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