1 /* 2 * Replication Block filter 3 * 4 * Copyright (c) 2016 HUAWEI TECHNOLOGIES CO., LTD. 5 * Copyright (c) 2016 Intel Corporation 6 * Copyright (c) 2016 FUJITSU LIMITED 7 * 8 * Author: 9 * Wen Congyang <wency@cn.fujitsu.com> 10 * 11 * This work is licensed under the terms of the GNU GPL, version 2 or later. 12 * See the COPYING file in the top-level directory. 13 */ 14 15 #include "qemu/osdep.h" 16 #include "qemu/module.h" 17 #include "qemu/option.h" 18 #include "block/nbd.h" 19 #include "block/blockjob.h" 20 #include "block/block_int.h" 21 #include "block/block_backup.h" 22 #include "sysemu/block-backend.h" 23 #include "qapi/error.h" 24 #include "qapi/qmp/qdict.h" 25 #include "replication.h" 26 27 typedef enum { 28 BLOCK_REPLICATION_NONE, /* block replication is not started */ 29 BLOCK_REPLICATION_RUNNING, /* block replication is running */ 30 BLOCK_REPLICATION_FAILOVER, /* failover is running in background */ 31 BLOCK_REPLICATION_FAILOVER_FAILED, /* failover failed */ 32 BLOCK_REPLICATION_DONE, /* block replication is done */ 33 } ReplicationStage; 34 35 typedef struct BDRVReplicationState { 36 ReplicationMode mode; 37 ReplicationStage stage; 38 BdrvChild *active_disk; 39 BlockJob *commit_job; 40 BdrvChild *hidden_disk; 41 BdrvChild *secondary_disk; 42 BlockJob *backup_job; 43 char *top_id; 44 ReplicationState *rs; 45 Error *blocker; 46 bool orig_hidden_read_only; 47 bool orig_secondary_read_only; 48 int error; 49 } BDRVReplicationState; 50 51 static void replication_start(ReplicationState *rs, ReplicationMode mode, 52 Error **errp); 53 static void replication_do_checkpoint(ReplicationState *rs, Error **errp); 54 static void replication_get_error(ReplicationState *rs, Error **errp); 55 static void replication_stop(ReplicationState *rs, bool failover, 56 Error **errp); 57 58 #define REPLICATION_MODE "mode" 59 #define REPLICATION_TOP_ID "top-id" 60 static QemuOptsList replication_runtime_opts = { 61 .name = "replication", 62 .head = QTAILQ_HEAD_INITIALIZER(replication_runtime_opts.head), 63 .desc = { 64 { 65 .name = REPLICATION_MODE, 66 .type = QEMU_OPT_STRING, 67 }, 68 { 69 .name = REPLICATION_TOP_ID, 70 .type = QEMU_OPT_STRING, 71 }, 72 { /* end of list */ } 73 }, 74 }; 75 76 static ReplicationOps replication_ops = { 77 .start = replication_start, 78 .checkpoint = replication_do_checkpoint, 79 .get_error = replication_get_error, 80 .stop = replication_stop, 81 }; 82 83 static int replication_open(BlockDriverState *bs, QDict *options, 84 int flags, Error **errp) 85 { 86 int ret; 87 BDRVReplicationState *s = bs->opaque; 88 QemuOpts *opts = NULL; 89 const char *mode; 90 const char *top_id; 91 92 bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds, 93 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, 94 false, errp); 95 if (!bs->file) { 96 return -EINVAL; 97 } 98 99 ret = -EINVAL; 100 opts = qemu_opts_create(&replication_runtime_opts, NULL, 0, &error_abort); 101 if (!qemu_opts_absorb_qdict(opts, options, errp)) { 102 goto fail; 103 } 104 105 mode = qemu_opt_get(opts, REPLICATION_MODE); 106 if (!mode) { 107 error_setg(errp, "Missing the option mode"); 108 goto fail; 109 } 110 111 if (!strcmp(mode, "primary")) { 112 s->mode = REPLICATION_MODE_PRIMARY; 113 top_id = qemu_opt_get(opts, REPLICATION_TOP_ID); 114 if (top_id) { 115 error_setg(errp, 116 "The primary side does not support option top-id"); 117 goto fail; 118 } 119 } else if (!strcmp(mode, "secondary")) { 120 s->mode = REPLICATION_MODE_SECONDARY; 121 top_id = qemu_opt_get(opts, REPLICATION_TOP_ID); 122 s->top_id = g_strdup(top_id); 123 if (!s->top_id) { 124 error_setg(errp, "Missing the option top-id"); 125 goto fail; 126 } 127 } else { 128 error_setg(errp, 129 "The option mode's value should be primary or secondary"); 130 goto fail; 131 } 132 133 s->rs = replication_new(bs, &replication_ops); 134 135 ret = 0; 136 137 fail: 138 qemu_opts_del(opts); 139 return ret; 140 } 141 142 static void replication_close(BlockDriverState *bs) 143 { 144 BDRVReplicationState *s = bs->opaque; 145 Job *commit_job; 146 147 if (s->stage == BLOCK_REPLICATION_RUNNING) { 148 replication_stop(s->rs, false, NULL); 149 } 150 if (s->stage == BLOCK_REPLICATION_FAILOVER) { 151 commit_job = &s->commit_job->job; 152 assert(commit_job->aio_context == qemu_get_current_aio_context()); 153 job_cancel_sync(commit_job); 154 } 155 156 if (s->mode == REPLICATION_MODE_SECONDARY) { 157 g_free(s->top_id); 158 } 159 160 replication_remove(s->rs); 161 } 162 163 static void replication_child_perm(BlockDriverState *bs, BdrvChild *c, 164 BdrvChildRole role, 165 BlockReopenQueue *reopen_queue, 166 uint64_t perm, uint64_t shared, 167 uint64_t *nperm, uint64_t *nshared) 168 { 169 *nperm = BLK_PERM_CONSISTENT_READ; 170 if ((bs->open_flags & (BDRV_O_INACTIVE | BDRV_O_RDWR)) == BDRV_O_RDWR) { 171 *nperm |= BLK_PERM_WRITE; 172 } 173 *nshared = BLK_PERM_CONSISTENT_READ 174 | BLK_PERM_WRITE 175 | BLK_PERM_WRITE_UNCHANGED; 176 return; 177 } 178 179 static int64_t replication_getlength(BlockDriverState *bs) 180 { 181 return bdrv_getlength(bs->file->bs); 182 } 183 184 static int replication_get_io_status(BDRVReplicationState *s) 185 { 186 switch (s->stage) { 187 case BLOCK_REPLICATION_NONE: 188 return -EIO; 189 case BLOCK_REPLICATION_RUNNING: 190 return 0; 191 case BLOCK_REPLICATION_FAILOVER: 192 return s->mode == REPLICATION_MODE_PRIMARY ? -EIO : 0; 193 case BLOCK_REPLICATION_FAILOVER_FAILED: 194 return s->mode == REPLICATION_MODE_PRIMARY ? -EIO : 1; 195 case BLOCK_REPLICATION_DONE: 196 /* 197 * active commit job completes, and active disk and secondary_disk 198 * is swapped, so we can operate bs->file directly 199 */ 200 return s->mode == REPLICATION_MODE_PRIMARY ? -EIO : 0; 201 default: 202 abort(); 203 } 204 } 205 206 static int replication_return_value(BDRVReplicationState *s, int ret) 207 { 208 if (s->mode == REPLICATION_MODE_SECONDARY) { 209 return ret; 210 } 211 212 if (ret < 0) { 213 s->error = ret; 214 ret = 0; 215 } 216 217 return ret; 218 } 219 220 static coroutine_fn int replication_co_readv(BlockDriverState *bs, 221 int64_t sector_num, 222 int remaining_sectors, 223 QEMUIOVector *qiov) 224 { 225 BDRVReplicationState *s = bs->opaque; 226 int ret; 227 228 if (s->mode == REPLICATION_MODE_PRIMARY) { 229 /* We only use it to forward primary write requests */ 230 return -EIO; 231 } 232 233 ret = replication_get_io_status(s); 234 if (ret < 0) { 235 return ret; 236 } 237 238 ret = bdrv_co_preadv(bs->file, sector_num * BDRV_SECTOR_SIZE, 239 remaining_sectors * BDRV_SECTOR_SIZE, qiov, 0); 240 241 return replication_return_value(s, ret); 242 } 243 244 static coroutine_fn int replication_co_writev(BlockDriverState *bs, 245 int64_t sector_num, 246 int remaining_sectors, 247 QEMUIOVector *qiov, 248 int flags) 249 { 250 BDRVReplicationState *s = bs->opaque; 251 QEMUIOVector hd_qiov; 252 uint64_t bytes_done = 0; 253 BdrvChild *top = bs->file; 254 BdrvChild *base = s->secondary_disk; 255 BdrvChild *target; 256 int ret; 257 int64_t n; 258 259 assert(!flags); 260 ret = replication_get_io_status(s); 261 if (ret < 0) { 262 goto out; 263 } 264 265 if (ret == 0) { 266 ret = bdrv_co_pwritev(top, sector_num * BDRV_SECTOR_SIZE, 267 remaining_sectors * BDRV_SECTOR_SIZE, qiov, 0); 268 return replication_return_value(s, ret); 269 } 270 271 /* 272 * Failover failed, only write to active disk if the sectors 273 * have already been allocated in active disk/hidden disk. 274 */ 275 qemu_iovec_init(&hd_qiov, qiov->niov); 276 while (remaining_sectors > 0) { 277 int64_t count; 278 279 ret = bdrv_is_allocated_above(top->bs, base->bs, false, 280 sector_num * BDRV_SECTOR_SIZE, 281 remaining_sectors * BDRV_SECTOR_SIZE, 282 &count); 283 if (ret < 0) { 284 goto out1; 285 } 286 287 assert(QEMU_IS_ALIGNED(count, BDRV_SECTOR_SIZE)); 288 n = count >> BDRV_SECTOR_BITS; 289 qemu_iovec_reset(&hd_qiov); 290 qemu_iovec_concat(&hd_qiov, qiov, bytes_done, count); 291 292 target = ret ? top : base; 293 ret = bdrv_co_pwritev(target, sector_num * BDRV_SECTOR_SIZE, 294 n * BDRV_SECTOR_SIZE, &hd_qiov, 0); 295 if (ret < 0) { 296 goto out1; 297 } 298 299 remaining_sectors -= n; 300 sector_num += n; 301 bytes_done += count; 302 } 303 304 out1: 305 qemu_iovec_destroy(&hd_qiov); 306 out: 307 return ret; 308 } 309 310 static void secondary_do_checkpoint(BDRVReplicationState *s, Error **errp) 311 { 312 Error *local_err = NULL; 313 int ret; 314 315 if (!s->backup_job) { 316 error_setg(errp, "Backup job was cancelled unexpectedly"); 317 return; 318 } 319 320 backup_do_checkpoint(s->backup_job, &local_err); 321 if (local_err) { 322 error_propagate(errp, local_err); 323 return; 324 } 325 326 if (!s->active_disk->bs->drv) { 327 error_setg(errp, "Active disk %s is ejected", 328 s->active_disk->bs->node_name); 329 return; 330 } 331 332 ret = bdrv_make_empty(s->active_disk, errp); 333 if (ret < 0) { 334 return; 335 } 336 337 if (!s->hidden_disk->bs->drv) { 338 error_setg(errp, "Hidden disk %s is ejected", 339 s->hidden_disk->bs->node_name); 340 return; 341 } 342 343 BlockBackend *blk = blk_new(qemu_get_current_aio_context(), 344 BLK_PERM_WRITE, BLK_PERM_ALL); 345 blk_insert_bs(blk, s->hidden_disk->bs, &local_err); 346 if (local_err) { 347 error_propagate(errp, local_err); 348 blk_unref(blk); 349 return; 350 } 351 352 ret = blk_make_empty(blk, errp); 353 blk_unref(blk); 354 if (ret < 0) { 355 return; 356 } 357 } 358 359 /* This function is supposed to be called twice: 360 * first with writable = true, then with writable = false. 361 * The first call puts s->hidden_disk and s->secondary_disk in 362 * r/w mode, and the second puts them back in their original state. 363 */ 364 static void reopen_backing_file(BlockDriverState *bs, bool writable, 365 Error **errp) 366 { 367 BDRVReplicationState *s = bs->opaque; 368 BlockReopenQueue *reopen_queue = NULL; 369 370 if (writable) { 371 s->orig_hidden_read_only = bdrv_is_read_only(s->hidden_disk->bs); 372 s->orig_secondary_read_only = bdrv_is_read_only(s->secondary_disk->bs); 373 } 374 375 bdrv_subtree_drained_begin(s->hidden_disk->bs); 376 bdrv_subtree_drained_begin(s->secondary_disk->bs); 377 378 if (s->orig_hidden_read_only) { 379 QDict *opts = qdict_new(); 380 qdict_put_bool(opts, BDRV_OPT_READ_ONLY, !writable); 381 reopen_queue = bdrv_reopen_queue(reopen_queue, s->hidden_disk->bs, 382 opts, true); 383 } 384 385 if (s->orig_secondary_read_only) { 386 QDict *opts = qdict_new(); 387 qdict_put_bool(opts, BDRV_OPT_READ_ONLY, !writable); 388 reopen_queue = bdrv_reopen_queue(reopen_queue, s->secondary_disk->bs, 389 opts, true); 390 } 391 392 if (reopen_queue) { 393 bdrv_reopen_multiple(reopen_queue, errp); 394 } 395 396 bdrv_subtree_drained_end(s->hidden_disk->bs); 397 bdrv_subtree_drained_end(s->secondary_disk->bs); 398 } 399 400 static void backup_job_cleanup(BlockDriverState *bs) 401 { 402 BDRVReplicationState *s = bs->opaque; 403 BlockDriverState *top_bs; 404 405 s->backup_job = NULL; 406 407 top_bs = bdrv_lookup_bs(s->top_id, s->top_id, NULL); 408 if (!top_bs) { 409 return; 410 } 411 bdrv_op_unblock_all(top_bs, s->blocker); 412 error_free(s->blocker); 413 reopen_backing_file(bs, false, NULL); 414 } 415 416 static void backup_job_completed(void *opaque, int ret) 417 { 418 BlockDriverState *bs = opaque; 419 BDRVReplicationState *s = bs->opaque; 420 421 if (s->stage != BLOCK_REPLICATION_FAILOVER) { 422 /* The backup job is cancelled unexpectedly */ 423 s->error = -EIO; 424 } 425 426 backup_job_cleanup(bs); 427 } 428 429 static bool check_top_bs(BlockDriverState *top_bs, BlockDriverState *bs) 430 { 431 BdrvChild *child; 432 433 /* The bs itself is the top_bs */ 434 if (top_bs == bs) { 435 return true; 436 } 437 438 /* Iterate over top_bs's children */ 439 QLIST_FOREACH(child, &top_bs->children, next) { 440 if (child->bs == bs || check_top_bs(child->bs, bs)) { 441 return true; 442 } 443 } 444 445 return false; 446 } 447 448 static void replication_start(ReplicationState *rs, ReplicationMode mode, 449 Error **errp) 450 { 451 BlockDriverState *bs = rs->opaque; 452 BDRVReplicationState *s; 453 BlockDriverState *top_bs; 454 int64_t active_length, hidden_length, disk_length; 455 AioContext *aio_context; 456 Error *local_err = NULL; 457 458 aio_context = bdrv_get_aio_context(bs); 459 aio_context_acquire(aio_context); 460 s = bs->opaque; 461 462 if (s->stage == BLOCK_REPLICATION_DONE || 463 s->stage == BLOCK_REPLICATION_FAILOVER) { 464 /* 465 * This case happens when a secondary is promoted to primary. 466 * Ignore the request because the secondary side of replication 467 * doesn't have to do anything anymore. 468 */ 469 aio_context_release(aio_context); 470 return; 471 } 472 473 if (s->stage != BLOCK_REPLICATION_NONE) { 474 error_setg(errp, "Block replication is running or done"); 475 aio_context_release(aio_context); 476 return; 477 } 478 479 if (s->mode != mode) { 480 error_setg(errp, "The parameter mode's value is invalid, needs %d," 481 " but got %d", s->mode, mode); 482 aio_context_release(aio_context); 483 return; 484 } 485 486 switch (s->mode) { 487 case REPLICATION_MODE_PRIMARY: 488 break; 489 case REPLICATION_MODE_SECONDARY: 490 s->active_disk = bs->file; 491 if (!s->active_disk || !s->active_disk->bs || 492 !s->active_disk->bs->backing) { 493 error_setg(errp, "Active disk doesn't have backing file"); 494 aio_context_release(aio_context); 495 return; 496 } 497 498 s->hidden_disk = s->active_disk->bs->backing; 499 if (!s->hidden_disk->bs || !s->hidden_disk->bs->backing) { 500 error_setg(errp, "Hidden disk doesn't have backing file"); 501 aio_context_release(aio_context); 502 return; 503 } 504 505 s->secondary_disk = s->hidden_disk->bs->backing; 506 if (!s->secondary_disk->bs || !bdrv_has_blk(s->secondary_disk->bs)) { 507 error_setg(errp, "The secondary disk doesn't have block backend"); 508 aio_context_release(aio_context); 509 return; 510 } 511 512 /* verify the length */ 513 active_length = bdrv_getlength(s->active_disk->bs); 514 hidden_length = bdrv_getlength(s->hidden_disk->bs); 515 disk_length = bdrv_getlength(s->secondary_disk->bs); 516 if (active_length < 0 || hidden_length < 0 || disk_length < 0 || 517 active_length != hidden_length || hidden_length != disk_length) { 518 error_setg(errp, "Active disk, hidden disk, secondary disk's length" 519 " are not the same"); 520 aio_context_release(aio_context); 521 return; 522 } 523 524 /* Must be true, or the bdrv_getlength() calls would have failed */ 525 assert(s->active_disk->bs->drv && s->hidden_disk->bs->drv); 526 527 if (!s->active_disk->bs->drv->bdrv_make_empty || 528 !s->hidden_disk->bs->drv->bdrv_make_empty) { 529 error_setg(errp, 530 "Active disk or hidden disk doesn't support make_empty"); 531 aio_context_release(aio_context); 532 return; 533 } 534 535 /* reopen the backing file in r/w mode */ 536 reopen_backing_file(bs, true, &local_err); 537 if (local_err) { 538 error_propagate(errp, local_err); 539 aio_context_release(aio_context); 540 return; 541 } 542 543 /* start backup job now */ 544 error_setg(&s->blocker, 545 "Block device is in use by internal backup job"); 546 547 top_bs = bdrv_lookup_bs(s->top_id, s->top_id, NULL); 548 if (!top_bs || !bdrv_is_root_node(top_bs) || 549 !check_top_bs(top_bs, bs)) { 550 error_setg(errp, "No top_bs or it is invalid"); 551 reopen_backing_file(bs, false, NULL); 552 aio_context_release(aio_context); 553 return; 554 } 555 bdrv_op_block_all(top_bs, s->blocker); 556 bdrv_op_unblock(top_bs, BLOCK_OP_TYPE_DATAPLANE, s->blocker); 557 558 s->backup_job = backup_job_create( 559 NULL, s->secondary_disk->bs, s->hidden_disk->bs, 560 0, MIRROR_SYNC_MODE_NONE, NULL, 0, false, NULL, 561 BLOCKDEV_ON_ERROR_REPORT, 562 BLOCKDEV_ON_ERROR_REPORT, JOB_INTERNAL, 563 backup_job_completed, bs, NULL, &local_err); 564 if (local_err) { 565 error_propagate(errp, local_err); 566 backup_job_cleanup(bs); 567 aio_context_release(aio_context); 568 return; 569 } 570 job_start(&s->backup_job->job); 571 break; 572 default: 573 aio_context_release(aio_context); 574 abort(); 575 } 576 577 s->stage = BLOCK_REPLICATION_RUNNING; 578 579 if (s->mode == REPLICATION_MODE_SECONDARY) { 580 secondary_do_checkpoint(s, errp); 581 } 582 583 s->error = 0; 584 aio_context_release(aio_context); 585 } 586 587 static void replication_do_checkpoint(ReplicationState *rs, Error **errp) 588 { 589 BlockDriverState *bs = rs->opaque; 590 BDRVReplicationState *s; 591 AioContext *aio_context; 592 593 aio_context = bdrv_get_aio_context(bs); 594 aio_context_acquire(aio_context); 595 s = bs->opaque; 596 597 if (s->stage == BLOCK_REPLICATION_DONE || 598 s->stage == BLOCK_REPLICATION_FAILOVER) { 599 /* 600 * This case happens when a secondary was promoted to primary. 601 * Ignore the request because the secondary side of replication 602 * doesn't have to do anything anymore. 603 */ 604 aio_context_release(aio_context); 605 return; 606 } 607 608 if (s->mode == REPLICATION_MODE_SECONDARY) { 609 secondary_do_checkpoint(s, errp); 610 } 611 aio_context_release(aio_context); 612 } 613 614 static void replication_get_error(ReplicationState *rs, Error **errp) 615 { 616 BlockDriverState *bs = rs->opaque; 617 BDRVReplicationState *s; 618 AioContext *aio_context; 619 620 aio_context = bdrv_get_aio_context(bs); 621 aio_context_acquire(aio_context); 622 s = bs->opaque; 623 624 if (s->stage == BLOCK_REPLICATION_NONE) { 625 error_setg(errp, "Block replication is not running"); 626 aio_context_release(aio_context); 627 return; 628 } 629 630 if (s->error) { 631 error_setg(errp, "I/O error occurred"); 632 aio_context_release(aio_context); 633 return; 634 } 635 aio_context_release(aio_context); 636 } 637 638 static void replication_done(void *opaque, int ret) 639 { 640 BlockDriverState *bs = opaque; 641 BDRVReplicationState *s = bs->opaque; 642 643 if (ret == 0) { 644 s->stage = BLOCK_REPLICATION_DONE; 645 646 s->active_disk = NULL; 647 s->secondary_disk = NULL; 648 s->hidden_disk = NULL; 649 s->error = 0; 650 } else { 651 s->stage = BLOCK_REPLICATION_FAILOVER_FAILED; 652 s->error = -EIO; 653 } 654 } 655 656 static void replication_stop(ReplicationState *rs, bool failover, Error **errp) 657 { 658 BlockDriverState *bs = rs->opaque; 659 BDRVReplicationState *s; 660 AioContext *aio_context; 661 662 aio_context = bdrv_get_aio_context(bs); 663 aio_context_acquire(aio_context); 664 s = bs->opaque; 665 666 if (s->stage == BLOCK_REPLICATION_DONE || 667 s->stage == BLOCK_REPLICATION_FAILOVER) { 668 /* 669 * This case happens when a secondary was promoted to primary. 670 * Ignore the request because the secondary side of replication 671 * doesn't have to do anything anymore. 672 */ 673 aio_context_release(aio_context); 674 return; 675 } 676 677 if (s->stage != BLOCK_REPLICATION_RUNNING) { 678 error_setg(errp, "Block replication is not running"); 679 aio_context_release(aio_context); 680 return; 681 } 682 683 switch (s->mode) { 684 case REPLICATION_MODE_PRIMARY: 685 s->stage = BLOCK_REPLICATION_DONE; 686 s->error = 0; 687 break; 688 case REPLICATION_MODE_SECONDARY: 689 /* 690 * This BDS will be closed, and the job should be completed 691 * before the BDS is closed, because we will access hidden 692 * disk, secondary disk in backup_job_completed(). 693 */ 694 if (s->backup_job) { 695 job_cancel_sync(&s->backup_job->job); 696 } 697 698 if (!failover) { 699 secondary_do_checkpoint(s, errp); 700 s->stage = BLOCK_REPLICATION_DONE; 701 aio_context_release(aio_context); 702 return; 703 } 704 705 s->stage = BLOCK_REPLICATION_FAILOVER; 706 s->commit_job = commit_active_start( 707 NULL, s->active_disk->bs, s->secondary_disk->bs, 708 JOB_INTERNAL, 0, BLOCKDEV_ON_ERROR_REPORT, 709 NULL, replication_done, bs, true, errp); 710 break; 711 default: 712 aio_context_release(aio_context); 713 abort(); 714 } 715 aio_context_release(aio_context); 716 } 717 718 static const char *const replication_strong_runtime_opts[] = { 719 REPLICATION_MODE, 720 REPLICATION_TOP_ID, 721 722 NULL 723 }; 724 725 static BlockDriver bdrv_replication = { 726 .format_name = "replication", 727 .instance_size = sizeof(BDRVReplicationState), 728 729 .bdrv_open = replication_open, 730 .bdrv_close = replication_close, 731 .bdrv_child_perm = replication_child_perm, 732 733 .bdrv_getlength = replication_getlength, 734 .bdrv_co_readv = replication_co_readv, 735 .bdrv_co_writev = replication_co_writev, 736 737 .is_filter = true, 738 739 .has_variable_length = true, 740 .strong_runtime_opts = replication_strong_runtime_opts, 741 }; 742 743 static void bdrv_replication_init(void) 744 { 745 bdrv_register(&bdrv_replication); 746 } 747 748 block_init(bdrv_replication_init); 749