migration/block: reset dirty bitmap before read in bulk phase

Reset the dirty bitmap before reading to make sure we don't miss
any new data.

Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Lieven <pl@kamp.de>
Message-Id: <1520507908-16743-3-git-send-email-pl@kamp.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
(cherry picked from commit 86b124bc76bd7137d0fb20696c4e349571b8533d)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

migration/block.c

@@ -331,11 +331,10 @@ static int mig_save_device_bulk(QEMUFile *f, BlkMigDevState *bmds)
      */
     qemu_mutex_lock_iothread();
     aio_context_acquire(blk_get_aio_context(bmds->blk));
-    blk->aiocb = blk_aio_preadv(bb, cur_sector * BDRV_SECTOR_SIZE, &blk->qiov,
-                                0, blk_mig_read_cb, blk);
-
     bdrv_reset_dirty_bitmap(bmds->dirty_bitmap, cur_sector * BDRV_SECTOR_SIZE,
                             nr_sectors * BDRV_SECTOR_SIZE);
+    blk->aiocb = blk_aio_preadv(bb, cur_sector * BDRV_SECTOR_SIZE, &blk->qiov,
+                                0, blk_mig_read_cb, blk);
     aio_context_release(blk_get_aio_context(bmds->blk));
     qemu_mutex_unlock_iothread();