Fixed upstream with the following series:

v5.10.0-82-gf5259ba402

commit f5259ba4027807e82ce040f63db40efe56e86925
Author: Peter Krempa <pkrempa>
Date:   Fri Dec 6 18:50:46 2019 +0100

    qemu: migration: Properly setup mirror for blockdev configurations
    
    With blockdev we need to refer to the nodename of the disk source image
    as the source argument for the blockdev-mirror operation while still
    keeping the old job name. With blockdev we must also persist the job in
    qemu.
    
commit 3e35156bd18badf9757cad0904493e7eda530320
Author: Peter Krempa <pkrempa>
Date:   Fri Dec 6 18:44:22 2019 +0100

    qemu: migration: Mention disk target rather than the drive name in debug msg
    
commit 69abc80f5e58ba2c0f30e1d7296be8524631246d
Author: Peter Krempa <pkrempa>
Date:   Fri Dec 6 17:47:46 2019 +0100

    qemu: migration: Split out setup of the migration target
    
    Separate out allocation of the virStorageSource corresponding to the
    target NBD export of the migration.
    
    As part of the splitout we allocate the export name explicitly as that
    one must not change regardless whether blockdev is used or not to
    provide compatibility.

commit 0d0b490a32be5cb4f8a3b103784e1f10ce6c51ce
Author: Peter Krempa <pkrempa>
Date:   Fri Dec 6 17:46:29 2019 +0100

    qemu: blockjob: Allow NULL 'mirror' for block copy jobs due to migration
    
    The non-shared-storage migration tracks the storage source used
    explicitly in the migration data so we must allow for processing of the
    block job which has NULL mirror as the mirror will not be populated.
    
commit e1910a1f3b5a1926bc130ddd16ebee0a3cf8db27
Author: Peter Krempa <pkrempa>
Date:   Fri Dec 6 17:26:01 2019 +0100

    qemu: migration: Simplify cleanup in qemuMigrationSrcNBDCopyCancelOne
    
    Now that the cleanup section does not exist remove the label.
    
commit 37e801340ac6902e63e83983f5e606fbc38a23e6
Author: Peter Krempa <pkrempa>
Date:   Fri Dec 6 17:22:53 2019 +0100

    qemu: migration: Access job name from job struct
    
    qemuMigrationSrcNBDCopyCancelOne uses the block job data structure but
    generated it's own job name rather than taking it from the block job
    data.
    
commit 5339f57a0bf958f5c432c6ae6b655bf234ea0971
Author: Peter Krempa <pkrempa>
Date:   Fri Dec 6 17:02:33 2019 +0100

    qemu: migration: Properly export backend for NBD storage migration
    
    With -blockdev we must use the nodename as the export but we must keep
    the name of the export as it was before to ensure compatiblity.

commit 83137f5d3710ffe5a36ba9218ddc382d6675dc32
Author: Peter Krempa <pkrempa>
Date:   Fri Dec 6 16:54:33 2019 +0100

    qemu: migration: Simplify handling of 'diskAlias' when adding NBD exports
    
    Declare the variable inside the loop with automatic clearing.

Hi Peter,

Libvirtd will not pre-create images on the target host with libvirt-6.0.0-1. Is there any change in this part?

Test steps:
1.The same pool in the both source and target host:
# virsh pool-list
 Name        State    Autostart
---------------------------------
 default     active   no


2.Show the image of the guest:
# virsh domblklist demo
 Target   Source
-----------------------------------------------------------------------------
 vdb      /var/lib/libvirt/images/RHEL-8.2.0-20191219.0-x86_64-ovmf.qcow2.2

3.Do storage migration:
# virsh migrate demo --live --verbose qemu+ssh://10.16.200.75/system  --copy-storage-all
root.200.75's password: 
error: Cannot access storage file '/var/lib/libvirt/images/RHEL-8.2.0-20191219.0-x86_64-ovmf.qcow2.2': No such file or directory

4.Check the libvirtd log and no disk info in the qemuMigrationBakeCookie:
2020-01-17 10:24:25.682+0000: 26801: debug : qemuMigrationBakeCookie:1460 : cookielen=638 cookie=<qemu-migration>
  <name>demo</name>
  <uuid>1261efdf-cf70-489c-8138-c18b2e75497e</uuid>
  <hostname>jgao-test1</hostname>
  <hostuuid>476175ba-a0b6-c361-c59e-61f3341b621f</hostuuid>
  <feature name='lockstate'/>
  <nbd/>
  <allowReboot value='yes'/>
  <capabilities>
    <cap name='xbzrle' auto='no'/>
    <cap name='auto-converge' auto='no'/>
    <cap name='rdma-pin-all' auto='no'/>
    <cap name='postcopy-ram' auto='no'/>
    <cap name='compress' auto='no'/>
    <cap name='pause-before-switchover' auto='yes'/>
    <cap name='late-block-activate' auto='no'/>
    <cap name='multifd' auto='no'/>
  </capabilities>
</qemu-migration>

It should work normally. What's the domain XML? Also this bug doesn't deal with the storage pre-creation at all.

(In reply to Peter Krempa from comment #4)
> It should work normally. What's the domain XML? Also this bug doesn't deal
> with the storage pre-creation at all.

This problem happened when i tried to verify this bug,and yafu helped to debug this issue.
And we found the description in man page:
 "--copy-storage-all indicates migration with non-shared storage  with
       full  disk  copy, --copy-storage-inc indicates migration with non-shared storage with incremental copy (same
       base image shared between source and destination).  In both cases the disk images have to exist on  destina‐
       tion  host"
But we remember that we can migrate with copying storage without "pre-create" the image in target in the latest libvirt version.
So please help to confirm why it doesn't work now?

The domain xml is:
<domain type='kvm' id='58'>
  <name>demo</name>
  <uuid>1261efdf-cf70-489c-8138-c18b2e75497e</uuid>
  <memory unit='KiB'>524288</memory>
  <currentMemory unit='KiB'>524288</currentMemory>
  <vcpu placement='static'>1</vcpu>
  <iothreads>4</iothreads>
  <resource>
    <partition>/machine</partition>
  </resource>
  <os>
    <type arch='x86_64' machine='pc-q35-rhel7.6.0'>hvm</type>
    <loader readonly='no' type='pflash'>/usr/share/OVMF/OVMF_CODE.secboot.fd</loader>
    <nvram>/usr/share/OVMF/OVMF_VARS.fd</nvram>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <vmport state='off'/>
    <smm state='on'>
      <tseg unit='MiB'>48</tseg>
    </smm>
  </features>
  <cpu mode='custom' match='exact' check='full'>
    <model fallback='forbid'>SandyBridge-IBRS</model>
    <vendor>Intel</vendor>
    <feature policy='require' name='vme'/>
    <feature policy='disable' name='ds'/>
    <feature policy='disable' name='acpi'/>
    <feature policy='require' name='ss'/>
    <feature policy='disable' name='ht'/>
    <feature policy='disable' name='tm'/>
    <feature policy='disable' name='pbe'/>
    <feature policy='disable' name='dtes64'/>
    <feature policy='disable' name='monitor'/>
    <feature policy='disable' name='ds_cpl'/>
    <feature policy='disable' name='vmx'/>
    <feature policy='disable' name='smx'/>
    <feature policy='disable' name='est'/>
    <feature policy='disable' name='tm2'/>
    <feature policy='disable' name='xtpr'/>
    <feature policy='disable' name='pdcm'/>
    <feature policy='require' name='pcid'/>
    <feature policy='require' name='arat'/>
    <feature policy='require' name='stibp'/>
    <feature policy='require' name='xsaveopt'/>
    <feature policy='require' name='hypervisor'/>
  </cpu>
  <clock offset='utc'>
    <timer name='rtc' tickpolicy='catchup'/>
    <timer name='pit' tickpolicy='delay'/>
    <timer name='pit' tickpolicy='delay'/>
    <timer name='hpet' present='no'/>
  </clock>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <pm>
    <suspend-to-mem enabled='no'/>
    <suspend-to-disk enabled='no'/>
  </pm>
  <devices>
    <emulator>/usr/libexec/qemu-kvm</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2' cache='none'/>
      <source file='/var/lib/libvirt/images/RHEL-8.2.0-20191219.0-x86_64-ovmf.qcow2.2' index='1'/>
      <backingStore/>
      <target dev='vdb' bus='virtio'/>
      <alias name='virtio-disk1'/>
      <address type='pci' domain='0x0000' bus='0x05' slot='0x00' function='0x0'/>
    </disk>
    <controller type='usb' index='0' model='ich9-ehci1'>
      <alias name='usb'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x1d' function='0x7'/>
    </controller>
    <controller type='usb' index='0' model='ich9-uhci1'>
      <alias name='usb'/>
      <master startport='0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x1a' function='0x0' multifunction='on'/>
    </controller>
    <controller type='usb' index='0' model='ich9-uhci2'>
      <alias name='usb'/>
      <master startport='2'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x1d' function='0x1'/>
    </controller>
    <controller type='usb' index='0' model='ich9-uhci3'>
      <alias name='usb'/>
      <master startport='4'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x1d' function='0x2'/>
    </controller>
    <controller type='sata' index='0'>
      <alias name='ide'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x1f' function='0x2'/>
    </controller>
    <controller type='pci' index='0' model='pcie-root'>
      <alias name='pcie.0'/>
    </controller>
    <controller type='pci' index='1' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='1' port='0x10'/>
      <alias name='pci.1'/>
</controller>
    <controller type='pci' index='2' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='2' port='0x11'/>
      <alias name='pci.2'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x1'/>
    </controller>
    <controller type='pci' index='3' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='3' port='0x12'/>
      <alias name='pci.3'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x2'/>
    </controller>
    <controller type='pci' index='4' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='4' port='0x13'/>
      <alias name='pci.4'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x3'/>
    </controller>
    <controller type='pci' index='5' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='5' port='0x15'/>
      <alias name='pci.5'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x5'/>
    </controller>
    <controller type='pci' index='6' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='6' port='0x16'/>
      <alias name='pci.6'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x6'/>
    </controller>
    <controller type='pci' index='7' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='7' port='0x17'/>
      <alias name='pci.7'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x7'/>
    </controller>
    <controller type='pci' index='8' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='8' port='0x14'/>
      <alias name='pci.8'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x4'/>
    </controller>
    <controller type='pci' index='9' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='9' port='0x18'/>
      <alias name='pci.9'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0' multifunction='on'/>
    </controller>
    <controller type='pci' index='10' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='10' port='0x19'/>
alias name='pci.10'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x1'/>
    </controller>
    <controller type='pci' index='11' model='pcie-to-pci-bridge'>
      <model name='pcie-pci-bridge'/>
      <alias name='pci.11'/>
      <address type='pci' domain='0x0000' bus='0x07' slot='0x00' function='0x0'/>
    </controller>
    <controller type='virtio-serial' index='0'>
      <alias name='virtio-serial0'/>
      <address type='pci' domain='0x0000' bus='0x02' slot='0x00' function='0x0'/>
    </controller>
    <controller type='scsi' index='0' model='virtio-scsi'>
      <alias name='scsi0'/>
      <address type='pci' domain='0x0000' bus='0x04' slot='0x00' function='0x0'/>
    </controller>
    <controller type='fdc' index='0'>
      <alias name='fdc0'/>
    </controller>
    <interface type='network'>
      <mac address='52:54:00:f4:d5:8b'/>
      <source network='default' portid='dbb9f25f-633c-49e1-b2b8-68d7d04217bf' bridge='virbr0'/>
      <target dev='vnet0'/>
      <model type='virtio'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
    </interface>
    <serial type='pty'>
      <source path='/dev/pts/2'/>
      <target type='isa-serial' port='0'>
        <model name='isa-serial'/>
      </target>
      <alias name='serial0'/>
    </serial>
    <console type='pty' tty='/dev/pts/2'>
      <source path='/dev/pts/2'/>
      <target type='serial' port='0'/>
      <alias name='serial0'/>
    </console>
    <channel type='spicevmc'>
      <target type='virtio' name='com.redhat.spice.0' state='disconnected'/>
      <alias name='channel0'/>
      <address type='virtio-serial' controller='0' bus='0' port='1'/>
    </channel>
    <input type='tablet' bus='usb'>
      <alias name='input0'/>
      <address type='usb' bus='0' port='1'/>
    </input>
    <input type='mouse' bus='ps2'>
<alias name='input1'/>
    </input>
    <input type='keyboard' bus='ps2'>
      <alias name='input2'/>
    </input>
    <graphics type='spice' port='5900' autoport='yes' listen='127.0.0.1'>
      <listen type='address' address='127.0.0.1'/>
    </graphics>
    <sound model='ich9'>
      <alias name='sound0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x1b' function='0x0'/>
    </sound>
    <video>
      <model type='qxl' ram='65536' vram='65536' vgamem='16384' heads='1' primary='yes'/>
      <alias name='video0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/>
    </video>
    <redirdev bus='usb' type='spicevmc'>
      <alias name='redir0'/>
      <address type='usb' bus='0' port='2'/>
    </redirdev>
    <redirdev bus='usb' type='spicevmc'>
      <alias name='redir1'/>
      <address type='usb' bus='0' port='3'/>
    </redirdev>
    <memballoon model='virtio'>
      <alias name='balloon0'/>
      <address type='pci' domain='0x0000' bus='0x03' slot='0x00' function='0x0'/>
    </memballoon>
  </devices>
  <seclabel type='dynamic' model='selinux' relabel='yes'>
    <label>system_u:system_r:svirt_t:s0:c450,c525</label>
    <imagelabel>system_u:object_r:svirt_image_t:s0:c450,c525</imagelabel>
  </seclabel>
  <seclabel type='dynamic' model='dac' relabel='yes'>
    <label>+107:+107</label>
    <imagelabel>+107:+107</imagelabel>
  </seclabel>
</domain>

At any rate, the storage pre-creation should work. If it does not, please open a separate bug as the symptoms are not relevant to this bug.

(In reply to Peter Krempa from comment #6)
> At any rate, the storage pre-creation should work. If it does not, please
> open a separate bug as the symptoms are not relevant to this bug.

I filed a new bug Bug 1793263 to track this issue.

Verified on:
libvirt-6.0.0-5.virtcov.el8.x86_64
qemu-kvm-4.2.0-10.module+el8.2.0+5740+c3dff59e.x86_64

Step:
1.Prepare a guest with local storage:
# virsh domblklist demo
 Target   Source
---------------------------------------------------------------------------
 vda      /var/lib/libvirt/images/RHEL-8.2.0-20191219.0-x86_64-ovmf.qcow2


2.Migrate the guest with copy-storage-all to another host:
# virsh migrate demo qemu+ssh://$ip/system --live --verbose --copy-storage-all
root@$ip's password: 
Migration: [100 %]

qemu log :
qemuMonitorSend:996 : QEMU_MONITOR_SEND_MSG: mon=0x7f92a00615c0 msg={"execute":"blockdev-mirror","arguments":{"job-id":"drive-virtio-disk0","device":"libvirt-1-format","target":"migration-vda-format","speed":9223372036853727232,"sync":"full","auto-finalize":true,"auto-dismiss":false},"id":"libvirt-437"}
QEMU_MONITOR_SEND_MSG: mon=0x7f92a00615c0 msg={"execute":"blockdev-add","arguments":{"driver":"nbd","server":{"type":"inet","host":"lenovo-sr630-06.lab.eng.pek2.redhat.com","port":"49153"},"export":"drive-virtio-disk0","node-name":"migration-vda-storage","read-only":false,"discard":"unmap"},"id":"libvirt-435"}

Node_name has pointed to the specific disk name.

3.Guest works well after migration

Work as expected.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2020:2017