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_pause(BlockJob *job)
  80 {
  81     job->pause_count++;
  82 }
  83
  84 static void block_job_resume(BlockJob *job)
  85 {
  86     assert(job->pause_count > 0);
  87     job->pause_count--;
  88     if (job->pause_count) {
  89         return;
  90     }
  91     block_job_enter(job);
  92 }
  93
  94 static void block_job_ref(BlockJob *job)
  95 {
  96     ++job->refcnt;
  97 }
  98
  99 static void block_job_attached_aio_context(AioContext *new_context,
 100                                            void *opaque);
 101 static void block_job_detach_aio_context(void *opaque);
 102
 103 static void block_job_unref(BlockJob *job)
 104 {
 105     if (--job->refcnt == 0) {
 106         BlockDriverState *bs = blk_bs(job->blk);
 107         bs->job = NULL;
 108         block_job_remove_all_bdrv(job);
 109         blk_remove_aio_context_notifier(job->blk,
 110                                         block_job_attached_aio_context,
 111                                         block_job_detach_aio_context, job);
 112         blk_unref(job->blk);
 113         error_free(job->blocker);
 114         g_free(job->id);
 115         QLIST_REMOVE(job, job_list);
 116         g_free(job);
 117     }
 118 }
 119
 120 static void block_job_attached_aio_context(AioContext *new_context,
 121                                            void *opaque)
 122 {
 123     BlockJob *job = opaque;
 124
 125     if (job->driver->attached_aio_context) {
 126         job->driver->attached_aio_context(job, new_context);
 127     }
 128
 129     block_job_resume(job);
 130 }
 131
 132 static void block_job_drain(BlockJob *job)
 133 {
 134     /* If job is !job->busy this kicks it into the next pause point. */
 135     block_job_enter(job);
 136
 137     blk_drain(job->blk);
 138     if (job->driver->drain) {
 139         job->driver->drain(job);
 140     }
 141 }
 142
 143 static void block_job_detach_aio_context(void *opaque)
 144 {
 145     BlockJob *job = opaque;
 146
 147     /* In case the job terminates during aio_poll()... */
 148     block_job_ref(job);
 149
 150     block_job_pause(job);
 151
 152     while (!job->paused && !job->completed) {
 153         block_job_drain(job);
 154     }
 155
 156     block_job_unref(job);
 157 }
 158
 159 static char *child_job_get_parent_desc(BdrvChild *c)
 160 {
 161     BlockJob *job = c->opaque;
 162     return g_strdup_printf("%s job '%s'",
 163                            BlockJobType_lookup[job->driver->job_type],
 164                            job->id);
 165 }
 166
 167 static const BdrvChildRole child_job = {
 168     .get_parent_desc    = child_job_get_parent_desc,
 169     .stay_at_node       = true,
 170 };
 171
 172 static void block_job_drained_begin(void *opaque)
 173 {
 174     BlockJob *job = opaque;
 175     block_job_pause(job);
 176 }
 177
 178 static void block_job_drained_end(void *opaque)
 179 {
 180     BlockJob *job = opaque;
 181     block_job_resume(job);
 182 }
 183
 184 static const BlockDevOps block_job_dev_ops = {
 185     .drained_begin = block_job_drained_begin,
 186     .drained_end = block_job_drained_end,
 187 };
 188
 189 void block_job_remove_all_bdrv(BlockJob *job)
 190 {
 191     GSList *l;
 192     for (l = job->nodes; l; l = l->next) {
 193         BdrvChild *c = l->data;
 194         bdrv_op_unblock_all(c->bs, job->blocker);
 195         bdrv_root_unref_child(c);
 196     }
 197     g_slist_free(job->nodes);
 198     job->nodes = NULL;
 199 }
 200
 201 int block_job_add_bdrv(BlockJob *job, const char *name, BlockDriverState *bs,
 202                        uint64_t perm, uint64_t shared_perm, Error **errp)
 203 {
 204     BdrvChild *c;
 205
 206     c = bdrv_root_attach_child(bs, name, &child_job, perm, shared_perm,
 207                                job, errp);
 208     if (c == NULL) {
 209         return -EPERM;
 210     }
 211
 212     job->nodes = g_slist_prepend(job->nodes, c);
 213     bdrv_ref(bs);
 214     bdrv_op_block_all(bs, job->blocker);
 215
 216     return 0;
 217 }
 218
 219 void *block_job_create(const char *job_id, const BlockJobDriver *driver,
 220                        BlockDriverState *bs, uint64_t perm,
 221                        uint64_t shared_perm, int64_t speed, int flags,
 222                        BlockCompletionFunc *cb, void *opaque, Error **errp)
 223 {
 224     BlockBackend *blk;
 225     BlockJob *job;
 226     int ret;
 227
 228     if (bs->job) {
 229         error_setg(errp, QERR_DEVICE_IN_USE, bdrv_get_device_name(bs));
 230         return NULL;
 231     }
 232
 233     if (job_id == NULL && !(flags & BLOCK_JOB_INTERNAL)) {
 234         job_id = bdrv_get_device_name(bs);
 235         if (!*job_id) {
 236             error_setg(errp, "An explicit job ID is required for this node");
 237             return NULL;
 238         }
 239     }
 240
 241     if (job_id) {
 242         if (flags & BLOCK_JOB_INTERNAL) {
 243             error_setg(errp, "Cannot specify job ID for internal block job");
 244             return NULL;
 245         }
 246
 247         if (!id_wellformed(job_id)) {
 248             error_setg(errp, "Invalid job ID '%s'", job_id);
 249             return NULL;
 250         }
 251
 252         if (block_job_get(job_id)) {
 253             error_setg(errp, "Job ID '%s' already in use", job_id);
 254             return NULL;
 255         }
 256     }
 257
 258     blk = blk_new(perm, shared_perm);
 259     ret = blk_insert_bs(blk, bs, errp);
 260     if (ret < 0) {
 261         blk_unref(blk);
 262         return NULL;
 263     }
 264
 265     job = g_malloc0(driver->instance_size);
 266     job->driver        = driver;
 267     job->id            = g_strdup(job_id);
 268     job->blk           = blk;
 269     job->cb            = cb;
 270     job->opaque        = opaque;
 271     job->busy          = false;
 272     job->paused        = true;
 273     job->pause_count   = 1;
 274     job->refcnt        = 1;
 275
 276     error_setg(&job->blocker, "block device is in use by block job: %s",
 277                BlockJobType_lookup[driver->job_type]);
 278     block_job_add_bdrv(job, "main node", bs, 0, BLK_PERM_ALL, &error_abort);
 279     bs->job = job;
 280
 281     blk_set_dev_ops(blk, &block_job_dev_ops, job);
 282     bdrv_op_unblock(bs, BLOCK_OP_TYPE_DATAPLANE, job->blocker);
 283
 284     QLIST_INSERT_HEAD(&block_jobs, job, job_list);
 285
 286     blk_add_aio_context_notifier(blk, block_job_attached_aio_context,
 287                                  block_job_detach_aio_context, job);
 288
 289     /* Only set speed when necessary to avoid NotSupported error */
 290     if (speed != 0) {
 291         Error *local_err = NULL;
 292
 293         block_job_set_speed(job, speed, &local_err);
 294         if (local_err) {
 295             block_job_unref(job);
 296             error_propagate(errp, local_err);
 297             return NULL;
 298         }
 299     }
 300     return job;
 301 }
 302
 303 bool block_job_is_internal(BlockJob *job)
 304 {
 305     return (job->id == NULL);
 306 }
 307
 308 static bool block_job_started(BlockJob *job)
 309 {
 310     return job->co;
 311 }
 312
 313 /**
 314  * All jobs must allow a pause point before entering their job proper. This
 315  * ensures that jobs can be paused prior to being started, then resumed later.
 316  */
 317 static void coroutine_fn block_job_co_entry(void *opaque)
 318 {
 319     BlockJob *job = opaque;
 320
 321     assert(job && job->driver && job->driver->start);
 322     block_job_pause_point(job);
 323     job->driver->start(job);
 324 }
 325
 326 void block_job_start(BlockJob *job)
 327 {
 328     assert(job && !block_job_started(job) && job->paused &&
 329            job->driver && job->driver->start);
 330     job->co = qemu_coroutine_create(block_job_co_entry, job);
 331     job->pause_count--;
 332     job->busy = true;
 333     job->paused = false;
 334     bdrv_coroutine_enter(blk_bs(job->blk), job->co);
 335 }
 336
 337 void block_job_early_fail(BlockJob *job)
 338 {
 339     block_job_unref(job);
 340 }
 341
 342 static void block_job_completed_single(BlockJob *job)
 343 {
 344     if (!job->ret) {
 345         if (job->driver->commit) {
 346             job->driver->commit(job);
 347         }
 348     } else {
 349         if (job->driver->abort) {
 350             job->driver->abort(job);
 351         }
 352     }
 353     if (job->driver->clean) {
 354         job->driver->clean(job);
 355     }
 356
 357     if (job->cb) {
 358         job->cb(job->opaque, job->ret);
 359     }
 360
 361     /* Emit events only if we actually started */
 362     if (block_job_started(job)) {
 363         if (block_job_is_cancelled(job)) {
 364             block_job_event_cancelled(job);
 365         } else {
 366             const char *msg = NULL;
 367             if (job->ret < 0) {
 368                 msg = strerror(-job->ret);
 369             }
 370             block_job_event_completed(job, msg);
 371         }
 372     }
 373
 374     if (job->txn) {
 375         QLIST_REMOVE(job, txn_list);
 376         block_job_txn_unref(job->txn);
 377     }
 378     block_job_unref(job);
 379 }
 380
 381 static void block_job_completed_txn_abort(BlockJob *job)
 382 {
 383     AioContext *ctx;
 384     BlockJobTxn *txn = job->txn;
 385     BlockJob *other_job, *next;
 386
 387     if (txn->aborting) {
 388         /*
 389          * We are cancelled by another job, which will handle everything.
 390          */
 391         return;
 392     }
 393     txn->aborting = true;
 394     /* We are the first failed job. Cancel other jobs. */
 395     QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
 396         ctx = blk_get_aio_context(other_job->blk);
 397         aio_context_acquire(ctx);
 398     }
 399     QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
 400         if (other_job == job || other_job->completed) {
 401             /* Other jobs are "effectively" cancelled by us, set the status for
 402              * them; this job, however, may or may not be cancelled, depending
 403              * on the caller, so leave it. */
 404             if (other_job != job) {
 405                 other_job->cancelled = true;
 406             }
 407             continue;
 408         }
 409         block_job_cancel_sync(other_job);
 410         assert(other_job->completed);
 411     }
 412     QLIST_FOREACH_SAFE(other_job, &txn->jobs, txn_list, next) {
 413         ctx = blk_get_aio_context(other_job->blk);
 414         block_job_completed_single(other_job);
 415         aio_context_release(ctx);
 416     }
 417 }
 418
 419 static void block_job_completed_txn_success(BlockJob *job)
 420 {
 421     AioContext *ctx;
 422     BlockJobTxn *txn = job->txn;
 423     BlockJob *other_job, *next;
 424     /*
 425      * Successful completion, see if there are other running jobs in this
 426      * txn.
 427      */
 428     QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
 429         if (!other_job->completed) {
 430             return;
 431         }
 432     }
 433     /* We are the last completed job, commit the transaction. */
 434     QLIST_FOREACH_SAFE(other_job, &txn->jobs, txn_list, next) {
 435         ctx = blk_get_aio_context(other_job->blk);
 436         aio_context_acquire(ctx);
 437         assert(other_job->ret == 0);
 438         block_job_completed_single(other_job);
 439         aio_context_release(ctx);
 440     }
 441 }
 442
 443 void block_job_completed(BlockJob *job, int ret)
 444 {
 445     assert(blk_bs(job->blk)->job == job);
 446     assert(!job->completed);
 447     job->completed = true;
 448     job->ret = ret;
 449     if (!job->txn) {
 450         block_job_completed_single(job);
 451     } else if (ret < 0 || block_job_is_cancelled(job)) {
 452         block_job_completed_txn_abort(job);
 453     } else {
 454         block_job_completed_txn_success(job);
 455     }
 456 }
 457
 458 void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp)
 459 {
 460     Error *local_err = NULL;
 461
 462     if (!job->driver->set_speed) {
 463         error_setg(errp, QERR_UNSUPPORTED);
 464         return;
 465     }
 466     job->driver->set_speed(job, speed, &local_err);
 467     if (local_err) {
 468         error_propagate(errp, local_err);
 469         return;
 470     }
 471
 472     job->speed = speed;
 473 }
 474
 475 void block_job_complete(BlockJob *job, Error **errp)
 476 {
 477     /* Should not be reachable via external interface for internal jobs */
 478     assert(job->id);
 479     if (job->pause_count || job->cancelled ||
 480         !block_job_started(job) || !job->driver->complete) {
 481         error_setg(errp, "The active block job '%s' cannot be completed",
 482                    job->id);
 483         return;
 484     }
 485
 486     job->driver->complete(job, errp);
 487 }
 488
 489 void block_job_user_pause(BlockJob *job)
 490 {
 491     job->user_paused = true;
 492     block_job_pause(job);
 493 }
 494
 495 static bool block_job_should_pause(BlockJob *job)
 496 {
 497     return job->pause_count > 0;
 498 }
 499
 500 bool block_job_user_paused(BlockJob *job)
 501 {
 502     return job->user_paused;
 503 }
 504
 505 void coroutine_fn block_job_pause_point(BlockJob *job)
 506 {
 507     assert(job && block_job_started(job));
 508
 509     if (!block_job_should_pause(job)) {
 510         return;
 511     }
 512     if (block_job_is_cancelled(job)) {
 513         return;
 514     }
 515
 516     if (job->driver->pause) {
 517         job->driver->pause(job);
 518     }
 519
 520     if (block_job_should_pause(job) && !block_job_is_cancelled(job)) {
 521         job->paused = true;
 522         job->busy = false;
 523         qemu_coroutine_yield(); /* wait for block_job_resume() */
 524         job->busy = true;
 525         job->paused = false;
 526     }
 527
 528     if (job->driver->resume) {
 529         job->driver->resume(job);
 530     }
 531 }
 532
 533 void block_job_user_resume(BlockJob *job)
 534 {
 535     if (job && job->user_paused && job->pause_count > 0) {
 536         job->user_paused = false;
 537         block_job_resume(job);
 538     }
 539 }
 540
 541 void block_job_enter(BlockJob *job)
 542 {
 543     if (job->co && !job->busy) {
 544         bdrv_coroutine_enter(blk_bs(job->blk), job->co);
 545     }
 546 }
 547
 548 void block_job_cancel(BlockJob *job)
 549 {
 550     if (block_job_started(job)) {
 551         job->cancelled = true;
 552         block_job_iostatus_reset(job);
 553         block_job_enter(job);
 554     } else {
 555         block_job_completed(job, -ECANCELED);
 556     }
 557 }
 558
 559 bool block_job_is_cancelled(BlockJob *job)
 560 {
 561     return job->cancelled;
 562 }
 563
 564 void block_job_iostatus_reset(BlockJob *job)
 565 {
 566     job->iostatus = BLOCK_DEVICE_IO_STATUS_OK;
 567 }
 568
 569 static int block_job_finish_sync(BlockJob *job,
 570                                  void (*finish)(BlockJob *, Error **errp),
 571                                  Error **errp)
 572 {
 573     Error *local_err = NULL;
 574     int ret;
 575
 576     assert(blk_bs(job->blk)->job == job);
 577
 578     block_job_ref(job);
 579
 580     finish(job, &local_err);
 581     if (local_err) {
 582         error_propagate(errp, local_err);
 583         block_job_unref(job);
 584         return -EBUSY;
 585     }
 586     /* block_job_drain calls block_job_enter, and it should be enough to
 587      * induce progress until the job completes or moves to the main thread.
 588     */
 589     while (!job->deferred_to_main_loop && !job->completed) {
 590         block_job_drain(job);
 591     }
 592     while (!job->completed) {
 593         aio_poll(qemu_get_aio_context(), true);
 594     }
 595     ret = (job->cancelled && job->ret == 0) ? -ECANCELED : job->ret;
 596     block_job_unref(job);
 597     return ret;
 598 }
 599
 600 /* A wrapper around block_job_cancel() taking an Error ** parameter so it may be
 601  * used with block_job_finish_sync() without the need for (rather nasty)
 602  * function pointer casts there. */
 603 static void block_job_cancel_err(BlockJob *job, Error **errp)
 604 {
 605     block_job_cancel(job);
 606 }
 607
 608 int block_job_cancel_sync(BlockJob *job)
 609 {
 610     return block_job_finish_sync(job, &block_job_cancel_err, NULL);
 611 }
 612
 613 void block_job_cancel_sync_all(void)
 614 {
 615     BlockJob *job;
 616     AioContext *aio_context;
 617
 618     while ((job = QLIST_FIRST(&block_jobs))) {
 619         aio_context = blk_get_aio_context(job->blk);
 620         aio_context_acquire(aio_context);
 621         block_job_cancel_sync(job);
 622         aio_context_release(aio_context);
 623     }
 624 }
 625
 626 int block_job_complete_sync(BlockJob *job, Error **errp)
 627 {
 628     return block_job_finish_sync(job, &block_job_complete, errp);
 629 }
 630
 631 void block_job_sleep_ns(BlockJob *job, QEMUClockType type, int64_t ns)
 632 {
 633     assert(job->busy);
 634
 635     /* Check cancellation *before* setting busy = false, too!  */
 636     if (block_job_is_cancelled(job)) {
 637         return;
 638     }
 639
 640     job->busy = false;
 641     if (!block_job_should_pause(job)) {
 642         co_aio_sleep_ns(blk_get_aio_context(job->blk), type, ns);
 643     }
 644     job->busy = true;
 645
 646     block_job_pause_point(job);
 647 }
 648
 649 void block_job_yield(BlockJob *job)
 650 {
 651     assert(job->busy);
 652
 653     /* Check cancellation *before* setting busy = false, too!  */
 654     if (block_job_is_cancelled(job)) {
 655         return;
 656     }
 657
 658     job->busy = false;
 659     if (!block_job_should_pause(job)) {
 660         qemu_coroutine_yield();
 661     }
 662     job->busy = true;
 663
 664     block_job_pause_point(job);
 665 }
 666
 667 BlockJobInfo *block_job_query(BlockJob *job, Error **errp)
 668 {
 669     BlockJobInfo *info;
 670
 671     if (block_job_is_internal(job)) {
 672         error_setg(errp, "Cannot query QEMU internal jobs");
 673         return NULL;
 674     }
 675     info = g_new0(BlockJobInfo, 1);
 676     info->type      = g_strdup(BlockJobType_lookup[job->driver->job_type]);
 677     info->device    = g_strdup(job->id);
 678     info->len       = job->len;
 679     info->busy      = job->busy;
 680     info->paused    = job->pause_count > 0;
 681     info->offset    = job->offset;
 682     info->speed     = job->speed;
 683     info->io_status = job->iostatus;
 684     info->ready     = job->ready;
 685     return info;
 686 }
 687
 688 static void block_job_iostatus_set_err(BlockJob *job, int error)
 689 {
 690     if (job->iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
 691         job->iostatus = error == ENOSPC ? BLOCK_DEVICE_IO_STATUS_NOSPACE :
 692                                           BLOCK_DEVICE_IO_STATUS_FAILED;
 693     }
 694 }
 695
 696 static void block_job_event_cancelled(BlockJob *job)
 697 {
 698     if (block_job_is_internal(job)) {
 699         return;
 700     }
 701
 702     qapi_event_send_block_job_cancelled(job->driver->job_type,
 703                                         job->id,
 704                                         job->len,
 705                                         job->offset,
 706                                         job->speed,
 707                                         &error_abort);
 708 }
 709
 710 static void block_job_event_completed(BlockJob *job, const char *msg)
 711 {
 712     if (block_job_is_internal(job)) {
 713         return;
 714     }
 715
 716     qapi_event_send_block_job_completed(job->driver->job_type,
 717                                         job->id,
 718                                         job->len,
 719                                         job->offset,
 720                                         job->speed,
 721                                         !!msg,
 722                                         msg,
 723                                         &error_abort);
 724 }
 725
 726 void block_job_pause_all(void)
 727 {
 728     BlockJob *job = NULL;
 729     while ((job = block_job_next(job))) {
 730         AioContext *aio_context = blk_get_aio_context(job->blk);
 731
 732         aio_context_acquire(aio_context);
 733         block_job_pause(job);
 734         aio_context_release(aio_context);
 735     }
 736 }
 737
 738 void block_job_resume_all(void)
 739 {
 740     BlockJob *job = NULL;
 741     while ((job = block_job_next(job))) {
 742         AioContext *aio_context = blk_get_aio_context(job->blk);
 743
 744         aio_context_acquire(aio_context);
 745         block_job_resume(job);
 746         aio_context_release(aio_context);
 747     }
 748 }
 749
 750 void block_job_event_ready(BlockJob *job)
 751 {
 752     job->ready = true;
 753
 754     if (block_job_is_internal(job)) {
 755         return;
 756     }
 757
 758     qapi_event_send_block_job_ready(job->driver->job_type,
 759                                     job->id,
 760                                     job->len,
 761                                     job->offset,
 762                                     job->speed, &error_abort);
 763 }
 764
 765 BlockErrorAction block_job_error_action(BlockJob *job, BlockdevOnError on_err,
 766                                         int is_read, int error)
 767 {
 768     BlockErrorAction action;
 769
 770     switch (on_err) {
 771     case BLOCKDEV_ON_ERROR_ENOSPC:
 772     case BLOCKDEV_ON_ERROR_AUTO:
 773         action = (error == ENOSPC) ?
 774                  BLOCK_ERROR_ACTION_STOP : BLOCK_ERROR_ACTION_REPORT;
 775         break;
 776     case BLOCKDEV_ON_ERROR_STOP:
 777         action = BLOCK_ERROR_ACTION_STOP;
 778         break;
 779     case BLOCKDEV_ON_ERROR_REPORT:
 780         action = BLOCK_ERROR_ACTION_REPORT;
 781         break;
 782     case BLOCKDEV_ON_ERROR_IGNORE:
 783         action = BLOCK_ERROR_ACTION_IGNORE;
 784         break;
 785     default:
 786         abort();
 787     }
 788     if (!block_job_is_internal(job)) {
 789         qapi_event_send_block_job_error(job->id,
 790                                         is_read ? IO_OPERATION_TYPE_READ :
 791                                         IO_OPERATION_TYPE_WRITE,
 792                                         action, &error_abort);
 793     }
 794     if (action == BLOCK_ERROR_ACTION_STOP) {
 795         /* make the pause user visible, which will be resumed from QMP. */
 796         block_job_user_pause(job);
 797         block_job_iostatus_set_err(job, error);
 798     }
 799     return action;
 800 }
 801
 802 typedef struct {
 803     BlockJob *job;
 804     AioContext *aio_context;
 805     BlockJobDeferToMainLoopFn *fn;
 806     void *opaque;
 807 } BlockJobDeferToMainLoopData;
 808
 809 static void block_job_defer_to_main_loop_bh(void *opaque)
 810 {
 811     BlockJobDeferToMainLoopData *data = opaque;
 812     AioContext *aio_context;
 813
 814     /* Prevent race with block_job_defer_to_main_loop() */
 815     aio_context_acquire(data->aio_context);
 816
 817     /* Fetch BDS AioContext again, in case it has changed */
 818     aio_context = blk_get_aio_context(data->job->blk);
 819     if (aio_context != data->aio_context) {
 820         aio_context_acquire(aio_context);
 821     }
 822
 823     data->job->deferred_to_main_loop = false;
 824     data->fn(data->job, data->opaque);
 825
 826     if (aio_context != data->aio_context) {
 827         aio_context_release(aio_context);
 828     }
 829
 830     aio_context_release(data->aio_context);
 831
 832     g_free(data);
 833 }
 834
 835 void block_job_defer_to_main_loop(BlockJob *job,
 836                                   BlockJobDeferToMainLoopFn *fn,
 837                                   void *opaque)
 838 {
 839     BlockJobDeferToMainLoopData *data = g_malloc(sizeof(*data));
 840     data->job = job;
 841     data->aio_context = blk_get_aio_context(job->blk);
 842     data->fn = fn;
 843     data->opaque = opaque;
 844     job->deferred_to_main_loop = true;
 845
 846     aio_bh_schedule_oneshot(qemu_get_aio_context(),
 847                             block_job_defer_to_main_loop_bh, data);
 848 }
 849
 850 BlockJobTxn *block_job_txn_new(void)
 851 {
 852     BlockJobTxn *txn = g_new0(BlockJobTxn, 1);
 853     QLIST_INIT(&txn->jobs);
 854     txn->refcnt = 1;
 855     return txn;
 856 }
 857
 858 static void block_job_txn_ref(BlockJobTxn *txn)
 859 {
 860     txn->refcnt++;
 861 }
 862
 863 void block_job_txn_unref(BlockJobTxn *txn)
 864 {
 865     if (txn && --txn->refcnt == 0) {
 866         g_free(txn);
 867     }
 868 }
 869
 870 void block_job_txn_add_job(BlockJobTxn *txn, BlockJob *job)
 871 {
 872     if (!txn) {
 873         return;
 874     }
 875
 876     assert(!job->txn);
 877     job->txn = txn;
 878
 879     QLIST_INSERT_HEAD(&txn->jobs, job, txn_list);
 880     block_job_txn_ref(txn);
 881 }