Public bug reported:
When creating a disk using qemu-img create command, if the destination
path of the qcow2 file already exists, it will show the error saying
that it cannot get a lock so it exits with exit status 1 but it will
corrupt the qcow2 file anyway.
Steps to reproduce:
1. Have a guest running with a root (vda) and a second device (vdc).
In my case is a clean Ubuntu 16.04 image with kernel 4.4.0-190-generic x86_64
vdc disk is called testadddisk-3.qcow2
2. vdc is an xfs over lvm.
pvcreacte /dev/vdc
vgcreate myVg /dev/vdc
lvcreate -l+100%FREE -n myLv myVg
mkfs.xfs /dev/mapper/myVg-myLv
mount /dev/mapper/myVg-myLv /mnt
3. Create disk IO on that device in the guest.
while true ; do dd if=/dev/zero of=/mnt/testfile bs=1024 count=1000 ; sleep 1;
done
4. Execute the command to create a new device but use the same name of the
device attached:
sudo qemu-img create -f qcow2 testadddisk-3.qcow2 20G
The output of the command is this:
Formatting 'testadddisk-3.qcow2', fmt=qcow2 size=21474836480 cluster_size=65536
lazy_refcounts=off refcount_bits=16
qemu-img: testadddisk-3.qcow2: Failed to get "write" lock
Is another process using the image?
The write continues in the guest but when it is shutdown, when it is powered on
again you get this:
error: Failed to start domain testadddisk
error: internal error: process exited while connecting to monitor:
2020-10-27T22:00:51.628374Z qemu-system-x86_64: -drive
file=/var/lib/vmImages/testadddisk-3.qcow2,format=qcow2,if=none,id=drive-virtio-disk2:
Image is not in qcow2 format
I run the qemu-img create command with an strace and I believe that
first it tries to open the file in write mode, then does a truncate on
it and after that says it cannot get a lock. The output is in the file
attached. As well as the guest xml just in case.
The host:
Ubuntu 18.04.5 LTS
4.15.0-112-generic x86_64
qemu packages installed:
ii qemu-block-extra:amd64 1:2.11+dfsg-1ubuntu7.32
amd64 extra block backend modules for qemu-system and
qemu-utils
ii qemu-kvm 1:2.11+dfsg-1ubuntu7.31
amd64 QEMU Full virtualization on x86 hardware
ii qemu-system-common 1:2.11+dfsg-1ubuntu7.32
amd64 QEMU full system emulation binaries (common files)
ii qemu-system-x86 1:2.11+dfsg-1ubuntu7.31
amd64 QEMU full system emulation binaries (x86)
ii qemu-utils 1:2.11+dfsg-1ubuntu7.32
amd64 QEMU utilities
** Affects: qemu
Importance: Undecided
Status: New
** Attachment added: "testadddisk-strace-dumxml.txt"
https://bugs.launchpad.net/bugs/1901892/+attachment/5428520/+files/testadddisk-strace-dumxml.txt
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https://bugs.launchpad.net/bugs/1901892
Title:
qemu-img create corrupts the qcow2 if the file already exists
Status in QEMU:
New
Bug description:
When creating a disk using qemu-img create command, if the destination
path of the qcow2 file already exists, it will show the error saying
that it cannot get a lock so it exits with exit status 1 but it will
corrupt the qcow2 file anyway.
Steps to reproduce:
1. Have a guest running with a root (vda) and a second device (vdc).
In my case is a clean Ubuntu 16.04 image with kernel 4.4.0-190-generic x86_64
vdc disk is called testadddisk-3.qcow2
2. vdc is an xfs over lvm.
pvcreacte /dev/vdc
vgcreate myVg /dev/vdc
lvcreate -l+100%FREE -n myLv myVg
mkfs.xfs /dev/mapper/myVg-myLv
mount /dev/mapper/myVg-myLv /mnt
3. Create disk IO on that device in the guest.
while true ; do dd if=/dev/zero of=/mnt/testfile bs=1024 count=1000 ; sleep
1; done
4. Execute the command to create a new device but use the same name of the
device attached:
sudo qemu-img create -f qcow2 testadddisk-3.qcow2 20G
The output of the command is this:
Formatting 'testadddisk-3.qcow2', fmt=qcow2 size=21474836480
cluster_size=65536 lazy_refcounts=off refcount_bits=16
qemu-img: testadddisk-3.qcow2: Failed to get "write" lock
Is another process using the image?
The write continues in the guest but when it is shutdown, when it is powered
on again you get this:
error: Failed to start domain testadddisk
error: internal error: process exited while connecting to monitor:
2020-10-27T22:00:51.628374Z qemu-system-x86_64: -drive
file=/var/lib/vmImages/testadddisk-3.qcow2,format=qcow2,if=none,id=drive-virtio-disk2:
Image is not in qcow2 format
I run the qemu-img create command with an strace and I believe that
first it tries to open the file in write mode, then does a truncate on
it and after that says it cannot get a lock. The output is in the file
attached. As well as the guest xml just in case.
The host:
Ubuntu 18.04.5 LTS
4.15.0-112-generic x86_64
qemu packages installed:
ii qemu-block-extra:amd64 1:2.11+dfsg-1ubuntu7.32
amd64 extra block backend modules for qemu-system and
qemu-utils
ii qemu-kvm 1:2.11+dfsg-1ubuntu7.31
amd64 QEMU Full virtualization on x86 hardware
ii qemu-system-common 1:2.11+dfsg-1ubuntu7.32
amd64 QEMU full system emulation binaries (common files)
ii qemu-system-x86 1:2.11+dfsg-1ubuntu7.31
amd64 QEMU full system emulation binaries (x86)
ii qemu-utils 1:2.11+dfsg-1ubuntu7.32
amd64 QEMU utilities
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