block/backup.c

   1 /*
   2  * QEMU backup
   3  *
   4  * Copyright (C) 2013 Proxmox Server Solutions
   5  *
   6  * Authors:
   7  *  Dietmar Maurer (dietmar@proxmox.com)
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  10  * See the COPYING file in the top-level directory.
  11  *
  12  */
  13
  14 #include "qemu/osdep.h"
  15
  16 #include "trace.h"
  17 #include "block/block.h"
  18 #include "block/block_int.h"
  19 #include "block/blockjob_int.h"
  20 #include "block/block_backup.h"
  21 #include "qapi/error.h"
  22 #include "qapi/qmp/qerror.h"
  23 #include "qemu/ratelimit.h"
  24 #include "qemu/cutils.h"
  25 #include "sysemu/block-backend.h"
  26 #include "qemu/bitmap.h"
  27 #include "qemu/error-report.h"
  28
  29 #define BACKUP_CLUSTER_SIZE_DEFAULT (1 << 16)
  30
  31 typedef struct CowRequest {
  32     int64_t start_byte;
  33     int64_t end_byte;
  34     QLIST_ENTRY(CowRequest) list;
  35     CoQueue wait_queue; /* coroutines blocked on this request */
  36 } CowRequest;
  37
  38 typedef struct BackupBlockJob {
  39     BlockJob common;
  40     BlockBackend *target;
  41     /* bitmap for sync=incremental */
  42     BdrvDirtyBitmap *sync_bitmap;
  43     MirrorSyncMode sync_mode;
  44     BlockdevOnError on_source_error;
  45     BlockdevOnError on_target_error;
  46     CoRwlock flush_rwlock;
  47     uint64_t len;
  48     uint64_t bytes_read;
  49     int64_t cluster_size;
  50     bool compress;
  51     NotifierWithReturn before_write;
  52     QLIST_HEAD(, CowRequest) inflight_reqs;
  53
  54     HBitmap *copy_bitmap;
  55     bool use_copy_range;
  56     int64_t copy_range_size;
  57
  58     bool serialize_target_writes;
  59 } BackupBlockJob;
  60
  61 static const BlockJobDriver backup_job_driver;
  62
  63 /* See if in-flight requests overlap and wait for them to complete */
  64 static void coroutine_fn wait_for_overlapping_requests(BackupBlockJob *job,
  65                                                        int64_t start,
  66                                                        int64_t end)
  67 {
  68     CowRequest *req;
  69     bool retry;
  70
  71     do {
  72         retry = false;
  73         QLIST_FOREACH(req, &job->inflight_reqs, list) {
  74             if (end > req->start_byte && start < req->end_byte) {
  75                 qemu_co_queue_wait(&req->wait_queue, NULL);
  76                 retry = true;
  77                 break;
  78             }
  79         }
  80     } while (retry);
  81 }
  82
  83 /* Keep track of an in-flight request */
  84 static void cow_request_begin(CowRequest *req, BackupBlockJob *job,
  85                               int64_t start, int64_t end)
  86 {
  87     req->start_byte = start;
  88     req->end_byte = end;
  89     qemu_co_queue_init(&req->wait_queue);
  90     QLIST_INSERT_HEAD(&job->inflight_reqs, req, list);
  91 }
  92
  93 /* Forget about a completed request */
  94 static void cow_request_end(CowRequest *req)
  95 {
  96     QLIST_REMOVE(req, list);
  97     qemu_co_queue_restart_all(&req->wait_queue);
  98 }
  99
 100 /* Copy range to target with a bounce buffer and return the bytes copied. If
 101  * error occurred, return a negative error number */
 102 static int coroutine_fn backup_cow_with_bounce_buffer(BackupBlockJob *job,
 103                                                       int64_t start,
 104                                                       int64_t end,
 105                                                       bool is_write_notifier,
 106                                                       bool *error_is_read,
 107                                                       void **bounce_buffer)
 108 {
 109     int ret;
 110     BlockBackend *blk = job->common.blk;
 111     int nbytes;
 112     int read_flags = is_write_notifier ? BDRV_REQ_NO_SERIALISING : 0;
 113     int write_flags = job->serialize_target_writes ? BDRV_REQ_SERIALISING : 0;
 114
 115     assert(QEMU_IS_ALIGNED(start, job->cluster_size));
 116     hbitmap_reset(job->copy_bitmap, start, job->cluster_size);
 117     nbytes = MIN(job->cluster_size, job->len - start);
 118     if (!*bounce_buffer) {
 119         *bounce_buffer = blk_blockalign(blk, job->cluster_size);
 120     }
 121
 122     ret = blk_co_pread(blk, start, nbytes, *bounce_buffer, read_flags);
 123     if (ret < 0) {
 124         trace_backup_do_cow_read_fail(job, start, ret);
 125         if (error_is_read) {
 126             *error_is_read = true;
 127         }
 128         goto fail;
 129     }
 130
 131     if (buffer_is_zero(*bounce_buffer, nbytes)) {
 132         ret = blk_co_pwrite_zeroes(job->target, start,
 133                                    nbytes, write_flags | BDRV_REQ_MAY_UNMAP);
 134     } else {
 135         ret = blk_co_pwrite(job->target, start,
 136                             nbytes, *bounce_buffer, write_flags |
 137                             (job->compress ? BDRV_REQ_WRITE_COMPRESSED : 0));
 138     }
 139     if (ret < 0) {
 140         trace_backup_do_cow_write_fail(job, start, ret);
 141         if (error_is_read) {
 142             *error_is_read = false;
 143         }
 144         goto fail;
 145     }
 146
 147     return nbytes;
 148 fail:
 149     hbitmap_set(job->copy_bitmap, start, job->cluster_size);
 150     return ret;
 151
 152 }
 153
 154 /* Copy range to target and return the bytes copied. If error occurred, return a
 155  * negative error number. */
 156 static int coroutine_fn backup_cow_with_offload(BackupBlockJob *job,
 157                                                 int64_t start,
 158                                                 int64_t end,
 159                                                 bool is_write_notifier)
 160 {
 161     int ret;
 162     int nr_clusters;
 163     BlockBackend *blk = job->common.blk;
 164     int nbytes;
 165     int read_flags = is_write_notifier ? BDRV_REQ_NO_SERIALISING : 0;
 166     int write_flags = job->serialize_target_writes ? BDRV_REQ_SERIALISING : 0;
 167
 168     assert(QEMU_IS_ALIGNED(job->copy_range_size, job->cluster_size));
 169     assert(QEMU_IS_ALIGNED(start, job->cluster_size));
 170     nbytes = MIN(job->copy_range_size, end - start);
 171     nr_clusters = DIV_ROUND_UP(nbytes, job->cluster_size);
 172     hbitmap_reset(job->copy_bitmap, start, job->cluster_size * nr_clusters);
 173     ret = blk_co_copy_range(blk, start, job->target, start, nbytes,
 174                             read_flags, write_flags);
 175     if (ret < 0) {
 176         trace_backup_do_cow_copy_range_fail(job, start, ret);
 177         hbitmap_set(job->copy_bitmap, start, job->cluster_size * nr_clusters);
 178         return ret;
 179     }
 180
 181     return nbytes;
 182 }
 183
 184 static int coroutine_fn backup_do_cow(BackupBlockJob *job,
 185                                       int64_t offset, uint64_t bytes,
 186                                       bool *error_is_read,
 187                                       bool is_write_notifier)
 188 {
 189     CowRequest cow_request;
 190     int ret = 0;
 191     int64_t start, end; /* bytes */
 192     void *bounce_buffer = NULL;
 193
 194     qemu_co_rwlock_rdlock(&job->flush_rwlock);
 195
 196     start = QEMU_ALIGN_DOWN(offset, job->cluster_size);
 197     end = QEMU_ALIGN_UP(bytes + offset, job->cluster_size);
 198
 199     trace_backup_do_cow_enter(job, start, offset, bytes);
 200
 201     wait_for_overlapping_requests(job, start, end);
 202     cow_request_begin(&cow_request, job, start, end);
 203
 204     while (start < end) {
 205         int64_t dirty_end;
 206
 207         if (!hbitmap_get(job->copy_bitmap, start)) {
 208             trace_backup_do_cow_skip(job, start);
 209             start += job->cluster_size;
 210             continue; /* already copied */
 211         }
 212
 213         dirty_end = hbitmap_next_zero(job->copy_bitmap, start, (end - start));
 214         if (dirty_end < 0) {
 215             dirty_end = end;
 216         }
 217
 218         trace_backup_do_cow_process(job, start);
 219
 220         if (job->use_copy_range) {
 221             ret = backup_cow_with_offload(job, start, dirty_end,
 222                                           is_write_notifier);
 223             if (ret < 0) {
 224                 job->use_copy_range = false;
 225             }
 226         }
 227         if (!job->use_copy_range) {
 228             ret = backup_cow_with_bounce_buffer(job, start, dirty_end,
 229                                                 is_write_notifier,
 230                                                 error_is_read, &bounce_buffer);
 231         }
 232         if (ret < 0) {
 233             break;
 234         }
 235
 236         /* Publish progress, guest I/O counts as progress too.  Note that the
 237          * offset field is an opaque progress value, it is not a disk offset.
 238          */
 239         start += ret;
 240         job->bytes_read += ret;
 241         job_progress_update(&job->common.job, ret);
 242         ret = 0;
 243     }
 244
 245     if (bounce_buffer) {
 246         qemu_vfree(bounce_buffer);
 247     }
 248
 249     cow_request_end(&cow_request);
 250
 251     trace_backup_do_cow_return(job, offset, bytes, ret);
 252
 253     qemu_co_rwlock_unlock(&job->flush_rwlock);
 254
 255     return ret;
 256 }
 257
 258 static int coroutine_fn backup_before_write_notify(
 259         NotifierWithReturn *notifier,
 260         void *opaque)
 261 {
 262     BackupBlockJob *job = container_of(notifier, BackupBlockJob, before_write);
 263     BdrvTrackedRequest *req = opaque;
 264
 265     assert(req->bs == blk_bs(job->common.blk));
 266     assert(QEMU_IS_ALIGNED(req->offset, BDRV_SECTOR_SIZE));
 267     assert(QEMU_IS_ALIGNED(req->bytes, BDRV_SECTOR_SIZE));
 268
 269     return backup_do_cow(job, req->offset, req->bytes, NULL, true);
 270 }
 271
 272 static void backup_cleanup_sync_bitmap(BackupBlockJob *job, int ret)
 273 {
 274     BdrvDirtyBitmap *bm;
 275     BlockDriverState *bs = blk_bs(job->common.blk);
 276
 277     if (ret < 0) {
 278         /* Merge the successor back into the parent, delete nothing. */
 279         bm = bdrv_reclaim_dirty_bitmap(bs, job->sync_bitmap, NULL);
 280         assert(bm);
 281     } else {
 282         /* Everything is fine, delete this bitmap and install the backup. */
 283         bm = bdrv_dirty_bitmap_abdicate(bs, job->sync_bitmap, NULL);
 284         assert(bm);
 285     }
 286 }
 287
 288 static void backup_commit(Job *job)
 289 {
 290     BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
 291     if (s->sync_bitmap) {
 292         backup_cleanup_sync_bitmap(s, 0);
 293     }
 294 }
 295
 296 static void backup_abort(Job *job)
 297 {
 298     BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
 299     if (s->sync_bitmap) {
 300         backup_cleanup_sync_bitmap(s, -1);
 301     }
 302 }
 303
 304 static void backup_clean(Job *job)
 305 {
 306     BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
 307     assert(s->target);
 308     blk_unref(s->target);
 309     s->target = NULL;
 310
 311     if (s->copy_bitmap) {
 312         hbitmap_free(s->copy_bitmap);
 313         s->copy_bitmap = NULL;
 314     }
 315 }
 316
 317 void backup_do_checkpoint(BlockJob *job, Error **errp)
 318 {
 319     BackupBlockJob *backup_job = container_of(job, BackupBlockJob, common);
 320
 321     assert(block_job_driver(job) == &backup_job_driver);
 322
 323     if (backup_job->sync_mode != MIRROR_SYNC_MODE_NONE) {
 324         error_setg(errp, "The backup job only supports block checkpoint in"
 325                    " sync=none mode");
 326         return;
 327     }
 328
 329     hbitmap_set(backup_job->copy_bitmap, 0, backup_job->len);
 330 }
 331
 332 static void backup_drain(BlockJob *job)
 333 {
 334     BackupBlockJob *s = container_of(job, BackupBlockJob, common);
 335
 336     /* Need to keep a reference in case blk_drain triggers execution
 337      * of backup_complete...
 338      */
 339     if (s->target) {
 340         BlockBackend *target = s->target;
 341         blk_ref(target);
 342         blk_drain(target);
 343         blk_unref(target);
 344     }
 345 }
 346
 347 static BlockErrorAction backup_error_action(BackupBlockJob *job,
 348                                             bool read, int error)
 349 {
 350     if (read) {
 351         return block_job_error_action(&job->common, job->on_source_error,
 352                                       true, error);
 353     } else {
 354         return block_job_error_action(&job->common, job->on_target_error,
 355                                       false, error);
 356     }
 357 }
 358
 359 static bool coroutine_fn yield_and_check(BackupBlockJob *job)
 360 {
 361     uint64_t delay_ns;
 362
 363     if (job_is_cancelled(&job->common.job)) {
 364         return true;
 365     }
 366
 367     /* We need to yield even for delay_ns = 0 so that bdrv_drain_all() can
 368      * return. Without a yield, the VM would not reboot. */
 369     delay_ns = block_job_ratelimit_get_delay(&job->common, job->bytes_read);
 370     job->bytes_read = 0;
 371     job_sleep_ns(&job->common.job, delay_ns);
 372
 373     if (job_is_cancelled(&job->common.job)) {
 374         return true;
 375     }
 376
 377     return false;
 378 }
 379
 380 static bool bdrv_is_unallocated_range(BlockDriverState *bs,
 381                                       int64_t offset, int64_t bytes)
 382 {
 383     int64_t end = offset + bytes;
 384
 385     while (offset < end && !bdrv_is_allocated(bs, offset, bytes, &bytes)) {
 386         if (bytes == 0) {
 387             return true;
 388         }
 389         offset += bytes;
 390         bytes = end - offset;
 391     }
 392
 393     return offset >= end;
 394 }
 395
 396 static int coroutine_fn backup_loop(BackupBlockJob *job)
 397 {
 398     int ret;
 399     bool error_is_read;
 400     int64_t offset;
 401     HBitmapIter hbi;
 402     BlockDriverState *bs = blk_bs(job->common.blk);
 403
 404     hbitmap_iter_init(&hbi, job->copy_bitmap, 0);
 405     while ((offset = hbitmap_iter_next(&hbi)) != -1) {
 406         if (job->sync_mode == MIRROR_SYNC_MODE_TOP &&
 407             bdrv_is_unallocated_range(bs, offset, job->cluster_size))
 408         {
 409             hbitmap_reset(job->copy_bitmap, offset, job->cluster_size);
 410             continue;
 411         }
 412
 413         do {
 414             if (yield_and_check(job)) {
 415                 return 0;
 416             }
 417             ret = backup_do_cow(job, offset,
 418                                 job->cluster_size, &error_is_read, false);
 419             if (ret < 0 && backup_error_action(job, error_is_read, -ret) ==
 420                            BLOCK_ERROR_ACTION_REPORT)
 421             {
 422                 return ret;
 423             }
 424         } while (ret < 0);
 425     }
 426
 427     return 0;
 428 }
 429
 430 /* init copy_bitmap from sync_bitmap */
 431 static void backup_incremental_init_copy_bitmap(BackupBlockJob *job)
 432 {
 433     uint64_t offset = 0;
 434     uint64_t bytes = job->len;
 435
 436     while (bdrv_dirty_bitmap_next_dirty_area(job->sync_bitmap,
 437                                              &offset, &bytes))
 438     {
 439         hbitmap_set(job->copy_bitmap, offset, bytes);
 440
 441         offset += bytes;
 442         if (offset >= job->len) {
 443             break;
 444         }
 445         bytes = job->len - offset;
 446     }
 447
 448     /* TODO job_progress_set_remaining() would make more sense */
 449     job_progress_update(&job->common.job,
 450         job->len - hbitmap_count(job->copy_bitmap));
 451 }
 452
 453 static int coroutine_fn backup_run(Job *job, Error **errp)
 454 {
 455     BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
 456     BlockDriverState *bs = blk_bs(s->common.blk);
 457     int ret = 0;
 458
 459     QLIST_INIT(&s->inflight_reqs);
 460     qemu_co_rwlock_init(&s->flush_rwlock);
 461
 462     job_progress_set_remaining(job, s->len);
 463
 464     if (s->sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) {
 465         backup_incremental_init_copy_bitmap(s);
 466     } else {
 467         hbitmap_set(s->copy_bitmap, 0, s->len);
 468     }
 469
 470     s->before_write.notify = backup_before_write_notify;
 471     bdrv_add_before_write_notifier(bs, &s->before_write);
 472
 473     if (s->sync_mode == MIRROR_SYNC_MODE_NONE) {
 474         /* All bits are set in copy_bitmap to allow any cluster to be copied.
 475          * This does not actually require them to be copied. */
 476         while (!job_is_cancelled(job)) {
 477             /* Yield until the job is cancelled.  We just let our before_write
 478              * notify callback service CoW requests. */
 479             job_yield(job);
 480         }
 481     } else {
 482         ret = backup_loop(s);
 483     }
 484
 485     notifier_with_return_remove(&s->before_write);
 486
 487     /* wait until pending backup_do_cow() calls have completed */
 488     qemu_co_rwlock_wrlock(&s->flush_rwlock);
 489     qemu_co_rwlock_unlock(&s->flush_rwlock);
 490
 491     return ret;
 492 }
 493
 494 static const BlockJobDriver backup_job_driver = {
 495     .job_driver = {
 496         .instance_size          = sizeof(BackupBlockJob),
 497         .job_type               = JOB_TYPE_BACKUP,
 498         .free                   = block_job_free,
 499         .user_resume            = block_job_user_resume,
 500         .drain                  = block_job_drain,
 501         .run                    = backup_run,
 502         .commit                 = backup_commit,
 503         .abort                  = backup_abort,
 504         .clean                  = backup_clean,
 505     },
 506     .drain                  = backup_drain,
 507 };
 508
 509 static int64_t backup_calculate_cluster_size(BlockDriverState *target,
 510                                              Error **errp)
 511 {
 512     int ret;
 513     BlockDriverInfo bdi;
 514
 515     /*
 516      * If there is no backing file on the target, we cannot rely on COW if our
 517      * backup cluster size is smaller than the target cluster size. Even for
 518      * targets with a backing file, try to avoid COW if possible.
 519      */
 520     ret = bdrv_get_info(target, &bdi);
 521     if (ret == -ENOTSUP && !target->backing) {
 522         /* Cluster size is not defined */
 523         warn_report("The target block device doesn't provide "
 524                     "information about the block size and it doesn't have a "
 525                     "backing file. The default block size of %u bytes is "
 526                     "used. If the actual block size of the target exceeds "
 527                     "this default, the backup may be unusable",
 528                     BACKUP_CLUSTER_SIZE_DEFAULT);
 529         return BACKUP_CLUSTER_SIZE_DEFAULT;
 530     } else if (ret < 0 && !target->backing) {
 531         error_setg_errno(errp, -ret,
 532             "Couldn't determine the cluster size of the target image, "
 533             "which has no backing file");
 534         error_append_hint(errp,
 535             "Aborting, since this may create an unusable destination image\n");
 536         return ret;
 537     } else if (ret < 0 && target->backing) {
 538         /* Not fatal; just trudge on ahead. */
 539         return BACKUP_CLUSTER_SIZE_DEFAULT;
 540     }
 541
 542     return MAX(BACKUP_CLUSTER_SIZE_DEFAULT, bdi.cluster_size);
 543 }
 544
 545 BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
 546                   BlockDriverState *target, int64_t speed,
 547                   MirrorSyncMode sync_mode, BdrvDirtyBitmap *sync_bitmap,
 548                   bool compress,
 549                   BlockdevOnError on_source_error,
 550                   BlockdevOnError on_target_error,
 551                   int creation_flags,
 552                   BlockCompletionFunc *cb, void *opaque,
 553                   JobTxn *txn, Error **errp)
 554 {
 555     int64_t len;
 556     BackupBlockJob *job = NULL;
 557     int ret;
 558     int64_t cluster_size;
 559     HBitmap *copy_bitmap = NULL;
 560
 561     assert(bs);
 562     assert(target);
 563
 564     if (bs == target) {
 565         error_setg(errp, "Source and target cannot be the same");
 566         return NULL;
 567     }
 568
 569     if (!bdrv_is_inserted(bs)) {
 570         error_setg(errp, "Device is not inserted: %s",
 571                    bdrv_get_device_name(bs));
 572         return NULL;
 573     }
 574
 575     if (!bdrv_is_inserted(target)) {
 576         error_setg(errp, "Device is not inserted: %s",
 577                    bdrv_get_device_name(target));
 578         return NULL;
 579     }
 580
 581     if (compress && target->drv->bdrv_co_pwritev_compressed == NULL) {
 582         error_setg(errp, "Compression is not supported for this drive %s",
 583                    bdrv_get_device_name(target));
 584         return NULL;
 585     }
 586
 587     if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) {
 588         return NULL;
 589     }
 590
 591     if (bdrv_op_is_blocked(target, BLOCK_OP_TYPE_BACKUP_TARGET, errp)) {
 592         return NULL;
 593     }
 594
 595     if (sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) {
 596         if (!sync_bitmap) {
 597             error_setg(errp, "must provide a valid bitmap name for "
 598                              "\"incremental\" sync mode");
 599             return NULL;
 600         }
 601
 602         /* Create a new bitmap, and freeze/disable this one. */
 603         if (bdrv_dirty_bitmap_create_successor(bs, sync_bitmap, errp) < 0) {
 604             return NULL;
 605         }
 606     } else if (sync_bitmap) {
 607         error_setg(errp,
 608                    "a sync_bitmap was provided to backup_run, "
 609                    "but received an incompatible sync_mode (%s)",
 610                    MirrorSyncMode_str(sync_mode));
 611         return NULL;
 612     }
 613
 614     len = bdrv_getlength(bs);
 615     if (len < 0) {
 616         error_setg_errno(errp, -len, "unable to get length for '%s'",
 617                          bdrv_get_device_name(bs));
 618         goto error;
 619     }
 620
 621     cluster_size = backup_calculate_cluster_size(target, errp);
 622     if (cluster_size < 0) {
 623         goto error;
 624     }
 625
 626     copy_bitmap = hbitmap_alloc(len, ctz32(cluster_size));
 627
 628     /* job->len is fixed, so we can't allow resize */
 629     job = block_job_create(job_id, &backup_job_driver, txn, bs,
 630                            BLK_PERM_CONSISTENT_READ,
 631                            BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE |
 632                            BLK_PERM_WRITE_UNCHANGED | BLK_PERM_GRAPH_MOD,
 633                            speed, creation_flags, cb, opaque, errp);
 634     if (!job) {
 635         goto error;
 636     }
 637
 638     /* The target must match the source in size, so no resize here either */
 639     job->target = blk_new(job->common.job.aio_context,
 640                           BLK_PERM_WRITE,
 641                           BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE |
 642                           BLK_PERM_WRITE_UNCHANGED | BLK_PERM_GRAPH_MOD);
 643     ret = blk_insert_bs(job->target, target, errp);
 644     if (ret < 0) {
 645         goto error;
 646     }
 647
 648     job->on_source_error = on_source_error;
 649     job->on_target_error = on_target_error;
 650     job->sync_mode = sync_mode;
 651     job->sync_bitmap = sync_mode == MIRROR_SYNC_MODE_INCREMENTAL ?
 652                        sync_bitmap : NULL;
 653     job->compress = compress;
 654
 655     /* Detect image-fleecing (and similar) schemes */
 656     job->serialize_target_writes = bdrv_chain_contains(target, bs);
 657     job->cluster_size = cluster_size;
 658     job->copy_bitmap = copy_bitmap;
 659     copy_bitmap = NULL;
 660     job->use_copy_range = !compress; /* compression isn't supported for it */
 661     job->copy_range_size = MIN_NON_ZERO(blk_get_max_transfer(job->common.blk),
 662                                         blk_get_max_transfer(job->target));
 663     job->copy_range_size = MAX(job->cluster_size,
 664                                QEMU_ALIGN_UP(job->copy_range_size,
 665                                              job->cluster_size));
 666
 667     /* Required permissions are already taken with target's blk_new() */
 668     block_job_add_bdrv(&job->common, "target", target, 0, BLK_PERM_ALL,
 669                        &error_abort);
 670     job->len = len;
 671
 672     return &job->common;
 673
 674  error:
 675     if (copy_bitmap) {
 676         assert(!job || !job->copy_bitmap);
 677         hbitmap_free(copy_bitmap);
 678     }
 679     if (sync_bitmap) {
 680         bdrv_reclaim_dirty_bitmap(bs, sync_bitmap, NULL);
 681     }
 682     if (job) {
 683         backup_clean(&job->common.job);
 684         job_early_fail(&job->common.job);
 685     }
 686
 687     return NULL;
 688 }