svc_rdma_recvfrom.c

   1// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
   2/*
   3 * Copyright (c) 2016-2018 Oracle. All rights reserved.
   4 * Copyright (c) 2014 Open Grid Computing, Inc. All rights reserved.
   5 * Copyright (c) 2005-2006 Network Appliance, Inc. All rights reserved.
   6 *
   7 * This software is available to you under a choice of one of two
   8 * licenses.  You may choose to be licensed under the terms of the GNU
   9 * General Public License (GPL) Version 2, available from the file
  10 * COPYING in the main directory of this source tree, or the BSD-type
  11 * license below:
  12 *
  13 * Redistribution and use in source and binary forms, with or without
  14 * modification, are permitted provided that the following conditions
  15 * are met:
  16 *
  17 *      Redistributions of source code must retain the above copyright
  18 *      notice, this list of conditions and the following disclaimer.
  19 *
  20 *      Redistributions in binary form must reproduce the above
  21 *      copyright notice, this list of conditions and the following
  22 *      disclaimer in the documentation and/or other materials provided
  23 *      with the distribution.
  24 *
  25 *      Neither the name of the Network Appliance, Inc. nor the names of
  26 *      its contributors may be used to endorse or promote products
  27 *      derived from this software without specific prior written
  28 *      permission.
  29 *
  30 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  31 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  32 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  33 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  34 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  35 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  36 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  37 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  38 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  39 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  40 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  41 *
  42 * Author: Tom Tucker <tom@opengridcomputing.com>
  43 */
  44
  45/* Operation
  46 *
  47 * The main entry point is svc_rdma_recvfrom. This is called from
  48 * svc_recv when the transport indicates there is incoming data to
  49 * be read. "Data Ready" is signaled when an RDMA Receive completes,
  50 * or when a set of RDMA Reads complete.
  51 *
  52 * An svc_rqst is passed in. This structure contains an array of
  53 * free pages (rq_pages) that will contain the incoming RPC message.
  54 *
  55 * Short messages are moved directly into svc_rqst::rq_arg, and
  56 * the RPC Call is ready to be processed by the Upper Layer.
  57 * svc_rdma_recvfrom returns the length of the RPC Call message,
  58 * completing the reception of the RPC Call.
  59 *
  60 * However, when an incoming message has Read chunks,
  61 * svc_rdma_recvfrom must post RDMA Reads to pull the RPC Call's
  62 * data payload from the client. svc_rdma_recvfrom sets up the
  63 * RDMA Reads using pages in svc_rqst::rq_pages, which are
  64 * transferred to an svc_rdma_recv_ctxt for the duration of the
  65 * I/O. svc_rdma_recvfrom then returns zero, since the RPC message
  66 * is still not yet ready.
  67 *
  68 * When the Read chunk payloads have become available on the
  69 * server, "Data Ready" is raised again, and svc_recv calls
  70 * svc_rdma_recvfrom again. This second call may use a different
  71 * svc_rqst than the first one, thus any information that needs
  72 * to be preserved across these two calls is kept in an
  73 * svc_rdma_recv_ctxt.
  74 *
  75 * The second call to svc_rdma_recvfrom performs final assembly
  76 * of the RPC Call message, using the RDMA Read sink pages kept in
  77 * the svc_rdma_recv_ctxt. The xdr_buf is copied from the
  78 * svc_rdma_recv_ctxt to the second svc_rqst. The second call returns
  79 * the length of the completed RPC Call message.
  80 *
  81 * Page Management
  82 *
  83 * Pages under I/O must be transferred from the first svc_rqst to an
  84 * svc_rdma_recv_ctxt before the first svc_rdma_recvfrom call returns.
  85 *
  86 * The first svc_rqst supplies pages for RDMA Reads. These are moved
  87 * from rqstp::rq_pages into ctxt::pages. The consumed elements of
  88 * the rq_pages array are set to NULL and refilled with the first
  89 * svc_rdma_recvfrom call returns.
  90 *
  91 * During the second svc_rdma_recvfrom call, RDMA Read sink pages
  92 * are transferred from the svc_rdma_recv_ctxt to the second svc_rqst.
  93 */
  94
  95#include <linux/slab.h>
  96#include <linux/spinlock.h>
  97#include <linux/unaligned.h>
  98#include <rdma/ib_verbs.h>
  99#include <rdma/rdma_cm.h>
 100
 101#include <linux/sunrpc/xdr.h>
 102#include <linux/sunrpc/debug.h>
 103#include <linux/sunrpc/rpc_rdma.h>
 104#include <linux/sunrpc/svc_rdma.h>
 105
 106#include "xprt_rdma.h"
 107#include <trace/events/rpcrdma.h>
 108
 109static void svc_rdma_wc_receive(struct ib_cq *cq, struct ib_wc *wc);
 110
 111static inline struct svc_rdma_recv_ctxt *
 112svc_rdma_next_recv_ctxt(struct list_head *list)
 113{
 114	return list_first_entry_or_null(list, struct svc_rdma_recv_ctxt,
 115					rc_list);
 116}
 117
 118static struct svc_rdma_recv_ctxt *
 119svc_rdma_recv_ctxt_alloc(struct svcxprt_rdma *rdma)
 120{
 121	int node = ibdev_to_node(rdma->sc_cm_id->device);
 122	struct svc_rdma_recv_ctxt *ctxt;
 123	unsigned long pages;
 124	dma_addr_t addr;
 125	void *buffer;
 126
 127	pages = svc_serv_maxpages(rdma->sc_xprt.xpt_server);
 128	ctxt = kzalloc_node(struct_size(ctxt, rc_pages, pages),
 129			    GFP_KERNEL, node);
 130	if (!ctxt)
 131		goto fail0;
 132	ctxt->rc_maxpages = pages;
 133	buffer = kmalloc_node(rdma->sc_max_req_size, GFP_KERNEL, node);
 134	if (!buffer)
 135		goto fail1;
 136	addr = ib_dma_map_single(rdma->sc_pd->device, buffer,
 137				 rdma->sc_max_req_size, DMA_FROM_DEVICE);
 138	if (ib_dma_mapping_error(rdma->sc_pd->device, addr))
 139		goto fail2;
 140
 141	svc_rdma_recv_cid_init(rdma, &ctxt->rc_cid);
 142	pcl_init(&ctxt->rc_call_pcl);
 143	pcl_init(&ctxt->rc_read_pcl);
 144	pcl_init(&ctxt->rc_write_pcl);
 145	pcl_init(&ctxt->rc_reply_pcl);
 146
 147	ctxt->rc_recv_wr.next = NULL;
 148	ctxt->rc_recv_wr.wr_cqe = &ctxt->rc_cqe;
 149	ctxt->rc_recv_wr.sg_list = &ctxt->rc_recv_sge;
 150	ctxt->rc_recv_wr.num_sge = 1;
 151	ctxt->rc_cqe.done = svc_rdma_wc_receive;
 152	ctxt->rc_recv_sge.addr = addr;
 153	ctxt->rc_recv_sge.length = rdma->sc_max_req_size;
 154	ctxt->rc_recv_sge.lkey = rdma->sc_pd->local_dma_lkey;
 155	ctxt->rc_recv_buf = buffer;
 156	svc_rdma_cc_init(rdma, &ctxt->rc_cc);
 157	return ctxt;
 158
 159fail2:
 160	kfree(buffer);
 161fail1:
 162	kfree(ctxt);
 163fail0:
 164	return NULL;
 165}
 166
 167static void svc_rdma_recv_ctxt_destroy(struct svcxprt_rdma *rdma,
 168				       struct svc_rdma_recv_ctxt *ctxt)
 169{
 170	ib_dma_unmap_single(rdma->sc_pd->device, ctxt->rc_recv_sge.addr,
 171			    ctxt->rc_recv_sge.length, DMA_FROM_DEVICE);
 172	kfree(ctxt->rc_recv_buf);
 173	kfree(ctxt);
 174}
 175
 176/**
 177 * svc_rdma_recv_ctxts_destroy - Release all recv_ctxt's for an xprt
 178 * @rdma: svcxprt_rdma being torn down
 179 *
 180 */
 181void svc_rdma_recv_ctxts_destroy(struct svcxprt_rdma *rdma)
 182{
 183	struct svc_rdma_recv_ctxt *ctxt;
 184	struct llist_node *node;
 185
 186	while ((node = llist_del_first(&rdma->sc_recv_ctxts))) {
 187		ctxt = llist_entry(node, struct svc_rdma_recv_ctxt, rc_node);
 188		svc_rdma_recv_ctxt_destroy(rdma, ctxt);
 189	}
 190}
 191
 192/**
 193 * svc_rdma_recv_ctxt_get - Allocate a recv_ctxt
 194 * @rdma: controlling svcxprt_rdma
 195 *
 196 * Returns a recv_ctxt or (rarely) NULL if none are available.
 197 */
 198struct svc_rdma_recv_ctxt *svc_rdma_recv_ctxt_get(struct svcxprt_rdma *rdma)
 199{
 200	struct svc_rdma_recv_ctxt *ctxt;
 201	struct llist_node *node;
 202
 203	node = llist_del_first(&rdma->sc_recv_ctxts);
 204	if (!node)
 205		return NULL;
 206
 207	ctxt = llist_entry(node, struct svc_rdma_recv_ctxt, rc_node);
 208	ctxt->rc_page_count = 0;
 209	return ctxt;
 210}
 211
 212/**
 213 * svc_rdma_recv_ctxt_put - Return recv_ctxt to free list
 214 * @rdma: controlling svcxprt_rdma
 215 * @ctxt: object to return to the free list
 216 *
 217 */
 218void svc_rdma_recv_ctxt_put(struct svcxprt_rdma *rdma,
 219			    struct svc_rdma_recv_ctxt *ctxt)
 220{
 221	svc_rdma_cc_release(rdma, &ctxt->rc_cc, DMA_FROM_DEVICE);
 222
 223	/* @rc_page_count is normally zero here, but error flows
 224	 * can leave pages in @rc_pages.
 225	 */
 226	release_pages(ctxt->rc_pages, ctxt->rc_page_count);
 227
 228	pcl_free(&ctxt->rc_call_pcl);
 229	pcl_free(&ctxt->rc_read_pcl);
 230	pcl_free(&ctxt->rc_write_pcl);
 231	pcl_free(&ctxt->rc_reply_pcl);
 232
 233	llist_add(&ctxt->rc_node, &rdma->sc_recv_ctxts);
 234}
 235
 236/**
 237 * svc_rdma_release_ctxt - Release transport-specific per-rqst resources
 238 * @xprt: the transport which owned the context
 239 * @vctxt: the context from rqstp->rq_xprt_ctxt or dr->xprt_ctxt
 240 *
 241 * Ensure that the recv_ctxt is released whether or not a Reply
 242 * was sent. For example, the client could close the connection,
 243 * or svc_process could drop an RPC, before the Reply is sent.
 244 */
 245void svc_rdma_release_ctxt(struct svc_xprt *xprt, void *vctxt)
 246{
 247	struct svc_rdma_recv_ctxt *ctxt = vctxt;
 248	struct svcxprt_rdma *rdma =
 249		container_of(xprt, struct svcxprt_rdma, sc_xprt);
 250
 251	if (ctxt)
 252		svc_rdma_recv_ctxt_put(rdma, ctxt);
 253}
 254
 255static bool svc_rdma_refresh_recvs(struct svcxprt_rdma *rdma,
 256				   unsigned int wanted)
 257{
 258	const struct ib_recv_wr *bad_wr = NULL;
 259	struct svc_rdma_recv_ctxt *ctxt;
 260	struct ib_recv_wr *recv_chain;
 261	int ret;
 262
 263	if (test_bit(XPT_CLOSE, &rdma->sc_xprt.xpt_flags))
 264		return false;
 265
 266	recv_chain = NULL;
 267	while (wanted--) {
 268		ctxt = svc_rdma_recv_ctxt_get(rdma);
 269		if (!ctxt)
 270			break;
 271
 272		trace_svcrdma_post_recv(&ctxt->rc_cid);
 273		ctxt->rc_recv_wr.next = recv_chain;
 274		recv_chain = &ctxt->rc_recv_wr;
 275		rdma->sc_pending_recvs++;
 276	}
 277	if (!recv_chain)
 278		return true;
 279
 280	ret = ib_post_recv(rdma->sc_qp, recv_chain, &bad_wr);
 281	if (ret)
 282		goto err_free;
 283	return true;
 284
 285err_free:
 286	trace_svcrdma_rq_post_err(rdma, ret);
 287	while (bad_wr) {
 288		ctxt = container_of(bad_wr, struct svc_rdma_recv_ctxt,
 289				    rc_recv_wr);
 290		bad_wr = bad_wr->next;
 291		svc_rdma_recv_ctxt_put(rdma, ctxt);
 292	}
 293	/* Since we're destroying the xprt, no need to reset
 294	 * sc_pending_recvs. */
 295	return false;
 296}
 297
 298/**
 299 * svc_rdma_post_recvs - Post initial set of Recv WRs
 300 * @rdma: fresh svcxprt_rdma
 301 *
 302 * Return values:
 303 *   %true: Receive Queue initialization successful
 304 *   %false: memory allocation or DMA error
 305 */
 306bool svc_rdma_post_recvs(struct svcxprt_rdma *rdma)
 307{
 308	unsigned int total;
 309
 310	/* For each credit, allocate enough recv_ctxts for one
 311	 * posted Receive and one RPC in process.
 312	 */
 313	total = (rdma->sc_max_requests * 2) + rdma->sc_recv_batch;
 314	while (total--) {
 315		struct svc_rdma_recv_ctxt *ctxt;
 316
 317		ctxt = svc_rdma_recv_ctxt_alloc(rdma);
 318		if (!ctxt)
 319			return false;
 320		llist_add(&ctxt->rc_node, &rdma->sc_recv_ctxts);
 321	}
 322
 323	return svc_rdma_refresh_recvs(rdma, rdma->sc_max_requests);
 324}
 325
 326/**
 327 * svc_rdma_wc_receive - Invoked by RDMA provider for each polled Receive WC
 328 * @cq: Completion Queue context
 329 * @wc: Work Completion object
 330 *
 331 */
 332static void svc_rdma_wc_receive(struct ib_cq *cq, struct ib_wc *wc)
 333{
 334	struct svcxprt_rdma *rdma = cq->cq_context;
 335	struct ib_cqe *cqe = wc->wr_cqe;
 336	struct svc_rdma_recv_ctxt *ctxt;
 337
 338	rdma->sc_pending_recvs--;
 339
 340	/* WARNING: Only wc->wr_cqe and wc->status are reliable */
 341	ctxt = container_of(cqe, struct svc_rdma_recv_ctxt, rc_cqe);
 342
 343	if (wc->status != IB_WC_SUCCESS)
 344		goto flushed;
 345	trace_svcrdma_wc_recv(wc, &ctxt->rc_cid);
 346
 347	/* If receive posting fails, the connection is about to be
 348	 * lost anyway. The server will not be able to send a reply
 349	 * for this RPC, and the client will retransmit this RPC
 350	 * anyway when it reconnects.
 351	 *
 352	 * Therefore we drop the Receive, even if status was SUCCESS
 353	 * to reduce the likelihood of replayed requests once the
 354	 * client reconnects.
 355	 */
 356	if (rdma->sc_pending_recvs < rdma->sc_max_requests)
 357		if (!svc_rdma_refresh_recvs(rdma, rdma->sc_recv_batch))
 358			goto dropped;
 359
 360	/* All wc fields are now known to be valid */
 361	ctxt->rc_byte_len = wc->byte_len;
 362
 363	spin_lock(&rdma->sc_rq_dto_lock);
 364	list_add_tail(&ctxt->rc_list, &rdma->sc_rq_dto_q);
 365	/* Note the unlock pairs with the smp_rmb in svc_xprt_ready: */
 366	set_bit(XPT_DATA, &rdma->sc_xprt.xpt_flags);
 367	spin_unlock(&rdma->sc_rq_dto_lock);
 368	if (!test_bit(RDMAXPRT_CONN_PENDING, &rdma->sc_flags))
 369		svc_xprt_enqueue(&rdma->sc_xprt);
 370	return;
 371
 372flushed:
 373	if (wc->status == IB_WC_WR_FLUSH_ERR)
 374		trace_svcrdma_wc_recv_flush(wc, &ctxt->rc_cid);
 375	else
 376		trace_svcrdma_wc_recv_err(wc, &ctxt->rc_cid);
 377dropped:
 378	svc_rdma_recv_ctxt_put(rdma, ctxt);
 379	svc_xprt_deferred_close(&rdma->sc_xprt);
 380}
 381
 382/**
 383 * svc_rdma_flush_recv_queues - Drain pending Receive work
 384 * @rdma: svcxprt_rdma being shut down
 385 *
 386 */
 387void svc_rdma_flush_recv_queues(struct svcxprt_rdma *rdma)
 388{
 389	struct svc_rdma_recv_ctxt *ctxt;
 390
 391	while ((ctxt = svc_rdma_next_recv_ctxt(&rdma->sc_read_complete_q))) {
 392		list_del(&ctxt->rc_list);
 393		svc_rdma_recv_ctxt_put(rdma, ctxt);
 394	}
 395	while ((ctxt = svc_rdma_next_recv_ctxt(&rdma->sc_rq_dto_q))) {
 396		list_del(&ctxt->rc_list);
 397		svc_rdma_recv_ctxt_put(rdma, ctxt);
 398	}
 399}
 400
 401static void svc_rdma_build_arg_xdr(struct svc_rqst *rqstp,
 402				   struct svc_rdma_recv_ctxt *ctxt)
 403{
 404	struct xdr_buf *arg = &rqstp->rq_arg;
 405
 406	arg->head[0].iov_base = ctxt->rc_recv_buf;
 407	arg->head[0].iov_len = ctxt->rc_byte_len;
 408	arg->tail[0].iov_base = NULL;
 409	arg->tail[0].iov_len = 0;
 410	arg->page_len = 0;
 411	arg->page_base = 0;
 412	arg->buflen = ctxt->rc_byte_len;
 413	arg->len = ctxt->rc_byte_len;
 414}
 415
 416/**
 417 * xdr_count_read_segments - Count number of Read segments in Read list
 418 * @rctxt: Ingress receive context
 419 * @p: Start of an un-decoded Read list
 420 *
 421 * Before allocating anything, ensure the ingress Read list is safe
 422 * to use.
 423 *
 424 * The segment count is limited to how many segments can fit in the
 425 * transport header without overflowing the buffer. That's about 40
 426 * Read segments for a 1KB inline threshold.
 427 *
 428 * Return values:
 429 *   %true: Read list is valid. @rctxt's xdr_stream is updated to point
 430 *	    to the first byte past the Read list. rc_read_pcl and
 431 *	    rc_call_pcl cl_count fields are set to the number of
 432 *	    Read segments in the list.
 433 *  %false: Read list is corrupt. @rctxt's xdr_stream is left in an
 434 *	    unknown state.
 435 */
 436static bool xdr_count_read_segments(struct svc_rdma_recv_ctxt *rctxt, __be32 *p)
 437{
 438	rctxt->rc_call_pcl.cl_count = 0;
 439	rctxt->rc_read_pcl.cl_count = 0;
 440	while (xdr_item_is_present(p)) {
 441		u32 position, handle, length;
 442		u64 offset;
 443
 444		p = xdr_inline_decode(&rctxt->rc_stream,
 445				      rpcrdma_readseg_maxsz * sizeof(*p));
 446		if (!p)
 447			return false;
 448
 449		xdr_decode_read_segment(p, &position, &handle,
 450					    &length, &offset);
 451		if (position) {
 452			if (position & 3)
 453				return false;
 454			++rctxt->rc_read_pcl.cl_count;
 455		} else {
 456			++rctxt->rc_call_pcl.cl_count;
 457		}
 458
 459		p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
 460		if (!p)
 461			return false;
 462	}
 463	return true;
 464}
 465
 466/* Sanity check the Read list.
 467 *
 468 * Sanity checks:
 469 * - Read list does not overflow Receive buffer.
 470 * - Chunk size limited by largest NFS data payload.
 471 *
 472 * Return values:
 473 *   %true: Read list is valid. @rctxt's xdr_stream is updated
 474 *	    to point to the first byte past the Read list.
 475 *  %false: Read list is corrupt. @rctxt's xdr_stream is left
 476 *	    in an unknown state.
 477 */
 478static bool xdr_check_read_list(struct svc_rdma_recv_ctxt *rctxt)
 479{
 480	__be32 *p;
 481
 482	p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
 483	if (!p)
 484		return false;
 485	if (!xdr_count_read_segments(rctxt, p))
 486		return false;
 487	if (!pcl_alloc_call(rctxt, p))
 488		return false;
 489	return pcl_alloc_read(rctxt, p);
 490}
 491
 492static bool xdr_check_write_chunk(struct svc_rdma_recv_ctxt *rctxt)
 493{
 494	u32 segcount;
 495	__be32 *p;
 496
 497	if (xdr_stream_decode_u32(&rctxt->rc_stream, &segcount))
 498		return false;
 499
 500	/* Before trusting the segcount value enough to use it in
 501	 * a computation, perform a simple range check. This is an
 502	 * arbitrary but sensible limit (ie, not architectural).
 503	 */
 504	if (unlikely(segcount > rctxt->rc_maxpages))
 505		return false;
 506
 507	p = xdr_inline_decode(&rctxt->rc_stream,
 508			      segcount * rpcrdma_segment_maxsz * sizeof(*p));
 509	return p != NULL;
 510}
 511
 512/**
 513 * xdr_count_write_chunks - Count number of Write chunks in Write list
 514 * @rctxt: Received header and decoding state
 515 * @p: start of an un-decoded Write list
 516 *
 517 * Before allocating anything, ensure the ingress Write list is
 518 * safe to use.
 519 *
 520 * Return values:
 521 *       %true: Write list is valid. @rctxt's xdr_stream is updated
 522 *		to point to the first byte past the Write list, and
 523 *		the number of Write chunks is in rc_write_pcl.cl_count.
 524 *      %false: Write list is corrupt. @rctxt's xdr_stream is left
 525 *		in an indeterminate state.
 526 */
 527static bool xdr_count_write_chunks(struct svc_rdma_recv_ctxt *rctxt, __be32 *p)
 528{
 529	rctxt->rc_write_pcl.cl_count = 0;
 530	while (xdr_item_is_present(p)) {
 531		if (!xdr_check_write_chunk(rctxt))
 532			return false;
 533		++rctxt->rc_write_pcl.cl_count;
 534		p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
 535		if (!p)
 536			return false;
 537	}
 538	return true;
 539}
 540
 541/* Sanity check the Write list.
 542 *
 543 * Implementation limits:
 544 * - This implementation currently supports only one Write chunk.
 545 *
 546 * Sanity checks:
 547 * - Write list does not overflow Receive buffer.
 548 * - Chunk size limited by largest NFS data payload.
 549 *
 550 * Return values:
 551 *       %true: Write list is valid. @rctxt's xdr_stream is updated
 552 *		to point to the first byte past the Write list.
 553 *      %false: Write list is corrupt. @rctxt's xdr_stream is left
 554 *		in an unknown state.
 555 */
 556static bool xdr_check_write_list(struct svc_rdma_recv_ctxt *rctxt)
 557{
 558	__be32 *p;
 559
 560	p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
 561	if (!p)
 562		return false;
 563	if (!xdr_count_write_chunks(rctxt, p))
 564		return false;
 565	if (!pcl_alloc_write(rctxt, &rctxt->rc_write_pcl, p))
 566		return false;
 567
 568	rctxt->rc_cur_result_payload = pcl_first_chunk(&rctxt->rc_write_pcl);
 569	return true;
 570}
 571
 572/* Sanity check the Reply chunk.
 573 *
 574 * Sanity checks:
 575 * - Reply chunk does not overflow Receive buffer.
 576 * - Chunk size limited by largest NFS data payload.
 577 *
 578 * Return values:
 579 *       %true: Reply chunk is valid. @rctxt's xdr_stream is updated
 580 *		to point to the first byte past the Reply chunk.
 581 *      %false: Reply chunk is corrupt. @rctxt's xdr_stream is left
 582 *		in an unknown state.
 583 */
 584static bool xdr_check_reply_chunk(struct svc_rdma_recv_ctxt *rctxt)
 585{
 586	__be32 *p;
 587
 588	p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
 589	if (!p)
 590		return false;
 591
 592	if (!xdr_item_is_present(p))
 593		return true;
 594	if (!xdr_check_write_chunk(rctxt))
 595		return false;
 596
 597	rctxt->rc_reply_pcl.cl_count = 1;
 598	return pcl_alloc_write(rctxt, &rctxt->rc_reply_pcl, p);
 599}
 600
 601/* RPC-over-RDMA Version One private extension: Remote Invalidation.
 602 * Responder's choice: requester signals it can handle Send With
 603 * Invalidate, and responder chooses one R_key to invalidate.
 604 *
 605 * If there is exactly one distinct R_key in the received transport
 606 * header, set rc_inv_rkey to that R_key. Otherwise, set it to zero.
 607 */
 608static void svc_rdma_get_inv_rkey(struct svcxprt_rdma *rdma,
 609				  struct svc_rdma_recv_ctxt *ctxt)
 610{
 611	struct svc_rdma_segment *segment;
 612	struct svc_rdma_chunk *chunk;
 613	u32 inv_rkey;
 614
 615	ctxt->rc_inv_rkey = 0;
 616
 617	if (!rdma->sc_snd_w_inv)
 618		return;
 619
 620	inv_rkey = 0;
 621	pcl_for_each_chunk(chunk, &ctxt->rc_call_pcl) {
 622		pcl_for_each_segment(segment, chunk) {
 623			if (inv_rkey == 0)
 624				inv_rkey = segment->rs_handle;
 625			else if (inv_rkey != segment->rs_handle)
 626				return;
 627		}
 628	}
 629	pcl_for_each_chunk(chunk, &ctxt->rc_read_pcl) {
 630		pcl_for_each_segment(segment, chunk) {
 631			if (inv_rkey == 0)
 632				inv_rkey = segment->rs_handle;
 633			else if (inv_rkey != segment->rs_handle)
 634				return;
 635		}
 636	}
 637	pcl_for_each_chunk(chunk, &ctxt->rc_write_pcl) {
 638		pcl_for_each_segment(segment, chunk) {
 639			if (inv_rkey == 0)
 640				inv_rkey = segment->rs_handle;
 641			else if (inv_rkey != segment->rs_handle)
 642				return;
 643		}
 644	}
 645	pcl_for_each_chunk(chunk, &ctxt->rc_reply_pcl) {
 646		pcl_for_each_segment(segment, chunk) {
 647			if (inv_rkey == 0)
 648				inv_rkey = segment->rs_handle;
 649			else if (inv_rkey != segment->rs_handle)
 650				return;
 651		}
 652	}
 653	ctxt->rc_inv_rkey = inv_rkey;
 654}
 655
 656/**
 657 * svc_rdma_xdr_decode_req - Decode the transport header
 658 * @rq_arg: xdr_buf containing ingress RPC/RDMA message
 659 * @rctxt: state of decoding
 660 *
 661 * On entry, xdr->head[0].iov_base points to first byte of the
 662 * RPC-over-RDMA transport header.
 663 *
 664 * On successful exit, head[0] points to first byte past the
 665 * RPC-over-RDMA header. For RDMA_MSG, this is the RPC message.
 666 *
 667 * The length of the RPC-over-RDMA header is returned.
 668 *
 669 * Assumptions:
 670 * - The transport header is entirely contained in the head iovec.
 671 */
 672static int svc_rdma_xdr_decode_req(struct xdr_buf *rq_arg,
 673				   struct svc_rdma_recv_ctxt *rctxt)
 674{
 675	__be32 *p, *rdma_argp;
 676	unsigned int hdr_len;
 677
 678	rdma_argp = rq_arg->head[0].iov_base;
 679	xdr_init_decode(&rctxt->rc_stream, rq_arg, rdma_argp, NULL);
 680
 681	p = xdr_inline_decode(&rctxt->rc_stream,
 682			      rpcrdma_fixed_maxsz * sizeof(*p));
 683	if (unlikely(!p))
 684		goto out_short;
 685	p++;
 686	if (*p != rpcrdma_version)
 687		goto out_version;
 688	p += 2;
 689	rctxt->rc_msgtype = *p;
 690	switch (rctxt->rc_msgtype) {
 691	case rdma_msg:
 692		break;
 693	case rdma_nomsg:
 694		break;
 695	case rdma_done:
 696		goto out_drop;
 697	case rdma_error:
 698		goto out_drop;
 699	default:
 700		goto out_proc;
 701	}
 702
 703	if (!xdr_check_read_list(rctxt))
 704		goto out_inval;
 705	if (!xdr_check_write_list(rctxt))
 706		goto out_inval;
 707	if (!xdr_check_reply_chunk(rctxt))
 708		goto out_inval;
 709
 710	rq_arg->head[0].iov_base = rctxt->rc_stream.p;
 711	hdr_len = xdr_stream_pos(&rctxt->rc_stream);
 712	rq_arg->head[0].iov_len -= hdr_len;
 713	rq_arg->len -= hdr_len;
 714	trace_svcrdma_decode_rqst(rctxt, rdma_argp, hdr_len);
 715	return hdr_len;
 716
 717out_short:
 718	trace_svcrdma_decode_short_err(rctxt, rq_arg->len);
 719	return -EINVAL;
 720
 721out_version:
 722	trace_svcrdma_decode_badvers_err(rctxt, rdma_argp);
 723	return -EPROTONOSUPPORT;
 724
 725out_drop:
 726	trace_svcrdma_decode_drop_err(rctxt, rdma_argp);
 727	return 0;
 728
 729out_proc:
 730	trace_svcrdma_decode_badproc_err(rctxt, rdma_argp);
 731	return -EINVAL;
 732
 733out_inval:
 734	trace_svcrdma_decode_parse_err(rctxt, rdma_argp);
 735	return -EINVAL;
 736}
 737
 738static void svc_rdma_send_error(struct svcxprt_rdma *rdma,
 739				struct svc_rdma_recv_ctxt *rctxt,
 740				int status)
 741{
 742	struct svc_rdma_send_ctxt *sctxt;
 743
 744	sctxt = svc_rdma_send_ctxt_get(rdma);
 745	if (!sctxt)
 746		return;
 747	svc_rdma_send_error_msg(rdma, sctxt, rctxt, status);
 748}
 749
 750/* By convention, backchannel calls arrive via rdma_msg type
 751 * messages, and never populate the chunk lists. This makes
 752 * the RPC/RDMA header small and fixed in size, so it is
 753 * straightforward to check the RPC header's direction field.
 754 */
 755static bool svc_rdma_is_reverse_direction_reply(struct svc_xprt *xprt,
 756						struct svc_rdma_recv_ctxt *rctxt)
 757{
 758	__be32 *p = rctxt->rc_recv_buf;
 759
 760	if (!xprt->xpt_bc_xprt)
 761		return false;
 762
 763	if (rctxt->rc_msgtype != rdma_msg)
 764		return false;
 765
 766	if (!pcl_is_empty(&rctxt->rc_call_pcl))
 767		return false;
 768	if (!pcl_is_empty(&rctxt->rc_read_pcl))
 769		return false;
 770	if (!pcl_is_empty(&rctxt->rc_write_pcl))
 771		return false;
 772	if (!pcl_is_empty(&rctxt->rc_reply_pcl))
 773		return false;
 774
 775	/* RPC call direction */
 776	if (*(p + 8) == cpu_to_be32(RPC_CALL))
 777		return false;
 778
 779	return true;
 780}
 781
 782/* Finish constructing the RPC Call message in rqstp::rq_arg.
 783 *
 784 * The incoming RPC/RDMA message is an RDMA_MSG type message
 785 * with a single Read chunk (only the upper layer data payload
 786 * was conveyed via RDMA Read).
 787 */
 788static void svc_rdma_read_complete_one(struct svc_rqst *rqstp,
 789				       struct svc_rdma_recv_ctxt *ctxt)
 790{
 791	struct svc_rdma_chunk *chunk = pcl_first_chunk(&ctxt->rc_read_pcl);
 792	struct xdr_buf *buf = &rqstp->rq_arg;
 793	unsigned int length;
 794
 795	/* Split the Receive buffer between the head and tail
 796	 * buffers at Read chunk's position. XDR roundup of the
 797	 * chunk is not included in either the pagelist or in
 798	 * the tail.
 799	 */
 800	buf->tail[0].iov_base = buf->head[0].iov_base + chunk->ch_position;
 801	buf->tail[0].iov_len = buf->head[0].iov_len - chunk->ch_position;
 802	buf->head[0].iov_len = chunk->ch_position;
 803
 804	/* Read chunk may need XDR roundup (see RFC 8166, s. 3.4.5.2).
 805	 *
 806	 * If the client already rounded up the chunk length, the
 807	 * length does not change. Otherwise, the length of the page
 808	 * list is increased to include XDR round-up.
 809	 *
 810	 * Currently these chunks always start at page offset 0,
 811	 * thus the rounded-up length never crosses a page boundary.
 812	 */
 813	buf->pages = &rqstp->rq_pages[0];
 814	length = xdr_align_size(chunk->ch_length);
 815	buf->page_len = length;
 816	buf->len += length;
 817	buf->buflen += length;
 818}
 819
 820/* Finish constructing the RPC Call message in rqstp::rq_arg.
 821 *
 822 * The incoming RPC/RDMA message is an RDMA_MSG type message
 823 * with payload in multiple Read chunks and no PZRC.
 824 */
 825static void svc_rdma_read_complete_multiple(struct svc_rqst *rqstp,
 826					    struct svc_rdma_recv_ctxt *ctxt)
 827{
 828	struct xdr_buf *buf = &rqstp->rq_arg;
 829
 830	buf->len += ctxt->rc_readbytes;
 831	buf->buflen += ctxt->rc_readbytes;
 832
 833	buf->head[0].iov_base = page_address(rqstp->rq_pages[0]);
 834	buf->head[0].iov_len = min_t(size_t, PAGE_SIZE, ctxt->rc_readbytes);
 835	buf->pages = &rqstp->rq_pages[1];
 836	buf->page_len = ctxt->rc_readbytes - buf->head[0].iov_len;
 837}
 838
 839/* Finish constructing the RPC Call message in rqstp::rq_arg.
 840 *
 841 * The incoming RPC/RDMA message is an RDMA_NOMSG type message
 842 * (the RPC message body was conveyed via RDMA Read).
 843 */
 844static void svc_rdma_read_complete_pzrc(struct svc_rqst *rqstp,
 845					struct svc_rdma_recv_ctxt *ctxt)
 846{
 847	struct xdr_buf *buf = &rqstp->rq_arg;
 848
 849	buf->len += ctxt->rc_readbytes;
 850	buf->buflen += ctxt->rc_readbytes;
 851
 852	buf->head[0].iov_base = page_address(rqstp->rq_pages[0]);
 853	buf->head[0].iov_len = min_t(size_t, PAGE_SIZE, ctxt->rc_readbytes);
 854	buf->pages = &rqstp->rq_pages[1];
 855	buf->page_len = ctxt->rc_readbytes - buf->head[0].iov_len;
 856}
 857
 858static noinline void svc_rdma_read_complete(struct svc_rqst *rqstp,
 859					    struct svc_rdma_recv_ctxt *ctxt)
 860{
 861	unsigned int i;
 862
 863	/* Transfer the Read chunk pages into @rqstp.rq_pages, replacing
 864	 * the rq_pages that were already allocated for this rqstp.
 865	 */
 866	release_pages(rqstp->rq_respages, ctxt->rc_page_count);
 867	for (i = 0; i < ctxt->rc_page_count; i++)
 868		rqstp->rq_pages[i] = ctxt->rc_pages[i];
 869
 870	/* Update @rqstp's result send buffer to start after the
 871	 * last page in the RDMA Read payload.
 872	 */
 873	rqstp->rq_respages = &rqstp->rq_pages[ctxt->rc_page_count];
 874	rqstp->rq_next_page = rqstp->rq_respages + 1;
 875
 876	/* Prevent svc_rdma_recv_ctxt_put() from releasing the
 877	 * pages in ctxt::rc_pages a second time.
 878	 */
 879	ctxt->rc_page_count = 0;
 880
 881	/* Finish constructing the RPC Call message. The exact
 882	 * procedure for that depends on what kind of RPC/RDMA
 883	 * chunks were provided by the client.
 884	 */
 885	rqstp->rq_arg = ctxt->rc_saved_arg;
 886	if (pcl_is_empty(&ctxt->rc_call_pcl)) {
 887		if (ctxt->rc_read_pcl.cl_count == 1)
 888			svc_rdma_read_complete_one(rqstp, ctxt);
 889		else
 890			svc_rdma_read_complete_multiple(rqstp, ctxt);
 891	} else {
 892		svc_rdma_read_complete_pzrc(rqstp, ctxt);
 893	}
 894
 895	trace_svcrdma_read_finished(&ctxt->rc_cid);
 896}
 897
 898/**
 899 * svc_rdma_recvfrom - Receive an RPC call
 900 * @rqstp: request structure into which to receive an RPC Call
 901 *
 902 * Returns:
 903 *	The positive number of bytes in the RPC Call message,
 904 *	%0 if there were no Calls ready to return,
 905 *	%-EINVAL if the Read chunk data is too large,
 906 *	%-ENOMEM if rdma_rw context pool was exhausted,
 907 *	%-ENOTCONN if posting failed (connection is lost),
 908 *	%-EIO if rdma_rw initialization failed (DMA mapping, etc).
 909 *
 910 * Called in a loop when XPT_DATA is set. XPT_DATA is cleared only
 911 * when there are no remaining ctxt's to process.
 912 *
 913 * The next ctxt is removed from the "receive" lists.
 914 *
 915 * - If the ctxt completes a Receive, then construct the Call
 916 *   message from the contents of the Receive buffer.
 917 *
 918 *   - If there are no Read chunks in this message, then finish
 919 *     assembling the Call message and return the number of bytes
 920 *     in the message.
 921 *
 922 *   - If there are Read chunks in this message, post Read WRs to
 923 *     pull that payload. When the Read WRs complete, build the
 924 *     full message and return the number of bytes in it.
 925 */
 926int svc_rdma_recvfrom(struct svc_rqst *rqstp)
 927{
 928	struct svc_xprt *xprt = rqstp->rq_xprt;
 929	struct svcxprt_rdma *rdma_xprt =
 930		container_of(xprt, struct svcxprt_rdma, sc_xprt);
 931	struct svc_rdma_recv_ctxt *ctxt;
 932	int ret;
 933
 934	/* Prevent svc_xprt_release() from releasing pages in rq_pages
 935	 * when returning 0 or an error.
 936	 */
 937	rqstp->rq_respages = rqstp->rq_pages;
 938	rqstp->rq_next_page = rqstp->rq_respages;
 939
 940	rqstp->rq_xprt_ctxt = NULL;
 941
 942	spin_lock(&rdma_xprt->sc_rq_dto_lock);
 943	ctxt = svc_rdma_next_recv_ctxt(&rdma_xprt->sc_read_complete_q);
 944	if (ctxt) {
 945		list_del(&ctxt->rc_list);
 946		spin_unlock(&rdma_xprt->sc_rq_dto_lock);
 947		svc_xprt_received(xprt);
 948		svc_rdma_read_complete(rqstp, ctxt);
 949		goto complete;
 950	}
 951	ctxt = svc_rdma_next_recv_ctxt(&rdma_xprt->sc_rq_dto_q);
 952	if (ctxt)
 953		list_del(&ctxt->rc_list);
 954	else
 955		/* No new incoming requests, terminate the loop */
 956		clear_bit(XPT_DATA, &xprt->xpt_flags);
 957	spin_unlock(&rdma_xprt->sc_rq_dto_lock);
 958
 959	/* Unblock the transport for the next receive */
 960	svc_xprt_received(xprt);
 961	if (!ctxt)
 962		return 0;
 963
 964	percpu_counter_inc(&svcrdma_stat_recv);
 965	ib_dma_sync_single_for_cpu(rdma_xprt->sc_pd->device,
 966				   ctxt->rc_recv_sge.addr, ctxt->rc_byte_len,
 967				   DMA_FROM_DEVICE);
 968	svc_rdma_build_arg_xdr(rqstp, ctxt);
 969
 970	ret = svc_rdma_xdr_decode_req(&rqstp->rq_arg, ctxt);
 971	if (ret < 0)
 972		goto out_err;
 973	if (ret == 0)
 974		goto out_drop;
 975
 976	if (svc_rdma_is_reverse_direction_reply(xprt, ctxt))
 977		goto out_backchannel;
 978
 979	svc_rdma_get_inv_rkey(rdma_xprt, ctxt);
 980
 981	if (!pcl_is_empty(&ctxt->rc_read_pcl) ||
 982	    !pcl_is_empty(&ctxt->rc_call_pcl))
 983		goto out_readlist;
 984
 985complete:
 986	rqstp->rq_xprt_ctxt = ctxt;
 987	rqstp->rq_prot = IPPROTO_MAX;
 988	svc_xprt_copy_addrs(rqstp, xprt);
 989	set_bit(RQ_SECURE, &rqstp->rq_flags);
 990	return rqstp->rq_arg.len;
 991
 992out_err:
 993	svc_rdma_send_error(rdma_xprt, ctxt, ret);
 994	svc_rdma_recv_ctxt_put(rdma_xprt, ctxt);
 995	return 0;
 996
 997out_readlist:
 998	/* This @rqstp is about to be recycled. Save the work
 999	 * already done constructing the Call message in rq_arg
1000	 * so it can be restored when the RDMA Reads have
1001	 * completed.
1002	 */
1003	ctxt->rc_saved_arg = rqstp->rq_arg;
1004
1005	ret = svc_rdma_process_read_list(rdma_xprt, rqstp, ctxt);
1006	if (ret < 0) {
1007		if (ret == -EINVAL)
1008			svc_rdma_send_error(rdma_xprt, ctxt, ret);
1009		svc_rdma_recv_ctxt_put(rdma_xprt, ctxt);
1010		svc_xprt_deferred_close(xprt);
1011		return ret;
1012	}
1013	return 0;
1014
1015out_backchannel:
1016	svc_rdma_handle_bc_reply(rqstp, ctxt);
1017out_drop:
1018	svc_rdma_recv_ctxt_put(rdma_xprt, ctxt);
1019	return 0;
1020}