block/nbd-client.c

   1 /*
   2  * QEMU Block driver for  NBD
   3  *
   4  * Copyright (C) 2016 Red Hat, Inc.
   5  * Copyright (C) 2008 Bull S.A.S.
   6  *     Author: Laurent Vivier <Laurent.Vivier@bull.net>
   7  *
   8  * Some parts:
   9  *    Copyright (C) 2007 Anthony Liguori <anthony@codemonkey.ws>
  10  *
  11  * Permission is hereby granted, free of charge, to any person obtaining a copy
  12  * of this software and associated documentation files (the "Software"), to deal
  13  * in the Software without restriction, including without limitation the rights
  14  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  15  * copies of the Software, and to permit persons to whom the Software is
  16  * furnished to do so, subject to the following conditions:
  17  *
  18  * The above copyright notice and this permission notice shall be included in
  19  * all copies or substantial portions of the Software.
  20  *
  21  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  22  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  23  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  24  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  25  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  26  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  27  * THE SOFTWARE.
  28  */
  29
  30 #include "qemu/osdep.h"
  31 #include "qapi/error.h"
  32 #include "nbd-client.h"
  33
  34 #define HANDLE_TO_INDEX(bs, handle) ((handle) ^ (uint64_t)(intptr_t)(bs))
  35 #define INDEX_TO_HANDLE(bs, index)  ((index)  ^ (uint64_t)(intptr_t)(bs))
  36
  37 static void nbd_recv_coroutines_wake_all(NBDClientSession *s)
  38 {
  39     int i;
  40
  41     for (i = 0; i < MAX_NBD_REQUESTS; i++) {
  42         NBDClientRequest *req = &s->requests[i];
  43
  44         if (req->coroutine && req->receiving) {
  45             aio_co_wake(req->coroutine);
  46         }
  47     }
  48 }
  49
  50 static void nbd_teardown_connection(BlockDriverState *bs)
  51 {
  52     NBDClientSession *client = nbd_get_client_session(bs);
  53
  54     if (!client->ioc) { /* Already closed */
  55         return;
  56     }
  57
  58     /* finish any pending coroutines */
  59     qio_channel_shutdown(client->ioc,
  60                          QIO_CHANNEL_SHUTDOWN_BOTH,
  61                          NULL);
  62     BDRV_POLL_WHILE(bs, client->read_reply_co);
  63
  64     nbd_client_detach_aio_context(bs);
  65     object_unref(OBJECT(client->sioc));
  66     client->sioc = NULL;
  67     object_unref(OBJECT(client->ioc));
  68     client->ioc = NULL;
  69 }
  70
  71 static coroutine_fn void nbd_read_reply_entry(void *opaque)
  72 {
  73     NBDClientSession *s = opaque;
  74     uint64_t i;
  75     int ret = 0;
  76     Error *local_err = NULL;
  77
  78     while (!s->quit) {
  79         assert(s->reply.handle == 0);
  80         ret = nbd_receive_reply(s->ioc, &s->reply, &local_err);
  81         if (local_err) {
  82             error_report_err(local_err);
  83         }
  84         if (ret <= 0) {
  85             break;
  86         }
  87
  88         /* There's no need for a mutex on the receive side, because the
  89          * handler acts as a synchronization point and ensures that only
  90          * one coroutine is called until the reply finishes.
  91          */
  92         i = HANDLE_TO_INDEX(s, s->reply.handle);
  93         if (i >= MAX_NBD_REQUESTS ||
  94             !s->requests[i].coroutine ||
  95             !s->requests[i].receiving ||
  96             (nbd_reply_is_structured(&s->reply) && !s->info.structured_reply))
  97         {
  98             break;
  99         }
 100
 101         /* We're woken up again by the request itself.  Note that there
 102          * is no race between yielding and reentering read_reply_co.  This
 103          * is because:
 104          *
 105          * - if the request runs on the same AioContext, it is only
 106          *   entered after we yield
 107          *
 108          * - if the request runs on a different AioContext, reentering
 109          *   read_reply_co happens through a bottom half, which can only
 110          *   run after we yield.
 111          */
 112         aio_co_wake(s->requests[i].coroutine);
 113         qemu_coroutine_yield();
 114     }
 115
 116     s->quit = true;
 117     nbd_recv_coroutines_wake_all(s);
 118     s->read_reply_co = NULL;
 119 }
 120
 121 static int nbd_co_send_request(BlockDriverState *bs,
 122                                NBDRequest *request,
 123                                QEMUIOVector *qiov)
 124 {
 125     NBDClientSession *s = nbd_get_client_session(bs);
 126     int rc, i;
 127
 128     qemu_co_mutex_lock(&s->send_mutex);
 129     while (s->in_flight == MAX_NBD_REQUESTS) {
 130         qemu_co_queue_wait(&s->free_sema, &s->send_mutex);
 131     }
 132     s->in_flight++;
 133
 134     for (i = 0; i < MAX_NBD_REQUESTS; i++) {
 135         if (s->requests[i].coroutine == NULL) {
 136             break;
 137         }
 138     }
 139
 140     g_assert(qemu_in_coroutine());
 141     assert(i < MAX_NBD_REQUESTS);
 142
 143     s->requests[i].coroutine = qemu_coroutine_self();
 144     s->requests[i].offset = request->from;
 145     s->requests[i].receiving = false;
 146
 147     request->handle = INDEX_TO_HANDLE(s, i);
 148
 149     if (s->quit) {
 150         rc = -EIO;
 151         goto err;
 152     }
 153     if (!s->ioc) {
 154         rc = -EPIPE;
 155         goto err;
 156     }
 157
 158     if (qiov) {
 159         qio_channel_set_cork(s->ioc, true);
 160         rc = nbd_send_request(s->ioc, request);
 161         if (rc >= 0 && !s->quit) {
 162             if (qio_channel_writev_all(s->ioc, qiov->iov, qiov->niov,
 163                                        NULL) < 0) {
 164                 rc = -EIO;
 165             }
 166         } else if (rc >= 0) {
 167             rc = -EIO;
 168         }
 169         qio_channel_set_cork(s->ioc, false);
 170     } else {
 171         rc = nbd_send_request(s->ioc, request);
 172     }
 173
 174 err:
 175     if (rc < 0) {
 176         s->quit = true;
 177         s->requests[i].coroutine = NULL;
 178         s->in_flight--;
 179         qemu_co_queue_next(&s->free_sema);
 180     }
 181     qemu_co_mutex_unlock(&s->send_mutex);
 182     return rc;
 183 }
 184
 185 static inline uint16_t payload_advance16(uint8_t **payload)
 186 {
 187     *payload += 2;
 188     return lduw_be_p(*payload - 2);
 189 }
 190
 191 static inline uint32_t payload_advance32(uint8_t **payload)
 192 {
 193     *payload += 4;
 194     return ldl_be_p(*payload - 4);
 195 }
 196
 197 static inline uint64_t payload_advance64(uint8_t **payload)
 198 {
 199     *payload += 8;
 200     return ldq_be_p(*payload - 8);
 201 }
 202
 203 static int nbd_parse_offset_hole_payload(NBDStructuredReplyChunk *chunk,
 204                                          uint8_t *payload, uint64_t orig_offset,
 205                                          QEMUIOVector *qiov, Error **errp)
 206 {
 207     uint64_t offset;
 208     uint32_t hole_size;
 209
 210     if (chunk->length != sizeof(offset) + sizeof(hole_size)) {
 211         error_setg(errp, "Protocol error: invalid payload for "
 212                          "NBD_REPLY_TYPE_OFFSET_HOLE");
 213         return -EINVAL;
 214     }
 215
 216     offset = payload_advance64(&payload);
 217     hole_size = payload_advance32(&payload);
 218
 219     if (!hole_size || offset < orig_offset || hole_size > qiov->size ||
 220         offset > orig_offset + qiov->size - hole_size) {
 221         error_setg(errp, "Protocol error: server sent chunk exceeding requested"
 222                          " region");
 223         return -EINVAL;
 224     }
 225
 226     qemu_iovec_memset(qiov, offset - orig_offset, 0, hole_size);
 227
 228     return 0;
 229 }
 230
 231 /* nbd_parse_error_payload
 232  * on success @errp contains message describing nbd error reply
 233  */
 234 static int nbd_parse_error_payload(NBDStructuredReplyChunk *chunk,
 235                                    uint8_t *payload, int *request_ret,
 236                                    Error **errp)
 237 {
 238     uint32_t error;
 239     uint16_t message_size;
 240
 241     assert(chunk->type & (1 << 15));
 242
 243     if (chunk->length < sizeof(error) + sizeof(message_size)) {
 244         error_setg(errp,
 245                    "Protocol error: invalid payload for structured error");
 246         return -EINVAL;
 247     }
 248
 249     error = nbd_errno_to_system_errno(payload_advance32(&payload));
 250     if (error == 0) {
 251         error_setg(errp, "Protocol error: server sent structured error chunk "
 252                          "with error = 0");
 253         return -EINVAL;
 254     }
 255
 256     *request_ret = -error;
 257     message_size = payload_advance16(&payload);
 258
 259     if (message_size > chunk->length - sizeof(error) - sizeof(message_size)) {
 260         error_setg(errp, "Protocol error: server sent structured error chunk "
 261                          "with incorrect message size");
 262         return -EINVAL;
 263     }
 264
 265     /* TODO: Add a trace point to mention the server complaint */
 266
 267     /* TODO handle ERROR_OFFSET */
 268
 269     return 0;
 270 }
 271
 272 static int nbd_co_receive_offset_data_payload(NBDClientSession *s,
 273                                               uint64_t orig_offset,
 274                                               QEMUIOVector *qiov, Error **errp)
 275 {
 276     QEMUIOVector sub_qiov;
 277     uint64_t offset;
 278     size_t data_size;
 279     int ret;
 280     NBDStructuredReplyChunk *chunk = &s->reply.structured;
 281
 282     assert(nbd_reply_is_structured(&s->reply));
 283
 284     /* The NBD spec requires at least one byte of payload */
 285     if (chunk->length <= sizeof(offset)) {
 286         error_setg(errp, "Protocol error: invalid payload for "
 287                          "NBD_REPLY_TYPE_OFFSET_DATA");
 288         return -EINVAL;
 289     }
 290
 291     if (nbd_read(s->ioc, &offset, sizeof(offset), errp) < 0) {
 292         return -EIO;
 293     }
 294     be64_to_cpus(&offset);
 295
 296     data_size = chunk->length - sizeof(offset);
 297     assert(data_size);
 298     if (offset < orig_offset || data_size > qiov->size ||
 299         offset > orig_offset + qiov->size - data_size) {
 300         error_setg(errp, "Protocol error: server sent chunk exceeding requested"
 301                          " region");
 302         return -EINVAL;
 303     }
 304
 305     qemu_iovec_init(&sub_qiov, qiov->niov);
 306     qemu_iovec_concat(&sub_qiov, qiov, offset - orig_offset, data_size);
 307     ret = qio_channel_readv_all(s->ioc, sub_qiov.iov, sub_qiov.niov, errp);
 308     qemu_iovec_destroy(&sub_qiov);
 309
 310     return ret < 0 ? -EIO : 0;
 311 }
 312
 313 #define NBD_MAX_MALLOC_PAYLOAD 1000
 314 /* nbd_co_receive_structured_payload
 315  */
 316 static coroutine_fn int nbd_co_receive_structured_payload(
 317         NBDClientSession *s, void **payload, Error **errp)
 318 {
 319     int ret;
 320     uint32_t len;
 321
 322     assert(nbd_reply_is_structured(&s->reply));
 323
 324     len = s->reply.structured.length;
 325
 326     if (len == 0) {
 327         return 0;
 328     }
 329
 330     if (payload == NULL) {
 331         error_setg(errp, "Unexpected structured payload");
 332         return -EINVAL;
 333     }
 334
 335     if (len > NBD_MAX_MALLOC_PAYLOAD) {
 336         error_setg(errp, "Payload too large");
 337         return -EINVAL;
 338     }
 339
 340     *payload = g_new(char, len);
 341     ret = nbd_read(s->ioc, *payload, len, errp);
 342     if (ret < 0) {
 343         g_free(*payload);
 344         *payload = NULL;
 345         return ret;
 346     }
 347
 348     return 0;
 349 }
 350
 351 /* nbd_co_do_receive_one_chunk
 352  * for simple reply:
 353  *   set request_ret to received reply error
 354  *   if qiov is not NULL: read payload to @qiov
 355  * for structured reply chunk:
 356  *   if error chunk: read payload, set @request_ret, do not set @payload
 357  *   else if offset_data chunk: read payload data to @qiov, do not set @payload
 358  *   else: read payload to @payload
 359  *
 360  * If function fails, @errp contains corresponding error message, and the
 361  * connection with the server is suspect.  If it returns 0, then the
 362  * transaction succeeded (although @request_ret may be a negative errno
 363  * corresponding to the server's error reply), and errp is unchanged.
 364  */
 365 static coroutine_fn int nbd_co_do_receive_one_chunk(
 366         NBDClientSession *s, uint64_t handle, bool only_structured,
 367         int *request_ret, QEMUIOVector *qiov, void **payload, Error **errp)
 368 {
 369     int ret;
 370     int i = HANDLE_TO_INDEX(s, handle);
 371     void *local_payload = NULL;
 372     NBDStructuredReplyChunk *chunk;
 373
 374     if (payload) {
 375         *payload = NULL;
 376     }
 377     *request_ret = 0;
 378
 379     /* Wait until we're woken up by nbd_read_reply_entry.  */
 380     s->requests[i].receiving = true;
 381     qemu_coroutine_yield();
 382     s->requests[i].receiving = false;
 383     if (!s->ioc || s->quit) {
 384         error_setg(errp, "Connection closed");
 385         return -EIO;
 386     }
 387
 388     assert(s->reply.handle == handle);
 389
 390     if (nbd_reply_is_simple(&s->reply)) {
 391         if (only_structured) {
 392             error_setg(errp, "Protocol error: simple reply when structured "
 393                              "reply chunk was expected");
 394             return -EINVAL;
 395         }
 396
 397         *request_ret = -nbd_errno_to_system_errno(s->reply.simple.error);
 398         if (*request_ret < 0 || !qiov) {
 399             return 0;
 400         }
 401
 402         return qio_channel_readv_all(s->ioc, qiov->iov, qiov->niov,
 403                                      errp) < 0 ? -EIO : 0;
 404     }
 405
 406     /* handle structured reply chunk */
 407     assert(s->info.structured_reply);
 408     chunk = &s->reply.structured;
 409
 410     if (chunk->type == NBD_REPLY_TYPE_NONE) {
 411         if (!(chunk->flags & NBD_REPLY_FLAG_DONE)) {
 412             error_setg(errp, "Protocol error: NBD_REPLY_TYPE_NONE chunk without"
 413                        " NBD_REPLY_FLAG_DONE flag set");
 414             return -EINVAL;
 415         }
 416         if (chunk->length) {
 417             error_setg(errp, "Protocol error: NBD_REPLY_TYPE_NONE chunk with"
 418                        " nonzero length");
 419             return -EINVAL;
 420         }
 421         return 0;
 422     }
 423
 424     if (chunk->type == NBD_REPLY_TYPE_OFFSET_DATA) {
 425         if (!qiov) {
 426             error_setg(errp, "Unexpected NBD_REPLY_TYPE_OFFSET_DATA chunk");
 427             return -EINVAL;
 428         }
 429
 430         return nbd_co_receive_offset_data_payload(s, s->requests[i].offset,
 431                                                   qiov, errp);
 432     }
 433
 434     if (nbd_reply_type_is_error(chunk->type)) {
 435         payload = &local_payload;
 436     }
 437
 438     ret = nbd_co_receive_structured_payload(s, payload, errp);
 439     if (ret < 0) {
 440         return ret;
 441     }
 442
 443     if (nbd_reply_type_is_error(chunk->type)) {
 444         ret = nbd_parse_error_payload(chunk, local_payload, request_ret, errp);
 445         g_free(local_payload);
 446         return ret;
 447     }
 448
 449     return 0;
 450 }
 451
 452 /* nbd_co_receive_one_chunk
 453  * Read reply, wake up read_reply_co and set s->quit if needed.
 454  * Return value is a fatal error code or normal nbd reply error code
 455  */
 456 static coroutine_fn int nbd_co_receive_one_chunk(
 457         NBDClientSession *s, uint64_t handle, bool only_structured,
 458         QEMUIOVector *qiov, NBDReply *reply, void **payload, Error **errp)
 459 {
 460     int request_ret;
 461     int ret = nbd_co_do_receive_one_chunk(s, handle, only_structured,
 462                                           &request_ret, qiov, payload, errp);
 463
 464     if (ret < 0) {
 465         s->quit = true;
 466     } else {
 467         /* For assert at loop start in nbd_read_reply_entry */
 468         if (reply) {
 469             *reply = s->reply;
 470         }
 471         s->reply.handle = 0;
 472         ret = request_ret;
 473     }
 474
 475     if (s->read_reply_co) {
 476         aio_co_wake(s->read_reply_co);
 477     }
 478
 479     return ret;
 480 }
 481
 482 typedef struct NBDReplyChunkIter {
 483     int ret;
 484     bool fatal;
 485     Error *err;
 486     bool done, only_structured;
 487 } NBDReplyChunkIter;
 488
 489 static void nbd_iter_error(NBDReplyChunkIter *iter, bool fatal,
 490                            int ret, Error **local_err)
 491 {
 492     assert(ret < 0);
 493
 494     if ((fatal && !iter->fatal) || iter->ret == 0) {
 495         if (iter->ret != 0) {
 496             error_free(iter->err);
 497             iter->err = NULL;
 498         }
 499         iter->fatal = fatal;
 500         iter->ret = ret;
 501         error_propagate(&iter->err, *local_err);
 502     } else {
 503         error_free(*local_err);
 504     }
 505
 506     *local_err = NULL;
 507 }
 508
 509 /* NBD_FOREACH_REPLY_CHUNK
 510  */
 511 #define NBD_FOREACH_REPLY_CHUNK(s, iter, handle, structured, \
 512                                 qiov, reply, payload) \
 513     for (iter = (NBDReplyChunkIter) { .only_structured = structured }; \
 514          nbd_reply_chunk_iter_receive(s, &iter, handle, qiov, reply, payload);)
 515
 516 /* nbd_reply_chunk_iter_receive
 517  */
 518 static bool nbd_reply_chunk_iter_receive(NBDClientSession *s,
 519                                          NBDReplyChunkIter *iter,
 520                                          uint64_t handle,
 521                                          QEMUIOVector *qiov, NBDReply *reply,
 522                                          void **payload)
 523 {
 524     int ret;
 525     NBDReply local_reply;
 526     NBDStructuredReplyChunk *chunk;
 527     Error *local_err = NULL;
 528     if (s->quit) {
 529         error_setg(&local_err, "Connection closed");
 530         nbd_iter_error(iter, true, -EIO, &local_err);
 531         goto break_loop;
 532     }
 533
 534     if (iter->done) {
 535         /* Previous iteration was last. */
 536         goto break_loop;
 537     }
 538
 539     if (reply == NULL) {
 540         reply = &local_reply;
 541     }
 542
 543     ret = nbd_co_receive_one_chunk(s, handle, iter->only_structured,
 544                                    qiov, reply, payload, &local_err);
 545     if (ret < 0) {
 546         /* If it is a fatal error s->quit is set by nbd_co_receive_one_chunk */
 547         nbd_iter_error(iter, s->quit, ret, &local_err);
 548     }
 549
 550     /* Do not execute the body of NBD_FOREACH_REPLY_CHUNK for simple reply. */
 551     if (nbd_reply_is_simple(&s->reply) || s->quit) {
 552         goto break_loop;
 553     }
 554
 555     chunk = &reply->structured;
 556     iter->only_structured = true;
 557
 558     if (chunk->type == NBD_REPLY_TYPE_NONE) {
 559         /* NBD_REPLY_FLAG_DONE is already checked in nbd_co_receive_one_chunk */
 560         assert(chunk->flags & NBD_REPLY_FLAG_DONE);
 561         goto break_loop;
 562     }
 563
 564     if (chunk->flags & NBD_REPLY_FLAG_DONE) {
 565         /* This iteration is last. */
 566         iter->done = true;
 567     }
 568
 569     /* Execute the loop body */
 570     return true;
 571
 572 break_loop:
 573     s->requests[HANDLE_TO_INDEX(s, handle)].coroutine = NULL;
 574
 575     qemu_co_mutex_lock(&s->send_mutex);
 576     s->in_flight--;
 577     qemu_co_queue_next(&s->free_sema);
 578     qemu_co_mutex_unlock(&s->send_mutex);
 579
 580     return false;
 581 }
 582
 583 static int nbd_co_receive_return_code(NBDClientSession *s, uint64_t handle,
 584                                       Error **errp)
 585 {
 586     NBDReplyChunkIter iter;
 587
 588     NBD_FOREACH_REPLY_CHUNK(s, iter, handle, false, NULL, NULL, NULL) {
 589         /* nbd_reply_chunk_iter_receive does all the work */
 590     }
 591
 592     error_propagate(errp, iter.err);
 593     return iter.ret;
 594 }
 595
 596 static int nbd_co_receive_cmdread_reply(NBDClientSession *s, uint64_t handle,
 597                                         uint64_t offset, QEMUIOVector *qiov,
 598                                         Error **errp)
 599 {
 600     NBDReplyChunkIter iter;
 601     NBDReply reply;
 602     void *payload = NULL;
 603     Error *local_err = NULL;
 604
 605     NBD_FOREACH_REPLY_CHUNK(s, iter, handle, s->info.structured_reply,
 606                             qiov, &reply, &payload)
 607     {
 608         int ret;
 609         NBDStructuredReplyChunk *chunk = &reply.structured;
 610
 611         assert(nbd_reply_is_structured(&reply));
 612
 613         switch (chunk->type) {
 614         case NBD_REPLY_TYPE_OFFSET_DATA:
 615             /* special cased in nbd_co_receive_one_chunk, data is already
 616              * in qiov */
 617             break;
 618         case NBD_REPLY_TYPE_OFFSET_HOLE:
 619             ret = nbd_parse_offset_hole_payload(&reply.structured, payload,
 620                                                 offset, qiov, &local_err);
 621             if (ret < 0) {
 622                 s->quit = true;
 623                 nbd_iter_error(&iter, true, ret, &local_err);
 624             }
 625             break;
 626         default:
 627             if (!nbd_reply_type_is_error(chunk->type)) {
 628                 /* not allowed reply type */
 629                 s->quit = true;
 630                 error_setg(&local_err,
 631                            "Unexpected reply type: %d (%s) for CMD_READ",
 632                            chunk->type, nbd_reply_type_lookup(chunk->type));
 633                 nbd_iter_error(&iter, true, -EINVAL, &local_err);
 634             }
 635         }
 636
 637         g_free(payload);
 638         payload = NULL;
 639     }
 640
 641     error_propagate(errp, iter.err);
 642     return iter.ret;
 643 }
 644
 645 static int nbd_co_request(BlockDriverState *bs, NBDRequest *request,
 646                           QEMUIOVector *write_qiov)
 647 {
 648     int ret;
 649     Error *local_err = NULL;
 650     NBDClientSession *client = nbd_get_client_session(bs);
 651
 652     assert(request->type != NBD_CMD_READ);
 653     if (write_qiov) {
 654         assert(request->type == NBD_CMD_WRITE);
 655         assert(request->len == iov_size(write_qiov->iov, write_qiov->niov));
 656     } else {
 657         assert(request->type != NBD_CMD_WRITE);
 658     }
 659     ret = nbd_co_send_request(bs, request, write_qiov);
 660     if (ret < 0) {
 661         return ret;
 662     }
 663
 664     ret = nbd_co_receive_return_code(client, request->handle, &local_err);
 665     if (local_err) {
 666         error_report_err(local_err);
 667     }
 668     return ret;
 669 }
 670
 671 int nbd_client_co_preadv(BlockDriverState *bs, uint64_t offset,
 672                          uint64_t bytes, QEMUIOVector *qiov, int flags)
 673 {
 674     int ret;
 675     Error *local_err = NULL;
 676     NBDClientSession *client = nbd_get_client_session(bs);
 677     NBDRequest request = {
 678         .type = NBD_CMD_READ,
 679         .from = offset,
 680         .len = bytes,
 681     };
 682
 683     assert(bytes <= NBD_MAX_BUFFER_SIZE);
 684     assert(!flags);
 685
 686     if (!bytes) {
 687         return 0;
 688     }
 689     ret = nbd_co_send_request(bs, &request, NULL);
 690     if (ret < 0) {
 691         return ret;
 692     }
 693
 694     ret = nbd_co_receive_cmdread_reply(client, request.handle, offset, qiov,
 695                                        &local_err);
 696     if (local_err) {
 697         error_report_err(local_err);
 698     }
 699     return ret;
 700 }
 701
 702 int nbd_client_co_pwritev(BlockDriverState *bs, uint64_t offset,
 703                           uint64_t bytes, QEMUIOVector *qiov, int flags)
 704 {
 705     NBDClientSession *client = nbd_get_client_session(bs);
 706     NBDRequest request = {
 707         .type = NBD_CMD_WRITE,
 708         .from = offset,
 709         .len = bytes,
 710     };
 711
 712     assert(!(client->info.flags & NBD_FLAG_READ_ONLY));
 713     if (flags & BDRV_REQ_FUA) {
 714         assert(client->info.flags & NBD_FLAG_SEND_FUA);
 715         request.flags |= NBD_CMD_FLAG_FUA;
 716     }
 717
 718     assert(bytes <= NBD_MAX_BUFFER_SIZE);
 719
 720     if (!bytes) {
 721         return 0;
 722     }
 723     return nbd_co_request(bs, &request, qiov);
 724 }
 725
 726 int nbd_client_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
 727                                 int bytes, BdrvRequestFlags flags)
 728 {
 729     NBDClientSession *client = nbd_get_client_session(bs);
 730     NBDRequest request = {
 731         .type = NBD_CMD_WRITE_ZEROES,
 732         .from = offset,
 733         .len = bytes,
 734     };
 735
 736     assert(!(client->info.flags & NBD_FLAG_READ_ONLY));
 737     if (!(client->info.flags & NBD_FLAG_SEND_WRITE_ZEROES)) {
 738         return -ENOTSUP;
 739     }
 740
 741     if (flags & BDRV_REQ_FUA) {
 742         assert(client->info.flags & NBD_FLAG_SEND_FUA);
 743         request.flags |= NBD_CMD_FLAG_FUA;
 744     }
 745     if (!(flags & BDRV_REQ_MAY_UNMAP)) {
 746         request.flags |= NBD_CMD_FLAG_NO_HOLE;
 747     }
 748
 749     if (!bytes) {
 750         return 0;
 751     }
 752     return nbd_co_request(bs, &request, NULL);
 753 }
 754
 755 int nbd_client_co_flush(BlockDriverState *bs)
 756 {
 757     NBDClientSession *client = nbd_get_client_session(bs);
 758     NBDRequest request = { .type = NBD_CMD_FLUSH };
 759
 760     if (!(client->info.flags & NBD_FLAG_SEND_FLUSH)) {
 761         return 0;
 762     }
 763
 764     request.from = 0;
 765     request.len = 0;
 766
 767     return nbd_co_request(bs, &request, NULL);
 768 }
 769
 770 int nbd_client_co_pdiscard(BlockDriverState *bs, int64_t offset, int bytes)
 771 {
 772     NBDClientSession *client = nbd_get_client_session(bs);
 773     NBDRequest request = {
 774         .type = NBD_CMD_TRIM,
 775         .from = offset,
 776         .len = bytes,
 777     };
 778
 779     assert(!(client->info.flags & NBD_FLAG_READ_ONLY));
 780     if (!(client->info.flags & NBD_FLAG_SEND_TRIM) || !bytes) {
 781         return 0;
 782     }
 783
 784     return nbd_co_request(bs, &request, NULL);
 785 }
 786
 787 void nbd_client_detach_aio_context(BlockDriverState *bs)
 788 {
 789     NBDClientSession *client = nbd_get_client_session(bs);
 790     qio_channel_detach_aio_context(QIO_CHANNEL(client->ioc));
 791 }
 792
 793 void nbd_client_attach_aio_context(BlockDriverState *bs,
 794                                    AioContext *new_context)
 795 {
 796     NBDClientSession *client = nbd_get_client_session(bs);
 797     qio_channel_attach_aio_context(QIO_CHANNEL(client->ioc), new_context);
 798     aio_co_schedule(new_context, client->read_reply_co);
 799 }
 800
 801 void nbd_client_close(BlockDriverState *bs)
 802 {
 803     NBDClientSession *client = nbd_get_client_session(bs);
 804     NBDRequest request = { .type = NBD_CMD_DISC };
 805
 806     if (client->ioc == NULL) {
 807         return;
 808     }
 809
 810     nbd_send_request(client->ioc, &request);
 811
 812     nbd_teardown_connection(bs);
 813 }
 814
 815 int nbd_client_init(BlockDriverState *bs,
 816                     QIOChannelSocket *sioc,
 817                     const char *export,
 818                     QCryptoTLSCreds *tlscreds,
 819                     const char *hostname,
 820                     Error **errp)
 821 {
 822     NBDClientSession *client = nbd_get_client_session(bs);
 823     int ret;
 824
 825     /* NBD handshake */
 826     logout("session init %s\n", export);
 827     qio_channel_set_blocking(QIO_CHANNEL(sioc), true, NULL);
 828
 829     client->info.request_sizes = true;
 830     client->info.structured_reply = true;
 831     ret = nbd_receive_negotiate(QIO_CHANNEL(sioc), export,
 832                                 tlscreds, hostname,
 833                                 &client->ioc, &client->info, errp);
 834     if (ret < 0) {
 835         logout("Failed to negotiate with the NBD server\n");
 836         return ret;
 837     }
 838     if (client->info.flags & NBD_FLAG_READ_ONLY &&
 839         !bdrv_is_read_only(bs)) {
 840         error_setg(errp,
 841                    "request for write access conflicts with read-only export");
 842         return -EACCES;
 843     }
 844     if (client->info.flags & NBD_FLAG_SEND_FUA) {
 845         bs->supported_write_flags = BDRV_REQ_FUA;
 846         bs->supported_zero_flags |= BDRV_REQ_FUA;
 847     }
 848     if (client->info.flags & NBD_FLAG_SEND_WRITE_ZEROES) {
 849         bs->supported_zero_flags |= BDRV_REQ_MAY_UNMAP;
 850     }
 851
 852     qemu_co_mutex_init(&client->send_mutex);
 853     qemu_co_queue_init(&client->free_sema);
 854     client->sioc = sioc;
 855     object_ref(OBJECT(client->sioc));
 856
 857     if (!client->ioc) {
 858         client->ioc = QIO_CHANNEL(sioc);
 859         object_ref(OBJECT(client->ioc));
 860     }
 861
 862     /* Now that we're connected, set the socket to be non-blocking and
 863      * kick the reply mechanism.  */
 864     qio_channel_set_blocking(QIO_CHANNEL(sioc), false, NULL);
 865     client->read_reply_co = qemu_coroutine_create(nbd_read_reply_entry, client);
 866     nbd_client_attach_aio_context(bs, bdrv_get_aio_context(bs));
 867
 868     logout("Established connection with NBD server\n");
 869     return 0;
 870 }