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 "block/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     BlockJob *commit_job;
  39     BdrvChild *hidden_disk;
  40     BdrvChild *secondary_disk;
  41     BlockJob *backup_job;
  42     char *top_id;
  43     ReplicationState *rs;
  44     Error *blocker;
  45     bool orig_hidden_read_only;
  46     bool orig_secondary_read_only;
  47     int error;
  48 } BDRVReplicationState;
  49
  50 static void replication_start(ReplicationState *rs, ReplicationMode mode,
  51                               Error **errp);
  52 static void replication_do_checkpoint(ReplicationState *rs, Error **errp);
  53 static void replication_get_error(ReplicationState *rs, Error **errp);
  54 static void replication_stop(ReplicationState *rs, bool failover,
  55                              Error **errp);
  56
  57 #define REPLICATION_MODE        "mode"
  58 #define REPLICATION_TOP_ID      "top-id"
  59 static QemuOptsList replication_runtime_opts = {
  60     .name = "replication",
  61     .head = QTAILQ_HEAD_INITIALIZER(replication_runtime_opts.head),
  62     .desc = {
  63         {
  64             .name = REPLICATION_MODE,
  65             .type = QEMU_OPT_STRING,
  66         },
  67         {
  68             .name = REPLICATION_TOP_ID,
  69             .type = QEMU_OPT_STRING,
  70         },
  71         { /* end of list */ }
  72     },
  73 };
  74
  75 static ReplicationOps replication_ops = {
  76     .start = replication_start,
  77     .checkpoint = replication_do_checkpoint,
  78     .get_error = replication_get_error,
  79     .stop = replication_stop,
  80 };
  81
  82 static int replication_open(BlockDriverState *bs, QDict *options,
  83                             int flags, Error **errp)
  84 {
  85     int ret;
  86     BDRVReplicationState *s = bs->opaque;
  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_of_bds,
  92                                BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
  93                                false, errp);
  94     if (!bs->file) {
  95         return -EINVAL;
  96     }
  97
  98     ret = -EINVAL;
  99     opts = qemu_opts_create(&replication_runtime_opts, NULL, 0, &error_abort);
 100     if (!qemu_opts_absorb_qdict(opts, options, errp)) {
 101         goto fail;
 102     }
 103
 104     mode = qemu_opt_get(opts, REPLICATION_MODE);
 105     if (!mode) {
 106         error_setg(errp, "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(errp,
 115                        "The primary side does not support option top-id");
 116             goto fail;
 117         }
 118     } else if (!strcmp(mode, "secondary")) {
 119         s->mode = REPLICATION_MODE_SECONDARY;
 120         top_id = qemu_opt_get(opts, REPLICATION_TOP_ID);
 121         s->top_id = g_strdup(top_id);
 122         if (!s->top_id) {
 123             error_setg(errp, "Missing the option top-id");
 124             goto fail;
 125         }
 126     } else {
 127         error_setg(errp,
 128                    "The option mode's value should be primary or secondary");
 129         goto fail;
 130     }
 131
 132     s->rs = replication_new(bs, &replication_ops);
 133
 134     ret = 0;
 135
 136 fail:
 137     qemu_opts_del(opts);
 138     return ret;
 139 }
 140
 141 static void replication_close(BlockDriverState *bs)
 142 {
 143     BDRVReplicationState *s = bs->opaque;
 144     Job *commit_job;
 145     GLOBAL_STATE_CODE();
 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, false);
 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     if (role & BDRV_CHILD_PRIMARY) {
 170         *nperm = BLK_PERM_CONSISTENT_READ;
 171     } else {
 172         *nperm = 0;
 173     }
 174
 175     if ((bs->open_flags & (BDRV_O_INACTIVE | BDRV_O_RDWR)) == BDRV_O_RDWR) {
 176         *nperm |= BLK_PERM_WRITE;
 177     }
 178     *nshared = BLK_PERM_CONSISTENT_READ
 179                | BLK_PERM_WRITE
 180                | BLK_PERM_WRITE_UNCHANGED;
 181     return;
 182 }
 183
 184 static int64_t replication_getlength(BlockDriverState *bs)
 185 {
 186     return bdrv_getlength(bs->file->bs);
 187 }
 188
 189 static int replication_get_io_status(BDRVReplicationState *s)
 190 {
 191     switch (s->stage) {
 192     case BLOCK_REPLICATION_NONE:
 193         return -EIO;
 194     case BLOCK_REPLICATION_RUNNING:
 195         return 0;
 196     case BLOCK_REPLICATION_FAILOVER:
 197         return s->mode == REPLICATION_MODE_PRIMARY ? -EIO : 0;
 198     case BLOCK_REPLICATION_FAILOVER_FAILED:
 199         return s->mode == REPLICATION_MODE_PRIMARY ? -EIO : 1;
 200     case BLOCK_REPLICATION_DONE:
 201         /*
 202          * active commit job completes, and active disk and secondary_disk
 203          * is swapped, so we can operate bs->file directly
 204          */
 205         return s->mode == REPLICATION_MODE_PRIMARY ? -EIO : 0;
 206     default:
 207         abort();
 208     }
 209 }
 210
 211 static int replication_return_value(BDRVReplicationState *s, int ret)
 212 {
 213     if (s->mode == REPLICATION_MODE_SECONDARY) {
 214         return ret;
 215     }
 216
 217     if (ret < 0) {
 218         s->error = ret;
 219         ret = 0;
 220     }
 221
 222     return ret;
 223 }
 224
 225 static coroutine_fn int replication_co_readv(BlockDriverState *bs,
 226                                              int64_t sector_num,
 227                                              int remaining_sectors,
 228                                              QEMUIOVector *qiov)
 229 {
 230     BDRVReplicationState *s = bs->opaque;
 231     int ret;
 232
 233     if (s->mode == REPLICATION_MODE_PRIMARY) {
 234         /* We only use it to forward primary write requests */
 235         return -EIO;
 236     }
 237
 238     ret = replication_get_io_status(s);
 239     if (ret < 0) {
 240         return ret;
 241     }
 242
 243     ret = bdrv_co_preadv(bs->file, sector_num * BDRV_SECTOR_SIZE,
 244                          remaining_sectors * BDRV_SECTOR_SIZE, qiov, 0);
 245
 246     return replication_return_value(s, ret);
 247 }
 248
 249 static coroutine_fn int replication_co_writev(BlockDriverState *bs,
 250                                               int64_t sector_num,
 251                                               int remaining_sectors,
 252                                               QEMUIOVector *qiov,
 253                                               int flags)
 254 {
 255     BDRVReplicationState *s = bs->opaque;
 256     QEMUIOVector hd_qiov;
 257     uint64_t bytes_done = 0;
 258     BdrvChild *top = bs->file;
 259     BdrvChild *base = s->secondary_disk;
 260     BdrvChild *target;
 261     int ret;
 262     int64_t n;
 263
 264     assert(!flags);
 265     ret = replication_get_io_status(s);
 266     if (ret < 0) {
 267         goto out;
 268     }
 269
 270     if (ret == 0) {
 271         ret = bdrv_co_pwritev(top, sector_num * BDRV_SECTOR_SIZE,
 272                               remaining_sectors * BDRV_SECTOR_SIZE, qiov, 0);
 273         return replication_return_value(s, ret);
 274     }
 275
 276     /*
 277      * Failover failed, only write to active disk if the sectors
 278      * have already been allocated in active disk/hidden disk.
 279      */
 280     qemu_iovec_init(&hd_qiov, qiov->niov);
 281     while (remaining_sectors > 0) {
 282         int64_t count;
 283
 284         ret = bdrv_is_allocated_above(top->bs, base->bs, false,
 285                                       sector_num * BDRV_SECTOR_SIZE,
 286                                       remaining_sectors * BDRV_SECTOR_SIZE,
 287                                       &count);
 288         if (ret < 0) {
 289             goto out1;
 290         }
 291
 292         assert(QEMU_IS_ALIGNED(count, BDRV_SECTOR_SIZE));
 293         n = count >> BDRV_SECTOR_BITS;
 294         qemu_iovec_reset(&hd_qiov);
 295         qemu_iovec_concat(&hd_qiov, qiov, bytes_done, count);
 296
 297         target = ret ? top : base;
 298         ret = bdrv_co_pwritev(target, sector_num * BDRV_SECTOR_SIZE,
 299                               n * BDRV_SECTOR_SIZE, &hd_qiov, 0);
 300         if (ret < 0) {
 301             goto out1;
 302         }
 303
 304         remaining_sectors -= n;
 305         sector_num += n;
 306         bytes_done += count;
 307     }
 308
 309 out1:
 310     qemu_iovec_destroy(&hd_qiov);
 311 out:
 312     return ret;
 313 }
 314
 315 static void secondary_do_checkpoint(BlockDriverState *bs, Error **errp)
 316 {
 317     BDRVReplicationState *s = bs->opaque;
 318     BdrvChild *active_disk = bs->file;
 319     Error *local_err = NULL;
 320     int ret;
 321
 322     if (!s->backup_job) {
 323         error_setg(errp, "Backup job was cancelled unexpectedly");
 324         return;
 325     }
 326
 327     backup_do_checkpoint(s->backup_job, &local_err);
 328     if (local_err) {
 329         error_propagate(errp, local_err);
 330         return;
 331     }
 332
 333     if (!active_disk->bs->drv) {
 334         error_setg(errp, "Active disk %s is ejected",
 335                    active_disk->bs->node_name);
 336         return;
 337     }
 338
 339     ret = bdrv_make_empty(active_disk, errp);
 340     if (ret < 0) {
 341         return;
 342     }
 343
 344     if (!s->hidden_disk->bs->drv) {
 345         error_setg(errp, "Hidden disk %s is ejected",
 346                    s->hidden_disk->bs->node_name);
 347         return;
 348     }
 349
 350     ret = bdrv_make_empty(s->hidden_disk, errp);
 351     if (ret < 0) {
 352         return;
 353     }
 354 }
 355
 356 /* This function is supposed to be called twice:
 357  * first with writable = true, then with writable = false.
 358  * The first call puts s->hidden_disk and s->secondary_disk in
 359  * r/w mode, and the second puts them back in their original state.
 360  */
 361 static void reopen_backing_file(BlockDriverState *bs, bool writable,
 362                                 Error **errp)
 363 {
 364     BDRVReplicationState *s = bs->opaque;
 365     BdrvChild *hidden_disk, *secondary_disk;
 366     BlockReopenQueue *reopen_queue = NULL;
 367
 368     /*
 369      * s->hidden_disk and s->secondary_disk may not be set yet, as they will
 370      * only be set after the children are writable.
 371      */
 372     hidden_disk = bs->file->bs->backing;
 373     secondary_disk = hidden_disk->bs->backing;
 374
 375     if (writable) {
 376         s->orig_hidden_read_only = bdrv_is_read_only(hidden_disk->bs);
 377         s->orig_secondary_read_only = bdrv_is_read_only(secondary_disk->bs);
 378     }
 379
 380     bdrv_subtree_drained_begin(hidden_disk->bs);
 381     bdrv_subtree_drained_begin(secondary_disk->bs);
 382
 383     if (s->orig_hidden_read_only) {
 384         QDict *opts = qdict_new();
 385         qdict_put_bool(opts, BDRV_OPT_READ_ONLY, !writable);
 386         reopen_queue = bdrv_reopen_queue(reopen_queue, hidden_disk->bs,
 387                                          opts, true);
 388     }
 389
 390     if (s->orig_secondary_read_only) {
 391         QDict *opts = qdict_new();
 392         qdict_put_bool(opts, BDRV_OPT_READ_ONLY, !writable);
 393         reopen_queue = bdrv_reopen_queue(reopen_queue, secondary_disk->bs,
 394                                          opts, true);
 395     }
 396
 397     if (reopen_queue) {
 398         AioContext *ctx = bdrv_get_aio_context(bs);
 399         if (ctx != qemu_get_aio_context()) {
 400             aio_context_release(ctx);
 401         }
 402         bdrv_reopen_multiple(reopen_queue, errp);
 403         if (ctx != qemu_get_aio_context()) {
 404             aio_context_acquire(ctx);
 405         }
 406     }
 407
 408     bdrv_subtree_drained_end(hidden_disk->bs);
 409     bdrv_subtree_drained_end(secondary_disk->bs);
 410 }
 411
 412 static void backup_job_cleanup(BlockDriverState *bs)
 413 {
 414     BDRVReplicationState *s = bs->opaque;
 415     BlockDriverState *top_bs;
 416
 417     s->backup_job = NULL;
 418
 419     top_bs = bdrv_lookup_bs(s->top_id, s->top_id, NULL);
 420     if (!top_bs) {
 421         return;
 422     }
 423     bdrv_op_unblock_all(top_bs, s->blocker);
 424     error_free(s->blocker);
 425     reopen_backing_file(bs, false, NULL);
 426 }
 427
 428 static void backup_job_completed(void *opaque, int ret)
 429 {
 430     BlockDriverState *bs = opaque;
 431     BDRVReplicationState *s = bs->opaque;
 432
 433     if (s->stage != BLOCK_REPLICATION_FAILOVER) {
 434         /* The backup job is cancelled unexpectedly */
 435         s->error = -EIO;
 436     }
 437
 438     backup_job_cleanup(bs);
 439 }
 440
 441 static bool check_top_bs(BlockDriverState *top_bs, BlockDriverState *bs)
 442 {
 443     BdrvChild *child;
 444
 445     /* The bs itself is the top_bs */
 446     if (top_bs == bs) {
 447         return true;
 448     }
 449
 450     /* Iterate over top_bs's children */
 451     QLIST_FOREACH(child, &top_bs->children, next) {
 452         if (child->bs == bs || check_top_bs(child->bs, bs)) {
 453             return true;
 454         }
 455     }
 456
 457     return false;
 458 }
 459
 460 static void replication_start(ReplicationState *rs, ReplicationMode mode,
 461                               Error **errp)
 462 {
 463     BlockDriverState *bs = rs->opaque;
 464     BDRVReplicationState *s;
 465     BlockDriverState *top_bs;
 466     BdrvChild *active_disk, *hidden_disk, *secondary_disk;
 467     int64_t active_length, hidden_length, disk_length;
 468     AioContext *aio_context;
 469     Error *local_err = NULL;
 470     BackupPerf perf = { .use_copy_range = true, .max_workers = 1 };
 471
 472     aio_context = bdrv_get_aio_context(bs);
 473     aio_context_acquire(aio_context);
 474     s = bs->opaque;
 475
 476     if (s->stage == BLOCK_REPLICATION_DONE ||
 477         s->stage == BLOCK_REPLICATION_FAILOVER) {
 478         /*
 479          * This case happens when a secondary is promoted to primary.
 480          * Ignore the request because the secondary side of replication
 481          * doesn't have to do anything anymore.
 482          */
 483         aio_context_release(aio_context);
 484         return;
 485     }
 486
 487     if (s->stage != BLOCK_REPLICATION_NONE) {
 488         error_setg(errp, "Block replication is running or done");
 489         aio_context_release(aio_context);
 490         return;
 491     }
 492
 493     if (s->mode != mode) {
 494         error_setg(errp, "The parameter mode's value is invalid, needs %d,"
 495                    " but got %d", s->mode, mode);
 496         aio_context_release(aio_context);
 497         return;
 498     }
 499
 500     switch (s->mode) {
 501     case REPLICATION_MODE_PRIMARY:
 502         break;
 503     case REPLICATION_MODE_SECONDARY:
 504         active_disk = bs->file;
 505         if (!active_disk || !active_disk->bs || !active_disk->bs->backing) {
 506             error_setg(errp, "Active disk doesn't have backing file");
 507             aio_context_release(aio_context);
 508             return;
 509         }
 510
 511         hidden_disk = active_disk->bs->backing;
 512         if (!hidden_disk->bs || !hidden_disk->bs->backing) {
 513             error_setg(errp, "Hidden disk doesn't have backing file");
 514             aio_context_release(aio_context);
 515             return;
 516         }
 517
 518         secondary_disk = hidden_disk->bs->backing;
 519         if (!secondary_disk->bs || !bdrv_has_blk(secondary_disk->bs)) {
 520             error_setg(errp, "The secondary disk doesn't have block backend");
 521             aio_context_release(aio_context);
 522             return;
 523         }
 524
 525         /* verify the length */
 526         active_length = bdrv_getlength(active_disk->bs);
 527         hidden_length = bdrv_getlength(hidden_disk->bs);
 528         disk_length = bdrv_getlength(secondary_disk->bs);
 529         if (active_length < 0 || hidden_length < 0 || disk_length < 0 ||
 530             active_length != hidden_length || hidden_length != disk_length) {
 531             error_setg(errp, "Active disk, hidden disk, secondary disk's length"
 532                        " are not the same");
 533             aio_context_release(aio_context);
 534             return;
 535         }
 536
 537         /* Must be true, or the bdrv_getlength() calls would have failed */
 538         assert(active_disk->bs->drv && hidden_disk->bs->drv);
 539
 540         if (!active_disk->bs->drv->bdrv_make_empty ||
 541             !hidden_disk->bs->drv->bdrv_make_empty) {
 542             error_setg(errp,
 543                        "Active disk or hidden disk doesn't support make_empty");
 544             aio_context_release(aio_context);
 545             return;
 546         }
 547
 548         /* reopen the backing file in r/w mode */
 549         reopen_backing_file(bs, true, &local_err);
 550         if (local_err) {
 551             error_propagate(errp, local_err);
 552             aio_context_release(aio_context);
 553             return;
 554         }
 555
 556         bdrv_ref(hidden_disk->bs);
 557         s->hidden_disk = bdrv_attach_child(bs, hidden_disk->bs, "hidden disk",
 558                                            &child_of_bds, BDRV_CHILD_DATA,
 559                                            &local_err);
 560         if (local_err) {
 561             error_propagate(errp, local_err);
 562             aio_context_release(aio_context);
 563             return;
 564         }
 565
 566         bdrv_ref(secondary_disk->bs);
 567         s->secondary_disk = bdrv_attach_child(bs, secondary_disk->bs,
 568                                               "secondary disk", &child_of_bds,
 569                                               BDRV_CHILD_DATA, &local_err);
 570         if (local_err) {
 571             error_propagate(errp, local_err);
 572             aio_context_release(aio_context);
 573             return;
 574         }
 575
 576         /* start backup job now */
 577         error_setg(&s->blocker,
 578                    "Block device is in use by internal backup job");
 579
 580         top_bs = bdrv_lookup_bs(s->top_id, s->top_id, NULL);
 581         if (!top_bs || !bdrv_is_root_node(top_bs) ||
 582             !check_top_bs(top_bs, bs)) {
 583             error_setg(errp, "No top_bs or it is invalid");
 584             reopen_backing_file(bs, false, NULL);
 585             aio_context_release(aio_context);
 586             return;
 587         }
 588         bdrv_op_block_all(top_bs, s->blocker);
 589         bdrv_op_unblock(top_bs, BLOCK_OP_TYPE_DATAPLANE, s->blocker);
 590
 591         s->backup_job = backup_job_create(
 592                                 NULL, s->secondary_disk->bs, s->hidden_disk->bs,
 593                                 0, MIRROR_SYNC_MODE_NONE, NULL, 0, false, NULL,
 594                                 &perf,
 595                                 BLOCKDEV_ON_ERROR_REPORT,
 596                                 BLOCKDEV_ON_ERROR_REPORT, JOB_INTERNAL,
 597                                 backup_job_completed, bs, NULL, &local_err);
 598         if (local_err) {
 599             error_propagate(errp, local_err);
 600             backup_job_cleanup(bs);
 601             aio_context_release(aio_context);
 602             return;
 603         }
 604         job_start(&s->backup_job->job);
 605         break;
 606     default:
 607         aio_context_release(aio_context);
 608         abort();
 609     }
 610
 611     s->stage = BLOCK_REPLICATION_RUNNING;
 612
 613     if (s->mode == REPLICATION_MODE_SECONDARY) {
 614         secondary_do_checkpoint(bs, errp);
 615     }
 616
 617     s->error = 0;
 618     aio_context_release(aio_context);
 619 }
 620
 621 static void replication_do_checkpoint(ReplicationState *rs, Error **errp)
 622 {
 623     BlockDriverState *bs = rs->opaque;
 624     BDRVReplicationState *s;
 625     AioContext *aio_context;
 626
 627     aio_context = bdrv_get_aio_context(bs);
 628     aio_context_acquire(aio_context);
 629     s = bs->opaque;
 630
 631     if (s->stage == BLOCK_REPLICATION_DONE ||
 632         s->stage == BLOCK_REPLICATION_FAILOVER) {
 633         /*
 634          * This case happens when a secondary was promoted to primary.
 635          * Ignore the request because the secondary side of replication
 636          * doesn't have to do anything anymore.
 637          */
 638         aio_context_release(aio_context);
 639         return;
 640     }
 641
 642     if (s->mode == REPLICATION_MODE_SECONDARY) {
 643         secondary_do_checkpoint(bs, errp);
 644     }
 645     aio_context_release(aio_context);
 646 }
 647
 648 static void replication_get_error(ReplicationState *rs, Error **errp)
 649 {
 650     BlockDriverState *bs = rs->opaque;
 651     BDRVReplicationState *s;
 652     AioContext *aio_context;
 653
 654     aio_context = bdrv_get_aio_context(bs);
 655     aio_context_acquire(aio_context);
 656     s = bs->opaque;
 657
 658     if (s->stage == BLOCK_REPLICATION_NONE) {
 659         error_setg(errp, "Block replication is not running");
 660         aio_context_release(aio_context);
 661         return;
 662     }
 663
 664     if (s->error) {
 665         error_setg(errp, "I/O error occurred");
 666         aio_context_release(aio_context);
 667         return;
 668     }
 669     aio_context_release(aio_context);
 670 }
 671
 672 static void replication_done(void *opaque, int ret)
 673 {
 674     BlockDriverState *bs = opaque;
 675     BDRVReplicationState *s = bs->opaque;
 676
 677     if (ret == 0) {
 678         s->stage = BLOCK_REPLICATION_DONE;
 679
 680         bdrv_unref_child(bs, s->secondary_disk);
 681         s->secondary_disk = NULL;
 682         bdrv_unref_child(bs, s->hidden_disk);
 683         s->hidden_disk = NULL;
 684         s->error = 0;
 685     } else {
 686         s->stage = BLOCK_REPLICATION_FAILOVER_FAILED;
 687         s->error = -EIO;
 688     }
 689 }
 690
 691 static void replication_stop(ReplicationState *rs, bool failover, Error **errp)
 692 {
 693     BlockDriverState *bs = rs->opaque;
 694     BDRVReplicationState *s;
 695     AioContext *aio_context;
 696
 697     aio_context = bdrv_get_aio_context(bs);
 698     aio_context_acquire(aio_context);
 699     s = bs->opaque;
 700
 701     if (s->stage == BLOCK_REPLICATION_DONE ||
 702         s->stage == BLOCK_REPLICATION_FAILOVER) {
 703         /*
 704          * This case happens when a secondary was promoted to primary.
 705          * Ignore the request because the secondary side of replication
 706          * doesn't have to do anything anymore.
 707          */
 708         aio_context_release(aio_context);
 709         return;
 710     }
 711
 712     if (s->stage != BLOCK_REPLICATION_RUNNING) {
 713         error_setg(errp, "Block replication is not running");
 714         aio_context_release(aio_context);
 715         return;
 716     }
 717
 718     switch (s->mode) {
 719     case REPLICATION_MODE_PRIMARY:
 720         s->stage = BLOCK_REPLICATION_DONE;
 721         s->error = 0;
 722         break;
 723     case REPLICATION_MODE_SECONDARY:
 724         /*
 725          * This BDS will be closed, and the job should be completed
 726          * before the BDS is closed, because we will access hidden
 727          * disk, secondary disk in backup_job_completed().
 728          */
 729         if (s->backup_job) {
 730             aio_context_release(aio_context);
 731             job_cancel_sync(&s->backup_job->job, true);
 732             aio_context_acquire(aio_context);
 733         }
 734
 735         if (!failover) {
 736             secondary_do_checkpoint(bs, errp);
 737             s->stage = BLOCK_REPLICATION_DONE;
 738             aio_context_release(aio_context);
 739             return;
 740         }
 741
 742         s->stage = BLOCK_REPLICATION_FAILOVER;
 743         s->commit_job = commit_active_start(
 744                             NULL, bs->file->bs, s->secondary_disk->bs,
 745                             JOB_INTERNAL, 0, BLOCKDEV_ON_ERROR_REPORT,
 746                             NULL, replication_done, bs, true, errp);
 747         break;
 748     default:
 749         aio_context_release(aio_context);
 750         abort();
 751     }
 752     aio_context_release(aio_context);
 753 }
 754
 755 static const char *const replication_strong_runtime_opts[] = {
 756     REPLICATION_MODE,
 757     REPLICATION_TOP_ID,
 758
 759     NULL
 760 };
 761
 762 static BlockDriver bdrv_replication = {
 763     .format_name                = "replication",
 764     .instance_size              = sizeof(BDRVReplicationState),
 765
 766     .bdrv_open                  = replication_open,
 767     .bdrv_close                 = replication_close,
 768     .bdrv_child_perm            = replication_child_perm,
 769
 770     .bdrv_getlength             = replication_getlength,
 771     .bdrv_co_readv              = replication_co_readv,
 772     .bdrv_co_writev             = replication_co_writev,
 773
 774     .is_filter                  = true,
 775
 776     .has_variable_length        = true,
 777     .strong_runtime_opts        = replication_strong_runtime_opts,
 778 };
 779
 780 static void bdrv_replication_init(void)
 781 {
 782     bdrv_register(&bdrv_replication);
 783 }
 784
 785 block_init(bdrv_replication_init);