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