block/replication.c

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