Bug 1631877

Summary: qemu dirty bitmap merge fails to update count
Product: Red Hat Enterprise Linux 7 Reporter: Eric Blake <eblake>
Component: qemu-kvm-rhevAssignee: John Snow <jsnow>
Status: CLOSED ERRATA QA Contact: aihua liang <aliang>
Severity: high Docs Contact:
Priority: high    
Version: 7.7CC: chayang, coli, jsnow, juzhang, ngu, qzhang, toneata, virt-maint
Target Milestone: rcKeywords: TestOnly
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2019-08-22 09:18:53 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1658343    
Bug Blocks: 1636224, 1651787    

Description Eric Blake 2018-09-21 19:12:15 UTC 
Description of problem:
When dirty bitmap bits are set or cleared, they update a count of affected sectors visible to the user via QMP 'query-block'. But when dirty bitmaps are merged with x-block-dirty-bitmap-merge, this count is not updated, leaving the destination with the same count it had prior to the merge even when it was otherwise updated.

Version-Release number of selected component (if applicable):
qemu-kvm-rhev-2.12.0-17.el7

How reproducible:
100%

Steps to Reproduce:
1. Attach bitmaps to a block device visible through 'query-bitmap', and perform various x-block-dirty-bitmap-merge and x-debug-block-dirty-bitmap-sha256 to track that contents were merged but count was not.
2.
3.

Actual results:
https://lists.gnu.org/archive/html/qemu-devel/2018-09/msg02550.html

Also, some places in the code short-circuit when count is zero. If you are trying to merge C into B, then B into A, but B started life empty, then bitmap A does NOT end up receiving the contents of C (because even though those contents were copied into B, the inaccurate size of 0 made the copy into A return early)

Expected results:
count should always be accurate, especially since libvirt wants to take query-block count and expose it to the end user as a way to estimate the resulting size of an incremental backup image.

Additional info:
Comment 1 Eric Blake 2018-09-21 19:12:58 UTC 
related to bug 1631052
Comment 3 John Snow 2018-10-09 20:34:35 UTC 
upstream, pending merge:
https://lists.gnu.org/archive/html/qemu-devel/2018-10/msg00641.html
Comment 4 John Snow 2018-12-11 23:23:08 UTC 
This fix is included as part of the patches for BZ #1658343 now in POST.
Setting dependency and marking TestOnly.
Comment 6 aihua liang 2019-02-15 07:19:56 UTC 
Test on qemu-kvm-rhev-2.12.0-23.el7.x86_64, don't hit this issue.

Test steps:
  1. start guest with qemu cmds:
      /usr/libexec/qemu-kvm \
    -S \
    -name 'avocado-vt-vm1' \
    -machine pc  \
    -nodefaults \
    -device VGA,bus=pci.0,addr=0x2  \
    -chardev socket,id=qmp_id_qmpmonitor1,path=/var/tmp/monitor-qmpmonitor1-20190123-032240-rOoB4cgD,server,nowait \
    -mon chardev=qmp_id_qmpmonitor1,mode=control  \
    -chardev socket,id=qmp_id_catch_monitor,path=/var/tmp/monitor-catch_monitor-20190123-032240-rOoB4cgD,server,nowait \
    -mon chardev=qmp_id_catch_monitor,mode=control \
    -device pvpanic,ioport=0x505,id=id8Ec4Bn  \
    -chardev socket,id=serial_id_serial0,path=/var/tmp/serial-serial0-20190123-032240-rOoB4cgD,server,nowait \
    -device isa-serial,chardev=serial_id_serial0  \
    -chardev socket,id=seabioslog_id_20190123-032240-rOoB4cgD,path=/var/tmp/seabios-20190123-032240-rOoB4cgD,server,nowait \
    -device isa-debugcon,chardev=seabioslog_id_20190123-032240-rOoB4cgD,iobase=0x402 \
    -device ich9-usb-ehci1,id=usb1,addr=0x1d.7,multifunction=on,bus=pci.0 \
    -device ich9-usb-uhci1,id=usb1.0,multifunction=on,masterbus=usb1.0,addr=0x1d.0,firstport=0,bus=pci.0 \
    -device ich9-usb-uhci2,id=usb1.1,multifunction=on,masterbus=usb1.0,addr=0x1d.2,firstport=2,bus=pci.0 \
    -device ich9-usb-uhci3,id=usb1.2,multifunction=on,masterbus=usb1.0,addr=0x1d.4,firstport=4,bus=pci.0 \
    -device virtio-scsi-pci,id=virtio_scsi_pci0,bus=pci.0,addr=0x3 \
    -blockdev driver=file,node-name=file_base,filename=/home/kvm_autotest_root/images/rhel80-64-virtio-scsi.qcow2,auto-read-only=on \
    -blockdev driver=qcow2,file=file_base,node-name=drive_image1,auto-read-only=on \
    -device scsi-hd,id=image1,drive=drive_image1 \
    -device virtio-net-pci,mac=9a:39:3a:3b:3c:3d,id=id1JNQsL,vectors=4,netdev=idVpZZ6A,bus=pci.0,addr=0x4  \
    -netdev tap,id=idVpZZ6A,vhost=on \
    -m 4096  \
    -smp 2,maxcpus=2,cores=1,threads=1,sockets=2  \
    -cpu 'Penryn',+kvm_pv_unhalt \
    -device usb-tablet,id=usb-tablet1,bus=usb1.0,port=1  \
    -vnc :0  \
    -rtc base=utc,clock=host,driftfix=slew  \
    -boot order=cdn,once=c,menu=off,strict=off \
    -enable-kvm \
    -monitor stdio \
    -qmp tcp:0:3000,server,nowait \

 2. Create bitmap0
    { "execute": "block-dirty-bitmap-add", "arguments": {"node": "drive_image1", "name":"bitmap0"}}

 3. Cont vm, wait for guest boot up, then check bitmap info
    (qemu)vm
    {"execute":"query-block"}
{"return": [{"device": "", "locked": false, "removable": false, "inserted": {"iops_rd": 0, "detect_zeroes": "off", "image": {"virtual-size": 21474836480, "filename": "/home/kvm_autotest_root/images/rhel80-64-virtio-scsi.qcow2", "cluster-size": 65536, "format": "qcow2", "actual-size": 4498259968, "format-specific": {"type": "qcow2", "data": {"compat": "1.1", "lazy-refcounts": false, "refcount-bits": 16, "corrupt": false}}, "dirty-flag": false}, "iops_wr": 0, "ro": false, "node-name": "drive_image1", "backing_file_depth": 0, "drv": "qcow2", "iops": 0, "bps_wr": 0, "write_threshold": 0, "encrypted": false, "bps": 0, "bps_rd": 0, "cache": {"no-flush": false, "direct": false, "writeback": true}, "file": "/home/kvm_autotest_root/images/rhel80-64-virtio-scsi.qcow2", "encryption_key_missing": false}, "qdev": "image1", "dirty-bitmaps": [{"name": "bitmap0", "status": "active", "granularity": 65536, "count": 62193664}], "type": "unknown"}]}

  4. Disable bitmap0
     { "execute":"x-block-dirty-bitmap-disable", "arguments": { "node": "drive_image1", "name": "bitmap0" } }

  5. Add a disabled bitmap:bitmap1, check bitmap info:
     { "execute": "block-dirty-bitmap-add", "arguments": { "node": "drive_image1", "name": "bitmap1", "x-disabled": true } }
     {"execute":"query-block"}
{"return": [{"device": "", "locked": false, "removable": false, "inserted": {"iops_rd": 0, "detect_zeroes": "off", "image": {"virtual-size": 21474836480, "filename": "/home/kvm_autotest_root/images/rhel80-64-virtio-scsi.qcow2", "cluster-size": 65536, "format": "qcow2", "actual-size": 4498259968, "format-specific": {"type": "qcow2", "data": {"compat": "1.1", "lazy-refcounts": false, "refcount-bits": 16, "corrupt": false}}, "dirty-flag": false}, "iops_wr": 0, "ro": false, "node-name": "drive_image1", "backing_file_depth": 0, "drv": "qcow2", "iops": 0, "bps_wr": 0, "write_threshold": 0, "encrypted": false, "bps": 0, "bps_rd": 0, "cache": {"no-flush": false, "direct": false, "writeback": true}, "file": "/home/kvm_autotest_root/images/rhel80-64-virtio-scsi.qcow2", "encryption_key_missing": false}, "qdev": "image1", "dirty-bitmaps": [{"name": "bitmap1", "status": "disabled", "granularity": 65536, "count": 0}, {"name": "bitmap0", "status": "disabled", "granularity": 65536, "count": 62259200}], "type": "unknown"}]}

  6. In guest, create a file a, then check bitmap info:
     (guest)# dd if=/dev/urandom of=/home/a bs=1M count=2 oflag=dsync
     {"execute":"query-block"}
{"return": [{"device": "", "locked": false, "removable": false, "inserted": {"iops_rd": 0, "detect_zeroes": "off", "image": {"virtual-size": 21474836480, "filename": "/home/kvm_autotest_root/images/rhel80-64-virtio-scsi.qcow2", "cluster-size": 65536, "format": "qcow2", "actual-size": 4498259968, "format-specific": {"type": "qcow2", "data": {"compat": "1.1", "lazy-refcounts": false, "refcount-bits": 16, "corrupt": false}}, "dirty-flag": false}, "iops_wr": 0, "ro": false, "node-name": "drive_image1", "backing_file_depth": 0, "drv": "qcow2", "iops": 0, "bps_wr": 0, "write_threshold": 0, "encrypted": false, "bps": 0, "bps_rd": 0, "cache": {"no-flush": false, "direct": false, "writeback": true}, "file": "/home/kvm_autotest_root/images/rhel80-64-virtio-scsi.qcow2", "encryption_key_missing": false}, "qdev": "image1", "dirty-bitmaps": [{"name": "bitmap1", "status": "disabled", "granularity": 65536, "count": 0}, {"name": "bitmap0", "status": "disabled", "granularity": 65536, "count": 62259200}], "type": "unknown"}]}

  7. Add bitmap bitmap_tmp, check bitmap info:
     { "execute": "block-dirty-bitmap-add", "arguments": {"node": "drive_image1", "name":"bitmap_tmp"}}
     {"execute":"query-block"}
{"return": [{"device": "", "locked": false, "removable": false, "inserted": {"iops_rd": 0, "detect_zeroes": "off", "image": {"virtual-size": 21474836480, "filename": "/home/kvm_autotest_root/images/rhel80-64-virtio-scsi.qcow2", "cluster-size": 65536, "format": "qcow2", "actual-size": 4498259968, "format-specific": {"type": "qcow2", "data": {"compat": "1.1", "lazy-refcounts": false, "refcount-bits": 16, "corrupt": false}}, "dirty-flag": false}, "iops_wr": 0, "ro": false, "node-name": "drive_image1", "backing_file_depth": 0, "drv": "qcow2", "iops": 0, "bps_wr": 0, "write_threshold": 0, "encrypted": false, "bps": 0, "bps_rd": 0, "cache": {"no-flush": false, "direct": false, "writeback": true}, "file": "/home/kvm_autotest_root/images/rhel80-64-virtio-scsi.qcow2", "encryption_key_missing": false}, "qdev": "image1", "dirty-bitmaps": [{"name": "bitmap_tmp", "status": "active", "granularity": 65536, "count": 0}, {"name": "bitmap1", "status": "disabled", "granularity": 65536, "count": 0}, {"name": "bitmap0", "status": "disabled", "granularity": 65536, "count": 62259200}], "type": "unknown"}]}

  8. Create file b in guest, then check bitmap info:
     (guest)# dd if=/dev/urandom of=/home/b bs=1M count=2 oflag=dsync
     {"execute":"query-block"}
{"return": [{"device": "", "locked": false, "removable": false, "inserted": {"iops_rd": 0, "detect_zeroes": "off", "image": {"virtual-size": 21474836480, "filename": "/home/kvm_autotest_root/images/rhel80-64-virtio-scsi.qcow2", "cluster-size": 65536, "format": "qcow2", "actual-size": 4498259968, "format-specific": {"type": "qcow2", "data": {"compat": "1.1", "lazy-refcounts": false, "refcount-bits": 16, "corrupt": false}}, "dirty-flag": false}, "iops_wr": 0, "ro": false, "node-name": "drive_image1", "backing_file_depth": 0, "drv": "qcow2", "iops": 0, "bps_wr": 0, "write_threshold": 0, "encrypted": false, "bps": 0, "bps_rd": 0, "cache": {"no-flush": false, "direct": false, "writeback": true}, "file": "/home/kvm_autotest_root/images/rhel80-64-virtio-scsi.qcow2", "encryption_key_missing": false}, "qdev": "image1", "dirty-bitmaps": [{"name": "bitmap_tmp", "status": "active", "granularity": 65536, "count": 2293760}, {"name": "bitmap1", "status": "disabled", "granularity": 65536, "count": 0}, {"name": "bitmap0", "status": "disabled", "granularity": 65536, "count": 62259200}], "type": "unknown"}]}

   9. Merge bitmap1 to bitmap_tmp, then check bitmap info:
      {"execute": "x-block-dirty-bitmap-merge","arguments":{"node": "drive_image1", "src_name": "bitmap1", "dst_name":"bitmap_tmp" } }
{"return": {}}
{"execute":"query-block"}
{"return": [{"device": "", "locked": false, "removable": false, "inserted": {"iops_rd": 0, "detect_zeroes": "off", "image": {"virtual-size": 21474836480, "filename": "/home/kvm_autotest_root/images/rhel80-64-virtio-scsi.qcow2", "cluster-size": 65536, "format": "qcow2", "actual-size": 4498259968, "format-specific": {"type": "qcow2", "data": {"compat": "1.1", "lazy-refcounts": false, "refcount-bits": 16, "corrupt": false}}, "dirty-flag": false}, "iops_wr": 0, "ro": false, "node-name": "drive_image1", "backing_file_depth": 0, "drv": "qcow2", "iops": 0, "bps_wr": 0, "write_threshold": 0, "encrypted": false, "bps": 0, "bps_rd": 0, "cache": {"no-flush": false, "direct": false, "writeback": true}, "file": "/home/kvm_autotest_root/images/rhel80-64-virtio-scsi.qcow2", "encryption_key_missing": false}, "qdev": "image1", "dirty-bitmaps": [{"name": "bitmap_tmp", "status": "active", "granularity": 65536, "count": 3604480}, {"name": "bitmap1", "status": "disabled", "granularity": 65536, "count": 0}, {"name": "bitmap0", "status": "disabled", "granularity": 65536, "count": 62259200}], "type": "unknown"}]}

   10. Disable bitmap_tmp, check bitmap info:
       { "execute":"x-block-dirty-bitmap-disable", "arguments": { "node": "drive_image1", "name": "bitmap_tmp"}}
{"return": {}}
{"execute":"query-block"}
{"return": [{"device": "", "locked": false, "removable": false, "inserted": {"iops_rd": 0, "detect_zeroes": "off", "image": {"virtual-size": 21474836480, "filename": "/home/kvm_autotest_root/images/rhel80-64-virtio-scsi.qcow2", "cluster-size": 65536, "format": "qcow2", "actual-size": 4498259968, "format-specific": {"type": "qcow2", "data": {"compat": "1.1", "lazy-refcounts": false, "refcount-bits": 16, "corrupt": false}}, "dirty-flag": false}, "iops_wr": 0, "ro": false, "node-name": "drive_image1", "backing_file_depth": 0, "drv": "qcow2", "iops": 0, "bps_wr": 0, "write_threshold": 0, "encrypted": false, "bps": 0, "bps_rd": 0, "cache": {"no-flush": false, "direct": false, "writeback": true}, "file": "/home/kvm_autotest_root/images/rhel80-64-virtio-scsi.qcow2", "encryption_key_missing": false}, "qdev": "image1", "dirty-bitmaps": [{"name": "bitmap_tmp", "status": "disabled", "granularity": 65536, "count": 3801088}, {"name": "bitmap1", "status": "disabled", "granularity": 65536, "count": 0}, {"name": "bitmap0", "status": "disabled", "granularity": 65536, "count": 62259200}], "type": "unknown"}]}

   11. Merge bitmap0 to bitmap_tmp, then check bitmap info:
       {"execute": "x-block-dirty-bitmap-merge","arguments":{"node": "drive_image1", "src_name": "bitmap0", "dst_name":"bitmap_tmp" } }
{"return": {}}
{"execute":"query-block"}
{"return": [{"device": "", "locked": false, "removable": false, "inserted": {"iops_rd": 0, "detect_zeroes": "off", "image": {"virtual-size": 21474836480, "filename": "/home/kvm_autotest_root/images/rhel80-64-virtio-scsi.qcow2", "cluster-size": 65536, "format": "qcow2", "actual-size": 4498259968, "format-specific": {"type": "qcow2", "data": {"compat": "1.1", "lazy-refcounts": false, "refcount-bits": 16, "corrupt": false}}, "dirty-flag": false}, "iops_wr": 0, "ro": false, "node-name": "drive_image1", "backing_file_depth": 0, "drv": "qcow2", "iops": 0, "bps_wr": 0, "write_threshold": 0, "encrypted": false, "bps": 0, "bps_rd": 0, "cache": {"no-flush": false, "direct": false, "writeback": true}, "file": "/home/kvm_autotest_root/images/rhel80-64-virtio-scsi.qcow2", "encryption_key_missing": false}, "qdev": "image1", "dirty-bitmaps": [{"name": "bitmap_tmp", "status": "disabled", "granularity": 65536, "count": 64487424}, {"name": "bitmap1", "status": "disabled", "granularity": 65536, "count": 0}, {"name": "bitmap0", "status": "disabled", "granularity": 65536, "count": 62259200}], "type": "unknown"}]}

 Test result:
  Count for active bitmap is updated for all operations.

 Will set bug's status to "Verified" after its status changed to "ON_QA".
Comment 7 aihua liang 2019-03-19 06:36:59 UTC 
Set bug's status to "Verified", for it has keywords "TestOnly", thanks.
Comment 9 errata-xmlrpc 2019-08-22 09:18:53 UTC 
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/RHSA-2019:2553