Re: [Qemu-block] [Qemu-devel] qemu process crash: Assertion failed: QLIST_EMPTY(&bs->tracked_requests)

[Stefan Hajnoczi]

On Thu, Dec 07, 2017 at 10:18:52AM +0000, Fernando Casas Schössow wrote:
> Hi there,
> 
> 
> Last night while doing a backup of a guest using the live snapshot mechanism 
> the qemu process for the guest seem to had crashed.
> 
> The snapshot succeeded then the backup of the VM disk had place and also 
> succeeded but the commit to the original disk after the backup seem to have 
> failed.
> 
> The command I use in the script to take the snapshot is:
> 
> 
> virsh snapshot-create-as --domain $VM backup-job.qcow2 --disk-only --atomic 
> --quiesce --no-metadata
> 
> 
> And then to commit back is:
> 
> 
> virsh blockcommit $VM $TARGETDISK --base $DISKFILE --top $SNAPFILE --active 
> --pivot
> 
> 
> In the qemu log for the guest I found the following while the commit back was 
> having place:
> 
> 
> Assertion failed: QLIST_EMPTY(&bs->tracked_requests) 
> (/home/buildozer/aports/main/qemu/src/qemu-2.10.1/block/mirror.c: mirror_run: 
> 884)
> 
> I'm running qemu 2.10.1 with libvirt 3.9.0 and kernel 4.9.65 on Alpine Linux 
> 3.7.
> 
> This is the complete guest info from the logs:
> 
> 
> LC_ALL=C 
> PATH=/bin:/sbin:/bin:/sbin:/usr/bin:/usr/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin
>  HOME=/root USER=root QEMU_AUDIO_DRV=spice /usr/bin/qemu-system-x86_64 -name 
> guest=DOCKER01,debug-threads=on -S -object 
> secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-6-DOCKER01/master-key.aes
>  -machine pc-i440fx-2.8,accel=kvm,usb=off,dump-guest-core=off -cpu 
> IvyBridge,ss=on,vmx=on,pcid=on,hypervisor=on,arat=on,tsc_adjust=on,xsaveopt=on
>  -drive 
> file=/usr/share/edk2.git/ovmf-x64/OVMF_CODE-pure-efi.fd,if=pflash,format=raw,unit=0,readonly=on
>  -drive 
> file=/var/lib/libvirt/qemu/nvram/DOCKER01_VARS.fd,if=pflash,format=raw,unit=1 
> -m 2048 -realtime mlock=off -smp 2,sockets=2,cores=1,threads=1 -uuid 
> 4705b146-3b14-4c20-923c-42105d47e7fc -no-user-config -nodefaults -chardev 
> socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-6-DOCKER01/monitor.sock,server,nowait
>  -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc,driftfix=slew 
> -global kvm-pit.lost_tick_policy=delay -no-hpet -no-shutdown -global 
> PIIX4_PM.disable_s3=1 -global PIIX4_PM.disable_s4=1 -boot strict=on -device 
> ich9-usb-ehci1,id=usb,bus=pci.0,addr=0x4.0x7 -device 
> ich9-usb-uhci1,masterbus=usb.0,firstport=0,bus=pci.0,multifunction=on,addr=0x4
>  -device ich9-usb-uhci2,masterbus=usb.0,firstport=2,bus=pci.0,addr=0x4.0x1 
> -device ich9-usb-uhci3,masterbus=usb.0,firstport=4,bus=pci.0,addr=0x4.0x2 
> -device ahci,id=sata0,bus=pci.0,addr=0x9 -device 
> virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x5 -drive 
> file=/storage/storage-ssd-vms/virtual_machines_ssd/docker01.qcow2,format=qcow2,if=none,id=drive-sata0-0-0,cache=none,aio=threads
>  -device ide-hd,bus=sata0.0,drive=drive-sata0-0-0,id=sata0-0-0,bootindex=1 
> -netdev tap,fd=33,id=hostnet0,vhost=on,vhostfd=35 -device 
> virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:1c:af:ce,bus=pci.0,addr=0x3
>  -chardev pty,id=charserial0 -device 
> isa-serial,chardev=charserial0,id=serial0 -chardev 
> socket,id=charchannel0,path=/var/lib/libvirt/qemu/channel/target/domain-6-DOCKER01/org.qemu.guest_agent.0,server,nowait
>  -device 
> virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=org.qemu.guest_agent.0
>  -chardev spicevmc,id=charchannel1,name=vdagent -device 
> virtserialport,bus=virtio-serial0.0,nr=2,chardev=charchannel1,id=channel1,name=com.redhat.spice.0
>  -spice port=5905,addr=127.0.0.1,disable-ticketing,seamless-migration=on 
> -device 
> qxl-vga,id=video0,ram_size=67108864,vram_size=67108864,vram64_size_mb=0,vgamem_mb=16,max_outputs=1,bus=pci.0,addr=0x2
>  -chardev spicevmc,id=charredir0,name=usbredir -device 
> usb-redir,chardev=charredir0,id=redir0,bus=usb.0,port=2 -chardev 
> spicevmc,id=charredir1,name=usbredir -device 
> usb-redir,chardev=charredir1,id=redir1,bus=usb.0,port=3 -device 
> virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x7 -object 
> rng-random,id=objrng0,filename=/dev/random -device 
> virtio-rng-pci,rng=objrng0,id=rng0,bus=pci.0,addr=0x8 -msg timestamp=on
> 
> 
> 
> I was running on qemu 2.8.1 for months and didn't have any problems with the 
> backups but yesterday I updated to qemu 2.10.1 and I hit this problem last 
> night.
> 
> 
> Is this a bug? Any ideas will be appreciated.

Thanks for reporting this bug.  Can you reproduce it reliably?

Stefan

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