block-migration.c

   1 /*
   2  * QEMU live block migration
   3  *
   4  * Copyright IBM, Corp. 2009
   5  *
   6  * Authors:
   7  *  Liran Schour   <lirans@il.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2.  See
  10  * the COPYING file in the top-level directory.
  11  *
  12  */
  13
  14 #include "qemu-common.h"
  15 #include "block_int.h"
  16 #include "hw/hw.h"
  17 #include "qemu-queue.h"
  18 #include "qemu-timer.h"
  19 #include "monitor.h"
  20 #include "block-migration.h"
  21 #include "migration.h"
  22 #include "blockdev.h"
  23 #include <assert.h>
  24
  25 #define BLOCK_SIZE (BDRV_SECTORS_PER_DIRTY_CHUNK << BDRV_SECTOR_BITS)
  26
  27 #define BLK_MIG_FLAG_DEVICE_BLOCK       0x01
  28 #define BLK_MIG_FLAG_EOS                0x02
  29 #define BLK_MIG_FLAG_PROGRESS           0x04
  30
  31 #define MAX_IS_ALLOCATED_SEARCH 65536
  32
  33 //#define DEBUG_BLK_MIGRATION
  34
  35 #ifdef DEBUG_BLK_MIGRATION
  36 #define DPRINTF(fmt, ...) \
  37     do { printf("blk_migration: " fmt, ## __VA_ARGS__); } while (0)
  38 #else
  39 #define DPRINTF(fmt, ...) \
  40     do { } while (0)
  41 #endif
  42
  43 typedef struct BlkMigDevState {
  44     BlockDriverState *bs;
  45     int bulk_completed;
  46     int shared_base;
  47     int64_t cur_sector;
  48     int64_t cur_dirty;
  49     int64_t completed_sectors;
  50     int64_t total_sectors;
  51     int64_t dirty;
  52     QSIMPLEQ_ENTRY(BlkMigDevState) entry;
  53     unsigned long *aio_bitmap;
  54 } BlkMigDevState;
  55
  56 typedef struct BlkMigBlock {
  57     uint8_t *buf;
  58     BlkMigDevState *bmds;
  59     int64_t sector;
  60     int nr_sectors;
  61     struct iovec iov;
  62     QEMUIOVector qiov;
  63     BlockDriverAIOCB *aiocb;
  64     int ret;
  65     int64_t time;
  66     QSIMPLEQ_ENTRY(BlkMigBlock) entry;
  67 } BlkMigBlock;
  68
  69 typedef struct BlkMigState {
  70     int blk_enable;
  71     int shared_base;
  72     QSIMPLEQ_HEAD(bmds_list, BlkMigDevState) bmds_list;
  73     QSIMPLEQ_HEAD(blk_list, BlkMigBlock) blk_list;
  74     int submitted;
  75     int read_done;
  76     int transferred;
  77     int64_t total_sector_sum;
  78     int prev_progress;
  79     int bulk_completed;
  80     long double total_time;
  81     int reads;
  82 } BlkMigState;
  83
  84 static BlkMigState block_mig_state;
  85
  86 static void blk_send(QEMUFile *f, BlkMigBlock * blk)
  87 {
  88     int len;
  89
  90     /* sector number and flags */
  91     qemu_put_be64(f, (blk->sector << BDRV_SECTOR_BITS)
  92                      | BLK_MIG_FLAG_DEVICE_BLOCK);
  93
  94     /* device name */
  95     len = strlen(blk->bmds->bs->device_name);
  96     qemu_put_byte(f, len);
  97     qemu_put_buffer(f, (uint8_t *)blk->bmds->bs->device_name, len);
  98
  99     qemu_put_buffer(f, blk->buf, BLOCK_SIZE);
 100 }
 101
 102 int blk_mig_active(void)
 103 {
 104     return !QSIMPLEQ_EMPTY(&block_mig_state.bmds_list);
 105 }
 106
 107 uint64_t blk_mig_bytes_transferred(void)
 108 {
 109     BlkMigDevState *bmds;
 110     uint64_t sum = 0;
 111
 112     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
 113         sum += bmds->completed_sectors;
 114     }
 115     return sum << BDRV_SECTOR_BITS;
 116 }
 117
 118 uint64_t blk_mig_bytes_remaining(void)
 119 {
 120     return blk_mig_bytes_total() - blk_mig_bytes_transferred();
 121 }
 122
 123 uint64_t blk_mig_bytes_total(void)
 124 {
 125     BlkMigDevState *bmds;
 126     uint64_t sum = 0;
 127
 128     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
 129         sum += bmds->total_sectors;
 130     }
 131     return sum << BDRV_SECTOR_BITS;
 132 }
 133
 134 static inline void add_avg_read_time(int64_t time)
 135 {
 136     block_mig_state.reads++;
 137     block_mig_state.total_time += time;
 138 }
 139
 140 static inline long double compute_read_bwidth(void)
 141 {
 142     assert(block_mig_state.total_time != 0);
 143     return (block_mig_state.reads / block_mig_state.total_time) * BLOCK_SIZE;
 144 }
 145
 146 static int bmds_aio_inflight(BlkMigDevState *bmds, int64_t sector)
 147 {
 148     int64_t chunk = sector / (int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK;
 149
 150     if ((sector << BDRV_SECTOR_BITS) < bdrv_getlength(bmds->bs)) {
 151         return !!(bmds->aio_bitmap[chunk / (sizeof(unsigned long) * 8)] &
 152             (1UL << (chunk % (sizeof(unsigned long) * 8))));
 153     } else {
 154         return 0;
 155     }
 156 }
 157
 158 static void bmds_set_aio_inflight(BlkMigDevState *bmds, int64_t sector_num,
 159                              int nb_sectors, int set)
 160 {
 161     int64_t start, end;
 162     unsigned long val, idx, bit;
 163
 164     start = sector_num / BDRV_SECTORS_PER_DIRTY_CHUNK;
 165     end = (sector_num + nb_sectors - 1) / BDRV_SECTORS_PER_DIRTY_CHUNK;
 166
 167     for (; start <= end; start++) {
 168         idx = start / (sizeof(unsigned long) * 8);
 169         bit = start % (sizeof(unsigned long) * 8);
 170         val = bmds->aio_bitmap[idx];
 171         if (set) {
 172             val |= 1UL << bit;
 173         } else {
 174             val &= ~(1UL << bit);
 175         }
 176         bmds->aio_bitmap[idx] = val;
 177     }
 178 }
 179
 180 static void alloc_aio_bitmap(BlkMigDevState *bmds)
 181 {
 182     BlockDriverState *bs = bmds->bs;
 183     int64_t bitmap_size;
 184
 185     bitmap_size = (bdrv_getlength(bs) >> BDRV_SECTOR_BITS) +
 186             BDRV_SECTORS_PER_DIRTY_CHUNK * 8 - 1;
 187     bitmap_size /= BDRV_SECTORS_PER_DIRTY_CHUNK * 8;
 188
 189     bmds->aio_bitmap = qemu_mallocz(bitmap_size);
 190 }
 191
 192 static void blk_mig_read_cb(void *opaque, int ret)
 193 {
 194     BlkMigBlock *blk = opaque;
 195
 196     blk->ret = ret;
 197
 198     blk->time = qemu_get_clock_ns(rt_clock) - blk->time;
 199
 200     add_avg_read_time(blk->time);
 201
 202     QSIMPLEQ_INSERT_TAIL(&block_mig_state.blk_list, blk, entry);
 203     bmds_set_aio_inflight(blk->bmds, blk->sector, blk->nr_sectors, 0);
 204
 205     block_mig_state.submitted--;
 206     block_mig_state.read_done++;
 207     assert(block_mig_state.submitted >= 0);
 208 }
 209
 210 static int mig_save_device_bulk(Monitor *mon, QEMUFile *f,
 211                                 BlkMigDevState *bmds)
 212 {
 213     int64_t total_sectors = bmds->total_sectors;
 214     int64_t cur_sector = bmds->cur_sector;
 215     BlockDriverState *bs = bmds->bs;
 216     BlkMigBlock *blk;
 217     int nr_sectors;
 218
 219     if (bmds->shared_base) {
 220         while (cur_sector < total_sectors &&
 221                !bdrv_is_allocated(bs, cur_sector, MAX_IS_ALLOCATED_SEARCH,
 222                                   &nr_sectors)) {
 223             cur_sector += nr_sectors;
 224         }
 225     }
 226
 227     if (cur_sector >= total_sectors) {
 228         bmds->cur_sector = bmds->completed_sectors = total_sectors;
 229         return 1;
 230     }
 231
 232     bmds->completed_sectors = cur_sector;
 233
 234     cur_sector &= ~((int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK - 1);
 235
 236     /* we are going to transfer a full block even if it is not allocated */
 237     nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
 238
 239     if (total_sectors - cur_sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {
 240         nr_sectors = total_sectors - cur_sector;
 241     }
 242
 243     blk = qemu_malloc(sizeof(BlkMigBlock));
 244     blk->buf = qemu_malloc(BLOCK_SIZE);
 245     blk->bmds = bmds;
 246     blk->sector = cur_sector;
 247     blk->nr_sectors = nr_sectors;
 248
 249     blk->iov.iov_base = blk->buf;
 250     blk->iov.iov_len = nr_sectors * BDRV_SECTOR_SIZE;
 251     qemu_iovec_init_external(&blk->qiov, &blk->iov, 1);
 252
 253     blk->time = qemu_get_clock_ns(rt_clock);
 254
 255     blk->aiocb = bdrv_aio_readv(bs, cur_sector, &blk->qiov,
 256                                 nr_sectors, blk_mig_read_cb, blk);
 257     if (!blk->aiocb) {
 258         goto error;
 259     }
 260     block_mig_state.submitted++;
 261
 262     bdrv_reset_dirty(bs, cur_sector, nr_sectors);
 263     bmds->cur_sector = cur_sector + nr_sectors;
 264
 265     return (bmds->cur_sector >= total_sectors);
 266
 267 error:
 268     monitor_printf(mon, "Error reading sector %" PRId64 "\n", cur_sector);
 269     qemu_file_set_error(f);
 270     qemu_free(blk->buf);
 271     qemu_free(blk);
 272     return 0;
 273 }
 274
 275 static void set_dirty_tracking(int enable)
 276 {
 277     BlkMigDevState *bmds;
 278
 279     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
 280         bdrv_set_dirty_tracking(bmds->bs, enable);
 281     }
 282 }
 283
 284 static void init_blk_migration_it(void *opaque, BlockDriverState *bs)
 285 {
 286     Monitor *mon = opaque;
 287     BlkMigDevState *bmds;
 288     int64_t sectors;
 289
 290     if (!bdrv_is_read_only(bs)) {
 291         sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
 292         if (sectors <= 0) {
 293             return;
 294         }
 295
 296         bmds = qemu_mallocz(sizeof(BlkMigDevState));
 297         bmds->bs = bs;
 298         bmds->bulk_completed = 0;
 299         bmds->total_sectors = sectors;
 300         bmds->completed_sectors = 0;
 301         bmds->shared_base = block_mig_state.shared_base;
 302         alloc_aio_bitmap(bmds);
 303         drive_get_ref(drive_get_by_blockdev(bs));
 304         bdrv_set_in_use(bs, 1);
 305
 306         block_mig_state.total_sector_sum += sectors;
 307
 308         if (bmds->shared_base) {
 309             monitor_printf(mon, "Start migration for %s with shared base "
 310                                 "image\n",
 311                            bs->device_name);
 312         } else {
 313             monitor_printf(mon, "Start full migration for %s\n",
 314                            bs->device_name);
 315         }
 316
 317         QSIMPLEQ_INSERT_TAIL(&block_mig_state.bmds_list, bmds, entry);
 318     }
 319 }
 320
 321 static void init_blk_migration(Monitor *mon, QEMUFile *f)
 322 {
 323     block_mig_state.submitted = 0;
 324     block_mig_state.read_done = 0;
 325     block_mig_state.transferred = 0;
 326     block_mig_state.total_sector_sum = 0;
 327     block_mig_state.prev_progress = -1;
 328     block_mig_state.bulk_completed = 0;
 329     block_mig_state.total_time = 0;
 330     block_mig_state.reads = 0;
 331
 332     bdrv_iterate(init_blk_migration_it, mon);
 333 }
 334
 335 static int blk_mig_save_bulked_block(Monitor *mon, QEMUFile *f)
 336 {
 337     int64_t completed_sector_sum = 0;
 338     BlkMigDevState *bmds;
 339     int progress;
 340     int ret = 0;
 341
 342     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
 343         if (bmds->bulk_completed == 0) {
 344             if (mig_save_device_bulk(mon, f, bmds) == 1) {
 345                 /* completed bulk section for this device */
 346                 bmds->bulk_completed = 1;
 347             }
 348             completed_sector_sum += bmds->completed_sectors;
 349             ret = 1;
 350             break;
 351         } else {
 352             completed_sector_sum += bmds->completed_sectors;
 353         }
 354     }
 355
 356     if (block_mig_state.total_sector_sum != 0) {
 357         progress = completed_sector_sum * 100 /
 358                    block_mig_state.total_sector_sum;
 359     } else {
 360         progress = 100;
 361     }
 362     if (progress != block_mig_state.prev_progress) {
 363         block_mig_state.prev_progress = progress;
 364         qemu_put_be64(f, (progress << BDRV_SECTOR_BITS)
 365                          | BLK_MIG_FLAG_PROGRESS);
 366         monitor_printf(mon, "Completed %d %%\r", progress);
 367         monitor_flush(mon);
 368     }
 369
 370     return ret;
 371 }
 372
 373 static void blk_mig_reset_dirty_cursor(void)
 374 {
 375     BlkMigDevState *bmds;
 376
 377     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
 378         bmds->cur_dirty = 0;
 379     }
 380 }
 381
 382 static int mig_save_device_dirty(Monitor *mon, QEMUFile *f,
 383                                  BlkMigDevState *bmds, int is_async)
 384 {
 385     BlkMigBlock *blk;
 386     int64_t total_sectors = bmds->total_sectors;
 387     int64_t sector;
 388     int nr_sectors;
 389
 390     for (sector = bmds->cur_dirty; sector < bmds->total_sectors;) {
 391         if (bmds_aio_inflight(bmds, sector)) {
 392             qemu_aio_flush();
 393         }
 394         if (bdrv_get_dirty(bmds->bs, sector)) {
 395
 396             if (total_sectors - sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {
 397                 nr_sectors = total_sectors - sector;
 398             } else {
 399                 nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
 400             }
 401             blk = qemu_malloc(sizeof(BlkMigBlock));
 402             blk->buf = qemu_malloc(BLOCK_SIZE);
 403             blk->bmds = bmds;
 404             blk->sector = sector;
 405             blk->nr_sectors = nr_sectors;
 406
 407             if (is_async) {
 408                 blk->iov.iov_base = blk->buf;
 409                 blk->iov.iov_len = nr_sectors * BDRV_SECTOR_SIZE;
 410                 qemu_iovec_init_external(&blk->qiov, &blk->iov, 1);
 411
 412                 blk->time = qemu_get_clock_ns(rt_clock);
 413
 414                 blk->aiocb = bdrv_aio_readv(bmds->bs, sector, &blk->qiov,
 415                                             nr_sectors, blk_mig_read_cb, blk);
 416                 if (!blk->aiocb) {
 417                     goto error;
 418                 }
 419                 block_mig_state.submitted++;
 420                 bmds_set_aio_inflight(bmds, sector, nr_sectors, 1);
 421             } else {
 422                 if (bdrv_read(bmds->bs, sector, blk->buf,
 423                               nr_sectors) < 0) {
 424                     goto error;
 425                 }
 426                 blk_send(f, blk);
 427
 428                 qemu_free(blk->buf);
 429                 qemu_free(blk);
 430             }
 431
 432             bdrv_reset_dirty(bmds->bs, sector, nr_sectors);
 433             break;
 434         }
 435         sector += BDRV_SECTORS_PER_DIRTY_CHUNK;
 436         bmds->cur_dirty = sector;
 437     }
 438
 439     return (bmds->cur_dirty >= bmds->total_sectors);
 440
 441 error:
 442     monitor_printf(mon, "Error reading sector %" PRId64 "\n", sector);
 443     qemu_file_set_error(f);
 444     qemu_free(blk->buf);
 445     qemu_free(blk);
 446     return 0;
 447 }
 448
 449 static int blk_mig_save_dirty_block(Monitor *mon, QEMUFile *f, int is_async)
 450 {
 451     BlkMigDevState *bmds;
 452     int ret = 0;
 453
 454     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
 455         if (mig_save_device_dirty(mon, f, bmds, is_async) == 0) {
 456             ret = 1;
 457             break;
 458         }
 459     }
 460
 461     return ret;
 462 }
 463
 464 static void flush_blks(QEMUFile* f)
 465 {
 466     BlkMigBlock *blk;
 467
 468     DPRINTF("%s Enter submitted %d read_done %d transferred %d\n",
 469             __FUNCTION__, block_mig_state.submitted, block_mig_state.read_done,
 470             block_mig_state.transferred);
 471
 472     while ((blk = QSIMPLEQ_FIRST(&block_mig_state.blk_list)) != NULL) {
 473         if (qemu_file_rate_limit(f)) {
 474             break;
 475         }
 476         if (blk->ret < 0) {
 477             qemu_file_set_error(f);
 478             break;
 479         }
 480         blk_send(f, blk);
 481
 482         QSIMPLEQ_REMOVE_HEAD(&block_mig_state.blk_list, entry);
 483         qemu_free(blk->buf);
 484         qemu_free(blk);
 485
 486         block_mig_state.read_done--;
 487         block_mig_state.transferred++;
 488         assert(block_mig_state.read_done >= 0);
 489     }
 490
 491     DPRINTF("%s Exit submitted %d read_done %d transferred %d\n", __FUNCTION__,
 492             block_mig_state.submitted, block_mig_state.read_done,
 493             block_mig_state.transferred);
 494 }
 495
 496 static int64_t get_remaining_dirty(void)
 497 {
 498     BlkMigDevState *bmds;
 499     int64_t dirty = 0;
 500
 501     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
 502         dirty += bdrv_get_dirty_count(bmds->bs);
 503     }
 504
 505     return dirty * BLOCK_SIZE;
 506 }
 507
 508 static int is_stage2_completed(void)
 509 {
 510     int64_t remaining_dirty;
 511     long double bwidth;
 512
 513     if (block_mig_state.bulk_completed == 1) {
 514
 515         remaining_dirty = get_remaining_dirty();
 516         if (remaining_dirty == 0) {
 517             return 1;
 518         }
 519
 520         bwidth = compute_read_bwidth();
 521
 522         if ((remaining_dirty / bwidth) <=
 523             migrate_max_downtime()) {
 524             /* finish stage2 because we think that we can finish remaing work
 525                below max_downtime */
 526
 527             return 1;
 528         }
 529     }
 530
 531     return 0;
 532 }
 533
 534 static void blk_mig_cleanup(Monitor *mon)
 535 {
 536     BlkMigDevState *bmds;
 537     BlkMigBlock *blk;
 538
 539     set_dirty_tracking(0);
 540
 541     while ((bmds = QSIMPLEQ_FIRST(&block_mig_state.bmds_list)) != NULL) {
 542         QSIMPLEQ_REMOVE_HEAD(&block_mig_state.bmds_list, entry);
 543         bdrv_set_in_use(bmds->bs, 0);
 544         drive_put_ref(drive_get_by_blockdev(bmds->bs));
 545         qemu_free(bmds->aio_bitmap);
 546         qemu_free(bmds);
 547     }
 548
 549     while ((blk = QSIMPLEQ_FIRST(&block_mig_state.blk_list)) != NULL) {
 550         QSIMPLEQ_REMOVE_HEAD(&block_mig_state.blk_list, entry);
 551         qemu_free(blk->buf);
 552         qemu_free(blk);
 553     }
 554
 555     monitor_printf(mon, "\n");
 556 }
 557
 558 static int block_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
 559 {
 560     DPRINTF("Enter save live stage %d submitted %d transferred %d\n",
 561             stage, block_mig_state.submitted, block_mig_state.transferred);
 562
 563     if (stage < 0) {
 564         blk_mig_cleanup(mon);
 565         return 0;
 566     }
 567
 568     if (block_mig_state.blk_enable != 1) {
 569         /* no need to migrate storage */
 570         qemu_put_be64(f, BLK_MIG_FLAG_EOS);
 571         return 1;
 572     }
 573
 574     if (stage == 1) {
 575         init_blk_migration(mon, f);
 576
 577         /* start track dirty blocks */
 578         set_dirty_tracking(1);
 579     }
 580
 581     flush_blks(f);
 582
 583     if (qemu_file_has_error(f)) {
 584         blk_mig_cleanup(mon);
 585         return 0;
 586     }
 587
 588     blk_mig_reset_dirty_cursor();
 589
 590     if (stage == 2) {
 591         /* control the rate of transfer */
 592         while ((block_mig_state.submitted +
 593                 block_mig_state.read_done) * BLOCK_SIZE <
 594                qemu_file_get_rate_limit(f)) {
 595             if (block_mig_state.bulk_completed == 0) {
 596                 /* first finish the bulk phase */
 597                 if (blk_mig_save_bulked_block(mon, f) == 0) {
 598                     /* finished saving bulk on all devices */
 599                     block_mig_state.bulk_completed = 1;
 600                 }
 601             } else {
 602                 if (blk_mig_save_dirty_block(mon, f, 1) == 0) {
 603                     /* no more dirty blocks */
 604                     break;
 605                 }
 606             }
 607         }
 608
 609         flush_blks(f);
 610
 611         if (qemu_file_has_error(f)) {
 612             blk_mig_cleanup(mon);
 613             return 0;
 614         }
 615     }
 616
 617     if (stage == 3) {
 618         /* we know for sure that save bulk is completed and
 619            all async read completed */
 620         assert(block_mig_state.submitted == 0);
 621
 622         while (blk_mig_save_dirty_block(mon, f, 0) != 0);
 623         blk_mig_cleanup(mon);
 624
 625         /* report completion */
 626         qemu_put_be64(f, (100 << BDRV_SECTOR_BITS) | BLK_MIG_FLAG_PROGRESS);
 627
 628         if (qemu_file_has_error(f)) {
 629             return 0;
 630         }
 631
 632         monitor_printf(mon, "Block migration completed\n");
 633     }
 634
 635     qemu_put_be64(f, BLK_MIG_FLAG_EOS);
 636
 637     return ((stage == 2) && is_stage2_completed());
 638 }
 639
 640 static int block_load(QEMUFile *f, void *opaque, int version_id)
 641 {
 642     static int banner_printed;
 643     int len, flags;
 644     char device_name[256];
 645     int64_t addr;
 646     BlockDriverState *bs, *bs_prev = NULL;
 647     uint8_t *buf;
 648     int64_t total_sectors = 0;
 649     int nr_sectors;
 650
 651     do {
 652         addr = qemu_get_be64(f);
 653
 654         flags = addr & ~BDRV_SECTOR_MASK;
 655         addr >>= BDRV_SECTOR_BITS;
 656
 657         if (flags & BLK_MIG_FLAG_DEVICE_BLOCK) {
 658             int ret;
 659             /* get device name */
 660             len = qemu_get_byte(f);
 661             qemu_get_buffer(f, (uint8_t *)device_name, len);
 662             device_name[len] = '\0';
 663
 664             bs = bdrv_find(device_name);
 665             if (!bs) {
 666                 fprintf(stderr, "Error unknown block device %s\n",
 667                         device_name);
 668                 return -EINVAL;
 669             }
 670
 671             if (bs != bs_prev) {
 672                 bs_prev = bs;
 673                 total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
 674                 if (total_sectors <= 0) {
 675                     error_report("Error getting length of block device %s\n",
 676                                  device_name);
 677                     return -EINVAL;
 678                 }
 679             }
 680
 681             if (total_sectors - addr < BDRV_SECTORS_PER_DIRTY_CHUNK) {
 682                 nr_sectors = total_sectors - addr;
 683             } else {
 684                 nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
 685             }
 686
 687             buf = qemu_malloc(BLOCK_SIZE);
 688
 689             qemu_get_buffer(f, buf, BLOCK_SIZE);
 690             ret = bdrv_write(bs, addr, buf, nr_sectors);
 691
 692             qemu_free(buf);
 693             if (ret < 0) {
 694                 return ret;
 695             }
 696         } else if (flags & BLK_MIG_FLAG_PROGRESS) {
 697             if (!banner_printed) {
 698                 printf("Receiving block device images\n");
 699                 banner_printed = 1;
 700             }
 701             printf("Completed %d %%%c", (int)addr,
 702                    (addr == 100) ? '\n' : '\r');
 703             fflush(stdout);
 704         } else if (!(flags & BLK_MIG_FLAG_EOS)) {
 705             fprintf(stderr, "Unknown flags\n");
 706             return -EINVAL;
 707         }
 708         if (qemu_file_has_error(f)) {
 709             return -EIO;
 710         }
 711     } while (!(flags & BLK_MIG_FLAG_EOS));
 712
 713     return 0;
 714 }
 715
 716 static void block_set_params(int blk_enable, int shared_base, void *opaque)
 717 {
 718     block_mig_state.blk_enable = blk_enable;
 719     block_mig_state.shared_base = shared_base;
 720
 721     /* shared base means that blk_enable = 1 */
 722     block_mig_state.blk_enable |= shared_base;
 723 }
 724
 725 void blk_mig_init(void)
 726 {
 727     QSIMPLEQ_INIT(&block_mig_state.bmds_list);
 728     QSIMPLEQ_INIT(&block_mig_state.blk_list);
 729
 730     register_savevm_live(NULL, "block", 0, 1, block_set_params,
 731                          block_save_live, NULL, block_load, &block_mig_state);
 732 }