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 BlockJob *block_job_next(BlockJob *job)
  59 {
  60     if (!job) {
  61         return QLIST_FIRST(&block_jobs);
  62     }
  63     return QLIST_NEXT(job, job_list);
  64 }
  65
  66 BlockJob *block_job_get(const char *id)
  67 {
  68     BlockJob *job;
  69
  70     QLIST_FOREACH(job, &block_jobs, job_list) {
  71         if (job->id && !strcmp(id, job->id)) {
  72             return job;
  73         }
  74     }
  75
  76     return NULL;
  77 }
  78
  79 static void block_job_attached_aio_context(AioContext *new_context,
  80                                            void *opaque)
  81 {
  82     BlockJob *job = opaque;
  83
  84     if (job->driver->attached_aio_context) {
  85         job->driver->attached_aio_context(job, new_context);
  86     }
  87
  88     block_job_resume(job);
  89 }
  90
  91 static void block_job_drain(BlockJob *job)
  92 {
  93     /* If job is !job->busy this kicks it into the next pause point. */
  94     block_job_enter(job);
  95
  96     blk_drain(job->blk);
  97     if (job->driver->drain) {
  98         job->driver->drain(job);
  99     }
 100 }
 101
 102 static void block_job_detach_aio_context(void *opaque)
 103 {
 104     BlockJob *job = opaque;
 105
 106     /* In case the job terminates during aio_poll()... */
 107     block_job_ref(job);
 108
 109     block_job_pause(job);
 110
 111     while (!job->paused && !job->completed) {
 112         block_job_drain(job);
 113     }
 114
 115     block_job_unref(job);
 116 }
 117
 118 void block_job_add_bdrv(BlockJob *job, BlockDriverState *bs)
 119 {
 120     job->nodes = g_slist_prepend(job->nodes, bs);
 121     bdrv_ref(bs);
 122     bdrv_op_block_all(bs, job->blocker);
 123 }
 124
 125 void *block_job_create(const char *job_id, const BlockJobDriver *driver,
 126                        BlockDriverState *bs, uint64_t perm,
 127                        uint64_t shared_perm, int64_t speed, int flags,
 128                        BlockCompletionFunc *cb, void *opaque, Error **errp)
 129 {
 130     BlockBackend *blk;
 131     BlockJob *job;
 132     int ret;
 133
 134     if (bs->job) {
 135         error_setg(errp, QERR_DEVICE_IN_USE, bdrv_get_device_name(bs));
 136         return NULL;
 137     }
 138
 139     if (job_id == NULL && !(flags & BLOCK_JOB_INTERNAL)) {
 140         job_id = bdrv_get_device_name(bs);
 141         if (!*job_id) {
 142             error_setg(errp, "An explicit job ID is required for this node");
 143             return NULL;
 144         }
 145     }
 146
 147     if (job_id) {
 148         if (flags & BLOCK_JOB_INTERNAL) {
 149             error_setg(errp, "Cannot specify job ID for internal block job");
 150             return NULL;
 151         }
 152
 153         if (!id_wellformed(job_id)) {
 154             error_setg(errp, "Invalid job ID '%s'", job_id);
 155             return NULL;
 156         }
 157
 158         if (block_job_get(job_id)) {
 159             error_setg(errp, "Job ID '%s' already in use", job_id);
 160             return NULL;
 161         }
 162     }
 163
 164     blk = blk_new(perm, shared_perm);
 165     ret = blk_insert_bs(blk, bs, errp);
 166     if (ret < 0) {
 167         blk_unref(blk);
 168         return NULL;
 169     }
 170
 171     job = g_malloc0(driver->instance_size);
 172     error_setg(&job->blocker, "block device is in use by block job: %s",
 173                BlockJobType_lookup[driver->job_type]);
 174     block_job_add_bdrv(job, bs);
 175     bdrv_op_unblock(bs, BLOCK_OP_TYPE_DATAPLANE, job->blocker);
 176
 177     job->driver        = driver;
 178     job->id            = g_strdup(job_id);
 179     job->blk           = blk;
 180     job->cb            = cb;
 181     job->opaque        = opaque;
 182     job->busy          = false;
 183     job->paused        = true;
 184     job->pause_count   = 1;
 185     job->refcnt        = 1;
 186     bs->job = job;
 187
 188     QLIST_INSERT_HEAD(&block_jobs, job, job_list);
 189
 190     blk_add_aio_context_notifier(blk, block_job_attached_aio_context,
 191                                  block_job_detach_aio_context, job);
 192
 193     /* Only set speed when necessary to avoid NotSupported error */
 194     if (speed != 0) {
 195         Error *local_err = NULL;
 196
 197         block_job_set_speed(job, speed, &local_err);
 198         if (local_err) {
 199             block_job_unref(job);
 200             error_propagate(errp, local_err);
 201             return NULL;
 202         }
 203     }
 204     return job;
 205 }
 206
 207 bool block_job_is_internal(BlockJob *job)
 208 {
 209     return (job->id == NULL);
 210 }
 211
 212 static bool block_job_started(BlockJob *job)
 213 {
 214     return job->co;
 215 }
 216
 217 void block_job_start(BlockJob *job)
 218 {
 219     assert(job && !block_job_started(job) && job->paused &&
 220            !job->busy && job->driver->start);
 221     job->co = qemu_coroutine_create(job->driver->start, job);
 222     if (--job->pause_count == 0) {
 223         job->paused = false;
 224         job->busy = true;
 225         qemu_coroutine_enter(job->co);
 226     }
 227 }
 228
 229 void block_job_ref(BlockJob *job)
 230 {
 231     ++job->refcnt;
 232 }
 233
 234 void block_job_unref(BlockJob *job)
 235 {
 236     if (--job->refcnt == 0) {
 237         GSList *l;
 238         BlockDriverState *bs = blk_bs(job->blk);
 239         bs->job = NULL;
 240         for (l = job->nodes; l; l = l->next) {
 241             bs = l->data;
 242             bdrv_op_unblock_all(bs, job->blocker);
 243             bdrv_unref(bs);
 244         }
 245         g_slist_free(job->nodes);
 246         blk_remove_aio_context_notifier(job->blk,
 247                                         block_job_attached_aio_context,
 248                                         block_job_detach_aio_context, job);
 249         blk_unref(job->blk);
 250         error_free(job->blocker);
 251         g_free(job->id);
 252         QLIST_REMOVE(job, job_list);
 253         g_free(job);
 254     }
 255 }
 256
 257 static void block_job_completed_single(BlockJob *job)
 258 {
 259     if (!job->ret) {
 260         if (job->driver->commit) {
 261             job->driver->commit(job);
 262         }
 263     } else {
 264         if (job->driver->abort) {
 265             job->driver->abort(job);
 266         }
 267     }
 268     if (job->driver->clean) {
 269         job->driver->clean(job);
 270     }
 271
 272     if (job->cb) {
 273         job->cb(job->opaque, job->ret);
 274     }
 275
 276     /* Emit events only if we actually started */
 277     if (block_job_started(job)) {
 278         if (block_job_is_cancelled(job)) {
 279             block_job_event_cancelled(job);
 280         } else {
 281             const char *msg = NULL;
 282             if (job->ret < 0) {
 283                 msg = strerror(-job->ret);
 284             }
 285             block_job_event_completed(job, msg);
 286         }
 287     }
 288
 289     if (job->txn) {
 290         QLIST_REMOVE(job, txn_list);
 291         block_job_txn_unref(job->txn);
 292     }
 293     block_job_unref(job);
 294 }
 295
 296 static void block_job_completed_txn_abort(BlockJob *job)
 297 {
 298     AioContext *ctx;
 299     BlockJobTxn *txn = job->txn;
 300     BlockJob *other_job, *next;
 301
 302     if (txn->aborting) {
 303         /*
 304          * We are cancelled by another job, which will handle everything.
 305          */
 306         return;
 307     }
 308     txn->aborting = true;
 309     /* We are the first failed job. Cancel other jobs. */
 310     QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
 311         ctx = blk_get_aio_context(other_job->blk);
 312         aio_context_acquire(ctx);
 313     }
 314     QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
 315         if (other_job == job || other_job->completed) {
 316             /* Other jobs are "effectively" cancelled by us, set the status for
 317              * them; this job, however, may or may not be cancelled, depending
 318              * on the caller, so leave it. */
 319             if (other_job != job) {
 320                 other_job->cancelled = true;
 321             }
 322             continue;
 323         }
 324         block_job_cancel_sync(other_job);
 325         assert(other_job->completed);
 326     }
 327     QLIST_FOREACH_SAFE(other_job, &txn->jobs, txn_list, next) {
 328         ctx = blk_get_aio_context(other_job->blk);
 329         block_job_completed_single(other_job);
 330         aio_context_release(ctx);
 331     }
 332 }
 333
 334 static void block_job_completed_txn_success(BlockJob *job)
 335 {
 336     AioContext *ctx;
 337     BlockJobTxn *txn = job->txn;
 338     BlockJob *other_job, *next;
 339     /*
 340      * Successful completion, see if there are other running jobs in this
 341      * txn.
 342      */
 343     QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
 344         if (!other_job->completed) {
 345             return;
 346         }
 347     }
 348     /* We are the last completed job, commit the transaction. */
 349     QLIST_FOREACH_SAFE(other_job, &txn->jobs, txn_list, next) {
 350         ctx = blk_get_aio_context(other_job->blk);
 351         aio_context_acquire(ctx);
 352         assert(other_job->ret == 0);
 353         block_job_completed_single(other_job);
 354         aio_context_release(ctx);
 355     }
 356 }
 357
 358 void block_job_completed(BlockJob *job, int ret)
 359 {
 360     assert(blk_bs(job->blk)->job == job);
 361     assert(!job->completed);
 362     job->completed = true;
 363     job->ret = ret;
 364     if (!job->txn) {
 365         block_job_completed_single(job);
 366     } else if (ret < 0 || block_job_is_cancelled(job)) {
 367         block_job_completed_txn_abort(job);
 368     } else {
 369         block_job_completed_txn_success(job);
 370     }
 371 }
 372
 373 void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp)
 374 {
 375     Error *local_err = NULL;
 376
 377     if (!job->driver->set_speed) {
 378         error_setg(errp, QERR_UNSUPPORTED);
 379         return;
 380     }
 381     job->driver->set_speed(job, speed, &local_err);
 382     if (local_err) {
 383         error_propagate(errp, local_err);
 384         return;
 385     }
 386
 387     job->speed = speed;
 388 }
 389
 390 void block_job_complete(BlockJob *job, Error **errp)
 391 {
 392     /* Should not be reachable via external interface for internal jobs */
 393     assert(job->id);
 394     if (job->pause_count || job->cancelled ||
 395         !block_job_started(job) || !job->driver->complete) {
 396         error_setg(errp, "The active block job '%s' cannot be completed",
 397                    job->id);
 398         return;
 399     }
 400
 401     job->driver->complete(job, errp);
 402 }
 403
 404 void block_job_pause(BlockJob *job)
 405 {
 406     job->pause_count++;
 407 }
 408
 409 void block_job_user_pause(BlockJob *job)
 410 {
 411     job->user_paused = true;
 412     block_job_pause(job);
 413 }
 414
 415 static bool block_job_should_pause(BlockJob *job)
 416 {
 417     return job->pause_count > 0;
 418 }
 419
 420 bool block_job_user_paused(BlockJob *job)
 421 {
 422     return job ? job->user_paused : 0;
 423 }
 424
 425 void coroutine_fn block_job_pause_point(BlockJob *job)
 426 {
 427     assert(job && block_job_started(job));
 428
 429     if (!block_job_should_pause(job)) {
 430         return;
 431     }
 432     if (block_job_is_cancelled(job)) {
 433         return;
 434     }
 435
 436     if (job->driver->pause) {
 437         job->driver->pause(job);
 438     }
 439
 440     if (block_job_should_pause(job) && !block_job_is_cancelled(job)) {
 441         job->paused = true;
 442         job->busy = false;
 443         qemu_coroutine_yield(); /* wait for block_job_resume() */
 444         job->busy = true;
 445         job->paused = false;
 446     }
 447
 448     if (job->driver->resume) {
 449         job->driver->resume(job);
 450     }
 451 }
 452
 453 void block_job_resume(BlockJob *job)
 454 {
 455     assert(job->pause_count > 0);
 456     job->pause_count--;
 457     if (job->pause_count) {
 458         return;
 459     }
 460     block_job_enter(job);
 461 }
 462
 463 void block_job_user_resume(BlockJob *job)
 464 {
 465     if (job && job->user_paused && job->pause_count > 0) {
 466         job->user_paused = false;
 467         block_job_resume(job);
 468     }
 469 }
 470
 471 void block_job_enter(BlockJob *job)
 472 {
 473     if (job->co && !job->busy) {
 474         qemu_coroutine_enter(job->co);
 475     }
 476 }
 477
 478 void block_job_cancel(BlockJob *job)
 479 {
 480     if (block_job_started(job)) {
 481         job->cancelled = true;
 482         block_job_iostatus_reset(job);
 483         block_job_enter(job);
 484     } else {
 485         block_job_completed(job, -ECANCELED);
 486     }
 487 }
 488
 489 bool block_job_is_cancelled(BlockJob *job)
 490 {
 491     return job->cancelled;
 492 }
 493
 494 void block_job_iostatus_reset(BlockJob *job)
 495 {
 496     job->iostatus = BLOCK_DEVICE_IO_STATUS_OK;
 497     if (job->driver->iostatus_reset) {
 498         job->driver->iostatus_reset(job);
 499     }
 500 }
 501
 502 static int block_job_finish_sync(BlockJob *job,
 503                                  void (*finish)(BlockJob *, Error **errp),
 504                                  Error **errp)
 505 {
 506     Error *local_err = NULL;
 507     int ret;
 508
 509     assert(blk_bs(job->blk)->job == job);
 510
 511     block_job_ref(job);
 512
 513     finish(job, &local_err);
 514     if (local_err) {
 515         error_propagate(errp, local_err);
 516         block_job_unref(job);
 517         return -EBUSY;
 518     }
 519     /* block_job_drain calls block_job_enter, and it should be enough to
 520      * induce progress until the job completes or moves to the main thread.
 521     */
 522     while (!job->deferred_to_main_loop && !job->completed) {
 523         block_job_drain(job);
 524     }
 525     while (!job->completed) {
 526         aio_poll(qemu_get_aio_context(), true);
 527     }
 528     ret = (job->cancelled && job->ret == 0) ? -ECANCELED : job->ret;
 529     block_job_unref(job);
 530     return ret;
 531 }
 532
 533 /* A wrapper around block_job_cancel() taking an Error ** parameter so it may be
 534  * used with block_job_finish_sync() without the need for (rather nasty)
 535  * function pointer casts there. */
 536 static void block_job_cancel_err(BlockJob *job, Error **errp)
 537 {
 538     block_job_cancel(job);
 539 }
 540
 541 int block_job_cancel_sync(BlockJob *job)
 542 {
 543     return block_job_finish_sync(job, &block_job_cancel_err, NULL);
 544 }
 545
 546 void block_job_cancel_sync_all(void)
 547 {
 548     BlockJob *job;
 549     AioContext *aio_context;
 550
 551     while ((job = QLIST_FIRST(&block_jobs))) {
 552         aio_context = blk_get_aio_context(job->blk);
 553         aio_context_acquire(aio_context);
 554         block_job_cancel_sync(job);
 555         aio_context_release(aio_context);
 556     }
 557 }
 558
 559 int block_job_complete_sync(BlockJob *job, Error **errp)
 560 {
 561     return block_job_finish_sync(job, &block_job_complete, errp);
 562 }
 563
 564 void block_job_sleep_ns(BlockJob *job, QEMUClockType type, int64_t ns)
 565 {
 566     assert(job->busy);
 567
 568     /* Check cancellation *before* setting busy = false, too!  */
 569     if (block_job_is_cancelled(job)) {
 570         return;
 571     }
 572
 573     job->busy = false;
 574     if (!block_job_should_pause(job)) {
 575         co_aio_sleep_ns(blk_get_aio_context(job->blk), type, ns);
 576     }
 577     job->busy = true;
 578
 579     block_job_pause_point(job);
 580 }
 581
 582 void block_job_yield(BlockJob *job)
 583 {
 584     assert(job->busy);
 585
 586     /* Check cancellation *before* setting busy = false, too!  */
 587     if (block_job_is_cancelled(job)) {
 588         return;
 589     }
 590
 591     job->busy = false;
 592     if (!block_job_should_pause(job)) {
 593         qemu_coroutine_yield();
 594     }
 595     job->busy = true;
 596
 597     block_job_pause_point(job);
 598 }
 599
 600 BlockJobInfo *block_job_query(BlockJob *job, Error **errp)
 601 {
 602     BlockJobInfo *info;
 603
 604     if (block_job_is_internal(job)) {
 605         error_setg(errp, "Cannot query QEMU internal jobs");
 606         return NULL;
 607     }
 608     info = g_new0(BlockJobInfo, 1);
 609     info->type      = g_strdup(BlockJobType_lookup[job->driver->job_type]);
 610     info->device    = g_strdup(job->id);
 611     info->len       = job->len;
 612     info->busy      = job->busy;
 613     info->paused    = job->pause_count > 0;
 614     info->offset    = job->offset;
 615     info->speed     = job->speed;
 616     info->io_status = job->iostatus;
 617     info->ready     = job->ready;
 618     return info;
 619 }
 620
 621 static void block_job_iostatus_set_err(BlockJob *job, int error)
 622 {
 623     if (job->iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
 624         job->iostatus = error == ENOSPC ? BLOCK_DEVICE_IO_STATUS_NOSPACE :
 625                                           BLOCK_DEVICE_IO_STATUS_FAILED;
 626     }
 627 }
 628
 629 static void block_job_event_cancelled(BlockJob *job)
 630 {
 631     if (block_job_is_internal(job)) {
 632         return;
 633     }
 634
 635     qapi_event_send_block_job_cancelled(job->driver->job_type,
 636                                         job->id,
 637                                         job->len,
 638                                         job->offset,
 639                                         job->speed,
 640                                         &error_abort);
 641 }
 642
 643 static void block_job_event_completed(BlockJob *job, const char *msg)
 644 {
 645     if (block_job_is_internal(job)) {
 646         return;
 647     }
 648
 649     qapi_event_send_block_job_completed(job->driver->job_type,
 650                                         job->id,
 651                                         job->len,
 652                                         job->offset,
 653                                         job->speed,
 654                                         !!msg,
 655                                         msg,
 656                                         &error_abort);
 657 }
 658
 659 void block_job_event_ready(BlockJob *job)
 660 {
 661     job->ready = true;
 662
 663     if (block_job_is_internal(job)) {
 664         return;
 665     }
 666
 667     qapi_event_send_block_job_ready(job->driver->job_type,
 668                                     job->id,
 669                                     job->len,
 670                                     job->offset,
 671                                     job->speed, &error_abort);
 672 }
 673
 674 BlockErrorAction block_job_error_action(BlockJob *job, BlockdevOnError on_err,
 675                                         int is_read, int error)
 676 {
 677     BlockErrorAction action;
 678
 679     switch (on_err) {
 680     case BLOCKDEV_ON_ERROR_ENOSPC:
 681     case BLOCKDEV_ON_ERROR_AUTO:
 682         action = (error == ENOSPC) ?
 683                  BLOCK_ERROR_ACTION_STOP : BLOCK_ERROR_ACTION_REPORT;
 684         break;
 685     case BLOCKDEV_ON_ERROR_STOP:
 686         action = BLOCK_ERROR_ACTION_STOP;
 687         break;
 688     case BLOCKDEV_ON_ERROR_REPORT:
 689         action = BLOCK_ERROR_ACTION_REPORT;
 690         break;
 691     case BLOCKDEV_ON_ERROR_IGNORE:
 692         action = BLOCK_ERROR_ACTION_IGNORE;
 693         break;
 694     default:
 695         abort();
 696     }
 697     if (!block_job_is_internal(job)) {
 698         qapi_event_send_block_job_error(job->id,
 699                                         is_read ? IO_OPERATION_TYPE_READ :
 700                                         IO_OPERATION_TYPE_WRITE,
 701                                         action, &error_abort);
 702     }
 703     if (action == BLOCK_ERROR_ACTION_STOP) {
 704         /* make the pause user visible, which will be resumed from QMP. */
 705         block_job_user_pause(job);
 706         block_job_iostatus_set_err(job, error);
 707     }
 708     return action;
 709 }
 710
 711 typedef struct {
 712     BlockJob *job;
 713     AioContext *aio_context;
 714     BlockJobDeferToMainLoopFn *fn;
 715     void *opaque;
 716 } BlockJobDeferToMainLoopData;
 717
 718 static void block_job_defer_to_main_loop_bh(void *opaque)
 719 {
 720     BlockJobDeferToMainLoopData *data = opaque;
 721     AioContext *aio_context;
 722
 723     /* Prevent race with block_job_defer_to_main_loop() */
 724     aio_context_acquire(data->aio_context);
 725
 726     /* Fetch BDS AioContext again, in case it has changed */
 727     aio_context = blk_get_aio_context(data->job->blk);
 728     aio_context_acquire(aio_context);
 729
 730     data->job->deferred_to_main_loop = false;
 731     data->fn(data->job, data->opaque);
 732
 733     aio_context_release(aio_context);
 734
 735     aio_context_release(data->aio_context);
 736
 737     g_free(data);
 738 }
 739
 740 void block_job_defer_to_main_loop(BlockJob *job,
 741                                   BlockJobDeferToMainLoopFn *fn,
 742                                   void *opaque)
 743 {
 744     BlockJobDeferToMainLoopData *data = g_malloc(sizeof(*data));
 745     data->job = job;
 746     data->aio_context = blk_get_aio_context(job->blk);
 747     data->fn = fn;
 748     data->opaque = opaque;
 749     job->deferred_to_main_loop = true;
 750
 751     aio_bh_schedule_oneshot(qemu_get_aio_context(),
 752                             block_job_defer_to_main_loop_bh, data);
 753 }
 754
 755 BlockJobTxn *block_job_txn_new(void)
 756 {
 757     BlockJobTxn *txn = g_new0(BlockJobTxn, 1);
 758     QLIST_INIT(&txn->jobs);
 759     txn->refcnt = 1;
 760     return txn;
 761 }
 762
 763 static void block_job_txn_ref(BlockJobTxn *txn)
 764 {
 765     txn->refcnt++;
 766 }
 767
 768 void block_job_txn_unref(BlockJobTxn *txn)
 769 {
 770     if (txn && --txn->refcnt == 0) {
 771         g_free(txn);
 772     }
 773 }
 774
 775 void block_job_txn_add_job(BlockJobTxn *txn, BlockJob *job)
 776 {
 777     if (!txn) {
 778         return;
 779     }
 780
 781     assert(!job->txn);
 782     job->txn = txn;
 783
 784     QLIST_INSERT_HEAD(&txn->jobs, job, txn_list);
 785     block_job_txn_ref(txn);
 786 }