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