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Description of problem:
QEMU should print an error message and refuse to hotplug with virtio-blk data-plane while the drive-mirror job is running, this can prevent data corruption according to bug 995530.
Version-Release number of selected component (if applicable):
host info:
# uname -r && rpm -q qemu-kvm-rhev
3.10.0-152.el7.x86_64
qemu-kvm-rhev-2.1.0-3.el7.x86_64
guest info:
# uname -r
3.10.0-152.el7.x86_64
How reproducible:
100%
Steps to Reproduce:
1.start QEMU with "-drive file=/home/RHEL-7.0-20140507.0-Server-x86_64.qcow2,if=none,id=drive-system-disk0,format=qcow2,cache=none,aio=native,werror=stop,rerror=stop"
2.the guest will be at the BIOS screen because there is no virtio-blk-pci device yet. Then start a drive-mirror operation on the QMP monitor: { "execute": "drive-mirror", "arguments": { "device": "drive-system-disk0", "target": "/root/sn1", "format": "qcow2", "mode": "absolute-paths", "sync": "full", "speed": 1000000000, "on-target-error": "stop" } }
3.do hotplug virtio-blk data-plane device.
{"execute":"device_add","arguments":{"driver":"virtio-blk-pci","drive":"drive-system-disk0","id":"system-disk0","iothread":"iothread0"}}
4.do system_rest to start KVM guest.
Actual results:
1.step 2 and step 3 QMP commands execute successfully, while the QEMU HMP monitor prompt a "cannot start dataplane thread: Device 'drive-system-disk0' is busy: block device is in use by block job: mirror" message.
{ "execute": "drive-mirror", "arguments": { "device": "drive-system-disk0", "target": "/root/sn1", "format": "qcow2", "mode": "absolute-paths", "sync": "full", "speed": 1000000000, "on-target-error": "stop" } }
{"return": {}}
{ "execute" : "query-block-jobs", "arguments" : {} }
{"return": [{"io-status": "ok", "device": "drive-system-disk0", "busy": true, "len": 10737418240, "offset": 3931963392, "paused": false, "speed": 1000000000, "type": "mirror"}]}
{"execute":"device_add","arguments":{"driver":"virtio-blk-pci","drive":"drive-system-disk0","id":"system-disk0","iothread":"iothread0"}}
{"return": {}}
(qemu) Formatting '/root/sn1', fmt=qcow2 size=10737418240 encryption=off cluster_size=65536 lazy_refcounts=off
cannot start dataplane thread: Device 'drive-system-disk0' is busy: block device is in use by block job: mirror
2.after step 4, guest boot up successfully.
{ "execute": "system_reset" }
{"return": {}}
Expected results:
QEMU should print an error message and refuse to hotplug with virtio-blk data-plane while the drive-mirror job is running, this can prevent data corruption.
So, step 3 should not hotplug successfully and step 4 guest should not boot up successfully.
Additional info:
Thanks, there was a regression upstream and I have submitted a patch:
[PATCH] dataplane: fix virtio_blk_data_plane_create() op blocker error path
Once it has been merged I will backport it.
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://rhn.redhat.com/errata/RHSA-2015-0624.html