
+		rs_length -= len;
+	}
+
+	if (last && rs_length == 0)
+		set_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags);
+	else
+		clear_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags);
+
+	/* Bump the key */
+	key = (u8)(frmr->mr->lkey & 0x000000FF);
+	ib_update_fast_reg_key(frmr->mr, ++key);
+
+	ctxt->sge[0].addr = (unsigned long)frmr->kva + *page_offset;
+	ctxt->sge[0].lkey = frmr->mr->lkey;
+	ctxt->sge[0].length = read;
+	ctxt->count = 1;
+	ctxt->read_hdr = head;
+
+	/* Prepare FASTREG WR */
+	memset(&fastreg_wr, 0, sizeof(fastreg_wr));
+	fastreg_wr.opcode = IB_WR_FAST_REG_MR;
+	fastreg_wr.send_flags = IB_SEND_SIGNALED;
+	fastreg_wr.wr.fast_reg.iova_start = (unsigned long)frmr->kva;
+	fastreg_wr.wr.fast_reg.page_list = frmr->page_list;
+	fastreg_wr.wr.fast_reg.page_list_len = frmr->page_list_len;
+	fastreg_wr.wr.fast_reg.page_shift = PAGE_SHIFT;
+	fastreg_wr.wr.fast_reg.length = frmr->map_len;
+	fastreg_wr.wr.fast_reg.access_flags = frmr->access_flags;
+	fastreg_wr.wr.fast_reg.rkey = frmr->mr->lkey;
+	fastreg_wr.next = &read_wr;
+
+	/* Prepare RDMA_READ */
+	memset(&read_wr, 0, sizeof(read_wr));
+	read_wr.send_flags = IB_SEND_SIGNALED;
+	read_wr.wr.rdma.rkey = rs_handle;
+	read_wr.wr.rdma.remote_addr = rs_offset;
+	read_wr.sg_list = ctxt->sge;
+	read_wr.num_sge = 1;
+	if (xprt->sc_dev_caps & SVCRDMA_DEVCAP_READ_W_INV) {
+		read_wr.opcode = IB_WR_RDMA_READ_WITH_INV;
+		read_wr.wr_id = (unsigned long)ctxt;
+		read_wr.ex.invalidate_rkey = ctxt->frmr->mr->lkey;
+	} else {
+		read_wr.opcode = IB_WR_RDMA_READ;
+		read_wr.next = &inv_wr;
+		/* Prepare invalidate */
+		memset(&inv_wr, 0, sizeof(inv_wr));
+		inv_wr.wr_id = (unsigned long)ctxt;
+		inv_wr.opcode = IB_WR_LOCAL_INV;
+		inv_wr.send_flags = IB_SEND_SIGNALED | IB_SEND_FENCE;
+		inv_wr.ex.invalidate_rkey = frmr->mr->lkey;
+	}
+	ctxt->wr_op = read_wr.opcode;
+
+	/* Post the chain */
+	ret = svc_rdma_send(xprt, &fastreg_wr);
+	if (ret) {
+		pr_err("svcrdma: Error %d posting RDMA_READ\n", ret);
+		set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
+		goto err;
+	}
+
+	/* return current location in page array */
+	*page_no = pg_no;
+	*page_offset = pg_off;
+	ret = read;
+	atomic_inc(&rdma_stat_read);
+	return ret;
+ err:
+	svc_rdma_unmap_dma(ctxt);
+	svc_rdma_put_context(ctxt, 0);
+	svc_rdma_put_frmr(xprt, frmr);
+	return ret;
+}
+
+static unsigned int
+rdma_rcl_chunk_count(struct rpcrdma_read_chunk *ch)
+{
+	unsigned int count;
+
+	for (count = 0; ch->rc_discrim != xdr_zero; ch++)
+		count++;
+	return count;
+}
+
+/* If there was additional inline content, append it to the end of arg.pages.
+ * Tail copy has to be done after the reader function has determined how many
+ * pages are needed for RDMA READ.
+ */
+static int
+rdma_copy_tail(struct svc_rqst *rqstp, struct svc_rdma_op_ctxt *head,
+	       u32 position, u32 byte_count, u32 page_offset, int page_no)
+{
+	char *srcp, *destp;
+	int ret;
+
+	ret = 0;
+	srcp = head->arg.head[0].iov_base + position;
+	byte_count = head->arg.head[0].iov_len - position;
+	if (byte_count > PAGE_SIZE) {
+		dprintk("svcrdma: large tail unsupported\n");
+		return 0;
+	}
+
+	/* Fit as much of the tail on the current page as possible */
+	if (page_offset != PAGE_SIZE) {
+		destp = page_address(rqstp->rq_arg.pages[page_no]);
+		destp += page_offset;
+		while (byte_count--) {
+			*destp++ = *srcp++;
+			page_offset++;
+			if (page_offset == PAGE_SIZE && byte_count)
+				goto more;
+		}
+		goto done;
+	}
+
+more:
+	/* Fit the rest on the next page */
+	page_no++;
+	destp = page_address(rqstp->rq_arg.pages[page_no]);
+	while (byte_count--)
+		*destp++ = *srcp++;
+
+	rqstp->rq_respages = &rqstp->rq_arg.pages[page_no+1];
+	rqstp->rq_next_page = rqstp->rq_respages + 1;
+
+done:
+	byte_count = head->arg.head[0].iov_len - position;
+	head->arg.page_len += byte_count;
+	head->arg.len += byte_count;
+	head->arg.buflen += byte_count;
+	return 1;
+}
+
+static int rdma_read_chunks(struct svcxprt_rdma *xprt,
+			    struct rpcrdma_msg *rmsgp,
+			    struct svc_rqst *rqstp,
+			    struct svc_rdma_op_ctxt *head)
+{
+	int page_no, ret;
+	struct rpcrdma_read_chunk *ch;
+	u32 handle, page_offset, byte_count;
+	u32 position;
+	u64 rs_offset;
+	bool last;
+
+	/* If no read list is present, return 0 */
+	ch = svc_rdma_get_read_chunk(rmsgp);
+	if (!ch)
+		return 0;
+
+	if (rdma_rcl_chunk_count(ch) > RPCSVC_MAXPAGES)
+		return -EINVAL;
+
+	/* The request is completed when the RDMA_READs complete. The
+	 * head context keeps all the pages that comprise the
+	 * request.
+	 */
+	head->arg.head[0] = rqstp->rq_arg.head[0];
+	head->arg.tail[0] = rqstp->rq_arg.tail[0];
+	head->hdr_count = head->count;
+	head->arg.page_base = 0;
+	head->arg.page_len = 0;
+	head->arg.len = rqstp->rq_arg.len;
+	head->arg.buflen = rqstp->rq_arg.buflen;
+
+	ch = (struct rpcrdma_read_chunk *)&rmsgp->rm_body.rm_chunks[0];
+	position = be32_to_cpu(ch->rc_position);
+
+	/* RDMA_NOMSG: RDMA READ data should land just after RDMA RECV data */
+	if (position == 0) {
+		head->arg.pages = &head->pages[0];
+		page_offset = head->byte_len;
+	} else {
+		head->arg.pages = &head->pages[head->count];
+		page_offset = 0;
+	}
+
+	ret = 0;
+	page_no = 0;
+	for (; ch->rc_discrim != xdr_zero; ch++) {
+		if (be32_to_cpu(ch->rc_position) != position)
+			goto err;
+
+		handle = be32_to_cpu(ch->rc_target.rs_handle),
+		byte_count = be32_to_cpu(ch->rc_target.rs_length);
+		xdr_decode_hyper((__be32 *)&ch->rc_target.rs_offset,
+				 &rs_offset);
+
+		while (byte_count > 0) {
+			last = (ch + 1)->rc_discrim == xdr_zero;
+			ret = xprt->sc_reader(xprt, rqstp, head,
+					      &page_no, &page_offset,
+					      handle, byte_count,
+					      rs_offset, last);
+			if (ret < 0)
+				goto err;
+			byte_count -= ret;
+			rs_offset += ret;
+			head->arg.buflen += ret;
+		}
+	}
+
+	/* Read list may need XDR round-up (see RFC 5666, s. 3.7) */
+	if (page_offset & 3) {
+		u32 pad = 4 - (page_offset & 3);
+
+		head->arg.page_len += pad;
+		head->arg.len += pad;
+		head->arg.buflen += pad;
+		page_offset += pad;
+	}
+
+	ret = 1;
+	if (position && position < head->arg.head[0].iov_len)
+		ret = rdma_copy_tail(rqstp, head, position,
+				     byte_count, page_offset, page_no);
+	head->arg.head[0].iov_len = position;
+	head->position = position;
+
+ err:
+	/* Detach arg pages. svc_recv will replenish them */
+	for (page_no = 0;
+	     &rqstp->rq_pages[page_no] < rqstp->rq_respages; page_no++)
+		rqstp->rq_pages[page_no] = NULL;
+
+	return ret;
+}
+
+static int rdma_read_complete(struct svc_rqst *rqstp,
+			      struct svc_rdma_op_ctxt *head)
+{
+	int page_no;
+	int ret;
+
+	/* Copy RPC pages */
+	for (page_no = 0; page_no < head->count; page_no++) {
+		put_page(rqstp->rq_pages[page_no]);
+		rqstp->rq_pages[page_no] = head->pages[page_no];
+	}
+
+	/* Adjustments made for RDMA_NOMSG type requests */
+	if (head->position == 0) {
+		if (head->arg.len <= head->sge[0].length) {
+			head->arg.head[0].iov_len = head->arg.len -
+							head->byte_len;
+			head->arg.page_len = 0;
+		} else {
+			head->arg.head[0].iov_len = head->sge[0].length -
+								head->byte_len;
+			head->arg.page_len = head->arg.len -
+						head->sge[0].length;
+		}
+	}
+
+	/* Point rq_arg.pages past header */
+	rqstp->rq_arg.pages = &rqstp->rq_pages[head->hdr_count];
+	rqstp->rq_arg.page_len = head->arg.page_len;
+	rqstp->rq_arg.page_base = head->arg.page_base;
+
+	/* rq_respages starts after the last arg page */
+	rqstp->rq_respages = &rqstp->rq_arg.pages[page_no];
+	rqstp->rq_next_page = rqstp->rq_respages + 1;
+
+	/* Rebuild rq_arg head and tail. */
+	rqstp->rq_arg.head[0] = head->arg.head[0];
+	rqstp->rq_arg.tail[0] = head->arg.tail[0];
+	rqstp->rq_arg.len = head->arg.len;
+	rqstp->rq_arg.buflen = head->arg.buflen;
+
+	/* Free the context */
+	svc_rdma_put_context(head, 0);
+
+	/* XXX: What should this be? */
+	rqstp->rq_prot = IPPROTO_MAX;
+	svc_xprt_copy_addrs(rqstp, rqstp->rq_xprt);
+
+	ret = rqstp->rq_arg.head[0].iov_len
+		+ rqstp->rq_arg.page_len
+		+ rqstp->rq_arg.tail[0].iov_len;
+	dprintk("svcrdma: deferred read ret=%d, rq_arg.len=%u, "
+		"rq_arg.head[0].iov_base=%p, rq_arg.head[0].iov_len=%zu\n",
+		ret, rqstp->rq_arg.len,	rqstp->rq_arg.head[0].iov_base,
+		rqstp->rq_arg.head[0].iov_len);
+
+	return ret;
+}
+
+/*
+ * Set up the rqstp thread context to point to the RQ buffer. If
+ * necessary, pull additional data from the client with an RDMA_READ
+ * request.
+ */
+int svc_rdma_recvfrom(struct svc_rqst *rqstp)
+{
+	struct svc_xprt *xprt = rqstp->rq_xprt;
+	struct svcxprt_rdma *rdma_xprt =
+		container_of(xprt, struct svcxprt_rdma, sc_xprt);
+	struct svc_rdma_op_ctxt *ctxt = NULL;
+	struct rpcrdma_msg *rmsgp;
+	int ret = 0;
+	int len;
+
+	dprintk("svcrdma: rqstp=%p\n", rqstp);
+
+	spin_lock_bh(&rdma_xprt->sc_rq_dto_lock);
+	if (!list_empty(&rdma_xprt->sc_read_complete_q)) {
+		ctxt = list_entry(rdma_xprt->sc_read_complete_q.next,
+				  struct svc_rdma_op_ctxt,
+				  dto_q);
+		list_del_init(&ctxt->dto_q);
+		spin_unlock_bh(&rdma_xprt->sc_rq_dto_lock);
+		return rdma_read_complete(rqstp, ctxt);
+	} else if (!list_empty(&rdma_xprt->sc_rq_dto_q)) {
+		ctxt = list_entry(rdma_xprt->sc_rq_dto_q.next,
+				  struct svc_rdma_op_ctxt,
+				  dto_q);
+		list_del_init(&ctxt->dto_q);
+	} else {
+		atomic_inc(&rdma_stat_rq_starve);
+		clear_bit(XPT_DATA, &xprt->xpt_flags);
+		ctxt = NULL;
+	}
+	spin_unlock_bh(&rdma_xprt->sc_rq_dto_lock);
+	if (!ctxt) {
+		/* This is the EAGAIN path. The svc_recv routine will
+		 * return -EAGAIN, the nfsd thread will go to call into
+		 * svc_recv again and we shouldn't be on the active
+		 * transport list
+		 */
+		if (test_bit(XPT_CLOSE, &xprt->xpt_flags))
+			goto close_out;
+
+		goto out;
+	}
+	dprintk("svcrdma: processing ctxt=%p on xprt=%p, rqstp=%p, status=%d\n",
+		ctxt, rdma_xprt, rqstp, ctxt->wc_status);
+	atomic_inc(&rdma_stat_recv);
+
+	/* Build up the XDR from the receive buffers. */
+	rdma_build_arg_xdr(rqstp, ctxt, ctxt->byte_len);
+
+	/* Decode the RDMA header. */
+	len = svc_rdma_xdr_decode_req(&rmsgp, rqstp);
+	rqstp->rq_xprt_hlen = len;
+
+	/* If the request is invalid, reply with an error */
+	if (len < 0) {
+		if (len == -ENOSYS)
+			svc_rdma_send_error(rdma_xprt, rmsgp, ERR_VERS);
+		goto close_out;
+	}
+
+	/* Read read-list data. */
+	ret = rdma_read_chunks(rdma_xprt, rmsgp, rqstp, ctxt);
+	if (ret > 0) {
+		/* read-list posted, defer until data received from client. */
+		goto defer;
+	} else if (ret < 0) {
+		/* Post of read-list failed, free context. */
+		svc_rdma_put_context(ctxt, 1);
+		return 0;
+	}
+
+	ret = rqstp->rq_arg.head[0].iov_len
+		+ rqstp->rq_arg.page_len
+		+ rqstp->rq_arg.tail[0].iov_len;
+	svc_rdma_put_context(ctxt, 0);
+ out:
+	dprintk("svcrdma: ret=%d, rq_arg.len=%u, "
+		"rq_arg.head[0].iov_base=%p, rq_arg.head[0].iov_len=%zd\n",
+		ret, rqstp->rq_arg.len,
+		rqstp->rq_arg.head[0].iov_base,
+		rqstp->rq_arg.head[0].iov_len);
+	rqstp->rq_prot = IPPROTO_MAX;
+	svc_xprt_copy_addrs(rqstp, xprt);
+	return ret;
+
+ close_out:
+	if (ctxt)
+		svc_rdma_put_context(ctxt, 1);
+	dprintk("svcrdma: transport %p is closing\n", xprt);
+	/*
+	 * Set the close bit and enqueue it. svc_recv will see the
+	 * close bit and call svc_xprt_delete
+	 */
+	set_bit(XPT_CLOSE, &xprt->xpt_flags);
+defer:
+	return 0;
+}