block-migration.c - qemu - Git at Google

 /*
  * QEMU live block migration
  *
  * Copyright IBM, Corp. 2009
  *
  * Authors:
  *  Liran Schour   <lirans@il.ibm.com>
  *
  * This work is licensed under the terms of the GNU GPL, version 2.  See
  * the COPYING file in the top-level directory.
  *
  * Contributions after 2012-01-13 are licensed under the terms of the
  * GNU GPL, version 2 or (at your option) any later version.
  */

 #include "qemu-common.h"
 #include "block/block_int.h"
 #include "hw/hw.h"
 #include "qemu/queue.h"
 #include "qemu/timer.h"
 #include "migration/block.h"
 #include "migration/migration.h"
 #include "sysemu/blockdev.h"
 #include <assert.h>

 #define BLOCK_SIZE                       (1 << 20)
 #define BDRV_SECTORS_PER_DIRTY_CHUNK     (BLOCK_SIZE >> BDRV_SECTOR_BITS)

 #define BLK_MIG_FLAG_DEVICE_BLOCK       0x01
 #define BLK_MIG_FLAG_EOS                0x02
 #define BLK_MIG_FLAG_PROGRESS           0x04
 #define BLK_MIG_FLAG_ZERO_BLOCK         0x08

 #define MAX_IS_ALLOCATED_SEARCH 65536

 //#define DEBUG_BLK_MIGRATION

 #ifdef DEBUG_BLK_MIGRATION
 #define DPRINTF(fmt, ...) \
     do { printf("blk_migration: " fmt, ## __VA_ARGS__); } while (0)
 #else
 #define DPRINTF(fmt, ...) \
     do { } while (0)
 #endif

 typedef struct BlkMigDevState {
     /* Written during setup phase.  Can be read without a lock.  */
     BlockDriverState *bs;
     int shared_base;
     int64_t total_sectors;
     QSIMPLEQ_ENTRY(BlkMigDevState) entry;

     /* Only used by migration thread.  Does not need a lock.  */
     int bulk_completed;
     int64_t cur_sector;
     int64_t cur_dirty;

     /* Protected by block migration lock.  */
     unsigned long *aio_bitmap;
     int64_t completed_sectors;
     BdrvDirtyBitmap *dirty_bitmap;
     Error *blocker;
 } BlkMigDevState;

 typedef struct BlkMigBlock {
     /* Only used by migration thread.  */
     uint8_t *buf;
     BlkMigDevState *bmds;
     int64_t sector;
     int nr_sectors;
     struct iovec iov;
     QEMUIOVector qiov;
     BlockDriverAIOCB *aiocb;

     /* Protected by block migration lock.  */
     int ret;
     QSIMPLEQ_ENTRY(BlkMigBlock) entry;
 } BlkMigBlock;

 typedef struct BlkMigState {
     /* Written during setup phase.  Can be read without a lock.  */
     int blk_enable;
     int shared_base;
     QSIMPLEQ_HEAD(bmds_list, BlkMigDevState) bmds_list;
     int64_t total_sector_sum;
     bool zero_blocks;

     /* Protected by lock.  */
     QSIMPLEQ_HEAD(blk_list, BlkMigBlock) blk_list;
     int submitted;
     int read_done;

     /* Only used by migration thread.  Does not need a lock.  */
     int transferred;
     int prev_progress;
     int bulk_completed;

     /* Lock must be taken _inside_ the iothread lock.  */
     QemuMutex lock;
 } BlkMigState;

 static BlkMigState block_mig_state;

 static void blk_mig_lock(void)
 {
     qemu_mutex_lock(&block_mig_state.lock);
 }

 static void blk_mig_unlock(void)
 {
     qemu_mutex_unlock(&block_mig_state.lock);
 }

 /* Must run outside of the iothread lock during the bulk phase,
  * or the VM will stall.
  */

 static void blk_send(QEMUFile *f, BlkMigBlock * blk)
 {
     int len;
     uint64_t flags = BLK_MIG_FLAG_DEVICE_BLOCK;

     if (block_mig_state.zero_blocks &&
         buffer_is_zero(blk->buf, BLOCK_SIZE)) {
         flags |= BLK_MIG_FLAG_ZERO_BLOCK;
     }

     /* sector number and flags */
     qemu_put_be64(f, (blk->sector << BDRV_SECTOR_BITS)
                      | flags);

     /* device name */
     len = strlen(blk->bmds->bs->device_name);
     qemu_put_byte(f, len);
     qemu_put_buffer(f, (uint8_t *)blk->bmds->bs->device_name, len);

     /* if a block is zero we need to flush here since the network
      * bandwidth is now a lot higher than the storage device bandwidth.
      * thus if we queue zero blocks we slow down the migration */
     if (flags & BLK_MIG_FLAG_ZERO_BLOCK) {
         qemu_fflush(f);
         return;
     }

     qemu_put_buffer(f, blk->buf, BLOCK_SIZE);
 }

 int blk_mig_active(void)
 {
     return !QSIMPLEQ_EMPTY(&block_mig_state.bmds_list);
 }

 uint64_t blk_mig_bytes_transferred(void)
 {
     BlkMigDevState *bmds;
     uint64_t sum = 0;

     blk_mig_lock();
     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
         sum += bmds->completed_sectors;
     }
     blk_mig_unlock();
     return sum << BDRV_SECTOR_BITS;
 }

 uint64_t blk_mig_bytes_remaining(void)
 {
     return blk_mig_bytes_total() - blk_mig_bytes_transferred();
 }

 uint64_t blk_mig_bytes_total(void)
 {
     BlkMigDevState *bmds;
     uint64_t sum = 0;

     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
         sum += bmds->total_sectors;
     }
     return sum << BDRV_SECTOR_BITS;
 }


 /* Called with migration lock held.  */

 static int bmds_aio_inflight(BlkMigDevState *bmds, int64_t sector)
 {
     int64_t chunk = sector / (int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK;

     if ((sector << BDRV_SECTOR_BITS) < bdrv_getlength(bmds->bs)) {
         return !!(bmds->aio_bitmap[chunk / (sizeof(unsigned long) * 8)] &
             (1UL << (chunk % (sizeof(unsigned long) * 8))));
     } else {
         return 0;
     }
 }

 /* Called with migration lock held.  */

 static void bmds_set_aio_inflight(BlkMigDevState *bmds, int64_t sector_num,
                              int nb_sectors, int set)
 {
     int64_t start, end;
     unsigned long val, idx, bit;

     start = sector_num / BDRV_SECTORS_PER_DIRTY_CHUNK;
     end = (sector_num + nb_sectors - 1) / BDRV_SECTORS_PER_DIRTY_CHUNK;

     for (; start <= end; start++) {
         idx = start / (sizeof(unsigned long) * 8);
         bit = start % (sizeof(unsigned long) * 8);
         val = bmds->aio_bitmap[idx];
         if (set) {
             val |= 1UL << bit;
         } else {
             val &= ~(1UL << bit);
         }
         bmds->aio_bitmap[idx] = val;
     }
 }

 static void alloc_aio_bitmap(BlkMigDevState *bmds)
 {
     BlockDriverState *bs = bmds->bs;
     int64_t bitmap_size;

     bitmap_size = (bdrv_getlength(bs) >> BDRV_SECTOR_BITS) +
             BDRV_SECTORS_PER_DIRTY_CHUNK * 8 - 1;
     bitmap_size /= BDRV_SECTORS_PER_DIRTY_CHUNK * 8;

     bmds->aio_bitmap = g_malloc0(bitmap_size);
 }

 /* Never hold migration lock when yielding to the main loop!  */

 static void blk_mig_read_cb(void *opaque, int ret)
 {
     BlkMigBlock *blk = opaque;

     blk_mig_lock();
     blk->ret = ret;

     QSIMPLEQ_INSERT_TAIL(&block_mig_state.blk_list, blk, entry);
     bmds_set_aio_inflight(blk->bmds, blk->sector, blk->nr_sectors, 0);

     block_mig_state.submitted--;
     block_mig_state.read_done++;
     assert(block_mig_state.submitted >= 0);
     blk_mig_unlock();
 }

 /* Called with no lock taken.  */

 static int mig_save_device_bulk(QEMUFile *f, BlkMigDevState *bmds)
 {
     int64_t total_sectors = bmds->total_sectors;
     int64_t cur_sector = bmds->cur_sector;
     BlockDriverState *bs = bmds->bs;
     BlkMigBlock *blk;
     int nr_sectors;

     if (bmds->shared_base) {
         qemu_mutex_lock_iothread();
         while (cur_sector < total_sectors &&
                !bdrv_is_allocated(bs, cur_sector, MAX_IS_ALLOCATED_SEARCH,
                                   &nr_sectors)) {
             cur_sector += nr_sectors;
         }
         qemu_mutex_unlock_iothread();
     }

     if (cur_sector >= total_sectors) {
         bmds->cur_sector = bmds->completed_sectors = total_sectors;
         return 1;
     }

     bmds->completed_sectors = cur_sector;

     cur_sector &= ~((int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK - 1);

     /* we are going to transfer a full block even if it is not allocated */
     nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;

     if (total_sectors - cur_sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {
         nr_sectors = total_sectors - cur_sector;
     }

     blk = g_malloc(sizeof(BlkMigBlock));
     blk->buf = g_malloc(BLOCK_SIZE);
     blk->bmds = bmds;
     blk->sector = cur_sector;
     blk->nr_sectors = nr_sectors;

     blk->iov.iov_base = blk->buf;
     blk->iov.iov_len = nr_sectors * BDRV_SECTOR_SIZE;
     qemu_iovec_init_external(&blk->qiov, &blk->iov, 1);

     blk_mig_lock();
     block_mig_state.submitted++;
     blk_mig_unlock();

     qemu_mutex_lock_iothread();
     blk->aiocb = bdrv_aio_readv(bs, cur_sector, &blk->qiov,
                                 nr_sectors, blk_mig_read_cb, blk);

     bdrv_reset_dirty(bs, cur_sector, nr_sectors);
     qemu_mutex_unlock_iothread();

     bmds->cur_sector = cur_sector + nr_sectors;
     return (bmds->cur_sector >= total_sectors);
 }

 /* Called with iothread lock taken.  */

 static int set_dirty_tracking(void)
 {
     BlkMigDevState *bmds;
     int ret;

     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
         bmds->dirty_bitmap = bdrv_create_dirty_bitmap(bmds->bs, BLOCK_SIZE,
                                                       NULL);
         if (!bmds->dirty_bitmap) {
             ret = -errno;
             goto fail;
         }
     }
     return 0;

 fail:
     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
         if (bmds->dirty_bitmap) {
             bdrv_release_dirty_bitmap(bmds->bs, bmds->dirty_bitmap);
         }
     }
     return ret;
 }

 static void unset_dirty_tracking(void)
 {
     BlkMigDevState *bmds;

     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
         bdrv_release_dirty_bitmap(bmds->bs, bmds->dirty_bitmap);
     }
 }

 static void init_blk_migration_it(void *opaque, BlockDriverState *bs)
 {
     BlkMigDevState *bmds;
     int64_t sectors;

     if (!bdrv_is_read_only(bs)) {
         sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
         if (sectors <= 0) {
             return;
         }

         bmds = g_malloc0(sizeof(BlkMigDevState));
         bmds->bs = bs;
         bmds->bulk_completed = 0;
         bmds->total_sectors = sectors;
         bmds->completed_sectors = 0;
         bmds->shared_base = block_mig_state.shared_base;
         alloc_aio_bitmap(bmds);
         error_setg(&bmds->blocker, "block device is in use by migration");
         bdrv_op_block_all(bs, bmds->blocker);
         bdrv_ref(bs);

         block_mig_state.total_sector_sum += sectors;

         if (bmds->shared_base) {
             DPRINTF("Start migration for %s with shared base image\n",
                     bs->device_name);
         } else {
             DPRINTF("Start full migration for %s\n", bs->device_name);
         }

         QSIMPLEQ_INSERT_TAIL(&block_mig_state.bmds_list, bmds, entry);
     }
 }

 static void init_blk_migration(QEMUFile *f)
 {
     block_mig_state.submitted = 0;
     block_mig_state.read_done = 0;
     block_mig_state.transferred = 0;
     block_mig_state.total_sector_sum = 0;
     block_mig_state.prev_progress = -1;
     block_mig_state.bulk_completed = 0;
     block_mig_state.zero_blocks = migrate_zero_blocks();

     bdrv_iterate(init_blk_migration_it, NULL);
 }

 /* Called with no lock taken.  */

 static int blk_mig_save_bulked_block(QEMUFile *f)
 {
     int64_t completed_sector_sum = 0;
     BlkMigDevState *bmds;
     int progress;
     int ret = 0;

     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
         if (bmds->bulk_completed == 0) {
             if (mig_save_device_bulk(f, bmds) == 1) {
                 /* completed bulk section for this device */
                 bmds->bulk_completed = 1;
             }
             completed_sector_sum += bmds->completed_sectors;
             ret = 1;
             break;
         } else {
             completed_sector_sum += bmds->completed_sectors;
         }
     }

     if (block_mig_state.total_sector_sum != 0) {
         progress = completed_sector_sum * 100 /
                    block_mig_state.total_sector_sum;
     } else {
         progress = 100;
     }
     if (progress != block_mig_state.prev_progress) {
         block_mig_state.prev_progress = progress;
         qemu_put_be64(f, (progress << BDRV_SECTOR_BITS)
                          | BLK_MIG_FLAG_PROGRESS);
         DPRINTF("Completed %d %%\r", progress);
     }

     return ret;
 }

 static void blk_mig_reset_dirty_cursor(void)
 {
     BlkMigDevState *bmds;

     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
         bmds->cur_dirty = 0;
     }
 }

 /* Called with iothread lock taken.  */

 static int mig_save_device_dirty(QEMUFile *f, BlkMigDevState *bmds,
                                  int is_async)
 {
     BlkMigBlock *blk;
     int64_t total_sectors = bmds->total_sectors;
     int64_t sector;
     int nr_sectors;
     int ret = -EIO;

     for (sector = bmds->cur_dirty; sector < bmds->total_sectors;) {
         blk_mig_lock();
         if (bmds_aio_inflight(bmds, sector)) {
             blk_mig_unlock();
             bdrv_drain_all();
         } else {
             blk_mig_unlock();
         }
         if (bdrv_get_dirty(bmds->bs, bmds->dirty_bitmap, sector)) {

             if (total_sectors - sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {
                 nr_sectors = total_sectors - sector;
             } else {
                 nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
             }
             blk = g_malloc(sizeof(BlkMigBlock));
             blk->buf = g_malloc(BLOCK_SIZE);
             blk->bmds = bmds;
             blk->sector = sector;
             blk->nr_sectors = nr_sectors;

             if (is_async) {
                 blk->iov.iov_base = blk->buf;
                 blk->iov.iov_len = nr_sectors * BDRV_SECTOR_SIZE;
                 qemu_iovec_init_external(&blk->qiov, &blk->iov, 1);

                 blk->aiocb = bdrv_aio_readv(bmds->bs, sector, &blk->qiov,
                                             nr_sectors, blk_mig_read_cb, blk);

                 blk_mig_lock();
                 block_mig_state.submitted++;
                 bmds_set_aio_inflight(bmds, sector, nr_sectors, 1);
                 blk_mig_unlock();
             } else {
                 ret = bdrv_read(bmds->bs, sector, blk->buf, nr_sectors);
                 if (ret < 0) {
                     goto error;
                 }
                 blk_send(f, blk);

                 g_free(blk->buf);
                 g_free(blk);
             }

             bdrv_reset_dirty(bmds->bs, sector, nr_sectors);
             break;
         }
         sector += BDRV_SECTORS_PER_DIRTY_CHUNK;
         bmds->cur_dirty = sector;
     }

     return (bmds->cur_dirty >= bmds->total_sectors);

 error:
     DPRINTF("Error reading sector %" PRId64 "\n", sector);
     g_free(blk->buf);
     g_free(blk);
     return ret;
 }

 /* Called with iothread lock taken.
  *
  * return value:
  * 0: too much data for max_downtime
  * 1: few enough data for max_downtime
 */
 static int blk_mig_save_dirty_block(QEMUFile *f, int is_async)
 {
     BlkMigDevState *bmds;
     int ret = 1;

     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
         ret = mig_save_device_dirty(f, bmds, is_async);
         if (ret <= 0) {
             break;
         }
     }

     return ret;
 }

 /* Called with no locks taken.  */

 static int flush_blks(QEMUFile *f)
 {
     BlkMigBlock *blk;
     int ret = 0;

     DPRINTF("%s Enter submitted %d read_done %d transferred %d\n",
             __FUNCTION__, block_mig_state.submitted, block_mig_state.read_done,
             block_mig_state.transferred);

     blk_mig_lock();
     while ((blk = QSIMPLEQ_FIRST(&block_mig_state.blk_list)) != NULL) {
         if (qemu_file_rate_limit(f)) {
             break;
         }
         if (blk->ret < 0) {
             ret = blk->ret;
             break;
         }

         QSIMPLEQ_REMOVE_HEAD(&block_mig_state.blk_list, entry);
         blk_mig_unlock();
         blk_send(f, blk);
         blk_mig_lock();

         g_free(blk->buf);
         g_free(blk);

         block_mig_state.read_done--;
         block_mig_state.transferred++;
         assert(block_mig_state.read_done >= 0);
     }
     blk_mig_unlock();

     DPRINTF("%s Exit submitted %d read_done %d transferred %d\n", __FUNCTION__,
             block_mig_state.submitted, block_mig_state.read_done,
             block_mig_state.transferred);
     return ret;
 }

 /* Called with iothread lock taken.  */

 static int64_t get_remaining_dirty(void)
 {
     BlkMigDevState *bmds;
     int64_t dirty = 0;

     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
         dirty += bdrv_get_dirty_count(bmds->bs, bmds->dirty_bitmap);
     }

     return dirty << BDRV_SECTOR_BITS;
 }

 /* Called with iothread lock taken.  */

 static void blk_mig_cleanup(void)
 {
     BlkMigDevState *bmds;
     BlkMigBlock *blk;

     bdrv_drain_all();

     unset_dirty_tracking();

     blk_mig_lock();
     while ((bmds = QSIMPLEQ_FIRST(&block_mig_state.bmds_list)) != NULL) {
         QSIMPLEQ_REMOVE_HEAD(&block_mig_state.bmds_list, entry);
         bdrv_op_unblock_all(bmds->bs, bmds->blocker);
         error_free(bmds->blocker);
         bdrv_unref(bmds->bs);
         g_free(bmds->aio_bitmap);
         g_free(bmds);
     }

     while ((blk = QSIMPLEQ_FIRST(&block_mig_state.blk_list)) != NULL) {
         QSIMPLEQ_REMOVE_HEAD(&block_mig_state.blk_list, entry);
         g_free(blk->buf);
         g_free(blk);
     }
     blk_mig_unlock();
 }

 static void block_migration_cancel(void *opaque)
 {
     blk_mig_cleanup();
 }

 static int block_save_setup(QEMUFile *f, void *opaque)
 {
     int ret;

     DPRINTF("Enter save live setup submitted %d transferred %d\n",
             block_mig_state.submitted, block_mig_state.transferred);

     qemu_mutex_lock_iothread();
     init_blk_migration(f);

     /* start track dirty blocks */
     ret = set_dirty_tracking();

     if (ret) {
         qemu_mutex_unlock_iothread();
         return ret;
     }

     qemu_mutex_unlock_iothread();

     ret = flush_blks(f);
     blk_mig_reset_dirty_cursor();
     qemu_put_be64(f, BLK_MIG_FLAG_EOS);

     return ret;
 }

 static int block_save_iterate(QEMUFile *f, void *opaque)
 {
     int ret;
     int64_t last_ftell = qemu_ftell(f);

     DPRINTF("Enter save live iterate submitted %d transferred %d\n",
             block_mig_state.submitted, block_mig_state.transferred);

     ret = flush_blks(f);
     if (ret) {
         return ret;
     }

     blk_mig_reset_dirty_cursor();

     /* control the rate of transfer */
     blk_mig_lock();
     while ((block_mig_state.submitted +
             block_mig_state.read_done) * BLOCK_SIZE <
            qemu_file_get_rate_limit(f)) {
         blk_mig_unlock();
         if (block_mig_state.bulk_completed == 0) {
             /* first finish the bulk phase */
             if (blk_mig_save_bulked_block(f) == 0) {
                 /* finished saving bulk on all devices */
                 block_mig_state.bulk_completed = 1;
             }
             ret = 0;
         } else {
             /* Always called with iothread lock taken for
              * simplicity, block_save_complete also calls it.
              */
             qemu_mutex_lock_iothread();
             ret = blk_mig_save_dirty_block(f, 1);
             qemu_mutex_unlock_iothread();
         }
         if (ret < 0) {
             return ret;
         }
         blk_mig_lock();
         if (ret != 0) {
             /* no more dirty blocks */
             break;
         }
     }
     blk_mig_unlock();

     ret = flush_blks(f);
     if (ret) {
         return ret;
     }

     qemu_put_be64(f, BLK_MIG_FLAG_EOS);
     return qemu_ftell(f) - last_ftell;
 }

 /* Called with iothread lock taken.  */

 static int block_save_complete(QEMUFile *f, void *opaque)
 {
     int ret;

     DPRINTF("Enter save live complete submitted %d transferred %d\n",
             block_mig_state.submitted, block_mig_state.transferred);

     ret = flush_blks(f);
     if (ret) {
         return ret;
     }

     blk_mig_reset_dirty_cursor();

     /* we know for sure that save bulk is completed and
        all async read completed */
     blk_mig_lock();
     assert(block_mig_state.submitted == 0);
     blk_mig_unlock();

     do {
         ret = blk_mig_save_dirty_block(f, 0);
         if (ret < 0) {
             return ret;
         }
     } while (ret == 0);

     /* report completion */
     qemu_put_be64(f, (100 << BDRV_SECTOR_BITS) | BLK_MIG_FLAG_PROGRESS);

     DPRINTF("Block migration completed\n");

     qemu_put_be64(f, BLK_MIG_FLAG_EOS);

     blk_mig_cleanup();
     return 0;
 }

 static uint64_t block_save_pending(QEMUFile *f, void *opaque, uint64_t max_size)
 {
     /* Estimate pending number of bytes to send */
     uint64_t pending;

     qemu_mutex_lock_iothread();
     blk_mig_lock();
     pending = get_remaining_dirty() +
                        block_mig_state.submitted * BLOCK_SIZE +
                        block_mig_state.read_done * BLOCK_SIZE;

     /* Report at least one block pending during bulk phase */
     if (pending == 0 && !block_mig_state.bulk_completed) {
         pending = BLOCK_SIZE;
     }
     blk_mig_unlock();
     qemu_mutex_unlock_iothread();

     DPRINTF("Enter save live pending  %" PRIu64 "\n", pending);
     return pending;
 }

 static int block_load(QEMUFile *f, void *opaque, int version_id)
 {
     static int banner_printed;
     int len, flags;
     char device_name[256];
     int64_t addr;
     BlockDriverState *bs, *bs_prev = NULL;
     uint8_t *buf;
     int64_t total_sectors = 0;
     int nr_sectors;
     int ret;

     do {
         addr = qemu_get_be64(f);

         flags = addr & ~BDRV_SECTOR_MASK;
         addr >>= BDRV_SECTOR_BITS;

         if (flags & BLK_MIG_FLAG_DEVICE_BLOCK) {
             /* get device name */
             len = qemu_get_byte(f);
             qemu_get_buffer(f, (uint8_t *)device_name, len);
             device_name[len] = '\0';

             bs = bdrv_find(device_name);
             if (!bs) {
                 fprintf(stderr, "Error unknown block device %s\n",
                         device_name);
                 return -EINVAL;
             }

             if (bs != bs_prev) {
                 bs_prev = bs;
                 total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
                 if (total_sectors <= 0) {
                     error_report("Error getting length of block device %s",
                                  device_name);
                     return -EINVAL;
                 }
             }

             if (total_sectors - addr < BDRV_SECTORS_PER_DIRTY_CHUNK) {
                 nr_sectors = total_sectors - addr;
             } else {
                 nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
             }

             if (flags & BLK_MIG_FLAG_ZERO_BLOCK) {
                 ret = bdrv_write_zeroes(bs, addr, nr_sectors,
                                         BDRV_REQ_MAY_UNMAP);
             } else {
                 buf = g_malloc(BLOCK_SIZE);
                 qemu_get_buffer(f, buf, BLOCK_SIZE);
                 ret = bdrv_write(bs, addr, buf, nr_sectors);
                 g_free(buf);
             }

             if (ret < 0) {
                 return ret;
             }
         } else if (flags & BLK_MIG_FLAG_PROGRESS) {
             if (!banner_printed) {
                 printf("Receiving block device images\n");
                 banner_printed = 1;
             }
             printf("Completed %d %%%c", (int)addr,
                    (addr == 100) ? '\n' : '\r');
             fflush(stdout);
         } else if (!(flags & BLK_MIG_FLAG_EOS)) {
             fprintf(stderr, "Unknown block migration flags: %#x\n", flags);
             return -EINVAL;
         }
         ret = qemu_file_get_error(f);
         if (ret != 0) {
             return ret;
         }
     } while (!(flags & BLK_MIG_FLAG_EOS));

     return 0;
 }

 static void block_set_params(const MigrationParams *params, void *opaque)
 {
     block_mig_state.blk_enable = params->blk;
     block_mig_state.shared_base = params->shared;

     /* shared base means that blk_enable = 1 */
     block_mig_state.blk_enable |= params->shared;
 }

 static bool block_is_active(void *opaque)
 {
     return block_mig_state.blk_enable == 1;
 }

 static SaveVMHandlers savevm_block_handlers = {
     .set_params = block_set_params,
     .save_live_setup = block_save_setup,
     .save_live_iterate = block_save_iterate,
     .save_live_complete = block_save_complete,
     .save_live_pending = block_save_pending,
     .load_state = block_load,
     .cancel = block_migration_cancel,
     .is_active = block_is_active,
 };

 void blk_mig_init(void)
 {
     QSIMPLEQ_INIT(&block_mig_state.bmds_list);
     QSIMPLEQ_INIT(&block_mig_state.blk_list);
     qemu_mutex_init(&block_mig_state.lock);

     register_savevm_live(NULL, "block", 0, 1, &savevm_block_handlers,
                          &block_mig_state);
 }
	/*
	* QEMU live block migration
	*
	* Copyright IBM, Corp. 2009
	*
	* Authors:
	* Liran Schour <lirans@il.ibm.com>
	*
	* This work is licensed under the terms of the GNU GPL, version 2. See
	* the COPYING file in the top-level directory.
	*
	* Contributions after 2012-01-13 are licensed under the terms of the
	* GNU GPL, version 2 or (at your option) any later version.
	*/

	#include "qemu-common.h"
	#include "block/block_int.h"
	#include "hw/hw.h"
	#include "qemu/queue.h"
	#include "qemu/timer.h"
	#include "migration/block.h"
	#include "migration/migration.h"
	#include "sysemu/blockdev.h"
	#include <assert.h>

	#define BLOCK_SIZE (1 << 20)
	#define BDRV_SECTORS_PER_DIRTY_CHUNK (BLOCK_SIZE >> BDRV_SECTOR_BITS)

	#define BLK_MIG_FLAG_DEVICE_BLOCK 0x01
	#define BLK_MIG_FLAG_EOS 0x02
	#define BLK_MIG_FLAG_PROGRESS 0x04
	#define BLK_MIG_FLAG_ZERO_BLOCK 0x08

	#define MAX_IS_ALLOCATED_SEARCH 65536

	//#define DEBUG_BLK_MIGRATION

	#ifdef DEBUG_BLK_MIGRATION
	#define DPRINTF(fmt, ...) \
	do { printf("blk_migration: " fmt, ## __VA_ARGS__); } while (0)
	#else
	#define DPRINTF(fmt, ...) \
	do { } while (0)
	#endif

	typedef struct BlkMigDevState {
	/* Written during setup phase. Can be read without a lock. */
	BlockDriverState *bs;
	int shared_base;
	int64_t total_sectors;
	QSIMPLEQ_ENTRY(BlkMigDevState) entry;

	/* Only used by migration thread. Does not need a lock. */
	int bulk_completed;
	int64_t cur_sector;
	int64_t cur_dirty;

	/* Protected by block migration lock. */
	unsigned long *aio_bitmap;
	int64_t completed_sectors;
	BdrvDirtyBitmap *dirty_bitmap;
	Error *blocker;
	} BlkMigDevState;

	typedef struct BlkMigBlock {
	/* Only used by migration thread. */
	uint8_t *buf;
	BlkMigDevState *bmds;
	int64_t sector;
	int nr_sectors;
	struct iovec iov;
	QEMUIOVector qiov;
	BlockDriverAIOCB *aiocb;

	/* Protected by block migration lock. */
	int ret;
	QSIMPLEQ_ENTRY(BlkMigBlock) entry;
	} BlkMigBlock;

	typedef struct BlkMigState {
	/* Written during setup phase. Can be read without a lock. */
	int blk_enable;
	int shared_base;
	QSIMPLEQ_HEAD(bmds_list, BlkMigDevState) bmds_list;
	int64_t total_sector_sum;
	bool zero_blocks;

	/* Protected by lock. */
	QSIMPLEQ_HEAD(blk_list, BlkMigBlock) blk_list;
	int submitted;
	int read_done;

	/* Only used by migration thread. Does not need a lock. */
	int transferred;
	int prev_progress;
	int bulk_completed;

	/* Lock must be taken _inside_ the iothread lock. */
	QemuMutex lock;
	} BlkMigState;

	static BlkMigState block_mig_state;

	static void blk_mig_lock(void)
	{
	qemu_mutex_lock(&block_mig_state.lock);
	}

	static void blk_mig_unlock(void)
	{
	qemu_mutex_unlock(&block_mig_state.lock);
	}

	/* Must run outside of the iothread lock during the bulk phase,
	* or the VM will stall.
	*/

	static void blk_send(QEMUFile f, BlkMigBlock blk)
	{
	int len;
	uint64_t flags = BLK_MIG_FLAG_DEVICE_BLOCK;

	if (block_mig_state.zero_blocks &&
	buffer_is_zero(blk->buf, BLOCK_SIZE)) {
	flags \|= BLK_MIG_FLAG_ZERO_BLOCK;
	}

	/* sector number and flags */
	qemu_put_be64(f, (blk->sector << BDRV_SECTOR_BITS)
	\| flags);

	/* device name */
	len = strlen(blk->bmds->bs->device_name);
	qemu_put_byte(f, len);
	qemu_put_buffer(f, (uint8_t *)blk->bmds->bs->device_name, len);

	/* if a block is zero we need to flush here since the network
	* bandwidth is now a lot higher than the storage device bandwidth.
	* thus if we queue zero blocks we slow down the migration */
	if (flags & BLK_MIG_FLAG_ZERO_BLOCK) {
	qemu_fflush(f);
	return;
	}

	qemu_put_buffer(f, blk->buf, BLOCK_SIZE);
	}

	int blk_mig_active(void)
	{
	return !QSIMPLEQ_EMPTY(&block_mig_state.bmds_list);
	}

	uint64_t blk_mig_bytes_transferred(void)
	{
	BlkMigDevState *bmds;
	uint64_t sum = 0;

	blk_mig_lock();
	QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
	sum += bmds->completed_sectors;
	}
	blk_mig_unlock();
	return sum << BDRV_SECTOR_BITS;
	}

	uint64_t blk_mig_bytes_remaining(void)
	{
	return blk_mig_bytes_total() - blk_mig_bytes_transferred();
	}

	uint64_t blk_mig_bytes_total(void)
	{
	BlkMigDevState *bmds;
	uint64_t sum = 0;

	QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
	sum += bmds->total_sectors;
	}
	return sum << BDRV_SECTOR_BITS;
	}


	/* Called with migration lock held. */

	static int bmds_aio_inflight(BlkMigDevState *bmds, int64_t sector)
	{
	int64_t chunk = sector / (int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK;

	if ((sector << BDRV_SECTOR_BITS) < bdrv_getlength(bmds->bs)) {
	return !!(bmds->aio_bitmap[chunk / (sizeof(unsigned long) * 8)] &
	(1UL << (chunk % (sizeof(unsigned long) * 8))));
	} else {
	return 0;
	}
	}

	/* Called with migration lock held. */

	static void bmds_set_aio_inflight(BlkMigDevState *bmds, int64_t sector_num,
	int nb_sectors, int set)
	{
	int64_t start, end;
	unsigned long val, idx, bit;

	start = sector_num / BDRV_SECTORS_PER_DIRTY_CHUNK;
	end = (sector_num + nb_sectors - 1) / BDRV_SECTORS_PER_DIRTY_CHUNK;

	for (; start <= end; start++) {
	idx = start / (sizeof(unsigned long) * 8);
	bit = start % (sizeof(unsigned long) * 8);
	val = bmds->aio_bitmap[idx];
	if (set) {
	val \|= 1UL << bit;
	} else {
	val &= ~(1UL << bit);
	}
	bmds->aio_bitmap[idx] = val;
	}
	}

	static void alloc_aio_bitmap(BlkMigDevState *bmds)
	{
	BlockDriverState *bs = bmds->bs;
	int64_t bitmap_size;

	bitmap_size = (bdrv_getlength(bs) >> BDRV_SECTOR_BITS) +
	BDRV_SECTORS_PER_DIRTY_CHUNK * 8 - 1;
	bitmap_size /= BDRV_SECTORS_PER_DIRTY_CHUNK * 8;

	bmds->aio_bitmap = g_malloc0(bitmap_size);
	}

	/* Never hold migration lock when yielding to the main loop! */

	static void blk_mig_read_cb(void *opaque, int ret)
	{
	BlkMigBlock *blk = opaque;

	blk_mig_lock();
	blk->ret = ret;

	QSIMPLEQ_INSERT_TAIL(&block_mig_state.blk_list, blk, entry);
	bmds_set_aio_inflight(blk->bmds, blk->sector, blk->nr_sectors, 0);

	block_mig_state.submitted--;
	block_mig_state.read_done++;
	assert(block_mig_state.submitted >= 0);
	blk_mig_unlock();
	}

	/* Called with no lock taken. */

	static int mig_save_device_bulk(QEMUFile f, BlkMigDevState bmds)
	{
	int64_t total_sectors = bmds->total_sectors;
	int64_t cur_sector = bmds->cur_sector;
	BlockDriverState *bs = bmds->bs;
	BlkMigBlock *blk;
	int nr_sectors;

	if (bmds->shared_base) {
	qemu_mutex_lock_iothread();
	while (cur_sector < total_sectors &&
	!bdrv_is_allocated(bs, cur_sector, MAX_IS_ALLOCATED_SEARCH,
	&nr_sectors)) {
	cur_sector += nr_sectors;
	}
	qemu_mutex_unlock_iothread();
	}

	if (cur_sector >= total_sectors) {
	bmds->cur_sector = bmds->completed_sectors = total_sectors;
	return 1;
	}

	bmds->completed_sectors = cur_sector;

	cur_sector &= ~((int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK - 1);

	/* we are going to transfer a full block even if it is not allocated */
	nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;

	if (total_sectors - cur_sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {
	nr_sectors = total_sectors - cur_sector;
	}

	blk = g_malloc(sizeof(BlkMigBlock));
	blk->buf = g_malloc(BLOCK_SIZE);
	blk->bmds = bmds;
	blk->sector = cur_sector;
	blk->nr_sectors = nr_sectors;

	blk->iov.iov_base = blk->buf;
	blk->iov.iov_len = nr_sectors * BDRV_SECTOR_SIZE;
	qemu_iovec_init_external(&blk->qiov, &blk->iov, 1);

	blk_mig_lock();
	block_mig_state.submitted++;
	blk_mig_unlock();

	qemu_mutex_lock_iothread();
	blk->aiocb = bdrv_aio_readv(bs, cur_sector, &blk->qiov,
	nr_sectors, blk_mig_read_cb, blk);

	bdrv_reset_dirty(bs, cur_sector, nr_sectors);
	qemu_mutex_unlock_iothread();

	bmds->cur_sector = cur_sector + nr_sectors;
	return (bmds->cur_sector >= total_sectors);
	}

	/* Called with iothread lock taken. */

	static int set_dirty_tracking(void)
	{
	BlkMigDevState *bmds;
	int ret;

	QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
	bmds->dirty_bitmap = bdrv_create_dirty_bitmap(bmds->bs, BLOCK_SIZE,
	NULL);
	if (!bmds->dirty_bitmap) {
	ret = -errno;
	goto fail;
	}
	}
	return 0;

	fail:
	QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
	if (bmds->dirty_bitmap) {
	bdrv_release_dirty_bitmap(bmds->bs, bmds->dirty_bitmap);
	}
	}
	return ret;
	}

	static void unset_dirty_tracking(void)
	{
	BlkMigDevState *bmds;

	QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
	bdrv_release_dirty_bitmap(bmds->bs, bmds->dirty_bitmap);
	}
	}

	static void init_blk_migration_it(void opaque, BlockDriverState bs)
	{
	BlkMigDevState *bmds;
	int64_t sectors;

	if (!bdrv_is_read_only(bs)) {
	sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
	if (sectors <= 0) {
	return;
	}

	bmds = g_malloc0(sizeof(BlkMigDevState));
	bmds->bs = bs;
	bmds->bulk_completed = 0;
	bmds->total_sectors = sectors;
	bmds->completed_sectors = 0;
	bmds->shared_base = block_mig_state.shared_base;
	alloc_aio_bitmap(bmds);
	error_setg(&bmds->blocker, "block device is in use by migration");
	bdrv_op_block_all(bs, bmds->blocker);
	bdrv_ref(bs);

	block_mig_state.total_sector_sum += sectors;

	if (bmds->shared_base) {
	DPRINTF("Start migration for %s with shared base image\n",
	bs->device_name);
	} else {
	DPRINTF("Start full migration for %s\n", bs->device_name);
	}

	QSIMPLEQ_INSERT_TAIL(&block_mig_state.bmds_list, bmds, entry);
	}
	}

	static void init_blk_migration(QEMUFile *f)
	{
	block_mig_state.submitted = 0;
	block_mig_state.read_done = 0;
	block_mig_state.transferred = 0;
	block_mig_state.total_sector_sum = 0;
	block_mig_state.prev_progress = -1;
	block_mig_state.bulk_completed = 0;
	block_mig_state.zero_blocks = migrate_zero_blocks();

	bdrv_iterate(init_blk_migration_it, NULL);
	}

	/* Called with no lock taken. */

	static int blk_mig_save_bulked_block(QEMUFile *f)
	{
	int64_t completed_sector_sum = 0;
	BlkMigDevState *bmds;
	int progress;
	int ret = 0;

	QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
	if (bmds->bulk_completed == 0) {
	if (mig_save_device_bulk(f, bmds) == 1) {
	/* completed bulk section for this device */
	bmds->bulk_completed = 1;
	}
	completed_sector_sum += bmds->completed_sectors;
	ret = 1;
	break;
	} else {
	completed_sector_sum += bmds->completed_sectors;
	}
	}

	if (block_mig_state.total_sector_sum != 0) {
	progress = completed_sector_sum * 100 /
	block_mig_state.total_sector_sum;
	} else {
	progress = 100;
	}
	if (progress != block_mig_state.prev_progress) {
	block_mig_state.prev_progress = progress;
	qemu_put_be64(f, (progress << BDRV_SECTOR_BITS)
	\| BLK_MIG_FLAG_PROGRESS);
	DPRINTF("Completed %d %%\r", progress);
	}

	return ret;
	}

	static void blk_mig_reset_dirty_cursor(void)
	{
	BlkMigDevState *bmds;

	QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
	bmds->cur_dirty = 0;
	}
	}

	/* Called with iothread lock taken. */

	static int mig_save_device_dirty(QEMUFile f, BlkMigDevState bmds,
	int is_async)
	{
	BlkMigBlock *blk;
	int64_t total_sectors = bmds->total_sectors;
	int64_t sector;
	int nr_sectors;
	int ret = -EIO;

	for (sector = bmds->cur_dirty; sector < bmds->total_sectors;) {
	blk_mig_lock();
	if (bmds_aio_inflight(bmds, sector)) {
	blk_mig_unlock();
	bdrv_drain_all();
	} else {
	blk_mig_unlock();
	}
	if (bdrv_get_dirty(bmds->bs, bmds->dirty_bitmap, sector)) {

	if (total_sectors - sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {
	nr_sectors = total_sectors - sector;
	} else {
	nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
	}
	blk = g_malloc(sizeof(BlkMigBlock));
	blk->buf = g_malloc(BLOCK_SIZE);
	blk->bmds = bmds;
	blk->sector = sector;
	blk->nr_sectors = nr_sectors;

	if (is_async) {
	blk->iov.iov_base = blk->buf;
	blk->iov.iov_len = nr_sectors * BDRV_SECTOR_SIZE;
	qemu_iovec_init_external(&blk->qiov, &blk->iov, 1);

	blk->aiocb = bdrv_aio_readv(bmds->bs, sector, &blk->qiov,
	nr_sectors, blk_mig_read_cb, blk);

	blk_mig_lock();
	block_mig_state.submitted++;
	bmds_set_aio_inflight(bmds, sector, nr_sectors, 1);
	blk_mig_unlock();
	} else {
	ret = bdrv_read(bmds->bs, sector, blk->buf, nr_sectors);
	if (ret < 0) {
	goto error;
	}
	blk_send(f, blk);

	g_free(blk->buf);
	g_free(blk);
	}

	bdrv_reset_dirty(bmds->bs, sector, nr_sectors);
	break;
	}
	sector += BDRV_SECTORS_PER_DIRTY_CHUNK;
	bmds->cur_dirty = sector;
	}

	return (bmds->cur_dirty >= bmds->total_sectors);

	error:
	DPRINTF("Error reading sector %" PRId64 "\n", sector);
	g_free(blk->buf);
	g_free(blk);
	return ret;
	}

	/* Called with iothread lock taken.
	*
	* return value:
	* 0: too much data for max_downtime
	* 1: few enough data for max_downtime
	*/
	static int blk_mig_save_dirty_block(QEMUFile *f, int is_async)
	{
	BlkMigDevState *bmds;
	int ret = 1;

	QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
	ret = mig_save_device_dirty(f, bmds, is_async);
	if (ret <= 0) {
	break;
	}
	}

	return ret;
	}

	/* Called with no locks taken. */

	static int flush_blks(QEMUFile *f)
	{
	BlkMigBlock *blk;
	int ret = 0;

	DPRINTF("%s Enter submitted %d read_done %d transferred %d\n",
	__FUNCTION__, block_mig_state.submitted, block_mig_state.read_done,
	block_mig_state.transferred);

	blk_mig_lock();
	while ((blk = QSIMPLEQ_FIRST(&block_mig_state.blk_list)) != NULL) {
	if (qemu_file_rate_limit(f)) {
	break;
	}
	if (blk->ret < 0) {
	ret = blk->ret;
	break;
	}

	QSIMPLEQ_REMOVE_HEAD(&block_mig_state.blk_list, entry);
	blk_mig_unlock();
	blk_send(f, blk);
	blk_mig_lock();

	g_free(blk->buf);
	g_free(blk);

	block_mig_state.read_done--;
	block_mig_state.transferred++;
	assert(block_mig_state.read_done >= 0);
	}
	blk_mig_unlock();

	DPRINTF("%s Exit submitted %d read_done %d transferred %d\n", __FUNCTION__,
	block_mig_state.submitted, block_mig_state.read_done,
	block_mig_state.transferred);
	return ret;
	}

	/* Called with iothread lock taken. */

	static int64_t get_remaining_dirty(void)
	{
	BlkMigDevState *bmds;
	int64_t dirty = 0;

	QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
	dirty += bdrv_get_dirty_count(bmds->bs, bmds->dirty_bitmap);
	}

	return dirty << BDRV_SECTOR_BITS;
	}

	/* Called with iothread lock taken. */

	static void blk_mig_cleanup(void)
	{
	BlkMigDevState *bmds;
	BlkMigBlock *blk;

	bdrv_drain_all();

	unset_dirty_tracking();

	blk_mig_lock();
	while ((bmds = QSIMPLEQ_FIRST(&block_mig_state.bmds_list)) != NULL) {
	QSIMPLEQ_REMOVE_HEAD(&block_mig_state.bmds_list, entry);
	bdrv_op_unblock_all(bmds->bs, bmds->blocker);
	error_free(bmds->blocker);
	bdrv_unref(bmds->bs);
	g_free(bmds->aio_bitmap);
	g_free(bmds);
	}

	while ((blk = QSIMPLEQ_FIRST(&block_mig_state.blk_list)) != NULL) {
	QSIMPLEQ_REMOVE_HEAD(&block_mig_state.blk_list, entry);
	g_free(blk->buf);
	g_free(blk);
	}
	blk_mig_unlock();
	}

	static void block_migration_cancel(void *opaque)
	{
	blk_mig_cleanup();
	}

	static int block_save_setup(QEMUFile f, void opaque)
	{
	int ret;

	DPRINTF("Enter save live setup submitted %d transferred %d\n",
	block_mig_state.submitted, block_mig_state.transferred);

	qemu_mutex_lock_iothread();
	init_blk_migration(f);

	/* start track dirty blocks */
	ret = set_dirty_tracking();

	if (ret) {
	qemu_mutex_unlock_iothread();
	return ret;
	}

	qemu_mutex_unlock_iothread();

	ret = flush_blks(f);
	blk_mig_reset_dirty_cursor();
	qemu_put_be64(f, BLK_MIG_FLAG_EOS);

	return ret;
	}

	static int block_save_iterate(QEMUFile f, void opaque)
	{
	int ret;
	int64_t last_ftell = qemu_ftell(f);

	DPRINTF("Enter save live iterate submitted %d transferred %d\n",
	block_mig_state.submitted, block_mig_state.transferred);

	ret = flush_blks(f);
	if (ret) {
	return ret;
	}

	blk_mig_reset_dirty_cursor();

	/* control the rate of transfer */
	blk_mig_lock();
	while ((block_mig_state.submitted +
	block_mig_state.read_done) * BLOCK_SIZE <
	qemu_file_get_rate_limit(f)) {
	blk_mig_unlock();
	if (block_mig_state.bulk_completed == 0) {
	/* first finish the bulk phase */
	if (blk_mig_save_bulked_block(f) == 0) {
	/* finished saving bulk on all devices */
	block_mig_state.bulk_completed = 1;
	}
	ret = 0;
	} else {
	/* Always called with iothread lock taken for
	* simplicity, block_save_complete also calls it.
	*/
	qemu_mutex_lock_iothread();
	ret = blk_mig_save_dirty_block(f, 1);
	qemu_mutex_unlock_iothread();
	}
	if (ret < 0) {
	return ret;
	}
	blk_mig_lock();
	if (ret != 0) {
	/* no more dirty blocks */
	break;
	}
	}
	blk_mig_unlock();

	ret = flush_blks(f);
	if (ret) {
	return ret;
	}

	qemu_put_be64(f, BLK_MIG_FLAG_EOS);
	return qemu_ftell(f) - last_ftell;
	}

	/* Called with iothread lock taken. */

	static int block_save_complete(QEMUFile f, void opaque)
	{
	int ret;

	DPRINTF("Enter save live complete submitted %d transferred %d\n",
	block_mig_state.submitted, block_mig_state.transferred);

	ret = flush_blks(f);
	if (ret) {
	return ret;
	}

	blk_mig_reset_dirty_cursor();

	/* we know for sure that save bulk is completed and
	all async read completed */
	blk_mig_lock();
	assert(block_mig_state.submitted == 0);
	blk_mig_unlock();

	do {
	ret = blk_mig_save_dirty_block(f, 0);
	if (ret < 0) {
	return ret;
	}
	} while (ret == 0);

	/* report completion */
	qemu_put_be64(f, (100 << BDRV_SECTOR_BITS) \| BLK_MIG_FLAG_PROGRESS);

	DPRINTF("Block migration completed\n");

	qemu_put_be64(f, BLK_MIG_FLAG_EOS);

	blk_mig_cleanup();
	return 0;
	}

	static uint64_t block_save_pending(QEMUFile f, void opaque, uint64_t max_size)
	{
	/* Estimate pending number of bytes to send */
	uint64_t pending;

	qemu_mutex_lock_iothread();
	blk_mig_lock();
	pending = get_remaining_dirty() +
	block_mig_state.submitted * BLOCK_SIZE +
	block_mig_state.read_done * BLOCK_SIZE;

	/* Report at least one block pending during bulk phase */
	if (pending == 0 && !block_mig_state.bulk_completed) {
	pending = BLOCK_SIZE;
	}
	blk_mig_unlock();
	qemu_mutex_unlock_iothread();

	DPRINTF("Enter save live pending %" PRIu64 "\n", pending);
	return pending;
	}

	static int block_load(QEMUFile f, void opaque, int version_id)
	{
	static int banner_printed;
	int len, flags;
	char device_name[256];
	int64_t addr;
	BlockDriverState bs, bs_prev = NULL;
	uint8_t *buf;
	int64_t total_sectors = 0;
	int nr_sectors;
	int ret;

	do {
	addr = qemu_get_be64(f);

	flags = addr & ~BDRV_SECTOR_MASK;
	addr >>= BDRV_SECTOR_BITS;

	if (flags & BLK_MIG_FLAG_DEVICE_BLOCK) {
	/* get device name */
	len = qemu_get_byte(f);
	qemu_get_buffer(f, (uint8_t *)device_name, len);
	device_name[len] = '\0';

	bs = bdrv_find(device_name);
	if (!bs) {
	fprintf(stderr, "Error unknown block device %s\n",
	device_name);
	return -EINVAL;
	}

	if (bs != bs_prev) {
	bs_prev = bs;
	total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
	if (total_sectors <= 0) {
	error_report("Error getting length of block device %s",
	device_name);
	return -EINVAL;
	}
	}

	if (total_sectors - addr < BDRV_SECTORS_PER_DIRTY_CHUNK) {
	nr_sectors = total_sectors - addr;
	} else {
	nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
	}

	if (flags & BLK_MIG_FLAG_ZERO_BLOCK) {
	ret = bdrv_write_zeroes(bs, addr, nr_sectors,
	BDRV_REQ_MAY_UNMAP);
	} else {
	buf = g_malloc(BLOCK_SIZE);
	qemu_get_buffer(f, buf, BLOCK_SIZE);
	ret = bdrv_write(bs, addr, buf, nr_sectors);
	g_free(buf);
	}

	if (ret < 0) {
	return ret;
	}
	} else if (flags & BLK_MIG_FLAG_PROGRESS) {
	if (!banner_printed) {
	printf("Receiving block device images\n");
	banner_printed = 1;
	}
	printf("Completed %d %%%c", (int)addr,
	(addr == 100) ? '\n' : '\r');
	fflush(stdout);
	} else if (!(flags & BLK_MIG_FLAG_EOS)) {
	fprintf(stderr, "Unknown block migration flags: %#x\n", flags);
	return -EINVAL;
	}
	ret = qemu_file_get_error(f);
	if (ret != 0) {
	return ret;
	}
	} while (!(flags & BLK_MIG_FLAG_EOS));

	return 0;
	}

	static void block_set_params(const MigrationParams params, void opaque)
	{
	block_mig_state.blk_enable = params->blk;
	block_mig_state.shared_base = params->shared;

	/* shared base means that blk_enable = 1 */
	block_mig_state.blk_enable \|= params->shared;
	}

	static bool block_is_active(void *opaque)
	{
	return block_mig_state.blk_enable == 1;
	}

	static SaveVMHandlers savevm_block_handlers = {
	.set_params = block_set_params,
	.save_live_setup = block_save_setup,
	.save_live_iterate = block_save_iterate,
	.save_live_complete = block_save_complete,
	.save_live_pending = block_save_pending,
	.load_state = block_load,
	.cancel = block_migration_cancel,
	.is_active = block_is_active,
	};

	void blk_mig_init(void)
	{
	QSIMPLEQ_INIT(&block_mig_state.bmds_list);
	QSIMPLEQ_INIT(&block_mig_state.blk_list);
	qemu_mutex_init(&block_mig_state.lock);

	register_savevm_live(NULL, "block", 0, 1, &savevm_block_handlers,
	&block_mig_state);
	}