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 /**
 254  * All jobs must allow a pause point before entering their job proper. This
 255  * ensures that jobs can be paused prior to being started, then resumed later.
 256  */
 257 static void coroutine_fn block_job_co_entry(void *opaque)
 258 {
 259     BlockJob *job = opaque;
 260
 261     assert(job && job->driver && job->driver->start);
 262     block_job_pause_point(job);
 263     job->driver->start(job);
 264 }
 265
 266 void block_job_start(BlockJob *job)
 267 {
 268     assert(job && !block_job_started(job) && job->paused &&
 269            job->driver && job->driver->start);
 270     job->co = qemu_coroutine_create(block_job_co_entry, job);
 271     job->pause_count--;
 272     job->busy = true;
 273     job->paused = false;
 274     qemu_coroutine_enter(job->co);
 275 }
 276
 277 void block_job_ref(BlockJob *job)
 278 {
 279     ++job->refcnt;
 280 }
 281
 282 void block_job_unref(BlockJob *job)
 283 {
 284     if (--job->refcnt == 0) {
 285         BlockDriverState *bs = blk_bs(job->blk);
 286         bs->job = NULL;
 287         block_job_remove_all_bdrv(job);
 288         blk_remove_aio_context_notifier(job->blk,
 289                                         block_job_attached_aio_context,
 290                                         block_job_detach_aio_context, job);
 291         blk_unref(job->blk);
 292         error_free(job->blocker);
 293         g_free(job->id);
 294         QLIST_REMOVE(job, job_list);
 295         g_free(job);
 296     }
 297 }
 298
 299 static void block_job_completed_single(BlockJob *job)
 300 {
 301     if (!job->ret) {
 302         if (job->driver->commit) {
 303             job->driver->commit(job);
 304         }
 305     } else {
 306         if (job->driver->abort) {
 307             job->driver->abort(job);
 308         }
 309     }
 310     if (job->driver->clean) {
 311         job->driver->clean(job);
 312     }
 313
 314     if (job->cb) {
 315         job->cb(job->opaque, job->ret);
 316     }
 317
 318     /* Emit events only if we actually started */
 319     if (block_job_started(job)) {
 320         if (block_job_is_cancelled(job)) {
 321             block_job_event_cancelled(job);
 322         } else {
 323             const char *msg = NULL;
 324             if (job->ret < 0) {
 325                 msg = strerror(-job->ret);
 326             }
 327             block_job_event_completed(job, msg);
 328         }
 329     }
 330
 331     if (job->txn) {
 332         QLIST_REMOVE(job, txn_list);
 333         block_job_txn_unref(job->txn);
 334     }
 335     block_job_unref(job);
 336 }
 337
 338 static void block_job_completed_txn_abort(BlockJob *job)
 339 {
 340     AioContext *ctx;
 341     BlockJobTxn *txn = job->txn;
 342     BlockJob *other_job, *next;
 343
 344     if (txn->aborting) {
 345         /*
 346          * We are cancelled by another job, which will handle everything.
 347          */
 348         return;
 349     }
 350     txn->aborting = true;
 351     /* We are the first failed job. Cancel other jobs. */
 352     QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
 353         ctx = blk_get_aio_context(other_job->blk);
 354         aio_context_acquire(ctx);
 355     }
 356     QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
 357         if (other_job == job || other_job->completed) {
 358             /* Other jobs are "effectively" cancelled by us, set the status for
 359              * them; this job, however, may or may not be cancelled, depending
 360              * on the caller, so leave it. */
 361             if (other_job != job) {
 362                 other_job->cancelled = true;
 363             }
 364             continue;
 365         }
 366         block_job_cancel_sync(other_job);
 367         assert(other_job->completed);
 368     }
 369     QLIST_FOREACH_SAFE(other_job, &txn->jobs, txn_list, next) {
 370         ctx = blk_get_aio_context(other_job->blk);
 371         block_job_completed_single(other_job);
 372         aio_context_release(ctx);
 373     }
 374 }
 375
 376 static void block_job_completed_txn_success(BlockJob *job)
 377 {
 378     AioContext *ctx;
 379     BlockJobTxn *txn = job->txn;
 380     BlockJob *other_job, *next;
 381     /*
 382      * Successful completion, see if there are other running jobs in this
 383      * txn.
 384      */
 385     QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
 386         if (!other_job->completed) {
 387             return;
 388         }
 389     }
 390     /* We are the last completed job, commit the transaction. */
 391     QLIST_FOREACH_SAFE(other_job, &txn->jobs, txn_list, next) {
 392         ctx = blk_get_aio_context(other_job->blk);
 393         aio_context_acquire(ctx);
 394         assert(other_job->ret == 0);
 395         block_job_completed_single(other_job);
 396         aio_context_release(ctx);
 397     }
 398 }
 399
 400 void block_job_completed(BlockJob *job, int ret)
 401 {
 402     assert(blk_bs(job->blk)->job == job);
 403     assert(!job->completed);
 404     job->completed = true;
 405     job->ret = ret;
 406     if (!job->txn) {
 407         block_job_completed_single(job);
 408     } else if (ret < 0 || block_job_is_cancelled(job)) {
 409         block_job_completed_txn_abort(job);
 410     } else {
 411         block_job_completed_txn_success(job);
 412     }
 413 }
 414
 415 void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp)
 416 {
 417     Error *local_err = NULL;
 418
 419     if (!job->driver->set_speed) {
 420         error_setg(errp, QERR_UNSUPPORTED);
 421         return;
 422     }
 423     job->driver->set_speed(job, speed, &local_err);
 424     if (local_err) {
 425         error_propagate(errp, local_err);
 426         return;
 427     }
 428
 429     job->speed = speed;
 430 }
 431
 432 void block_job_complete(BlockJob *job, Error **errp)
 433 {
 434     /* Should not be reachable via external interface for internal jobs */
 435     assert(job->id);
 436     if (job->pause_count || job->cancelled ||
 437         !block_job_started(job) || !job->driver->complete) {
 438         error_setg(errp, "The active block job '%s' cannot be completed",
 439                    job->id);
 440         return;
 441     }
 442
 443     job->driver->complete(job, errp);
 444 }
 445
 446 void block_job_pause(BlockJob *job)
 447 {
 448     job->pause_count++;
 449 }
 450
 451 void block_job_user_pause(BlockJob *job)
 452 {
 453     job->user_paused = true;
 454     block_job_pause(job);
 455 }
 456
 457 static bool block_job_should_pause(BlockJob *job)
 458 {
 459     return job->pause_count > 0;
 460 }
 461
 462 bool block_job_user_paused(BlockJob *job)
 463 {
 464     return job ? job->user_paused : 0;
 465 }
 466
 467 void coroutine_fn block_job_pause_point(BlockJob *job)
 468 {
 469     assert(job && block_job_started(job));
 470
 471     if (!block_job_should_pause(job)) {
 472         return;
 473     }
 474     if (block_job_is_cancelled(job)) {
 475         return;
 476     }
 477
 478     if (job->driver->pause) {
 479         job->driver->pause(job);
 480     }
 481
 482     if (block_job_should_pause(job) && !block_job_is_cancelled(job)) {
 483         job->paused = true;
 484         job->busy = false;
 485         qemu_coroutine_yield(); /* wait for block_job_resume() */
 486         job->busy = true;
 487         job->paused = false;
 488     }
 489
 490     if (job->driver->resume) {
 491         job->driver->resume(job);
 492     }
 493 }
 494
 495 void block_job_resume(BlockJob *job)
 496 {
 497     assert(job->pause_count > 0);
 498     job->pause_count--;
 499     if (job->pause_count) {
 500         return;
 501     }
 502     block_job_enter(job);
 503 }
 504
 505 void block_job_user_resume(BlockJob *job)
 506 {
 507     if (job && job->user_paused && job->pause_count > 0) {
 508         job->user_paused = false;
 509         block_job_resume(job);
 510     }
 511 }
 512
 513 void block_job_enter(BlockJob *job)
 514 {
 515     if (job->co && !job->busy) {
 516         qemu_coroutine_enter(job->co);
 517     }
 518 }
 519
 520 void block_job_cancel(BlockJob *job)
 521 {
 522     if (block_job_started(job)) {
 523         job->cancelled = true;
 524         block_job_iostatus_reset(job);
 525         block_job_enter(job);
 526     } else {
 527         block_job_completed(job, -ECANCELED);
 528     }
 529 }
 530
 531 bool block_job_is_cancelled(BlockJob *job)
 532 {
 533     return job->cancelled;
 534 }
 535
 536 void block_job_iostatus_reset(BlockJob *job)
 537 {
 538     job->iostatus = BLOCK_DEVICE_IO_STATUS_OK;
 539     if (job->driver->iostatus_reset) {
 540         job->driver->iostatus_reset(job);
 541     }
 542 }
 543
 544 static int block_job_finish_sync(BlockJob *job,
 545                                  void (*finish)(BlockJob *, Error **errp),
 546                                  Error **errp)
 547 {
 548     Error *local_err = NULL;
 549     int ret;
 550
 551     assert(blk_bs(job->blk)->job == job);
 552
 553     block_job_ref(job);
 554
 555     finish(job, &local_err);
 556     if (local_err) {
 557         error_propagate(errp, local_err);
 558         block_job_unref(job);
 559         return -EBUSY;
 560     }
 561     /* block_job_drain calls block_job_enter, and it should be enough to
 562      * induce progress until the job completes or moves to the main thread.
 563     */
 564     while (!job->deferred_to_main_loop && !job->completed) {
 565         block_job_drain(job);
 566     }
 567     while (!job->completed) {
 568         aio_poll(qemu_get_aio_context(), true);
 569     }
 570     ret = (job->cancelled && job->ret == 0) ? -ECANCELED : job->ret;
 571     block_job_unref(job);
 572     return ret;
 573 }
 574
 575 /* A wrapper around block_job_cancel() taking an Error ** parameter so it may be
 576  * used with block_job_finish_sync() without the need for (rather nasty)
 577  * function pointer casts there. */
 578 static void block_job_cancel_err(BlockJob *job, Error **errp)
 579 {
 580     block_job_cancel(job);
 581 }
 582
 583 int block_job_cancel_sync(BlockJob *job)
 584 {
 585     return block_job_finish_sync(job, &block_job_cancel_err, NULL);
 586 }
 587
 588 void block_job_cancel_sync_all(void)
 589 {
 590     BlockJob *job;
 591     AioContext *aio_context;
 592
 593     while ((job = QLIST_FIRST(&block_jobs))) {
 594         aio_context = blk_get_aio_context(job->blk);
 595         aio_context_acquire(aio_context);
 596         block_job_cancel_sync(job);
 597         aio_context_release(aio_context);
 598     }
 599 }
 600
 601 int block_job_complete_sync(BlockJob *job, Error **errp)
 602 {
 603     return block_job_finish_sync(job, &block_job_complete, errp);
 604 }
 605
 606 void block_job_sleep_ns(BlockJob *job, QEMUClockType type, int64_t ns)
 607 {
 608     assert(job->busy);
 609
 610     /* Check cancellation *before* setting busy = false, too!  */
 611     if (block_job_is_cancelled(job)) {
 612         return;
 613     }
 614
 615     job->busy = false;
 616     if (!block_job_should_pause(job)) {
 617         co_aio_sleep_ns(blk_get_aio_context(job->blk), type, ns);
 618     }
 619     job->busy = true;
 620
 621     block_job_pause_point(job);
 622 }
 623
 624 void block_job_yield(BlockJob *job)
 625 {
 626     assert(job->busy);
 627
 628     /* Check cancellation *before* setting busy = false, too!  */
 629     if (block_job_is_cancelled(job)) {
 630         return;
 631     }
 632
 633     job->busy = false;
 634     if (!block_job_should_pause(job)) {
 635         qemu_coroutine_yield();
 636     }
 637     job->busy = true;
 638
 639     block_job_pause_point(job);
 640 }
 641
 642 BlockJobInfo *block_job_query(BlockJob *job, Error **errp)
 643 {
 644     BlockJobInfo *info;
 645
 646     if (block_job_is_internal(job)) {
 647         error_setg(errp, "Cannot query QEMU internal jobs");
 648         return NULL;
 649     }
 650     info = g_new0(BlockJobInfo, 1);
 651     info->type      = g_strdup(BlockJobType_lookup[job->driver->job_type]);
 652     info->device    = g_strdup(job->id);
 653     info->len       = job->len;
 654     info->busy      = job->busy;
 655     info->paused    = job->pause_count > 0;
 656     info->offset    = job->offset;
 657     info->speed     = job->speed;
 658     info->io_status = job->iostatus;
 659     info->ready     = job->ready;
 660     return info;
 661 }
 662
 663 static void block_job_iostatus_set_err(BlockJob *job, int error)
 664 {
 665     if (job->iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
 666         job->iostatus = error == ENOSPC ? BLOCK_DEVICE_IO_STATUS_NOSPACE :
 667                                           BLOCK_DEVICE_IO_STATUS_FAILED;
 668     }
 669 }
 670
 671 static void block_job_event_cancelled(BlockJob *job)
 672 {
 673     if (block_job_is_internal(job)) {
 674         return;
 675     }
 676
 677     qapi_event_send_block_job_cancelled(job->driver->job_type,
 678                                         job->id,
 679                                         job->len,
 680                                         job->offset,
 681                                         job->speed,
 682                                         &error_abort);
 683 }
 684
 685 static void block_job_event_completed(BlockJob *job, const char *msg)
 686 {
 687     if (block_job_is_internal(job)) {
 688         return;
 689     }
 690
 691     qapi_event_send_block_job_completed(job->driver->job_type,
 692                                         job->id,
 693                                         job->len,
 694                                         job->offset,
 695                                         job->speed,
 696                                         !!msg,
 697                                         msg,
 698                                         &error_abort);
 699 }
 700
 701 void block_job_event_ready(BlockJob *job)
 702 {
 703     job->ready = true;
 704
 705     if (block_job_is_internal(job)) {
 706         return;
 707     }
 708
 709     qapi_event_send_block_job_ready(job->driver->job_type,
 710                                     job->id,
 711                                     job->len,
 712                                     job->offset,
 713                                     job->speed, &error_abort);
 714 }
 715
 716 BlockErrorAction block_job_error_action(BlockJob *job, BlockdevOnError on_err,
 717                                         int is_read, int error)
 718 {
 719     BlockErrorAction action;
 720
 721     switch (on_err) {
 722     case BLOCKDEV_ON_ERROR_ENOSPC:
 723     case BLOCKDEV_ON_ERROR_AUTO:
 724         action = (error == ENOSPC) ?
 725                  BLOCK_ERROR_ACTION_STOP : BLOCK_ERROR_ACTION_REPORT;
 726         break;
 727     case BLOCKDEV_ON_ERROR_STOP:
 728         action = BLOCK_ERROR_ACTION_STOP;
 729         break;
 730     case BLOCKDEV_ON_ERROR_REPORT:
 731         action = BLOCK_ERROR_ACTION_REPORT;
 732         break;
 733     case BLOCKDEV_ON_ERROR_IGNORE:
 734         action = BLOCK_ERROR_ACTION_IGNORE;
 735         break;
 736     default:
 737         abort();
 738     }
 739     if (!block_job_is_internal(job)) {
 740         qapi_event_send_block_job_error(job->id,
 741                                         is_read ? IO_OPERATION_TYPE_READ :
 742                                         IO_OPERATION_TYPE_WRITE,
 743                                         action, &error_abort);
 744     }
 745     if (action == BLOCK_ERROR_ACTION_STOP) {
 746         /* make the pause user visible, which will be resumed from QMP. */
 747         block_job_user_pause(job);
 748         block_job_iostatus_set_err(job, error);
 749     }
 750     return action;
 751 }
 752
 753 typedef struct {
 754     BlockJob *job;
 755     AioContext *aio_context;
 756     BlockJobDeferToMainLoopFn *fn;
 757     void *opaque;
 758 } BlockJobDeferToMainLoopData;
 759
 760 static void block_job_defer_to_main_loop_bh(void *opaque)
 761 {
 762     BlockJobDeferToMainLoopData *data = opaque;
 763     AioContext *aio_context;
 764
 765     /* Prevent race with block_job_defer_to_main_loop() */
 766     aio_context_acquire(data->aio_context);
 767
 768     /* Fetch BDS AioContext again, in case it has changed */
 769     aio_context = blk_get_aio_context(data->job->blk);
 770     if (aio_context != data->aio_context) {
 771         aio_context_acquire(aio_context);
 772     }
 773
 774     data->job->deferred_to_main_loop = false;
 775     data->fn(data->job, data->opaque);
 776
 777     if (aio_context != data->aio_context) {
 778         aio_context_release(aio_context);
 779     }
 780
 781     aio_context_release(data->aio_context);
 782
 783     g_free(data);
 784 }
 785
 786 void block_job_defer_to_main_loop(BlockJob *job,
 787                                   BlockJobDeferToMainLoopFn *fn,
 788                                   void *opaque)
 789 {
 790     BlockJobDeferToMainLoopData *data = g_malloc(sizeof(*data));
 791     data->job = job;
 792     data->aio_context = blk_get_aio_context(job->blk);
 793     data->fn = fn;
 794     data->opaque = opaque;
 795     job->deferred_to_main_loop = true;
 796
 797     aio_bh_schedule_oneshot(qemu_get_aio_context(),
 798                             block_job_defer_to_main_loop_bh, data);
 799 }
 800
 801 BlockJobTxn *block_job_txn_new(void)
 802 {
 803     BlockJobTxn *txn = g_new0(BlockJobTxn, 1);
 804     QLIST_INIT(&txn->jobs);
 805     txn->refcnt = 1;
 806     return txn;
 807 }
 808
 809 static void block_job_txn_ref(BlockJobTxn *txn)
 810 {
 811     txn->refcnt++;
 812 }
 813
 814 void block_job_txn_unref(BlockJobTxn *txn)
 815 {
 816     if (txn && --txn->refcnt == 0) {
 817         g_free(txn);
 818     }
 819 }
 820
 821 void block_job_txn_add_job(BlockJobTxn *txn, BlockJob *job)
 822 {
 823     if (!txn) {
 824         return;
 825     }
 826
 827     assert(!job->txn);
 828     job->txn = txn;
 829
 830     QLIST_INSERT_HEAD(&txn->jobs, job, txn_list);
 831     block_job_txn_ref(txn);
 832 }