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 /*
  59  * The block job API is composed of two categories of functions.
  60  *
  61  * The first includes functions used by the monitor.  The monitor is
  62  * peculiar in that it accesses the block job list with block_job_get, and
  63  * therefore needs consistency across block_job_get and the actual operation
  64  * (e.g. block_job_set_speed).  The consistency is achieved with
  65  * aio_context_acquire/release.  These functions are declared in blockjob.h.
  66  *
  67  * The second includes functions used by the block job drivers and sometimes
  68  * by the core block layer.  These do not care about locking, because the
  69  * whole coroutine runs under the AioContext lock, and are declared in
  70  * blockjob_int.h.
  71  */
  72
  73 BlockJob *block_job_next(BlockJob *job)
  74 {
  75     if (!job) {
  76         return QLIST_FIRST(&block_jobs);
  77     }
  78     return QLIST_NEXT(job, job_list);
  79 }
  80
  81 BlockJob *block_job_get(const char *id)
  82 {
  83     BlockJob *job;
  84
  85     QLIST_FOREACH(job, &block_jobs, job_list) {
  86         if (job->id && !strcmp(id, job->id)) {
  87             return job;
  88         }
  89     }
  90
  91     return NULL;
  92 }
  93
  94 static void block_job_pause(BlockJob *job)
  95 {
  96     job->pause_count++;
  97 }
  98
  99 static void block_job_resume(BlockJob *job)
 100 {
 101     assert(job->pause_count > 0);
 102     job->pause_count--;
 103     if (job->pause_count) {
 104         return;
 105     }
 106     block_job_enter(job);
 107 }
 108
 109 static void block_job_ref(BlockJob *job)
 110 {
 111     ++job->refcnt;
 112 }
 113
 114 static void block_job_attached_aio_context(AioContext *new_context,
 115                                            void *opaque);
 116 static void block_job_detach_aio_context(void *opaque);
 117
 118 static void block_job_unref(BlockJob *job)
 119 {
 120     if (--job->refcnt == 0) {
 121         BlockDriverState *bs = blk_bs(job->blk);
 122         bs->job = NULL;
 123         block_job_remove_all_bdrv(job);
 124         blk_remove_aio_context_notifier(job->blk,
 125                                         block_job_attached_aio_context,
 126                                         block_job_detach_aio_context, job);
 127         blk_unref(job->blk);
 128         error_free(job->blocker);
 129         g_free(job->id);
 130         QLIST_REMOVE(job, job_list);
 131         g_free(job);
 132     }
 133 }
 134
 135 static void block_job_attached_aio_context(AioContext *new_context,
 136                                            void *opaque)
 137 {
 138     BlockJob *job = opaque;
 139
 140     if (job->driver->attached_aio_context) {
 141         job->driver->attached_aio_context(job, new_context);
 142     }
 143
 144     block_job_resume(job);
 145 }
 146
 147 static void block_job_drain(BlockJob *job)
 148 {
 149     /* If job is !job->busy this kicks it into the next pause point. */
 150     block_job_enter(job);
 151
 152     blk_drain(job->blk);
 153     if (job->driver->drain) {
 154         job->driver->drain(job);
 155     }
 156 }
 157
 158 static void block_job_detach_aio_context(void *opaque)
 159 {
 160     BlockJob *job = opaque;
 161
 162     /* In case the job terminates during aio_poll()... */
 163     block_job_ref(job);
 164
 165     block_job_pause(job);
 166
 167     while (!job->paused && !job->completed) {
 168         block_job_drain(job);
 169     }
 170
 171     block_job_unref(job);
 172 }
 173
 174 static char *child_job_get_parent_desc(BdrvChild *c)
 175 {
 176     BlockJob *job = c->opaque;
 177     return g_strdup_printf("%s job '%s'",
 178                            BlockJobType_lookup[job->driver->job_type],
 179                            job->id);
 180 }
 181
 182 static const BdrvChildRole child_job = {
 183     .get_parent_desc    = child_job_get_parent_desc,
 184     .stay_at_node       = true,
 185 };
 186
 187 static void block_job_drained_begin(void *opaque)
 188 {
 189     BlockJob *job = opaque;
 190     block_job_pause(job);
 191 }
 192
 193 static void block_job_drained_end(void *opaque)
 194 {
 195     BlockJob *job = opaque;
 196     block_job_resume(job);
 197 }
 198
 199 static const BlockDevOps block_job_dev_ops = {
 200     .drained_begin = block_job_drained_begin,
 201     .drained_end = block_job_drained_end,
 202 };
 203
 204 void block_job_remove_all_bdrv(BlockJob *job)
 205 {
 206     GSList *l;
 207     for (l = job->nodes; l; l = l->next) {
 208         BdrvChild *c = l->data;
 209         bdrv_op_unblock_all(c->bs, job->blocker);
 210         bdrv_root_unref_child(c);
 211     }
 212     g_slist_free(job->nodes);
 213     job->nodes = NULL;
 214 }
 215
 216 int block_job_add_bdrv(BlockJob *job, const char *name, BlockDriverState *bs,
 217                        uint64_t perm, uint64_t shared_perm, Error **errp)
 218 {
 219     BdrvChild *c;
 220
 221     c = bdrv_root_attach_child(bs, name, &child_job, perm, shared_perm,
 222                                job, errp);
 223     if (c == NULL) {
 224         return -EPERM;
 225     }
 226
 227     job->nodes = g_slist_prepend(job->nodes, c);
 228     bdrv_ref(bs);
 229     bdrv_op_block_all(bs, job->blocker);
 230
 231     return 0;
 232 }
 233
 234 bool block_job_is_internal(BlockJob *job)
 235 {
 236     return (job->id == NULL);
 237 }
 238
 239 static bool block_job_started(BlockJob *job)
 240 {
 241     return job->co;
 242 }
 243
 244 /**
 245  * All jobs must allow a pause point before entering their job proper. This
 246  * ensures that jobs can be paused prior to being started, then resumed later.
 247  */
 248 static void coroutine_fn block_job_co_entry(void *opaque)
 249 {
 250     BlockJob *job = opaque;
 251
 252     assert(job && job->driver && job->driver->start);
 253     block_job_pause_point(job);
 254     job->driver->start(job);
 255 }
 256
 257 void block_job_start(BlockJob *job)
 258 {
 259     assert(job && !block_job_started(job) && job->paused &&
 260            job->driver && job->driver->start);
 261     job->co = qemu_coroutine_create(block_job_co_entry, job);
 262     job->pause_count--;
 263     job->busy = true;
 264     job->paused = false;
 265     bdrv_coroutine_enter(blk_bs(job->blk), job->co);
 266 }
 267
 268 static void block_job_completed_single(BlockJob *job)
 269 {
 270     if (!job->ret) {
 271         if (job->driver->commit) {
 272             job->driver->commit(job);
 273         }
 274     } else {
 275         if (job->driver->abort) {
 276             job->driver->abort(job);
 277         }
 278     }
 279     if (job->driver->clean) {
 280         job->driver->clean(job);
 281     }
 282
 283     if (job->cb) {
 284         job->cb(job->opaque, job->ret);
 285     }
 286
 287     /* Emit events only if we actually started */
 288     if (block_job_started(job)) {
 289         if (block_job_is_cancelled(job)) {
 290             block_job_event_cancelled(job);
 291         } else {
 292             const char *msg = NULL;
 293             if (job->ret < 0) {
 294                 msg = strerror(-job->ret);
 295             }
 296             block_job_event_completed(job, msg);
 297         }
 298     }
 299
 300     if (job->txn) {
 301         QLIST_REMOVE(job, txn_list);
 302         block_job_txn_unref(job->txn);
 303     }
 304     block_job_unref(job);
 305 }
 306
 307 static void block_job_completed_txn_abort(BlockJob *job)
 308 {
 309     AioContext *ctx;
 310     BlockJobTxn *txn = job->txn;
 311     BlockJob *other_job, *next;
 312
 313     if (txn->aborting) {
 314         /*
 315          * We are cancelled by another job, which will handle everything.
 316          */
 317         return;
 318     }
 319     txn->aborting = true;
 320     /* We are the first failed job. Cancel other jobs. */
 321     QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
 322         ctx = blk_get_aio_context(other_job->blk);
 323         aio_context_acquire(ctx);
 324     }
 325     QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
 326         if (other_job == job || other_job->completed) {
 327             /* Other jobs are "effectively" cancelled by us, set the status for
 328              * them; this job, however, may or may not be cancelled, depending
 329              * on the caller, so leave it. */
 330             if (other_job != job) {
 331                 other_job->cancelled = true;
 332             }
 333             continue;
 334         }
 335         block_job_cancel_sync(other_job);
 336         assert(other_job->completed);
 337     }
 338     QLIST_FOREACH_SAFE(other_job, &txn->jobs, txn_list, next) {
 339         ctx = blk_get_aio_context(other_job->blk);
 340         block_job_completed_single(other_job);
 341         aio_context_release(ctx);
 342     }
 343 }
 344
 345 static void block_job_completed_txn_success(BlockJob *job)
 346 {
 347     AioContext *ctx;
 348     BlockJobTxn *txn = job->txn;
 349     BlockJob *other_job, *next;
 350     /*
 351      * Successful completion, see if there are other running jobs in this
 352      * txn.
 353      */
 354     QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
 355         if (!other_job->completed) {
 356             return;
 357         }
 358     }
 359     /* We are the last completed job, commit the transaction. */
 360     QLIST_FOREACH_SAFE(other_job, &txn->jobs, txn_list, next) {
 361         ctx = blk_get_aio_context(other_job->blk);
 362         aio_context_acquire(ctx);
 363         assert(other_job->ret == 0);
 364         block_job_completed_single(other_job);
 365         aio_context_release(ctx);
 366     }
 367 }
 368
 369 void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp)
 370 {
 371     Error *local_err = NULL;
 372
 373     if (!job->driver->set_speed) {
 374         error_setg(errp, QERR_UNSUPPORTED);
 375         return;
 376     }
 377     job->driver->set_speed(job, speed, &local_err);
 378     if (local_err) {
 379         error_propagate(errp, local_err);
 380         return;
 381     }
 382
 383     job->speed = speed;
 384 }
 385
 386 void block_job_complete(BlockJob *job, Error **errp)
 387 {
 388     /* Should not be reachable via external interface for internal jobs */
 389     assert(job->id);
 390     if (job->pause_count || job->cancelled ||
 391         !block_job_started(job) || !job->driver->complete) {
 392         error_setg(errp, "The active block job '%s' cannot be completed",
 393                    job->id);
 394         return;
 395     }
 396
 397     job->driver->complete(job, errp);
 398 }
 399
 400 void block_job_user_pause(BlockJob *job)
 401 {
 402     job->user_paused = true;
 403     block_job_pause(job);
 404 }
 405
 406 bool block_job_user_paused(BlockJob *job)
 407 {
 408     return job->user_paused;
 409 }
 410
 411 void block_job_user_resume(BlockJob *job)
 412 {
 413     if (job && job->user_paused && job->pause_count > 0) {
 414         job->user_paused = false;
 415         block_job_resume(job);
 416     }
 417 }
 418
 419 void block_job_cancel(BlockJob *job)
 420 {
 421     if (block_job_started(job)) {
 422         job->cancelled = true;
 423         block_job_iostatus_reset(job);
 424         block_job_enter(job);
 425     } else {
 426         block_job_completed(job, -ECANCELED);
 427     }
 428 }
 429
 430 void block_job_iostatus_reset(BlockJob *job)
 431 {
 432     job->iostatus = BLOCK_DEVICE_IO_STATUS_OK;
 433 }
 434
 435 static int block_job_finish_sync(BlockJob *job,
 436                                  void (*finish)(BlockJob *, Error **errp),
 437                                  Error **errp)
 438 {
 439     Error *local_err = NULL;
 440     int ret;
 441
 442     assert(blk_bs(job->blk)->job == job);
 443
 444     block_job_ref(job);
 445
 446     finish(job, &local_err);
 447     if (local_err) {
 448         error_propagate(errp, local_err);
 449         block_job_unref(job);
 450         return -EBUSY;
 451     }
 452     /* block_job_drain calls block_job_enter, and it should be enough to
 453      * induce progress until the job completes or moves to the main thread.
 454     */
 455     while (!job->deferred_to_main_loop && !job->completed) {
 456         block_job_drain(job);
 457     }
 458     while (!job->completed) {
 459         aio_poll(qemu_get_aio_context(), true);
 460     }
 461     ret = (job->cancelled && job->ret == 0) ? -ECANCELED : job->ret;
 462     block_job_unref(job);
 463     return ret;
 464 }
 465
 466 /* A wrapper around block_job_cancel() taking an Error ** parameter so it may be
 467  * used with block_job_finish_sync() without the need for (rather nasty)
 468  * function pointer casts there. */
 469 static void block_job_cancel_err(BlockJob *job, Error **errp)
 470 {
 471     block_job_cancel(job);
 472 }
 473
 474 int block_job_cancel_sync(BlockJob *job)
 475 {
 476     return block_job_finish_sync(job, &block_job_cancel_err, NULL);
 477 }
 478
 479 void block_job_cancel_sync_all(void)
 480 {
 481     BlockJob *job;
 482     AioContext *aio_context;
 483
 484     while ((job = QLIST_FIRST(&block_jobs))) {
 485         aio_context = blk_get_aio_context(job->blk);
 486         aio_context_acquire(aio_context);
 487         block_job_cancel_sync(job);
 488         aio_context_release(aio_context);
 489     }
 490 }
 491
 492 int block_job_complete_sync(BlockJob *job, Error **errp)
 493 {
 494     return block_job_finish_sync(job, &block_job_complete, errp);
 495 }
 496
 497 BlockJobInfo *block_job_query(BlockJob *job, Error **errp)
 498 {
 499     BlockJobInfo *info;
 500
 501     if (block_job_is_internal(job)) {
 502         error_setg(errp, "Cannot query QEMU internal jobs");
 503         return NULL;
 504     }
 505     info = g_new0(BlockJobInfo, 1);
 506     info->type      = g_strdup(BlockJobType_lookup[job->driver->job_type]);
 507     info->device    = g_strdup(job->id);
 508     info->len       = job->len;
 509     info->busy      = job->busy;
 510     info->paused    = job->pause_count > 0;
 511     info->offset    = job->offset;
 512     info->speed     = job->speed;
 513     info->io_status = job->iostatus;
 514     info->ready     = job->ready;
 515     return info;
 516 }
 517
 518 static void block_job_iostatus_set_err(BlockJob *job, int error)
 519 {
 520     if (job->iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
 521         job->iostatus = error == ENOSPC ? BLOCK_DEVICE_IO_STATUS_NOSPACE :
 522                                           BLOCK_DEVICE_IO_STATUS_FAILED;
 523     }
 524 }
 525
 526 static void block_job_event_cancelled(BlockJob *job)
 527 {
 528     if (block_job_is_internal(job)) {
 529         return;
 530     }
 531
 532     qapi_event_send_block_job_cancelled(job->driver->job_type,
 533                                         job->id,
 534                                         job->len,
 535                                         job->offset,
 536                                         job->speed,
 537                                         &error_abort);
 538 }
 539
 540 static void block_job_event_completed(BlockJob *job, const char *msg)
 541 {
 542     if (block_job_is_internal(job)) {
 543         return;
 544     }
 545
 546     qapi_event_send_block_job_completed(job->driver->job_type,
 547                                         job->id,
 548                                         job->len,
 549                                         job->offset,
 550                                         job->speed,
 551                                         !!msg,
 552                                         msg,
 553                                         &error_abort);
 554 }
 555
 556 /*
 557  * API for block job drivers and the block layer.  These functions are
 558  * declared in blockjob_int.h.
 559  */
 560
 561 void *block_job_create(const char *job_id, const BlockJobDriver *driver,
 562                        BlockDriverState *bs, uint64_t perm,
 563                        uint64_t shared_perm, int64_t speed, int flags,
 564                        BlockCompletionFunc *cb, void *opaque, Error **errp)
 565 {
 566     BlockBackend *blk;
 567     BlockJob *job;
 568     int ret;
 569
 570     if (bs->job) {
 571         error_setg(errp, QERR_DEVICE_IN_USE, bdrv_get_device_name(bs));
 572         return NULL;
 573     }
 574
 575     if (job_id == NULL && !(flags & BLOCK_JOB_INTERNAL)) {
 576         job_id = bdrv_get_device_name(bs);
 577         if (!*job_id) {
 578             error_setg(errp, "An explicit job ID is required for this node");
 579             return NULL;
 580         }
 581     }
 582
 583     if (job_id) {
 584         if (flags & BLOCK_JOB_INTERNAL) {
 585             error_setg(errp, "Cannot specify job ID for internal block job");
 586             return NULL;
 587         }
 588
 589         if (!id_wellformed(job_id)) {
 590             error_setg(errp, "Invalid job ID '%s'", job_id);
 591             return NULL;
 592         }
 593
 594         if (block_job_get(job_id)) {
 595             error_setg(errp, "Job ID '%s' already in use", job_id);
 596             return NULL;
 597         }
 598     }
 599
 600     blk = blk_new(perm, shared_perm);
 601     ret = blk_insert_bs(blk, bs, errp);
 602     if (ret < 0) {
 603         blk_unref(blk);
 604         return NULL;
 605     }
 606
 607     job = g_malloc0(driver->instance_size);
 608     job->driver        = driver;
 609     job->id            = g_strdup(job_id);
 610     job->blk           = blk;
 611     job->cb            = cb;
 612     job->opaque        = opaque;
 613     job->busy          = false;
 614     job->paused        = true;
 615     job->pause_count   = 1;
 616     job->refcnt        = 1;
 617
 618     error_setg(&job->blocker, "block device is in use by block job: %s",
 619                BlockJobType_lookup[driver->job_type]);
 620     block_job_add_bdrv(job, "main node", bs, 0, BLK_PERM_ALL, &error_abort);
 621     bs->job = job;
 622
 623     blk_set_dev_ops(blk, &block_job_dev_ops, job);
 624     bdrv_op_unblock(bs, BLOCK_OP_TYPE_DATAPLANE, job->blocker);
 625
 626     QLIST_INSERT_HEAD(&block_jobs, job, job_list);
 627
 628     blk_add_aio_context_notifier(blk, block_job_attached_aio_context,
 629                                  block_job_detach_aio_context, job);
 630
 631     /* Only set speed when necessary to avoid NotSupported error */
 632     if (speed != 0) {
 633         Error *local_err = NULL;
 634
 635         block_job_set_speed(job, speed, &local_err);
 636         if (local_err) {
 637             block_job_unref(job);
 638             error_propagate(errp, local_err);
 639             return NULL;
 640         }
 641     }
 642     return job;
 643 }
 644
 645 void block_job_pause_all(void)
 646 {
 647     BlockJob *job = NULL;
 648     while ((job = block_job_next(job))) {
 649         AioContext *aio_context = blk_get_aio_context(job->blk);
 650
 651         aio_context_acquire(aio_context);
 652         block_job_pause(job);
 653         aio_context_release(aio_context);
 654     }
 655 }
 656
 657 void block_job_early_fail(BlockJob *job)
 658 {
 659     block_job_unref(job);
 660 }
 661
 662 void block_job_completed(BlockJob *job, int ret)
 663 {
 664     assert(blk_bs(job->blk)->job == job);
 665     assert(!job->completed);
 666     job->completed = true;
 667     job->ret = ret;
 668     if (!job->txn) {
 669         block_job_completed_single(job);
 670     } else if (ret < 0 || block_job_is_cancelled(job)) {
 671         block_job_completed_txn_abort(job);
 672     } else {
 673         block_job_completed_txn_success(job);
 674     }
 675 }
 676
 677 static bool block_job_should_pause(BlockJob *job)
 678 {
 679     return job->pause_count > 0;
 680 }
 681
 682 void coroutine_fn block_job_pause_point(BlockJob *job)
 683 {
 684     assert(job && block_job_started(job));
 685
 686     if (!block_job_should_pause(job)) {
 687         return;
 688     }
 689     if (block_job_is_cancelled(job)) {
 690         return;
 691     }
 692
 693     if (job->driver->pause) {
 694         job->driver->pause(job);
 695     }
 696
 697     if (block_job_should_pause(job) && !block_job_is_cancelled(job)) {
 698         job->paused = true;
 699         job->busy = false;
 700         qemu_coroutine_yield(); /* wait for block_job_resume() */
 701         job->busy = true;
 702         job->paused = false;
 703     }
 704
 705     if (job->driver->resume) {
 706         job->driver->resume(job);
 707     }
 708 }
 709
 710 void block_job_resume_all(void)
 711 {
 712     BlockJob *job = NULL;
 713     while ((job = block_job_next(job))) {
 714         AioContext *aio_context = blk_get_aio_context(job->blk);
 715
 716         aio_context_acquire(aio_context);
 717         block_job_resume(job);
 718         aio_context_release(aio_context);
 719     }
 720 }
 721
 722 void block_job_enter(BlockJob *job)
 723 {
 724     if (job->co && !job->busy) {
 725         bdrv_coroutine_enter(blk_bs(job->blk), job->co);
 726     }
 727 }
 728
 729 bool block_job_is_cancelled(BlockJob *job)
 730 {
 731     return job->cancelled;
 732 }
 733
 734 void block_job_sleep_ns(BlockJob *job, QEMUClockType type, int64_t ns)
 735 {
 736     assert(job->busy);
 737
 738     /* Check cancellation *before* setting busy = false, too!  */
 739     if (block_job_is_cancelled(job)) {
 740         return;
 741     }
 742
 743     job->busy = false;
 744     if (!block_job_should_pause(job)) {
 745         co_aio_sleep_ns(blk_get_aio_context(job->blk), type, ns);
 746     }
 747     job->busy = true;
 748
 749     block_job_pause_point(job);
 750 }
 751
 752 void block_job_yield(BlockJob *job)
 753 {
 754     assert(job->busy);
 755
 756     /* Check cancellation *before* setting busy = false, too!  */
 757     if (block_job_is_cancelled(job)) {
 758         return;
 759     }
 760
 761     job->busy = false;
 762     if (!block_job_should_pause(job)) {
 763         qemu_coroutine_yield();
 764     }
 765     job->busy = true;
 766
 767     block_job_pause_point(job);
 768 }
 769
 770 void block_job_event_ready(BlockJob *job)
 771 {
 772     job->ready = true;
 773
 774     if (block_job_is_internal(job)) {
 775         return;
 776     }
 777
 778     qapi_event_send_block_job_ready(job->driver->job_type,
 779                                     job->id,
 780                                     job->len,
 781                                     job->offset,
 782                                     job->speed, &error_abort);
 783 }
 784
 785 BlockErrorAction block_job_error_action(BlockJob *job, BlockdevOnError on_err,
 786                                         int is_read, int error)
 787 {
 788     BlockErrorAction action;
 789
 790     switch (on_err) {
 791     case BLOCKDEV_ON_ERROR_ENOSPC:
 792     case BLOCKDEV_ON_ERROR_AUTO:
 793         action = (error == ENOSPC) ?
 794                  BLOCK_ERROR_ACTION_STOP : BLOCK_ERROR_ACTION_REPORT;
 795         break;
 796     case BLOCKDEV_ON_ERROR_STOP:
 797         action = BLOCK_ERROR_ACTION_STOP;
 798         break;
 799     case BLOCKDEV_ON_ERROR_REPORT:
 800         action = BLOCK_ERROR_ACTION_REPORT;
 801         break;
 802     case BLOCKDEV_ON_ERROR_IGNORE:
 803         action = BLOCK_ERROR_ACTION_IGNORE;
 804         break;
 805     default:
 806         abort();
 807     }
 808     if (!block_job_is_internal(job)) {
 809         qapi_event_send_block_job_error(job->id,
 810                                         is_read ? IO_OPERATION_TYPE_READ :
 811                                         IO_OPERATION_TYPE_WRITE,
 812                                         action, &error_abort);
 813     }
 814     if (action == BLOCK_ERROR_ACTION_STOP) {
 815         /* make the pause user visible, which will be resumed from QMP. */
 816         block_job_user_pause(job);
 817         block_job_iostatus_set_err(job, error);
 818     }
 819     return action;
 820 }
 821
 822 typedef struct {
 823     BlockJob *job;
 824     AioContext *aio_context;
 825     BlockJobDeferToMainLoopFn *fn;
 826     void *opaque;
 827 } BlockJobDeferToMainLoopData;
 828
 829 static void block_job_defer_to_main_loop_bh(void *opaque)
 830 {
 831     BlockJobDeferToMainLoopData *data = opaque;
 832     AioContext *aio_context;
 833
 834     /* Prevent race with block_job_defer_to_main_loop() */
 835     aio_context_acquire(data->aio_context);
 836
 837     /* Fetch BDS AioContext again, in case it has changed */
 838     aio_context = blk_get_aio_context(data->job->blk);
 839     if (aio_context != data->aio_context) {
 840         aio_context_acquire(aio_context);
 841     }
 842
 843     data->job->deferred_to_main_loop = false;
 844     data->fn(data->job, data->opaque);
 845
 846     if (aio_context != data->aio_context) {
 847         aio_context_release(aio_context);
 848     }
 849
 850     aio_context_release(data->aio_context);
 851
 852     g_free(data);
 853 }
 854
 855 void block_job_defer_to_main_loop(BlockJob *job,
 856                                   BlockJobDeferToMainLoopFn *fn,
 857                                   void *opaque)
 858 {
 859     BlockJobDeferToMainLoopData *data = g_malloc(sizeof(*data));
 860     data->job = job;
 861     data->aio_context = blk_get_aio_context(job->blk);
 862     data->fn = fn;
 863     data->opaque = opaque;
 864     job->deferred_to_main_loop = true;
 865
 866     aio_bh_schedule_oneshot(qemu_get_aio_context(),
 867                             block_job_defer_to_main_loop_bh, data);
 868 }
 869
 870 BlockJobTxn *block_job_txn_new(void)
 871 {
 872     BlockJobTxn *txn = g_new0(BlockJobTxn, 1);
 873     QLIST_INIT(&txn->jobs);
 874     txn->refcnt = 1;
 875     return txn;
 876 }
 877
 878 static void block_job_txn_ref(BlockJobTxn *txn)
 879 {
 880     txn->refcnt++;
 881 }
 882
 883 void block_job_txn_unref(BlockJobTxn *txn)
 884 {
 885     if (txn && --txn->refcnt == 0) {
 886         g_free(txn);
 887     }
 888 }
 889
 890 void block_job_txn_add_job(BlockJobTxn *txn, BlockJob *job)
 891 {
 892     if (!txn) {
 893         return;
 894     }
 895
 896     assert(!job->txn);
 897     job->txn = txn;
 898
 899     QLIST_INSERT_HEAD(&txn->jobs, job, txn_list);
 900     block_job_txn_ref(txn);
 901 }