net/sunrpc/xprtrdma/svc_rdma_recvfrom.c

   1 /*
   2  * Copyright (c) 2014 Open Grid Computing, Inc. All rights reserved.
   3  * Copyright (c) 2005-2006 Network Appliance, Inc. All rights reserved.
   4  *
   5  * This software is available to you under a choice of one of two
   6  * licenses.  You may choose to be licensed under the terms of the GNU
   7  * General Public License (GPL) Version 2, available from the file
   8  * COPYING in the main directory of this source tree, or the BSD-type
   9  * license below:
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  *
  15  *      Redistributions of source code must retain the above copyright
  16  *      notice, this list of conditions and the following disclaimer.
  17  *
  18  *      Redistributions in binary form must reproduce the above
  19  *      copyright notice, this list of conditions and the following
  20  *      disclaimer in the documentation and/or other materials provided
  21  *      with the distribution.
  22  *
  23  *      Neither the name of the Network Appliance, Inc. nor the names of
  24  *      its contributors may be used to endorse or promote products
  25  *      derived from this software without specific prior written
  26  *      permission.
  27  *
  28  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  29  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  30  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  31  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  32  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  33  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  34  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  35  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  36  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  37  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  38  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  39  *
  40  * Author: Tom Tucker <tom@opengridcomputing.com>
  41  */
  42
  43 #include <linux/sunrpc/debug.h>
  44 #include <linux/sunrpc/rpc_rdma.h>
  45 #include <linux/spinlock.h>
  46 #include <asm/unaligned.h>
  47 #include <rdma/ib_verbs.h>
  48 #include <rdma/rdma_cm.h>
  49 #include <linux/sunrpc/svc_rdma.h>
  50
  51 #define RPCDBG_FACILITY RPCDBG_SVCXPRT
  52
  53 /*
  54  * Replace the pages in the rq_argpages array with the pages from the SGE in
  55  * the RDMA_RECV completion. The SGL should contain full pages up until the
  56  * last one.
  57  */
  58 static void rdma_build_arg_xdr(struct svc_rqst *rqstp,
  59                                struct svc_rdma_op_ctxt *ctxt,
  60                                u32 byte_count)
  61 {
  62         struct rpcrdma_msg *rmsgp;
  63         struct page *page;
  64         u32 bc;
  65         int sge_no;
  66
  67         /* Swap the page in the SGE with the page in argpages */
  68         page = ctxt->pages[0];
  69         put_page(rqstp->rq_pages[0]);
  70         rqstp->rq_pages[0] = page;
  71
  72         /* Set up the XDR head */
  73         rqstp->rq_arg.head[0].iov_base = page_address(page);
  74         rqstp->rq_arg.head[0].iov_len =
  75                 min_t(size_t, byte_count, ctxt->sge[0].length);
  76         rqstp->rq_arg.len = byte_count;
  77         rqstp->rq_arg.buflen = byte_count;
  78
  79         /* Compute bytes past head in the SGL */
  80         bc = byte_count - rqstp->rq_arg.head[0].iov_len;
  81
  82         /* If data remains, store it in the pagelist */
  83         rqstp->rq_arg.page_len = bc;
  84         rqstp->rq_arg.page_base = 0;
  85
  86         /* RDMA_NOMSG: RDMA READ data should land just after RDMA RECV data */
  87         rmsgp = (struct rpcrdma_msg *)rqstp->rq_arg.head[0].iov_base;
  88         if (rmsgp->rm_type == rdma_nomsg)
  89                 rqstp->rq_arg.pages = &rqstp->rq_pages[0];
  90         else
  91                 rqstp->rq_arg.pages = &rqstp->rq_pages[1];
  92
  93         sge_no = 1;
  94         while (bc && sge_no < ctxt->count) {
  95                 page = ctxt->pages[sge_no];
  96                 put_page(rqstp->rq_pages[sge_no]);
  97                 rqstp->rq_pages[sge_no] = page;
  98                 bc -= min_t(u32, bc, ctxt->sge[sge_no].length);
  99                 rqstp->rq_arg.buflen += ctxt->sge[sge_no].length;
 100                 sge_no++;
 101         }
 102         rqstp->rq_respages = &rqstp->rq_pages[sge_no];
 103         rqstp->rq_next_page = rqstp->rq_respages + 1;
 104
 105         /* If not all pages were used from the SGL, free the remaining ones */
 106         bc = sge_no;
 107         while (sge_no < ctxt->count) {
 108                 page = ctxt->pages[sge_no++];
 109                 put_page(page);
 110         }
 111         ctxt->count = bc;
 112
 113         /* Set up tail */
 114         rqstp->rq_arg.tail[0].iov_base = NULL;
 115         rqstp->rq_arg.tail[0].iov_len = 0;
 116 }
 117
 118 /* Issue an RDMA_READ using the local lkey to map the data sink */
 119 int rdma_read_chunk_lcl(struct svcxprt_rdma *xprt,
 120                         struct svc_rqst *rqstp,
 121                         struct svc_rdma_op_ctxt *head,
 122                         int *page_no,
 123                         u32 *page_offset,
 124                         u32 rs_handle,
 125                         u32 rs_length,
 126                         u64 rs_offset,
 127                         bool last)
 128 {
 129         struct ib_rdma_wr read_wr;
 130         int pages_needed = PAGE_ALIGN(*page_offset + rs_length) >> PAGE_SHIFT;
 131         struct svc_rdma_op_ctxt *ctxt = svc_rdma_get_context(xprt);
 132         int ret, read, pno;
 133         u32 pg_off = *page_offset;
 134         u32 pg_no = *page_no;
 135
 136         ctxt->direction = DMA_FROM_DEVICE;
 137         ctxt->read_hdr = head;
 138         pages_needed = min_t(int, pages_needed, xprt->sc_max_sge_rd);
 139         read = min_t(int, (pages_needed << PAGE_SHIFT) - *page_offset,
 140                      rs_length);
 141
 142         for (pno = 0; pno < pages_needed; pno++) {
 143                 int len = min_t(int, rs_length, PAGE_SIZE - pg_off);
 144
 145                 head->arg.pages[pg_no] = rqstp->rq_arg.pages[pg_no];
 146                 head->arg.page_len += len;
 147
 148                 head->arg.len += len;
 149                 if (!pg_off)
 150                         head->count++;
 151                 rqstp->rq_respages = &rqstp->rq_arg.pages[pg_no+1];
 152                 rqstp->rq_next_page = rqstp->rq_respages + 1;
 153                 ctxt->sge[pno].addr =
 154                         ib_dma_map_page(xprt->sc_cm_id->device,
 155                                         head->arg.pages[pg_no], pg_off,
 156                                         PAGE_SIZE - pg_off,
 157                                         DMA_FROM_DEVICE);
 158                 ret = ib_dma_mapping_error(xprt->sc_cm_id->device,
 159                                            ctxt->sge[pno].addr);
 160                 if (ret)
 161                         goto err;
 162                 svc_rdma_count_mappings(xprt, ctxt);
 163
 164                 ctxt->sge[pno].lkey = xprt->sc_pd->local_dma_lkey;
 165                 ctxt->sge[pno].length = len;
 166                 ctxt->count++;
 167
 168                 /* adjust offset and wrap to next page if needed */
 169                 pg_off += len;
 170                 if (pg_off == PAGE_SIZE) {
 171                         pg_off = 0;
 172                         pg_no++;
 173                 }
 174                 rs_length -= len;
 175         }
 176
 177         if (last && rs_length == 0)
 178                 set_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags);
 179         else
 180                 clear_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags);
 181
 182         memset(&read_wr, 0, sizeof(read_wr));
 183         ctxt->cqe.done = svc_rdma_wc_read;
 184         read_wr.wr.wr_cqe = &ctxt->cqe;
 185         read_wr.wr.opcode = IB_WR_RDMA_READ;
 186         read_wr.wr.send_flags = IB_SEND_SIGNALED;
 187         read_wr.rkey = rs_handle;
 188         read_wr.remote_addr = rs_offset;
 189         read_wr.wr.sg_list = ctxt->sge;
 190         read_wr.wr.num_sge = pages_needed;
 191
 192         ret = svc_rdma_send(xprt, &read_wr.wr);
 193         if (ret) {
 194                 pr_err("svcrdma: Error %d posting RDMA_READ\n", ret);
 195                 set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
 196                 goto err;
 197         }
 198
 199         /* return current location in page array */
 200         *page_no = pg_no;
 201         *page_offset = pg_off;
 202         ret = read;
 203         atomic_inc(&rdma_stat_read);
 204         return ret;
 205  err:
 206         svc_rdma_unmap_dma(ctxt);
 207         svc_rdma_put_context(ctxt, 0);
 208         return ret;
 209 }
 210
 211 /* Issue an RDMA_READ using an FRMR to map the data sink */
 212 int rdma_read_chunk_frmr(struct svcxprt_rdma *xprt,
 213                          struct svc_rqst *rqstp,
 214                          struct svc_rdma_op_ctxt *head,
 215                          int *page_no,
 216                          u32 *page_offset,
 217                          u32 rs_handle,
 218                          u32 rs_length,
 219                          u64 rs_offset,
 220                          bool last)
 221 {
 222         struct ib_rdma_wr read_wr;
 223         struct ib_send_wr inv_wr;
 224         struct ib_reg_wr reg_wr;
 225         u8 key;
 226         int nents = PAGE_ALIGN(*page_offset + rs_length) >> PAGE_SHIFT;
 227         struct svc_rdma_op_ctxt *ctxt = svc_rdma_get_context(xprt);
 228         struct svc_rdma_fastreg_mr *frmr = svc_rdma_get_frmr(xprt);
 229         int ret, read, pno, dma_nents, n;
 230         u32 pg_off = *page_offset;
 231         u32 pg_no = *page_no;
 232
 233         if (IS_ERR(frmr))
 234                 return -ENOMEM;
 235
 236         ctxt->direction = DMA_FROM_DEVICE;
 237         ctxt->frmr = frmr;
 238         nents = min_t(unsigned int, nents, xprt->sc_frmr_pg_list_len);
 239         read = min_t(int, (nents << PAGE_SHIFT) - *page_offset, rs_length);
 240
 241         frmr->direction = DMA_FROM_DEVICE;
 242         frmr->access_flags = (IB_ACCESS_LOCAL_WRITE|IB_ACCESS_REMOTE_WRITE);
 243         frmr->sg_nents = nents;
 244
 245         for (pno = 0; pno < nents; pno++) {
 246                 int len = min_t(int, rs_length, PAGE_SIZE - pg_off);
 247
 248                 head->arg.pages[pg_no] = rqstp->rq_arg.pages[pg_no];
 249                 head->arg.page_len += len;
 250                 head->arg.len += len;
 251                 if (!pg_off)
 252                         head->count++;
 253
 254                 sg_set_page(&frmr->sg[pno], rqstp->rq_arg.pages[pg_no],
 255                             len, pg_off);
 256
 257                 rqstp->rq_respages = &rqstp->rq_arg.pages[pg_no+1];
 258                 rqstp->rq_next_page = rqstp->rq_respages + 1;
 259
 260                 /* adjust offset and wrap to next page if needed */
 261                 pg_off += len;
 262                 if (pg_off == PAGE_SIZE) {
 263                         pg_off = 0;
 264                         pg_no++;
 265                 }
 266                 rs_length -= len;
 267         }
 268
 269         if (last && rs_length == 0)
 270                 set_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags);
 271         else
 272                 clear_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags);
 273
 274         dma_nents = ib_dma_map_sg(xprt->sc_cm_id->device,
 275                                   frmr->sg, frmr->sg_nents,
 276                                   frmr->direction);
 277         if (!dma_nents) {
 278                 pr_err("svcrdma: failed to dma map sg %p\n",
 279                        frmr->sg);
 280                 return -ENOMEM;
 281         }
 282         atomic_inc(&xprt->sc_dma_used);
 283
 284         n = ib_map_mr_sg(frmr->mr, frmr->sg, frmr->sg_nents, NULL, PAGE_SIZE);
 285         if (unlikely(n != frmr->sg_nents)) {
 286                 pr_err("svcrdma: failed to map mr %p (%d/%d elements)\n",
 287                        frmr->mr, n, frmr->sg_nents);
 288                 return n < 0 ? n : -EINVAL;
 289         }
 290
 291         /* Bump the key */
 292         key = (u8)(frmr->mr->lkey & 0x000000FF);
 293         ib_update_fast_reg_key(frmr->mr, ++key);
 294
 295         ctxt->sge[0].addr = frmr->mr->iova;
 296         ctxt->sge[0].lkey = frmr->mr->lkey;
 297         ctxt->sge[0].length = frmr->mr->length;
 298         ctxt->count = 1;
 299         ctxt->read_hdr = head;
 300
 301         /* Prepare REG WR */
 302         ctxt->reg_cqe.done = svc_rdma_wc_reg;
 303         reg_wr.wr.wr_cqe = &ctxt->reg_cqe;
 304         reg_wr.wr.opcode = IB_WR_REG_MR;
 305         reg_wr.wr.send_flags = IB_SEND_SIGNALED;
 306         reg_wr.wr.num_sge = 0;
 307         reg_wr.mr = frmr->mr;
 308         reg_wr.key = frmr->mr->lkey;
 309         reg_wr.access = frmr->access_flags;
 310         reg_wr.wr.next = &read_wr.wr;
 311
 312         /* Prepare RDMA_READ */
 313         memset(&read_wr, 0, sizeof(read_wr));
 314         ctxt->cqe.done = svc_rdma_wc_read;
 315         read_wr.wr.wr_cqe = &ctxt->cqe;
 316         read_wr.wr.send_flags = IB_SEND_SIGNALED;
 317         read_wr.rkey = rs_handle;
 318         read_wr.remote_addr = rs_offset;
 319         read_wr.wr.sg_list = ctxt->sge;
 320         read_wr.wr.num_sge = 1;
 321         if (xprt->sc_dev_caps & SVCRDMA_DEVCAP_READ_W_INV) {
 322                 read_wr.wr.opcode = IB_WR_RDMA_READ_WITH_INV;
 323                 read_wr.wr.ex.invalidate_rkey = ctxt->frmr->mr->lkey;
 324         } else {
 325                 read_wr.wr.opcode = IB_WR_RDMA_READ;
 326                 read_wr.wr.next = &inv_wr;
 327                 /* Prepare invalidate */
 328                 memset(&inv_wr, 0, sizeof(inv_wr));
 329                 ctxt->inv_cqe.done = svc_rdma_wc_inv;
 330                 inv_wr.wr_cqe = &ctxt->inv_cqe;
 331                 inv_wr.opcode = IB_WR_LOCAL_INV;
 332                 inv_wr.send_flags = IB_SEND_SIGNALED | IB_SEND_FENCE;
 333                 inv_wr.ex.invalidate_rkey = frmr->mr->lkey;
 334         }
 335
 336         /* Post the chain */
 337         ret = svc_rdma_send(xprt, &reg_wr.wr);
 338         if (ret) {
 339                 pr_err("svcrdma: Error %d posting RDMA_READ\n", ret);
 340                 set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
 341                 goto err;
 342         }
 343
 344         /* return current location in page array */
 345         *page_no = pg_no;
 346         *page_offset = pg_off;
 347         ret = read;
 348         atomic_inc(&rdma_stat_read);
 349         return ret;
 350  err:
 351         svc_rdma_put_context(ctxt, 0);
 352         svc_rdma_put_frmr(xprt, frmr);
 353         return ret;
 354 }
 355
 356 static unsigned int
 357 rdma_rcl_chunk_count(struct rpcrdma_read_chunk *ch)
 358 {
 359         unsigned int count;
 360
 361         for (count = 0; ch->rc_discrim != xdr_zero; ch++)
 362                 count++;
 363         return count;
 364 }
 365
 366 /* If there was additional inline content, append it to the end of arg.pages.
 367  * Tail copy has to be done after the reader function has determined how many
 368  * pages are needed for RDMA READ.
 369  */
 370 static int
 371 rdma_copy_tail(struct svc_rqst *rqstp, struct svc_rdma_op_ctxt *head,
 372                u32 position, u32 byte_count, u32 page_offset, int page_no)
 373 {
 374         char *srcp, *destp;
 375         int ret;
 376
 377         ret = 0;
 378         srcp = head->arg.head[0].iov_base + position;
 379         byte_count = head->arg.head[0].iov_len - position;
 380         if (byte_count > PAGE_SIZE) {
 381                 dprintk("svcrdma: large tail unsupported\n");
 382                 return 0;
 383         }
 384
 385         /* Fit as much of the tail on the current page as possible */
 386         if (page_offset != PAGE_SIZE) {
 387                 destp = page_address(rqstp->rq_arg.pages[page_no]);
 388                 destp += page_offset;
 389                 while (byte_count--) {
 390                         *destp++ = *srcp++;
 391                         page_offset++;
 392                         if (page_offset == PAGE_SIZE && byte_count)
 393                                 goto more;
 394                 }
 395                 goto done;
 396         }
 397
 398 more:
 399         /* Fit the rest on the next page */
 400         page_no++;
 401         destp = page_address(rqstp->rq_arg.pages[page_no]);
 402         while (byte_count--)
 403                 *destp++ = *srcp++;
 404
 405         rqstp->rq_respages = &rqstp->rq_arg.pages[page_no+1];
 406         rqstp->rq_next_page = rqstp->rq_respages + 1;
 407
 408 done:
 409         byte_count = head->arg.head[0].iov_len - position;
 410         head->arg.page_len += byte_count;
 411         head->arg.len += byte_count;
 412         head->arg.buflen += byte_count;
 413         return 1;
 414 }
 415
 416 static int rdma_read_chunks(struct svcxprt_rdma *xprt,
 417                             struct rpcrdma_msg *rmsgp,
 418                             struct svc_rqst *rqstp,
 419                             struct svc_rdma_op_ctxt *head)
 420 {
 421         int page_no, ret;
 422         struct rpcrdma_read_chunk *ch;
 423         u32 handle, page_offset, byte_count;
 424         u32 position;
 425         u64 rs_offset;
 426         bool last;
 427
 428         /* If no read list is present, return 0 */
 429         ch = svc_rdma_get_read_chunk(rmsgp);
 430         if (!ch)
 431                 return 0;
 432
 433         if (rdma_rcl_chunk_count(ch) > RPCSVC_MAXPAGES)
 434                 return -EINVAL;
 435
 436         /* The request is completed when the RDMA_READs complete. The
 437          * head context keeps all the pages that comprise the
 438          * request.
 439          */
 440         head->arg.head[0] = rqstp->rq_arg.head[0];
 441         head->arg.tail[0] = rqstp->rq_arg.tail[0];
 442         head->hdr_count = head->count;
 443         head->arg.page_base = 0;
 444         head->arg.page_len = 0;
 445         head->arg.len = rqstp->rq_arg.len;
 446         head->arg.buflen = rqstp->rq_arg.buflen;
 447
 448         /* RDMA_NOMSG: RDMA READ data should land just after RDMA RECV data */
 449         position = be32_to_cpu(ch->rc_position);
 450         if (position == 0) {
 451                 head->arg.pages = &head->pages[0];
 452                 page_offset = head->byte_len;
 453         } else {
 454                 head->arg.pages = &head->pages[head->count];
 455                 page_offset = 0;
 456         }
 457
 458         ret = 0;
 459         page_no = 0;
 460         for (; ch->rc_discrim != xdr_zero; ch++) {
 461                 if (be32_to_cpu(ch->rc_position) != position)
 462                         goto err;
 463
 464                 handle = be32_to_cpu(ch->rc_target.rs_handle),
 465                 byte_count = be32_to_cpu(ch->rc_target.rs_length);
 466                 xdr_decode_hyper((__be32 *)&ch->rc_target.rs_offset,
 467                                  &rs_offset);
 468
 469                 while (byte_count > 0) {
 470                         last = (ch + 1)->rc_discrim == xdr_zero;
 471                         ret = xprt->sc_reader(xprt, rqstp, head,
 472                                               &page_no, &page_offset,
 473                                               handle, byte_count,
 474                                               rs_offset, last);
 475                         if (ret < 0)
 476                                 goto err;
 477                         byte_count -= ret;
 478                         rs_offset += ret;
 479                         head->arg.buflen += ret;
 480                 }
 481         }
 482
 483         /* Read list may need XDR round-up (see RFC 5666, s. 3.7) */
 484         if (page_offset & 3) {
 485                 u32 pad = 4 - (page_offset & 3);
 486
 487                 head->arg.tail[0].iov_len += pad;
 488                 head->arg.len += pad;
 489                 head->arg.buflen += pad;
 490                 page_offset += pad;
 491         }
 492
 493         ret = 1;
 494         if (position && position < head->arg.head[0].iov_len)
 495                 ret = rdma_copy_tail(rqstp, head, position,
 496                                      byte_count, page_offset, page_no);
 497         head->arg.head[0].iov_len = position;
 498         head->position = position;
 499
 500  err:
 501         /* Detach arg pages. svc_recv will replenish them */
 502         for (page_no = 0;
 503              &rqstp->rq_pages[page_no] < rqstp->rq_respages; page_no++)
 504                 rqstp->rq_pages[page_no] = NULL;
 505
 506         return ret;
 507 }
 508
 509 static void rdma_read_complete(struct svc_rqst *rqstp,
 510                                struct svc_rdma_op_ctxt *head)
 511 {
 512         int page_no;
 513
 514         /* Copy RPC pages */
 515         for (page_no = 0; page_no < head->count; page_no++) {
 516                 put_page(rqstp->rq_pages[page_no]);
 517                 rqstp->rq_pages[page_no] = head->pages[page_no];
 518         }
 519
 520         /* Adjustments made for RDMA_NOMSG type requests */
 521         if (head->position == 0) {
 522                 if (head->arg.len <= head->sge[0].length) {
 523                         head->arg.head[0].iov_len = head->arg.len -
 524                                                         head->byte_len;
 525                         head->arg.page_len = 0;
 526                 } else {
 527                         head->arg.head[0].iov_len = head->sge[0].length -
 528                                                                 head->byte_len;
 529                         head->arg.page_len = head->arg.len -
 530                                                 head->sge[0].length;
 531                 }
 532         }
 533
 534         /* Point rq_arg.pages past header */
 535         rqstp->rq_arg.pages = &rqstp->rq_pages[head->hdr_count];
 536         rqstp->rq_arg.page_len = head->arg.page_len;
 537         rqstp->rq_arg.page_base = head->arg.page_base;
 538
 539         /* rq_respages starts after the last arg page */
 540         rqstp->rq_respages = &rqstp->rq_pages[page_no];
 541         rqstp->rq_next_page = rqstp->rq_respages + 1;
 542
 543         /* Rebuild rq_arg head and tail. */
 544         rqstp->rq_arg.head[0] = head->arg.head[0];
 545         rqstp->rq_arg.tail[0] = head->arg.tail[0];
 546         rqstp->rq_arg.len = head->arg.len;
 547         rqstp->rq_arg.buflen = head->arg.buflen;
 548 }
 549
 550 /* By convention, backchannel calls arrive via rdma_msg type
 551  * messages, and never populate the chunk lists. This makes
 552  * the RPC/RDMA header small and fixed in size, so it is
 553  * straightforward to check the RPC header's direction field.
 554  */
 555 static bool
 556 svc_rdma_is_backchannel_reply(struct svc_xprt *xprt, struct rpcrdma_msg *rmsgp)
 557 {
 558         __be32 *p = (__be32 *)rmsgp;
 559
 560         if (!xprt->xpt_bc_xprt)
 561                 return false;
 562
 563         if (rmsgp->rm_type != rdma_msg)
 564                 return false;
 565         if (rmsgp->rm_body.rm_chunks[0] != xdr_zero)
 566                 return false;
 567         if (rmsgp->rm_body.rm_chunks[1] != xdr_zero)
 568                 return false;
 569         if (rmsgp->rm_body.rm_chunks[2] != xdr_zero)
 570                 return false;
 571
 572         /* sanity */
 573         if (p[7] != rmsgp->rm_xid)
 574                 return false;
 575         /* call direction */
 576         if (p[8] == cpu_to_be32(RPC_CALL))
 577                 return false;
 578
 579         return true;
 580 }
 581
 582 /*
 583  * Set up the rqstp thread context to point to the RQ buffer. If
 584  * necessary, pull additional data from the client with an RDMA_READ
 585  * request.
 586  */
 587 int svc_rdma_recvfrom(struct svc_rqst *rqstp)
 588 {
 589         struct svc_xprt *xprt = rqstp->rq_xprt;
 590         struct svcxprt_rdma *rdma_xprt =
 591                 container_of(xprt, struct svcxprt_rdma, sc_xprt);
 592         struct svc_rdma_op_ctxt *ctxt = NULL;
 593         struct rpcrdma_msg *rmsgp;
 594         int ret = 0;
 595
 596         dprintk("svcrdma: rqstp=%p\n", rqstp);
 597
 598         spin_lock_bh(&rdma_xprt->sc_rq_dto_lock);
 599         if (!list_empty(&rdma_xprt->sc_read_complete_q)) {
 600                 ctxt = list_entry(rdma_xprt->sc_read_complete_q.next,
 601                                   struct svc_rdma_op_ctxt,
 602                                   dto_q);
 603                 list_del_init(&ctxt->dto_q);
 604                 spin_unlock_bh(&rdma_xprt->sc_rq_dto_lock);
 605                 rdma_read_complete(rqstp, ctxt);
 606                 goto complete;
 607         } else if (!list_empty(&rdma_xprt->sc_rq_dto_q)) {
 608                 ctxt = list_entry(rdma_xprt->sc_rq_dto_q.next,
 609                                   struct svc_rdma_op_ctxt,
 610                                   dto_q);
 611                 list_del_init(&ctxt->dto_q);
 612         } else {
 613                 atomic_inc(&rdma_stat_rq_starve);
 614                 clear_bit(XPT_DATA, &xprt->xpt_flags);
 615                 ctxt = NULL;
 616         }
 617         spin_unlock_bh(&rdma_xprt->sc_rq_dto_lock);
 618         if (!ctxt) {
 619                 /* This is the EAGAIN path. The svc_recv routine will
 620                  * return -EAGAIN, the nfsd thread will go to call into
 621                  * svc_recv again and we shouldn't be on the active
 622                  * transport list
 623                  */
 624                 if (test_bit(XPT_CLOSE, &xprt->xpt_flags))
 625                         goto defer;
 626                 goto out;
 627         }
 628         dprintk("svcrdma: processing ctxt=%p on xprt=%p, rqstp=%p, status=%d\n",
 629                 ctxt, rdma_xprt, rqstp, ctxt->wc_status);
 630         atomic_inc(&rdma_stat_recv);
 631
 632         /* Build up the XDR from the receive buffers. */
 633         rdma_build_arg_xdr(rqstp, ctxt, ctxt->byte_len);
 634
 635         /* Decode the RDMA header. */
 636         rmsgp = (struct rpcrdma_msg *)rqstp->rq_arg.head[0].iov_base;
 637         ret = svc_rdma_xdr_decode_req(&rqstp->rq_arg);
 638         if (ret < 0)
 639                 goto out_err;
 640         if (ret == 0)
 641                 goto out_drop;
 642         rqstp->rq_xprt_hlen = ret;
 643
 644         if (svc_rdma_is_backchannel_reply(xprt, rmsgp)) {
 645                 ret = svc_rdma_handle_bc_reply(xprt->xpt_bc_xprt, rmsgp,
 646                                                &rqstp->rq_arg);
 647                 svc_rdma_put_context(ctxt, 0);
 648                 if (ret)
 649                         goto repost;
 650                 return ret;
 651         }
 652
 653         /* Read read-list data. */
 654         ret = rdma_read_chunks(rdma_xprt, rmsgp, rqstp, ctxt);
 655         if (ret > 0) {
 656                 /* read-list posted, defer until data received from client. */
 657                 goto defer;
 658         } else if (ret < 0) {
 659                 /* Post of read-list failed, free context. */
 660                 svc_rdma_put_context(ctxt, 1);
 661                 return 0;
 662         }
 663
 664 complete:
 665         ret = rqstp->rq_arg.head[0].iov_len
 666                 + rqstp->rq_arg.page_len
 667                 + rqstp->rq_arg.tail[0].iov_len;
 668         svc_rdma_put_context(ctxt, 0);
 669  out:
 670         dprintk("svcrdma: ret=%d, rq_arg.len=%u, "
 671                 "rq_arg.head[0].iov_base=%p, rq_arg.head[0].iov_len=%zd\n",
 672                 ret, rqstp->rq_arg.len,
 673                 rqstp->rq_arg.head[0].iov_base,
 674                 rqstp->rq_arg.head[0].iov_len);
 675         rqstp->rq_prot = IPPROTO_MAX;
 676         svc_xprt_copy_addrs(rqstp, xprt);
 677         return ret;
 678
 679 out_err:
 680         svc_rdma_send_error(rdma_xprt, rmsgp, ret);
 681         svc_rdma_put_context(ctxt, 0);
 682         return 0;
 683
 684 defer:
 685         return 0;
 686
 687 out_drop:
 688         svc_rdma_put_context(ctxt, 1);
 689 repost:
 690         return svc_rdma_repost_recv(rdma_xprt, GFP_KERNEL);
 691 }