Bug 1799010

Implemented upstream:

commit 7b2163c8bf53cb4877bbfe8483f908b0593f737f
Author: Peter Krempa <pkrempa>
Date:   Fri Jun 26 15:29:34 2020 +0200

    qemu: backup: integrate with blockpull
    
    Merge the bitmaps when finalizing a block pull job so that backups work
    properly afterwards.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1799010
    
    Signed-off-by: Peter Krempa <pkrempa>
    Reviewed-by: Eric Blake <eblake>

Test with: libvirt-6.6.0-2.module+el8.3.0+7567+dc41c0a9.x86_64
Result: PASS

========================================================
check bitmap merged when do blockpull
========================================================
1. prepare a qcow2 image to test
[root@dell-per740xd-11 ~]# qemu-img create -f qcow2 /var/lib/libvirt/images/vdb.qcow2 100M
Formatting '/var/lib/libvirt/images/vdb.qcow2', fmt=qcow2 cluster_size=65536 compression_type=zlib size=104857600 lazy_refcounts=off refcount_bits=16

[root@dell-per740xd-11 ~]# virsh start vm1
virshDomain vm1 started

 [root@dell-per740xd-11 ~]# virsh domblklist vm1
 Target   Source
--------------------------------------------------------
...
 vdb      /var/lib/libvirt/images/vdb.qcow2


2. create checkpoint_0 xml 
[root@dell-per740xd-11 ~]# cat checkpoint_0.xml 
<domaincheckpoint>
  <disks>
    <disk checkpoint="no" name="vda" />
    <disk checkpoint="bitmap" name="vdb" />
  </disks>
  <name>cp0</name>
  <description>cp0</description>
</domaincheckpoint>

[root@dell-per740xd-11 ~]# virsh checkpoint-create vm1 checkpoint_0.xml 
Domain checkpoint cp0 created from 'checkpoint_0.xml'

[root@dell-per740xd-11 ~]# virsh qemu-monitor-command vm1 --cmd '{"execute": "x-debug-block-dirty-bitmap-sha256","arguments": {"node":"libvirt-1-format","name":"cp0"}}'
{"return":{"sha256":"6d9c54dee5660c46886f32d80e57e9dd0ffa57ee0cd2a762b036d9c8e0c3a33a"},"id":"libvirt-383"}

4. generate size=1MB data from seek=10MB in vdb and get the hash value of bitmap cp0
IN VM:
[root@localhost ~]# dddd if=/dev/urandom of=/dev/vdb bs=1M seek=10 count=1; sync 
[root@localhost ~]# dd if=/dev/urandom of=/dev/vdb bs=1M seek=10 count=1; sync
1+0 records in
1+0 records out
1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.0210256 s, 49.9 MB/s

IN HOST:
[root@dell-per740xd-11 ~]# virsh qemu-monitor-command vm1 --cmd '{"execute": "x-debug-block-dirty-bitmap-sha256","arguments": {"node":"libvirt-1-format","name":"cp0"}}'
{"return":{"sha256":"ebc3a32a3860f015d7cb19bdfc5518c8fcfcf85cff0b09c75511ea9ca068aaf8"},"id":"libvirt-381"}


5. create disk only snapshot_0
[root@dell-per740xd-11 ~]# virsh snapshot-create-as vm1 sp0 --disk-only
Domain snapshot sp0 created

In libvirtd log, we can see the node-name for vdb.sn0 is libvirt-4-format
2020-09-08 08:38:46.015+0000: 249672: info : qemuMonitorIOWrite:433 : QEMU_MONITOR_IO_WRITE: mon=0x7f9da4037320 buf={"execute":"blockdev-create","arguments":{"job-id":"create-libvirt-4-format","options":{"driver":"qcow2","file":"libvirt-4-storage","size":104857600,"backing-file":"/var/lib/libvirt/images/vdb.qcow2","backing-fmt":"qcow2"}},"id":"libvirt-392"}

6. create checkpoint_1
[root@dell-per740xd-11 ~]# cat checkpoint_1.xml 
<domaincheckpoint>
  <disks>
    <disk checkpoint="no" name="vda" />
    <disk checkpoint="bitmap" name="vdb" />
  </disks>
  <name>cp1</name>
  <description>cp1</description>
</domaincheckpoint>

[root@dell-per740xd-11 ~]# virsh checkpoint-create vm1 checkpoint_1.xml 
Domain checkpoint cp0 created from 'checkpoint_1.xml'

7. generate size=2MB data from seek=20MB in vdb and get the hash value of bitmap cp1
IN VM:
[root@localhost ~]# dd if=/dev/urandom of=/dev/vdb bs=1M seek=20 count=2; sync
2+0 records in
2+0 records out
2097152 bytes (2.1 MB, 2.0 MiB) copied, 0.0284196 s, 73.8 MB/s

IN HOST:
[root@dell-per740xd-11 ~]# virsh qemu-monitor-command vm1 --cmd '{"execute": "x-debug-block-dirty-bitmap-sha256","arguments": {"node":"libvirt-4-format","name":"cp1"}}'
{"return":{"sha256":"a974226d477231a42607948568f993c837551308f6d61a3312e58b4163242381"},"id":"libvirt-395"}



8. create disk only snapshot_1
[root@dell-per740xd-11 ~]# virsh snapshot-create-as vm1 sp1 --disk-only
Domain snapshot sp1 created

In libvirtd log, we can see the node-name for vdb.sn1 is libvirt-6-format
2020-09-08 08:50:26.418+0000: 249672: info : qemuMonitorIOWrite:433 : QEMU_MONITOR_IO_WRITE: mon=0x7f9da4037320 buf={"execute":"blockdev-create","arguments":{"job-id":"create-libvirt-6-format","options":{"driver":"qcow2","file":"libvirt-6-storage","size":104857600,"backing-file":"/var/lib/libvirt/images/vdb.sp0","backing-fmt":"qcow2"}},"id":"libvirt-421"}

9. create checkpoint_2
[root@dell-per740xd-11 ~]# cat checkpoint_2.xml 
<domaincheckpoint>
  <disks>
    <disk checkpoint="no" name="vda" />
    <disk checkpoint="bitmap" name="vdb" />
  </disks>
  <name>cp2</name>
  <description>cp2</description>
</domaincheckpoint>

[root@dell-per740xd-11 ~]# virsh checkpoint-create vm1 checkpoint_2.xml 
Domain checkpoint cp2 created from 'checkpoint_2.xml'

10. generate size=3MB data from seek=30MB in vdb and get the hash value of bitmap cp2
IN VM:
[root@localhost ~]# dd if=/dev/urandom of=/dev/vdb bs=1M seek=30 count=3; sync
3+0 records in
3+0 records out
3145728 bytes (3.1 MB, 3.0 MiB) copied, 0.0383979 s, 81.9 MB/s

IN HOST:
[root@dell-per740xd-11 ~]# virsh qemu-monitor-command vm1 --cmd '{"execute": "x-debug-block-dirty-bitmap-sha256","arguments": {"node":"libvirt-6-format","name":"cp2"}}'
{"return":{"sha256":"01f1873b1b22b39e76adb7686551e5e5dafc1d516dee781476d306767e740db2"},"id":"libvirt-409"}

11. current dirty bitmap info (same as above steps):
cp0 should be different in vdb.qcow2, vdb.sp0 and vdb.sp1
    vdb.qcow2:
    [root@dell-per740xd-11 ~]# virsh qemu-monitor-command vm1 --cmd '{"execute": "x-debug-block-dirty-bitmap-sha256","arguments": {"node":"libvirt-1-format","name":"cp0"}}'
    {"return":{"sha256":"ebc3a32a3860f015d7cb19bdfc5518c8fcfcf85cff0b09c75511ea9ca068aaf8"},"id":"libvirt-410"}

    vdb.sp0:
    [root@dell-per740xd-11 ~]# virsh qemu-monitor-command vm1 --cmd '{"execute": "x-debug-block-dirty-bitmap-sha256","arguments": {"node":"libvirt-4-format","name":"cp0"}}'
    {"return":{"sha256":"a974226d477231a42607948568f993c837551308f6d61a3312e58b4163242381"},"id":"libvirt-411"}

    vdb.sp1:
    [root@dell-per740xd-11 ~]# virsh qemu-monitor-command vm1 --cmd '{"execute": "x-debug-block-dirty-bitmap-sha256","arguments": {"node":"libvirt-6-format","name":"cp0"}}'
    {"return":{"sha256":"01f1873b1b22b39e76adb7686551e5e5dafc1d516dee781476d306767e740db2"},"id":"libvirt-412"}

cp1 should be different in vdb.sp0 and vdb.sp1:
    vdb.sp0:
    [root@dell-per740xd-11 ~]# virsh qemu-monitor-command vm1 --cmd '{"execute": "x-debug-block-dirty-bitmap-sha256","arguments": {"node":"libvirt-4-format","name":"cp1"}}'
    {"return":{"sha256":"a974226d477231a42607948568f993c837551308f6d61a3312e58b4163242381"},"id":"libvirt-413"}

    vdb.sp1:
    [root@dell-per740xd-11 ~]# virsh qemu-monitor-command vm1 --cmd '{"execute": "x-debug-block-dirty-bitmap-sha256","arguments": {"node":"libvirt-6-format","name":"cp1"}}'
    {"return":{"sha256":"01f1873b1b22b39e76adb7686551e5e5dafc1d516dee781476d306767e740db2"},"id":"libvirt-414"}

cp2 should only exist in vdb.sp1:
    [root@dell-per740xd-11 ~]# virsh qemu-monitor-command vm1 --cmd '{"execute": "x-debug-block-dirty-bitmap-sha256","arguments": {"node":"libvirt-6-format","name":"cp2"}}'
    {"return":{"sha256":"01f1873b1b22b39e76adb7686551e5e5dafc1d516dee781476d306767e740db2"},"id":"libvirt-415"}



12. block pull from vdb.sp0 and check the dirty bitmap
Current disk xml:
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2'/>
      <source file='/var/lib/libvirt/images/vdb.sp1' index='6'/>
      <backingStore type='file' index='4'>
        <format type='qcow2'/>
        <source file='/var/lib/libvirt/images/vdb.sp0'/>
        <backingStore type='file' index='1'>
          <format type='qcow2'/>
          <source file='/var/lib/libvirt/images/vdb.qcow2'/>
          <backingStore/>
        </backingStore>
      </backingStore>
      <target dev='vdb' bus='virtio'/>
      <alias name='virtio-disk1'/>
      <address type='pci' domain='0x0000' bus='0x07' slot='0x00' function='0x0'/>
    </disk>

[root@dell-per740xd-11 ~]# virsh blockpull vm1 vdb --base /var/lib/libvirt/images/vdb.sp0 --wait --verbose
Block Pull: [100 %]
Pull complete

[root@dell-per740xd-11 ~]# virsh qemu-monitor-command vm1 --cmd '{"execute": "x-debug-block-dirty-bitmap-sha256","arguments": {"node":"libvirt-6-format","name":"cp2"}}'
{"return":{"sha256":"01f1873b1b22b39e76adb7686551e5e5dafc1d516dee781476d306767e740db2"},"id":"libvirt-425"}

[root@dell-per740xd-11 ~]# virsh qemu-monitor-command vm1 --cmd '{"execute": "x-debug-block-dirty-bitmap-sha256","arguments": {"node":"libvirt-6-format","name":"cp1"}}'
{"return":{"sha256":"01f1873b1b22b39e76adb7686551e5e5dafc1d516dee781476d306767e740db2"},"id":"libvirt-426"}

[root@dell-per740xd-11 ~]# virsh qemu-monitor-command vm1 --cmd '{"execute": "x-debug-block-dirty-bitmap-sha256","arguments": {"node":"libvirt-6-format","name":"cp0"}}'
{"return":{"sha256":"01f1873b1b22b39e76adb7686551e5e5dafc1d516dee781476d306767e740db2"},"id":"libvirt-427"}
<=== nothing wrong, all same as vdb.sp1 info in step 11


13. block pull from vdb.qcow2 and check the dirty bitmap
[root@dell-per740xd-11 ~]# virsh blockpull vm1 vdb --base /var/lib/libvirt/images/vdb.qcow2 --wait --verbose
Block Pull: [100 %]
Pull complete
[root@dell-per740xd-11 ~]# virsh qemu-monitor-command vm1 --cmd '{"execute": "x-debug-block-dirty-bitmap-sha256","arguments": {"node":"libvirt-6-format","name":"cp0"}}'
{"return":{"sha256":"50fd3ca0b5134aaf14ac9a459ad924910773efa392b7a8a695405268834134a9"},"id":"libvirt-437"}


[root@dell-per740xd-11 ~]# virsh qemu-monitor-command vm1 --cmd '{"execute": "x-debug-block-dirty-bitmap-sha256","arguments": {"node":"libvirt-6-format","name":"cp1"}}'
{"return":{"sha256":"50fd3ca0b5134aaf14ac9a459ad924910773efa392b7a8a695405268834134a9"},"id":"libvirt-438"}


[root@dell-per740xd-11 ~]# virsh qemu-monitor-command vm1 --cmd '{"execute": "x-debug-block-dirty-bitmap-sha256","arguments": {"node":"libvirt-6-format","name":"cp2"}}'
{"return":{"sha256":"01f1873b1b22b39e76adb7686551e5e5dafc1d516dee781476d306767e740db2"},"id":"libvirt-440"}
<=== cp0 and cp1's dirty-bitmap merged, and they are same due to vdb.sp1 now backing on vdb.qcow2, expected


================================================================================
Automation scripts to check the full/incremental backup content is correct
================================================================================
Can be found in corresponding test run resut in our CI testing page with build: libvirt-6.6.0-2.module+el8.3.0+7567+dc41c0a9.x86_64
backing_chain.blockpull.base_to_top.original_disk_local.nbd_tcp.libvirt_snapshot.scratch_to_file
backing_chain.blockpull.base_to_top.original_disk_local.nbd_tcp.shutoff_snapshot.scratch_to_file
backing_chain.blockpull.mid_to_top.original_disk_local.nbd_tcp.libvirt_snapshot.scratch_to_file
backing_chain.blockpull.mid_to_top.original_disk_local.nbd_tcp.shutoff_snapshot.scratch_to_file

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 (virt:8.3 bug fix and enhancement update), 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-2020:5137