blockjob.c

   1 /*
   2  * QEMU System Emulator block driver
   3  *
   4  * Copyright (c) 2011 IBM Corp.
   5  * Copyright (c) 2012 Red Hat, Inc.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to deal
   9  * in the Software without restriction, including without limitation the rights
  10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11  * copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  23  * THE SOFTWARE.
  24  */
  25
  26 #include "qemu/osdep.h"
  27 #include "qemu-common.h"
  28 #include "block/block.h"
  29 #include "block/blockjob_int.h"
  30 #include "block/block_int.h"
  31 #include "sysemu/block-backend.h"
  32 #include "qapi/qmp/qerror.h"
  33 #include "qapi/qmp/qjson.h"
  34 #include "qemu/coroutine.h"
  35 #include "qemu/id.h"
  36 #include "qmp-commands.h"
  37 #include "qemu/timer.h"
  38 #include "qapi-event.h"
  39
  40 static void block_job_event_cancelled(BlockJob *job);
  41 static void block_job_event_completed(BlockJob *job, const char *msg);
  42
  43 /* Transactional group of block jobs */
  44 struct BlockJobTxn {
  45
  46     /* Is this txn being cancelled? */
  47     bool aborting;
  48
  49     /* List of jobs */
  50     QLIST_HEAD(, BlockJob) jobs;
  51
  52     /* Reference count */
  53     int refcnt;
  54 };
  55
  56 static QLIST_HEAD(, BlockJob) block_jobs = QLIST_HEAD_INITIALIZER(block_jobs);
  57
  58 static char *child_job_get_parent_desc(BdrvChild *c)
  59 {
  60     BlockJob *job = c->opaque;
  61     return g_strdup_printf("%s job '%s'",
  62                            BlockJobType_lookup[job->driver->job_type],
  63                            job->id);
  64 }
  65
  66 static const BdrvChildRole child_job = {
  67     .get_parent_desc    = child_job_get_parent_desc,
  68     .stay_at_node       = true,
  69 };
  70
  71 static void block_job_drained_begin(void *opaque)
  72 {
  73     BlockJob *job = opaque;
  74     block_job_pause(job);
  75 }
  76
  77 static void block_job_drained_end(void *opaque)
  78 {
  79     BlockJob *job = opaque;
  80     block_job_resume(job);
  81 }
  82
  83 static const BlockDevOps block_job_dev_ops = {
  84     .drained_begin = block_job_drained_begin,
  85     .drained_end = block_job_drained_end,
  86 };
  87
  88 BlockJob *block_job_next(BlockJob *job)
  89 {
  90     if (!job) {
  91         return QLIST_FIRST(&block_jobs);
  92     }
  93     return QLIST_NEXT(job, job_list);
  94 }
  95
  96 BlockJob *block_job_get(const char *id)
  97 {
  98     BlockJob *job;
  99
 100     QLIST_FOREACH(job, &block_jobs, job_list) {
 101         if (job->id && !strcmp(id, job->id)) {
 102             return job;
 103         }
 104     }
 105
 106     return NULL;
 107 }
 108
 109 static void block_job_attached_aio_context(AioContext *new_context,
 110                                            void *opaque)
 111 {
 112     BlockJob *job = opaque;
 113
 114     if (job->driver->attached_aio_context) {
 115         job->driver->attached_aio_context(job, new_context);
 116     }
 117
 118     block_job_resume(job);
 119 }
 120
 121 static void block_job_drain(BlockJob *job)
 122 {
 123     /* If job is !job->busy this kicks it into the next pause point. */
 124     block_job_enter(job);
 125
 126     blk_drain(job->blk);
 127     if (job->driver->drain) {
 128         job->driver->drain(job);
 129     }
 130 }
 131
 132 static void block_job_detach_aio_context(void *opaque)
 133 {
 134     BlockJob *job = opaque;
 135
 136     /* In case the job terminates during aio_poll()... */
 137     block_job_ref(job);
 138
 139     block_job_pause(job);
 140
 141     while (!job->paused && !job->completed) {
 142         block_job_drain(job);
 143     }
 144
 145     block_job_unref(job);
 146 }
 147
 148 void block_job_remove_all_bdrv(BlockJob *job)
 149 {
 150     GSList *l;
 151     for (l = job->nodes; l; l = l->next) {
 152         BdrvChild *c = l->data;
 153         bdrv_op_unblock_all(c->bs, job->blocker);
 154         bdrv_root_unref_child(c);
 155     }
 156     g_slist_free(job->nodes);
 157     job->nodes = NULL;
 158 }
 159
 160 int block_job_add_bdrv(BlockJob *job, const char *name, BlockDriverState *bs,
 161                        uint64_t perm, uint64_t shared_perm, Error **errp)
 162 {
 163     BdrvChild *c;
 164
 165     c = bdrv_root_attach_child(bs, name, &child_job, perm, shared_perm,
 166                                job, errp);
 167     if (c == NULL) {
 168         return -EPERM;
 169     }
 170
 171     job->nodes = g_slist_prepend(job->nodes, c);
 172     bdrv_ref(bs);
 173     bdrv_op_block_all(bs, job->blocker);
 174
 175     return 0;
 176 }
 177
 178 void *block_job_create(const char *job_id, const BlockJobDriver *driver,
 179                        BlockDriverState *bs, uint64_t perm,
 180                        uint64_t shared_perm, int64_t speed, int flags,
 181                        BlockCompletionFunc *cb, void *opaque, Error **errp)
 182 {
 183     BlockBackend *blk;
 184     BlockJob *job;
 185     int ret;
 186
 187     if (bs->job) {
 188         error_setg(errp, QERR_DEVICE_IN_USE, bdrv_get_device_name(bs));
 189         return NULL;
 190     }
 191
 192     if (job_id == NULL && !(flags & BLOCK_JOB_INTERNAL)) {
 193         job_id = bdrv_get_device_name(bs);
 194         if (!*job_id) {
 195             error_setg(errp, "An explicit job ID is required for this node");
 196             return NULL;
 197         }
 198     }
 199
 200     if (job_id) {
 201         if (flags & BLOCK_JOB_INTERNAL) {
 202             error_setg(errp, "Cannot specify job ID for internal block job");
 203             return NULL;
 204         }
 205
 206         if (!id_wellformed(job_id)) {
 207             error_setg(errp, "Invalid job ID '%s'", job_id);
 208             return NULL;
 209         }
 210
 211         if (block_job_get(job_id)) {
 212             error_setg(errp, "Job ID '%s' already in use", job_id);
 213             return NULL;
 214         }
 215     }
 216
 217     blk = blk_new(perm, shared_perm);
 218     ret = blk_insert_bs(blk, bs, errp);
 219     if (ret < 0) {
 220         blk_unref(blk);
 221         return NULL;
 222     }
 223
 224     job = g_malloc0(driver->instance_size);
 225     job->driver        = driver;
 226     job->id            = g_strdup(job_id);
 227     job->blk           = blk;
 228     job->cb            = cb;
 229     job->opaque        = opaque;
 230     job->busy          = false;
 231     job->paused        = true;
 232     job->pause_count   = 1;
 233     job->refcnt        = 1;
 234
 235     error_setg(&job->blocker, "block device is in use by block job: %s",
 236                BlockJobType_lookup[driver->job_type]);
 237     block_job_add_bdrv(job, "main node", bs, 0, BLK_PERM_ALL, &error_abort);
 238     bs->job = job;
 239
 240     blk_set_dev_ops(blk, &block_job_dev_ops, job);
 241     bdrv_op_unblock(bs, BLOCK_OP_TYPE_DATAPLANE, job->blocker);
 242
 243     QLIST_INSERT_HEAD(&block_jobs, job, job_list);
 244
 245     blk_add_aio_context_notifier(blk, block_job_attached_aio_context,
 246                                  block_job_detach_aio_context, job);
 247
 248     /* Only set speed when necessary to avoid NotSupported error */
 249     if (speed != 0) {
 250         Error *local_err = NULL;
 251
 252         block_job_set_speed(job, speed, &local_err);
 253         if (local_err) {
 254             block_job_unref(job);
 255             error_propagate(errp, local_err);
 256             return NULL;
 257         }
 258     }
 259     return job;
 260 }
 261
 262 bool block_job_is_internal(BlockJob *job)
 263 {
 264     return (job->id == NULL);
 265 }
 266
 267 static bool block_job_started(BlockJob *job)
 268 {
 269     return job->co;
 270 }
 271
 272 /**
 273  * All jobs must allow a pause point before entering their job proper. This
 274  * ensures that jobs can be paused prior to being started, then resumed later.
 275  */
 276 static void coroutine_fn block_job_co_entry(void *opaque)
 277 {
 278     BlockJob *job = opaque;
 279
 280     assert(job && job->driver && job->driver->start);
 281     block_job_pause_point(job);
 282     job->driver->start(job);
 283 }
 284
 285 void block_job_start(BlockJob *job)
 286 {
 287     assert(job && !block_job_started(job) && job->paused &&
 288            job->driver && job->driver->start);
 289     job->co = qemu_coroutine_create(block_job_co_entry, job);
 290     job->pause_count--;
 291     job->busy = true;
 292     job->paused = false;
 293     qemu_coroutine_enter(job->co);
 294 }
 295
 296 void block_job_ref(BlockJob *job)
 297 {
 298     ++job->refcnt;
 299 }
 300
 301 void block_job_unref(BlockJob *job)
 302 {
 303     if (--job->refcnt == 0) {
 304         BlockDriverState *bs = blk_bs(job->blk);
 305         bs->job = NULL;
 306         block_job_remove_all_bdrv(job);
 307         blk_remove_aio_context_notifier(job->blk,
 308                                         block_job_attached_aio_context,
 309                                         block_job_detach_aio_context, job);
 310         blk_unref(job->blk);
 311         error_free(job->blocker);
 312         g_free(job->id);
 313         QLIST_REMOVE(job, job_list);
 314         g_free(job);
 315     }
 316 }
 317
 318 static void block_job_completed_single(BlockJob *job)
 319 {
 320     if (!job->ret) {
 321         if (job->driver->commit) {
 322             job->driver->commit(job);
 323         }
 324     } else {
 325         if (job->driver->abort) {
 326             job->driver->abort(job);
 327         }
 328     }
 329     if (job->driver->clean) {
 330         job->driver->clean(job);
 331     }
 332
 333     if (job->cb) {
 334         job->cb(job->opaque, job->ret);
 335     }
 336
 337     /* Emit events only if we actually started */
 338     if (block_job_started(job)) {
 339         if (block_job_is_cancelled(job)) {
 340             block_job_event_cancelled(job);
 341         } else {
 342             const char *msg = NULL;
 343             if (job->ret < 0) {
 344                 msg = strerror(-job->ret);
 345             }
 346             block_job_event_completed(job, msg);
 347         }
 348     }
 349
 350     if (job->txn) {
 351         QLIST_REMOVE(job, txn_list);
 352         block_job_txn_unref(job->txn);
 353     }
 354     block_job_unref(job);
 355 }
 356
 357 static void block_job_completed_txn_abort(BlockJob *job)
 358 {
 359     AioContext *ctx;
 360     BlockJobTxn *txn = job->txn;
 361     BlockJob *other_job, *next;
 362
 363     if (txn->aborting) {
 364         /*
 365          * We are cancelled by another job, which will handle everything.
 366          */
 367         return;
 368     }
 369     txn->aborting = true;
 370     /* We are the first failed job. Cancel other jobs. */
 371     QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
 372         ctx = blk_get_aio_context(other_job->blk);
 373         aio_context_acquire(ctx);
 374     }
 375     QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
 376         if (other_job == job || other_job->completed) {
 377             /* Other jobs are "effectively" cancelled by us, set the status for
 378              * them; this job, however, may or may not be cancelled, depending
 379              * on the caller, so leave it. */
 380             if (other_job != job) {
 381                 other_job->cancelled = true;
 382             }
 383             continue;
 384         }
 385         block_job_cancel_sync(other_job);
 386         assert(other_job->completed);
 387     }
 388     QLIST_FOREACH_SAFE(other_job, &txn->jobs, txn_list, next) {
 389         ctx = blk_get_aio_context(other_job->blk);
 390         block_job_completed_single(other_job);
 391         aio_context_release(ctx);
 392     }
 393 }
 394
 395 static void block_job_completed_txn_success(BlockJob *job)
 396 {
 397     AioContext *ctx;
 398     BlockJobTxn *txn = job->txn;
 399     BlockJob *other_job, *next;
 400     /*
 401      * Successful completion, see if there are other running jobs in this
 402      * txn.
 403      */
 404     QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
 405         if (!other_job->completed) {
 406             return;
 407         }
 408     }
 409     /* We are the last completed job, commit the transaction. */
 410     QLIST_FOREACH_SAFE(other_job, &txn->jobs, txn_list, next) {
 411         ctx = blk_get_aio_context(other_job->blk);
 412         aio_context_acquire(ctx);
 413         assert(other_job->ret == 0);
 414         block_job_completed_single(other_job);
 415         aio_context_release(ctx);
 416     }
 417 }
 418
 419 void block_job_completed(BlockJob *job, int ret)
 420 {
 421     assert(blk_bs(job->blk)->job == job);
 422     assert(!job->completed);
 423     job->completed = true;
 424     job->ret = ret;
 425     if (!job->txn) {
 426         block_job_completed_single(job);
 427     } else if (ret < 0 || block_job_is_cancelled(job)) {
 428         block_job_completed_txn_abort(job);
 429     } else {
 430         block_job_completed_txn_success(job);
 431     }
 432 }
 433
 434 void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp)
 435 {
 436     Error *local_err = NULL;
 437
 438     if (!job->driver->set_speed) {
 439         error_setg(errp, QERR_UNSUPPORTED);
 440         return;
 441     }
 442     job->driver->set_speed(job, speed, &local_err);
 443     if (local_err) {
 444         error_propagate(errp, local_err);
 445         return;
 446     }
 447
 448     job->speed = speed;
 449 }
 450
 451 void block_job_complete(BlockJob *job, Error **errp)
 452 {
 453     /* Should not be reachable via external interface for internal jobs */
 454     assert(job->id);
 455     if (job->pause_count || job->cancelled ||
 456         !block_job_started(job) || !job->driver->complete) {
 457         error_setg(errp, "The active block job '%s' cannot be completed",
 458                    job->id);
 459         return;
 460     }
 461
 462     job->driver->complete(job, errp);
 463 }
 464
 465 void block_job_pause(BlockJob *job)
 466 {
 467     job->pause_count++;
 468 }
 469
 470 void block_job_user_pause(BlockJob *job)
 471 {
 472     job->user_paused = true;
 473     block_job_pause(job);
 474 }
 475
 476 static bool block_job_should_pause(BlockJob *job)
 477 {
 478     return job->pause_count > 0;
 479 }
 480
 481 bool block_job_user_paused(BlockJob *job)
 482 {
 483     return job ? job->user_paused : 0;
 484 }
 485
 486 void coroutine_fn block_job_pause_point(BlockJob *job)
 487 {
 488     assert(job && block_job_started(job));
 489
 490     if (!block_job_should_pause(job)) {
 491         return;
 492     }
 493     if (block_job_is_cancelled(job)) {
 494         return;
 495     }
 496
 497     if (job->driver->pause) {
 498         job->driver->pause(job);
 499     }
 500
 501     if (block_job_should_pause(job) && !block_job_is_cancelled(job)) {
 502         job->paused = true;
 503         job->busy = false;
 504         qemu_coroutine_yield(); /* wait for block_job_resume() */
 505         job->busy = true;
 506         job->paused = false;
 507     }
 508
 509     if (job->driver->resume) {
 510         job->driver->resume(job);
 511     }
 512 }
 513
 514 void block_job_resume(BlockJob *job)
 515 {
 516     assert(job->pause_count > 0);
 517     job->pause_count--;
 518     if (job->pause_count) {
 519         return;
 520     }
 521     block_job_enter(job);
 522 }
 523
 524 void block_job_user_resume(BlockJob *job)
 525 {
 526     if (job && job->user_paused && job->pause_count > 0) {
 527         job->user_paused = false;
 528         block_job_resume(job);
 529     }
 530 }
 531
 532 void block_job_enter(BlockJob *job)
 533 {
 534     if (job->co && !job->busy) {
 535         qemu_coroutine_enter(job->co);
 536     }
 537 }
 538
 539 void block_job_cancel(BlockJob *job)
 540 {
 541     if (block_job_started(job)) {
 542         job->cancelled = true;
 543         block_job_iostatus_reset(job);
 544         block_job_enter(job);
 545     } else {
 546         block_job_completed(job, -ECANCELED);
 547     }
 548 }
 549
 550 bool block_job_is_cancelled(BlockJob *job)
 551 {
 552     return job->cancelled;
 553 }
 554
 555 void block_job_iostatus_reset(BlockJob *job)
 556 {
 557     job->iostatus = BLOCK_DEVICE_IO_STATUS_OK;
 558     if (job->driver->iostatus_reset) {
 559         job->driver->iostatus_reset(job);
 560     }
 561 }
 562
 563 static int block_job_finish_sync(BlockJob *job,
 564                                  void (*finish)(BlockJob *, Error **errp),
 565                                  Error **errp)
 566 {
 567     Error *local_err = NULL;
 568     int ret;
 569
 570     assert(blk_bs(job->blk)->job == job);
 571
 572     block_job_ref(job);
 573
 574     finish(job, &local_err);
 575     if (local_err) {
 576         error_propagate(errp, local_err);
 577         block_job_unref(job);
 578         return -EBUSY;
 579     }
 580     /* block_job_drain calls block_job_enter, and it should be enough to
 581      * induce progress until the job completes or moves to the main thread.
 582     */
 583     while (!job->deferred_to_main_loop && !job->completed) {
 584         block_job_drain(job);
 585     }
 586     while (!job->completed) {
 587         aio_poll(qemu_get_aio_context(), true);
 588     }
 589     ret = (job->cancelled && job->ret == 0) ? -ECANCELED : job->ret;
 590     block_job_unref(job);
 591     return ret;
 592 }
 593
 594 /* A wrapper around block_job_cancel() taking an Error ** parameter so it may be
 595  * used with block_job_finish_sync() without the need for (rather nasty)
 596  * function pointer casts there. */
 597 static void block_job_cancel_err(BlockJob *job, Error **errp)
 598 {
 599     block_job_cancel(job);
 600 }
 601
 602 int block_job_cancel_sync(BlockJob *job)
 603 {
 604     return block_job_finish_sync(job, &block_job_cancel_err, NULL);
 605 }
 606
 607 void block_job_cancel_sync_all(void)
 608 {
 609     BlockJob *job;
 610     AioContext *aio_context;
 611
 612     while ((job = QLIST_FIRST(&block_jobs))) {
 613         aio_context = blk_get_aio_context(job->blk);
 614         aio_context_acquire(aio_context);
 615         block_job_cancel_sync(job);
 616         aio_context_release(aio_context);
 617     }
 618 }
 619
 620 int block_job_complete_sync(BlockJob *job, Error **errp)
 621 {
 622     return block_job_finish_sync(job, &block_job_complete, errp);
 623 }
 624
 625 void block_job_sleep_ns(BlockJob *job, QEMUClockType type, int64_t ns)
 626 {
 627     assert(job->busy);
 628
 629     /* Check cancellation *before* setting busy = false, too!  */
 630     if (block_job_is_cancelled(job)) {
 631         return;
 632     }
 633
 634     job->busy = false;
 635     if (!block_job_should_pause(job)) {
 636         co_aio_sleep_ns(blk_get_aio_context(job->blk), type, ns);
 637     }
 638     job->busy = true;
 639
 640     block_job_pause_point(job);
 641 }
 642
 643 void block_job_yield(BlockJob *job)
 644 {
 645     assert(job->busy);
 646
 647     /* Check cancellation *before* setting busy = false, too!  */
 648     if (block_job_is_cancelled(job)) {
 649         return;
 650     }
 651
 652     job->busy = false;
 653     if (!block_job_should_pause(job)) {
 654         qemu_coroutine_yield();
 655     }
 656     job->busy = true;
 657
 658     block_job_pause_point(job);
 659 }
 660
 661 BlockJobInfo *block_job_query(BlockJob *job, Error **errp)
 662 {
 663     BlockJobInfo *info;
 664
 665     if (block_job_is_internal(job)) {
 666         error_setg(errp, "Cannot query QEMU internal jobs");
 667         return NULL;
 668     }
 669     info = g_new0(BlockJobInfo, 1);
 670     info->type      = g_strdup(BlockJobType_lookup[job->driver->job_type]);
 671     info->device    = g_strdup(job->id);
 672     info->len       = job->len;
 673     info->busy      = job->busy;
 674     info->paused    = job->pause_count > 0;
 675     info->offset    = job->offset;
 676     info->speed     = job->speed;
 677     info->io_status = job->iostatus;
 678     info->ready     = job->ready;
 679     return info;
 680 }
 681
 682 static void block_job_iostatus_set_err(BlockJob *job, int error)
 683 {
 684     if (job->iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
 685         job->iostatus = error == ENOSPC ? BLOCK_DEVICE_IO_STATUS_NOSPACE :
 686                                           BLOCK_DEVICE_IO_STATUS_FAILED;
 687     }
 688 }
 689
 690 static void block_job_event_cancelled(BlockJob *job)
 691 {
 692     if (block_job_is_internal(job)) {
 693         return;
 694     }
 695
 696     qapi_event_send_block_job_cancelled(job->driver->job_type,
 697                                         job->id,
 698                                         job->len,
 699                                         job->offset,
 700                                         job->speed,
 701                                         &error_abort);
 702 }
 703
 704 static void block_job_event_completed(BlockJob *job, const char *msg)
 705 {
 706     if (block_job_is_internal(job)) {
 707         return;
 708     }
 709
 710     qapi_event_send_block_job_completed(job->driver->job_type,
 711                                         job->id,
 712                                         job->len,
 713                                         job->offset,
 714                                         job->speed,
 715                                         !!msg,
 716                                         msg,
 717                                         &error_abort);
 718 }
 719
 720 void block_job_event_ready(BlockJob *job)
 721 {
 722     job->ready = true;
 723
 724     if (block_job_is_internal(job)) {
 725         return;
 726     }
 727
 728     qapi_event_send_block_job_ready(job->driver->job_type,
 729                                     job->id,
 730                                     job->len,
 731                                     job->offset,
 732                                     job->speed, &error_abort);
 733 }
 734
 735 BlockErrorAction block_job_error_action(BlockJob *job, BlockdevOnError on_err,
 736                                         int is_read, int error)
 737 {
 738     BlockErrorAction action;
 739
 740     switch (on_err) {
 741     case BLOCKDEV_ON_ERROR_ENOSPC:
 742     case BLOCKDEV_ON_ERROR_AUTO:
 743         action = (error == ENOSPC) ?
 744                  BLOCK_ERROR_ACTION_STOP : BLOCK_ERROR_ACTION_REPORT;
 745         break;
 746     case BLOCKDEV_ON_ERROR_STOP:
 747         action = BLOCK_ERROR_ACTION_STOP;
 748         break;
 749     case BLOCKDEV_ON_ERROR_REPORT:
 750         action = BLOCK_ERROR_ACTION_REPORT;
 751         break;
 752     case BLOCKDEV_ON_ERROR_IGNORE:
 753         action = BLOCK_ERROR_ACTION_IGNORE;
 754         break;
 755     default:
 756         abort();
 757     }
 758     if (!block_job_is_internal(job)) {
 759         qapi_event_send_block_job_error(job->id,
 760                                         is_read ? IO_OPERATION_TYPE_READ :
 761                                         IO_OPERATION_TYPE_WRITE,
 762                                         action, &error_abort);
 763     }
 764     if (action == BLOCK_ERROR_ACTION_STOP) {
 765         /* make the pause user visible, which will be resumed from QMP. */
 766         block_job_user_pause(job);
 767         block_job_iostatus_set_err(job, error);
 768     }
 769     return action;
 770 }
 771
 772 typedef struct {
 773     BlockJob *job;
 774     AioContext *aio_context;
 775     BlockJobDeferToMainLoopFn *fn;
 776     void *opaque;
 777 } BlockJobDeferToMainLoopData;
 778
 779 static void block_job_defer_to_main_loop_bh(void *opaque)
 780 {
 781     BlockJobDeferToMainLoopData *data = opaque;
 782     AioContext *aio_context;
 783
 784     /* Prevent race with block_job_defer_to_main_loop() */
 785     aio_context_acquire(data->aio_context);
 786
 787     /* Fetch BDS AioContext again, in case it has changed */
 788     aio_context = blk_get_aio_context(data->job->blk);
 789     if (aio_context != data->aio_context) {
 790         aio_context_acquire(aio_context);
 791     }
 792
 793     data->job->deferred_to_main_loop = false;
 794     data->fn(data->job, data->opaque);
 795
 796     if (aio_context != data->aio_context) {
 797         aio_context_release(aio_context);
 798     }
 799
 800     aio_context_release(data->aio_context);
 801
 802     g_free(data);
 803 }
 804
 805 void block_job_defer_to_main_loop(BlockJob *job,
 806                                   BlockJobDeferToMainLoopFn *fn,
 807                                   void *opaque)
 808 {
 809     BlockJobDeferToMainLoopData *data = g_malloc(sizeof(*data));
 810     data->job = job;
 811     data->aio_context = blk_get_aio_context(job->blk);
 812     data->fn = fn;
 813     data->opaque = opaque;
 814     job->deferred_to_main_loop = true;
 815
 816     aio_bh_schedule_oneshot(qemu_get_aio_context(),
 817                             block_job_defer_to_main_loop_bh, data);
 818 }
 819
 820 BlockJobTxn *block_job_txn_new(void)
 821 {
 822     BlockJobTxn *txn = g_new0(BlockJobTxn, 1);
 823     QLIST_INIT(&txn->jobs);
 824     txn->refcnt = 1;
 825     return txn;
 826 }
 827
 828 static void block_job_txn_ref(BlockJobTxn *txn)
 829 {
 830     txn->refcnt++;
 831 }
 832
 833 void block_job_txn_unref(BlockJobTxn *txn)
 834 {
 835     if (txn && --txn->refcnt == 0) {
 836         g_free(txn);
 837     }
 838 }
 839
 840 void block_job_txn_add_job(BlockJobTxn *txn, BlockJob *job)
 841 {
 842     if (!txn) {
 843         return;
 844     }
 845
 846     assert(!job->txn);
 847     job->txn = txn;
 848
 849     QLIST_INSERT_HEAD(&txn->jobs, job, txn_list);
 850     block_job_txn_ref(txn);
 851 }