block/mirror.c

   1 /*
   2  * Image mirroring
   3  *
   4  * Copyright Red Hat, Inc. 2012
   5  *
   6  * Authors:
   7  *  Paolo Bonzini  <pbonzini@redhat.com>
   8  *
   9  * This work is licensed under the terms of the GNU LGPL, version 2 or later.
  10  * See the COPYING.LIB file in the top-level directory.
  11  *
  12  */
  13
  14 #include "trace.h"
  15 #include "block/blockjob.h"
  16 #include "block/block_int.h"
  17 #include "qemu/ratelimit.h"
  18 #include "qemu/bitmap.h"
  19
  20 #define SLICE_TIME    100000000ULL /* ns */
  21 #define MAX_IN_FLIGHT 16
  22
  23 /* The mirroring buffer is a list of granularity-sized chunks.
  24  * Free chunks are organized in a list.
  25  */
  26 typedef struct MirrorBuffer {
  27     QSIMPLEQ_ENTRY(MirrorBuffer) next;
  28 } MirrorBuffer;
  29
  30 typedef struct MirrorBlockJob {
  31     BlockJob common;
  32     RateLimit limit;
  33     BlockDriverState *target;
  34     BlockDriverState *base;
  35     /* The name of the graph node to replace */
  36     char *replaces;
  37     /* The BDS to replace */
  38     BlockDriverState *to_replace;
  39     /* Used to block operations on the drive-mirror-replace target */
  40     Error *replace_blocker;
  41     bool is_none_mode;
  42     BlockdevOnError on_source_error, on_target_error;
  43     bool synced;
  44     bool should_complete;
  45     int64_t sector_num;
  46     int64_t granularity;
  47     size_t buf_size;
  48     int64_t bdev_length;
  49     unsigned long *cow_bitmap;
  50     BdrvDirtyBitmap *dirty_bitmap;
  51     HBitmapIter hbi;
  52     uint8_t *buf;
  53     QSIMPLEQ_HEAD(, MirrorBuffer) buf_free;
  54     int buf_free_count;
  55
  56     unsigned long *in_flight_bitmap;
  57     int in_flight;
  58     int sectors_in_flight;
  59     int ret;
  60 } MirrorBlockJob;
  61
  62 typedef struct MirrorOp {
  63     MirrorBlockJob *s;
  64     QEMUIOVector qiov;
  65     int64_t sector_num;
  66     int nb_sectors;
  67 } MirrorOp;
  68
  69 static BlockErrorAction mirror_error_action(MirrorBlockJob *s, bool read,
  70                                             int error)
  71 {
  72     s->synced = false;
  73     if (read) {
  74         return block_job_error_action(&s->common, s->common.bs,
  75                                       s->on_source_error, true, error);
  76     } else {
  77         return block_job_error_action(&s->common, s->target,
  78                                       s->on_target_error, false, error);
  79     }
  80 }
  81
  82 static void mirror_iteration_done(MirrorOp *op, int ret)
  83 {
  84     MirrorBlockJob *s = op->s;
  85     struct iovec *iov;
  86     int64_t chunk_num;
  87     int i, nb_chunks, sectors_per_chunk;
  88
  89     trace_mirror_iteration_done(s, op->sector_num, op->nb_sectors, ret);
  90
  91     s->in_flight--;
  92     s->sectors_in_flight -= op->nb_sectors;
  93     iov = op->qiov.iov;
  94     for (i = 0; i < op->qiov.niov; i++) {
  95         MirrorBuffer *buf = (MirrorBuffer *) iov[i].iov_base;
  96         QSIMPLEQ_INSERT_TAIL(&s->buf_free, buf, next);
  97         s->buf_free_count++;
  98     }
  99
 100     sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
 101     chunk_num = op->sector_num / sectors_per_chunk;
 102     nb_chunks = op->nb_sectors / sectors_per_chunk;
 103     bitmap_clear(s->in_flight_bitmap, chunk_num, nb_chunks);
 104     if (ret >= 0) {
 105         if (s->cow_bitmap) {
 106             bitmap_set(s->cow_bitmap, chunk_num, nb_chunks);
 107         }
 108         s->common.offset += (uint64_t)op->nb_sectors * BDRV_SECTOR_SIZE;
 109     }
 110
 111     qemu_iovec_destroy(&op->qiov);
 112     g_slice_free(MirrorOp, op);
 113
 114     /* Enter coroutine when it is not sleeping.  The coroutine sleeps to
 115      * rate-limit itself.  The coroutine will eventually resume since there is
 116      * a sleep timeout so don't wake it early.
 117      */
 118     if (s->common.busy) {
 119         qemu_coroutine_enter(s->common.co, NULL);
 120     }
 121 }
 122
 123 static void mirror_write_complete(void *opaque, int ret)
 124 {
 125     MirrorOp *op = opaque;
 126     MirrorBlockJob *s = op->s;
 127     if (ret < 0) {
 128         BlockDriverState *source = s->common.bs;
 129         BlockErrorAction action;
 130
 131         bdrv_set_dirty(source, op->sector_num, op->nb_sectors);
 132         action = mirror_error_action(s, false, -ret);
 133         if (action == BLOCK_ERROR_ACTION_REPORT && s->ret >= 0) {
 134             s->ret = ret;
 135         }
 136     }
 137     mirror_iteration_done(op, ret);
 138 }
 139
 140 static void mirror_read_complete(void *opaque, int ret)
 141 {
 142     MirrorOp *op = opaque;
 143     MirrorBlockJob *s = op->s;
 144     if (ret < 0) {
 145         BlockDriverState *source = s->common.bs;
 146         BlockErrorAction action;
 147
 148         bdrv_set_dirty(source, op->sector_num, op->nb_sectors);
 149         action = mirror_error_action(s, true, -ret);
 150         if (action == BLOCK_ERROR_ACTION_REPORT && s->ret >= 0) {
 151             s->ret = ret;
 152         }
 153
 154         mirror_iteration_done(op, ret);
 155         return;
 156     }
 157     bdrv_aio_writev(s->target, op->sector_num, &op->qiov, op->nb_sectors,
 158                     mirror_write_complete, op);
 159 }
 160
 161 static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
 162 {
 163     BlockDriverState *source = s->common.bs;
 164     int nb_sectors, sectors_per_chunk, nb_chunks;
 165     int64_t end, sector_num, next_chunk, next_sector, hbitmap_next_sector;
 166     uint64_t delay_ns = 0;
 167     MirrorOp *op;
 168
 169     s->sector_num = hbitmap_iter_next(&s->hbi);
 170     if (s->sector_num < 0) {
 171         bdrv_dirty_iter_init(source, s->dirty_bitmap, &s->hbi);
 172         s->sector_num = hbitmap_iter_next(&s->hbi);
 173         trace_mirror_restart_iter(s,
 174                                   bdrv_get_dirty_count(source, s->dirty_bitmap));
 175         assert(s->sector_num >= 0);
 176     }
 177
 178     hbitmap_next_sector = s->sector_num;
 179     sector_num = s->sector_num;
 180     sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
 181     end = s->bdev_length / BDRV_SECTOR_SIZE;
 182
 183     /* Extend the QEMUIOVector to include all adjacent blocks that will
 184      * be copied in this operation.
 185      *
 186      * We have to do this if we have no backing file yet in the destination,
 187      * and the cluster size is very large.  Then we need to do COW ourselves.
 188      * The first time a cluster is copied, copy it entirely.  Note that,
 189      * because both the granularity and the cluster size are powers of two,
 190      * the number of sectors to copy cannot exceed one cluster.
 191      *
 192      * We also want to extend the QEMUIOVector to include more adjacent
 193      * dirty blocks if possible, to limit the number of I/O operations and
 194      * run efficiently even with a small granularity.
 195      */
 196     nb_chunks = 0;
 197     nb_sectors = 0;
 198     next_sector = sector_num;
 199     next_chunk = sector_num / sectors_per_chunk;
 200
 201     /* Wait for I/O to this cluster (from a previous iteration) to be done.  */
 202     while (test_bit(next_chunk, s->in_flight_bitmap)) {
 203         trace_mirror_yield_in_flight(s, sector_num, s->in_flight);
 204         qemu_coroutine_yield();
 205     }
 206
 207     do {
 208         int added_sectors, added_chunks;
 209
 210         if (!bdrv_get_dirty(source, s->dirty_bitmap, next_sector) ||
 211             test_bit(next_chunk, s->in_flight_bitmap)) {
 212             assert(nb_sectors > 0);
 213             break;
 214         }
 215
 216         added_sectors = sectors_per_chunk;
 217         if (s->cow_bitmap && !test_bit(next_chunk, s->cow_bitmap)) {
 218             bdrv_round_to_clusters(s->target,
 219                                    next_sector, added_sectors,
 220                                    &next_sector, &added_sectors);
 221
 222             /* On the first iteration, the rounding may make us copy
 223              * sectors before the first dirty one.
 224              */
 225             if (next_sector < sector_num) {
 226                 assert(nb_sectors == 0);
 227                 sector_num = next_sector;
 228                 next_chunk = next_sector / sectors_per_chunk;
 229             }
 230         }
 231
 232         added_sectors = MIN(added_sectors, end - (sector_num + nb_sectors));
 233         added_chunks = (added_sectors + sectors_per_chunk - 1) / sectors_per_chunk;
 234
 235         /* When doing COW, it may happen that there is not enough space for
 236          * a full cluster.  Wait if that is the case.
 237          */
 238         while (nb_chunks == 0 && s->buf_free_count < added_chunks) {
 239             trace_mirror_yield_buf_busy(s, nb_chunks, s->in_flight);
 240             qemu_coroutine_yield();
 241         }
 242         if (s->buf_free_count < nb_chunks + added_chunks) {
 243             trace_mirror_break_buf_busy(s, nb_chunks, s->in_flight);
 244             break;
 245         }
 246
 247         /* We have enough free space to copy these sectors.  */
 248         bitmap_set(s->in_flight_bitmap, next_chunk, added_chunks);
 249
 250         nb_sectors += added_sectors;
 251         nb_chunks += added_chunks;
 252         next_sector += added_sectors;
 253         next_chunk += added_chunks;
 254         if (!s->synced && s->common.speed) {
 255             delay_ns = ratelimit_calculate_delay(&s->limit, added_sectors);
 256         }
 257     } while (delay_ns == 0 && next_sector < end);
 258
 259     /* Allocate a MirrorOp that is used as an AIO callback.  */
 260     op = g_slice_new(MirrorOp);
 261     op->s = s;
 262     op->sector_num = sector_num;
 263     op->nb_sectors = nb_sectors;
 264
 265     /* Now make a QEMUIOVector taking enough granularity-sized chunks
 266      * from s->buf_free.
 267      */
 268     qemu_iovec_init(&op->qiov, nb_chunks);
 269     next_sector = sector_num;
 270     while (nb_chunks-- > 0) {
 271         MirrorBuffer *buf = QSIMPLEQ_FIRST(&s->buf_free);
 272         size_t remaining = (nb_sectors * BDRV_SECTOR_SIZE) - op->qiov.size;
 273
 274         QSIMPLEQ_REMOVE_HEAD(&s->buf_free, next);
 275         s->buf_free_count--;
 276         qemu_iovec_add(&op->qiov, buf, MIN(s->granularity, remaining));
 277
 278         /* Advance the HBitmapIter in parallel, so that we do not examine
 279          * the same sector twice.
 280          */
 281         if (next_sector > hbitmap_next_sector
 282             && bdrv_get_dirty(source, s->dirty_bitmap, next_sector)) {
 283             hbitmap_next_sector = hbitmap_iter_next(&s->hbi);
 284         }
 285
 286         next_sector += sectors_per_chunk;
 287     }
 288
 289     bdrv_reset_dirty(source, sector_num, nb_sectors);
 290
 291     /* Copy the dirty cluster.  */
 292     s->in_flight++;
 293     s->sectors_in_flight += nb_sectors;
 294     trace_mirror_one_iteration(s, sector_num, nb_sectors);
 295     bdrv_aio_readv(source, sector_num, &op->qiov, nb_sectors,
 296                    mirror_read_complete, op);
 297     return delay_ns;
 298 }
 299
 300 static void mirror_free_init(MirrorBlockJob *s)
 301 {
 302     int granularity = s->granularity;
 303     size_t buf_size = s->buf_size;
 304     uint8_t *buf = s->buf;
 305
 306     assert(s->buf_free_count == 0);
 307     QSIMPLEQ_INIT(&s->buf_free);
 308     while (buf_size != 0) {
 309         MirrorBuffer *cur = (MirrorBuffer *)buf;
 310         QSIMPLEQ_INSERT_TAIL(&s->buf_free, cur, next);
 311         s->buf_free_count++;
 312         buf_size -= granularity;
 313         buf += granularity;
 314     }
 315 }
 316
 317 static void mirror_drain(MirrorBlockJob *s)
 318 {
 319     while (s->in_flight > 0) {
 320         qemu_coroutine_yield();
 321     }
 322 }
 323
 324 typedef struct {
 325     int ret;
 326 } MirrorExitData;
 327
 328 static void mirror_exit(BlockJob *job, void *opaque)
 329 {
 330     MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
 331     MirrorExitData *data = opaque;
 332     AioContext *replace_aio_context = NULL;
 333
 334     if (s->to_replace) {
 335         replace_aio_context = bdrv_get_aio_context(s->to_replace);
 336         aio_context_acquire(replace_aio_context);
 337     }
 338
 339     if (s->should_complete && data->ret == 0) {
 340         BlockDriverState *to_replace = s->common.bs;
 341         if (s->to_replace) {
 342             to_replace = s->to_replace;
 343         }
 344         if (bdrv_get_flags(s->target) != bdrv_get_flags(to_replace)) {
 345             bdrv_reopen(s->target, bdrv_get_flags(to_replace), NULL);
 346         }
 347         bdrv_swap(s->target, to_replace);
 348         if (s->common.driver->job_type == BLOCK_JOB_TYPE_COMMIT) {
 349             /* drop the bs loop chain formed by the swap: break the loop then
 350              * trigger the unref from the top one */
 351             BlockDriverState *p = s->base->backing_hd;
 352             bdrv_set_backing_hd(s->base, NULL);
 353             bdrv_unref(p);
 354         }
 355     }
 356     if (s->to_replace) {
 357         bdrv_op_unblock_all(s->to_replace, s->replace_blocker);
 358         error_free(s->replace_blocker);
 359         bdrv_unref(s->to_replace);
 360     }
 361     if (replace_aio_context) {
 362         aio_context_release(replace_aio_context);
 363     }
 364     g_free(s->replaces);
 365     bdrv_unref(s->target);
 366     block_job_completed(&s->common, data->ret);
 367     g_free(data);
 368 }
 369
 370 static void coroutine_fn mirror_run(void *opaque)
 371 {
 372     MirrorBlockJob *s = opaque;
 373     MirrorExitData *data;
 374     BlockDriverState *bs = s->common.bs;
 375     int64_t sector_num, end, sectors_per_chunk, length;
 376     uint64_t last_pause_ns;
 377     BlockDriverInfo bdi;
 378     char backing_filename[1024];
 379     int ret = 0;
 380     int n;
 381
 382     if (block_job_is_cancelled(&s->common)) {
 383         goto immediate_exit;
 384     }
 385
 386     s->bdev_length = bdrv_getlength(bs);
 387     if (s->bdev_length < 0) {
 388         ret = s->bdev_length;
 389         goto immediate_exit;
 390     } else if (s->bdev_length == 0) {
 391         /* Report BLOCK_JOB_READY and wait for complete. */
 392         block_job_event_ready(&s->common);
 393         s->synced = true;
 394         while (!block_job_is_cancelled(&s->common) && !s->should_complete) {
 395             block_job_yield(&s->common);
 396         }
 397         s->common.cancelled = false;
 398         goto immediate_exit;
 399     }
 400
 401     length = DIV_ROUND_UP(s->bdev_length, s->granularity);
 402     s->in_flight_bitmap = bitmap_new(length);
 403
 404     /* If we have no backing file yet in the destination, we cannot let
 405      * the destination do COW.  Instead, we copy sectors around the
 406      * dirty data if needed.  We need a bitmap to do that.
 407      */
 408     bdrv_get_backing_filename(s->target, backing_filename,
 409                               sizeof(backing_filename));
 410     if (backing_filename[0] && !s->target->backing_hd) {
 411         ret = bdrv_get_info(s->target, &bdi);
 412         if (ret < 0) {
 413             goto immediate_exit;
 414         }
 415         if (s->granularity < bdi.cluster_size) {
 416             s->buf_size = MAX(s->buf_size, bdi.cluster_size);
 417             s->cow_bitmap = bitmap_new(length);
 418         }
 419     }
 420
 421     end = s->bdev_length / BDRV_SECTOR_SIZE;
 422     s->buf = qemu_try_blockalign(bs, s->buf_size);
 423     if (s->buf == NULL) {
 424         ret = -ENOMEM;
 425         goto immediate_exit;
 426     }
 427
 428     sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
 429     mirror_free_init(s);
 430
 431     if (!s->is_none_mode) {
 432         /* First part, loop on the sectors and initialize the dirty bitmap.  */
 433         BlockDriverState *base = s->base;
 434         for (sector_num = 0; sector_num < end; ) {
 435             int64_t next = (sector_num | (sectors_per_chunk - 1)) + 1;
 436             ret = bdrv_is_allocated_above(bs, base,
 437                                           sector_num, next - sector_num, &n);
 438
 439             if (ret < 0) {
 440                 goto immediate_exit;
 441             }
 442
 443             assert(n > 0);
 444             if (ret == 1) {
 445                 bdrv_set_dirty(bs, sector_num, n);
 446                 sector_num = next;
 447             } else {
 448                 sector_num += n;
 449             }
 450         }
 451     }
 452
 453     bdrv_dirty_iter_init(bs, s->dirty_bitmap, &s->hbi);
 454     last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
 455     for (;;) {
 456         uint64_t delay_ns = 0;
 457         int64_t cnt;
 458         bool should_complete;
 459
 460         if (s->ret < 0) {
 461             ret = s->ret;
 462             goto immediate_exit;
 463         }
 464
 465         cnt = bdrv_get_dirty_count(bs, s->dirty_bitmap);
 466         /* s->common.offset contains the number of bytes already processed so
 467          * far, cnt is the number of dirty sectors remaining and
 468          * s->sectors_in_flight is the number of sectors currently being
 469          * processed; together those are the current total operation length */
 470         s->common.len = s->common.offset +
 471                         (cnt + s->sectors_in_flight) * BDRV_SECTOR_SIZE;
 472
 473         /* Note that even when no rate limit is applied we need to yield
 474          * periodically with no pending I/O so that qemu_aio_flush() returns.
 475          * We do so every SLICE_TIME nanoseconds, or when there is an error,
 476          * or when the source is clean, whichever comes first.
 477          */
 478         if (qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - last_pause_ns < SLICE_TIME &&
 479             s->common.iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
 480             if (s->in_flight == MAX_IN_FLIGHT || s->buf_free_count == 0 ||
 481                 (cnt == 0 && s->in_flight > 0)) {
 482                 trace_mirror_yield(s, s->in_flight, s->buf_free_count, cnt);
 483                 qemu_coroutine_yield();
 484                 continue;
 485             } else if (cnt != 0) {
 486                 delay_ns = mirror_iteration(s);
 487                 if (delay_ns == 0) {
 488                     continue;
 489                 }
 490             }
 491         }
 492
 493         should_complete = false;
 494         if (s->in_flight == 0 && cnt == 0) {
 495             trace_mirror_before_flush(s);
 496             ret = bdrv_flush(s->target);
 497             if (ret < 0) {
 498                 if (mirror_error_action(s, false, -ret) ==
 499                     BLOCK_ERROR_ACTION_REPORT) {
 500                     goto immediate_exit;
 501                 }
 502             } else {
 503                 /* We're out of the streaming phase.  From now on, if the job
 504                  * is cancelled we will actually complete all pending I/O and
 505                  * report completion.  This way, block-job-cancel will leave
 506                  * the target in a consistent state.
 507                  */
 508                 if (!s->synced) {
 509                     block_job_event_ready(&s->common);
 510                     s->synced = true;
 511                 }
 512
 513                 should_complete = s->should_complete ||
 514                     block_job_is_cancelled(&s->common);
 515                 cnt = bdrv_get_dirty_count(bs, s->dirty_bitmap);
 516             }
 517         }
 518
 519         if (cnt == 0 && should_complete) {
 520             /* The dirty bitmap is not updated while operations are pending.
 521              * If we're about to exit, wait for pending operations before
 522              * calling bdrv_get_dirty_count(bs), or we may exit while the
 523              * source has dirty data to copy!
 524              *
 525              * Note that I/O can be submitted by the guest while
 526              * mirror_populate runs.
 527              */
 528             trace_mirror_before_drain(s, cnt);
 529             bdrv_drain(bs);
 530             cnt = bdrv_get_dirty_count(bs, s->dirty_bitmap);
 531         }
 532
 533         ret = 0;
 534         trace_mirror_before_sleep(s, cnt, s->synced, delay_ns);
 535         if (!s->synced) {
 536             block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);
 537             if (block_job_is_cancelled(&s->common)) {
 538                 break;
 539             }
 540         } else if (!should_complete) {
 541             delay_ns = (s->in_flight == 0 && cnt == 0 ? SLICE_TIME : 0);
 542             block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);
 543         } else if (cnt == 0) {
 544             /* The two disks are in sync.  Exit and report successful
 545              * completion.
 546              */
 547             assert(QLIST_EMPTY(&bs->tracked_requests));
 548             s->common.cancelled = false;
 549             break;
 550         }
 551         last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
 552     }
 553
 554 immediate_exit:
 555     if (s->in_flight > 0) {
 556         /* We get here only if something went wrong.  Either the job failed,
 557          * or it was cancelled prematurely so that we do not guarantee that
 558          * the target is a copy of the source.
 559          */
 560         assert(ret < 0 || (!s->synced && block_job_is_cancelled(&s->common)));
 561         mirror_drain(s);
 562     }
 563
 564     assert(s->in_flight == 0);
 565     qemu_vfree(s->buf);
 566     g_free(s->cow_bitmap);
 567     g_free(s->in_flight_bitmap);
 568     bdrv_release_dirty_bitmap(bs, s->dirty_bitmap);
 569     bdrv_iostatus_disable(s->target);
 570
 571     data = g_malloc(sizeof(*data));
 572     data->ret = ret;
 573     block_job_defer_to_main_loop(&s->common, mirror_exit, data);
 574 }
 575
 576 static void mirror_set_speed(BlockJob *job, int64_t speed, Error **errp)
 577 {
 578     MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
 579
 580     if (speed < 0) {
 581         error_set(errp, QERR_INVALID_PARAMETER, "speed");
 582         return;
 583     }
 584     ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME);
 585 }
 586
 587 static void mirror_iostatus_reset(BlockJob *job)
 588 {
 589     MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
 590
 591     bdrv_iostatus_reset(s->target);
 592 }
 593
 594 static void mirror_complete(BlockJob *job, Error **errp)
 595 {
 596     MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
 597     Error *local_err = NULL;
 598     int ret;
 599
 600     ret = bdrv_open_backing_file(s->target, NULL, &local_err);
 601     if (ret < 0) {
 602         error_propagate(errp, local_err);
 603         return;
 604     }
 605     if (!s->synced) {
 606         error_set(errp, QERR_BLOCK_JOB_NOT_READY,
 607                   bdrv_get_device_name(job->bs));
 608         return;
 609     }
 610
 611     /* check the target bs is not blocked and block all operations on it */
 612     if (s->replaces) {
 613         AioContext *replace_aio_context;
 614
 615         s->to_replace = check_to_replace_node(s->replaces, &local_err);
 616         if (!s->to_replace) {
 617             error_propagate(errp, local_err);
 618             return;
 619         }
 620
 621         replace_aio_context = bdrv_get_aio_context(s->to_replace);
 622         aio_context_acquire(replace_aio_context);
 623
 624         error_setg(&s->replace_blocker,
 625                    "block device is in use by block-job-complete");
 626         bdrv_op_block_all(s->to_replace, s->replace_blocker);
 627         bdrv_ref(s->to_replace);
 628
 629         aio_context_release(replace_aio_context);
 630     }
 631
 632     s->should_complete = true;
 633     block_job_resume(job);
 634 }
 635
 636 static const BlockJobDriver mirror_job_driver = {
 637     .instance_size = sizeof(MirrorBlockJob),
 638     .job_type      = BLOCK_JOB_TYPE_MIRROR,
 639     .set_speed     = mirror_set_speed,
 640     .iostatus_reset= mirror_iostatus_reset,
 641     .complete      = mirror_complete,
 642 };
 643
 644 static const BlockJobDriver commit_active_job_driver = {
 645     .instance_size = sizeof(MirrorBlockJob),
 646     .job_type      = BLOCK_JOB_TYPE_COMMIT,
 647     .set_speed     = mirror_set_speed,
 648     .iostatus_reset
 649                    = mirror_iostatus_reset,
 650     .complete      = mirror_complete,
 651 };
 652
 653 static void mirror_start_job(BlockDriverState *bs, BlockDriverState *target,
 654                              const char *replaces,
 655                              int64_t speed, int64_t granularity,
 656                              int64_t buf_size,
 657                              BlockdevOnError on_source_error,
 658                              BlockdevOnError on_target_error,
 659                              BlockCompletionFunc *cb,
 660                              void *opaque, Error **errp,
 661                              const BlockJobDriver *driver,
 662                              bool is_none_mode, BlockDriverState *base)
 663 {
 664     MirrorBlockJob *s;
 665
 666     if (granularity == 0) {
 667         /* Choose the default granularity based on the target file's cluster
 668          * size, clamped between 4k and 64k.  */
 669         BlockDriverInfo bdi;
 670         if (bdrv_get_info(target, &bdi) >= 0 && bdi.cluster_size != 0) {
 671             granularity = MAX(4096, bdi.cluster_size);
 672             granularity = MIN(65536, granularity);
 673         } else {
 674             granularity = 65536;
 675         }
 676     }
 677
 678     assert ((granularity & (granularity - 1)) == 0);
 679
 680     if ((on_source_error == BLOCKDEV_ON_ERROR_STOP ||
 681          on_source_error == BLOCKDEV_ON_ERROR_ENOSPC) &&
 682         !bdrv_iostatus_is_enabled(bs)) {
 683         error_set(errp, QERR_INVALID_PARAMETER, "on-source-error");
 684         return;
 685     }
 686
 687
 688     s = block_job_create(driver, bs, speed, cb, opaque, errp);
 689     if (!s) {
 690         return;
 691     }
 692
 693     s->replaces = g_strdup(replaces);
 694     s->on_source_error = on_source_error;
 695     s->on_target_error = on_target_error;
 696     s->target = target;
 697     s->is_none_mode = is_none_mode;
 698     s->base = base;
 699     s->granularity = granularity;
 700     s->buf_size = MAX(buf_size, granularity);
 701
 702     s->dirty_bitmap = bdrv_create_dirty_bitmap(bs, granularity, errp);
 703     if (!s->dirty_bitmap) {
 704         return;
 705     }
 706     bdrv_set_enable_write_cache(s->target, true);
 707     bdrv_set_on_error(s->target, on_target_error, on_target_error);
 708     bdrv_iostatus_enable(s->target);
 709     s->common.co = qemu_coroutine_create(mirror_run);
 710     trace_mirror_start(bs, s, s->common.co, opaque);
 711     qemu_coroutine_enter(s->common.co, s);
 712 }
 713
 714 void mirror_start(BlockDriverState *bs, BlockDriverState *target,
 715                   const char *replaces,
 716                   int64_t speed, int64_t granularity, int64_t buf_size,
 717                   MirrorSyncMode mode, BlockdevOnError on_source_error,
 718                   BlockdevOnError on_target_error,
 719                   BlockCompletionFunc *cb,
 720                   void *opaque, Error **errp)
 721 {
 722     bool is_none_mode;
 723     BlockDriverState *base;
 724
 725     is_none_mode = mode == MIRROR_SYNC_MODE_NONE;
 726     base = mode == MIRROR_SYNC_MODE_TOP ? bs->backing_hd : NULL;
 727     mirror_start_job(bs, target, replaces,
 728                      speed, granularity, buf_size,
 729                      on_source_error, on_target_error, cb, opaque, errp,
 730                      &mirror_job_driver, is_none_mode, base);
 731 }
 732
 733 void commit_active_start(BlockDriverState *bs, BlockDriverState *base,
 734                          int64_t speed,
 735                          BlockdevOnError on_error,
 736                          BlockCompletionFunc *cb,
 737                          void *opaque, Error **errp)
 738 {
 739     int64_t length, base_length;
 740     int orig_base_flags;
 741     int ret;
 742     Error *local_err = NULL;
 743
 744     orig_base_flags = bdrv_get_flags(base);
 745
 746     if (bdrv_reopen(base, bs->open_flags, errp)) {
 747         return;
 748     }
 749
 750     length = bdrv_getlength(bs);
 751     if (length < 0) {
 752         error_setg_errno(errp, -length,
 753                          "Unable to determine length of %s", bs->filename);
 754         goto error_restore_flags;
 755     }
 756
 757     base_length = bdrv_getlength(base);
 758     if (base_length < 0) {
 759         error_setg_errno(errp, -base_length,
 760                          "Unable to determine length of %s", base->filename);
 761         goto error_restore_flags;
 762     }
 763
 764     if (length > base_length) {
 765         ret = bdrv_truncate(base, length);
 766         if (ret < 0) {
 767             error_setg_errno(errp, -ret,
 768                             "Top image %s is larger than base image %s, and "
 769                              "resize of base image failed",
 770                              bs->filename, base->filename);
 771             goto error_restore_flags;
 772         }
 773     }
 774
 775     bdrv_ref(base);
 776     mirror_start_job(bs, base, NULL, speed, 0, 0,
 777                      on_error, on_error, cb, opaque, &local_err,
 778                      &commit_active_job_driver, false, base);
 779     if (local_err) {
 780         error_propagate(errp, local_err);
 781         goto error_restore_flags;
 782     }
 783
 784     return;
 785
 786 error_restore_flags:
 787     /* ignore error and errp for bdrv_reopen, because we want to propagate
 788      * the original error */
 789     bdrv_reopen(base, orig_base_flags, NULL);
 790     return;
 791 }