[Bug 712392] [NEW] qemu-img convert blocks other tasks

Thu Feb 3 11:41:23 UTC 2011

Public bug reported:

Binary package hint: qemu-kvm

Steps to reproduce:
- Use qemu-img convert to convert an image. e.g. a large (40GB) raw file to a compressed qcow2 image
- Watch the load rise
- kernel messages will be like "INFO: task blocked for more than 120 seconds". (Also see below)

In some cases this will bring down the server. When running libvirt too, all virtual servers will timeout/crash.
Using ionice to renice qemu-img convert does not really prevent the issue.

kvm           D 0000000000000000     0  9632      1 0x00000000
 ffff8801a4269ca8 0000000000000086 0000000000015bc0 0000000000015bc0
 ffff8802004fdf38 ffff8801a4269fd8 0000000000015bc0 ffff8802004fdb80
 0000000000015bc0 ffff8801a4269fd8 0000000000015bc0 ffff8802004fdf38
Call Trace:
 [<ffffffff815596b7>] __mutex_lock_slowpath+0x107/0x190
 [<ffffffff815590b3>] mutex_lock+0x23/0x50
 [<ffffffff810f5899>] generic_file_aio_write+0x59/0xe0
 [<ffffffff811d7879>] ext4_file_write+0x39/0xb0
 [<ffffffff81143a8a>] do_sync_write+0xfa/0x140
 [<ffffffff81084380>] ? autoremove_wake_function+0x0/0x40
 [<ffffffff81252316>] ? security_file_permission+0x16/0x20
 [<ffffffff81143d88>] vfs_write+0xb8/0x1a0
 [<ffffffff81144722>] sys_pwrite64+0x82/0xa0
 [<ffffffff810121b2>] system_call_fastpath+0x16/0x1b
kdmflush      D 0000000000000002     0   396      2 0x00000000
 ffff88022eeb3d10 0000000000000046 0000000000015bc0 0000000000015bc0
 ffff88022f489a98 ffff88022eeb3fd8 0000000000015bc0 ffff88022f4896e0
 0000000000015bc0 ffff88022eeb3fd8 0000000000015bc0 ffff88022f489a98

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: qemu-kvm 0.12.3+noroms-0ubuntu9.3
ProcVersionSignature: Ubuntu 2.6.32-28.55-server 2.6.32.27+drm33.12
Uname: Linux 2.6.32-28-server x86_64
Architecture: amd64
Date: Thu Feb  3 12:34:13 2011
KvmCmdLine:
 UID        PID  PPID  C    SZ   RSS PSR STIME TTY          TIME CMD
 root      1809     1  0 188145 517408 3 Jan31 ?        00:21:36 /usr/bin/kvm -S -M pc-0.11 -enable-kvm -m 512 -smp 1 -name jessica -uuid 76a39821-a89d-1ac7-65c2-40464dc21043 -chardev socket,id=monitor,path=/var/lib/libvirt/qemu/jessica.monitor,server,nowait -monitor chardev:monitor -boot c -drive if=ide,media=cdrom,index=2,format=raw -drive file=/var/lib/libvirt/images/jessica.img,if=virtio,index=0,boot=on,format=qcow2 -net nic,macaddr=54:52:00:5f:d8:2c,vlan=0,model=virtio,name=virtio.0 -net tap,fd=39,vlan=0,name=tap.0 -chardev pty,id=serial0 -serial chardev:serial0 -parallel none -usb -vnc 127.0.0.1:0 -vga cirrus
 root      1909     1  0 248235 625280 3 Jan31 ?        00:21:14 /usr/bin/kvm -S -M pc-0.11 -enable-kvm -m 768 -smp 1 -name gurney -uuid 7a21a182-8349-b17d-7eff-64f9bb3e7e30 -chardev socket,id=monitor,path=/var/lib/libvirt/qemu/gurney.monitor,server,nowait -monitor chardev:monitor -boot c -drive if=ide,media=cdrom,index=2,format=raw -drive file=/var/lib/libvirt/images/gurney.img,if=virtio,index=0,boot=on,format=qcow2 -net nic,macaddr=54:52:00:52:dc:a0,vlan=0,model=virtio,name=virtio.0 -net tap,fd=41,vlan=0,name=tap.0 -chardev pty,id=serial0 -serial chardev:serial0 -parallel none -usb -vnc 127.0.0.1:2 -vga cirrus
 root     27120     1  0 193095 552120 0 Jan31 ?        00:27:52 /usr/bin/kvm -S -M pc-0.11 -cpu qemu32 -enable-kvm -m 512 -smp 1 -name kolab -uuid 79b2a347-7841-39df-8399-c072b05e7f6f -chardev socket,id=monitor,path=/var/lib/libvirt/qemu/kolab.monitor,server,nowait -monitor chardev:monitor -boot c -drive if=ide,media=cdrom,index=2,format=raw -drive file=/srv/libvirt/leto/kolab.img,if=virtio,index=0,boot=on,format=qcow2 -net nic,macaddr=54:52:00:63:ee:4f,vlan=0,model=virtio,name=virtio.0 -net tap,fd=40,vlan=0,name=tap.0 -chardev pty,id=serial0 -serial chardev:serial0 -parallel none -usb -vnc 127.0.0.1:1 -vga cirrus
ProcCmdLine: BOOT_IMAGE=/vmlinuz-2.6.32-28-server root=/dev/mapper/vg0-root ro quiet splash delayacct
ProcEnviron:
 PATH=(custom, user)
 LANG=C
 SHELL=/bin/bash
SourcePackage: qemu-kvm
dmi.bios.date: 02/23/2010
dmi.bios.vendor: Intel Corp.
dmi.bios.version: CBQ4510H.86A.0119.2010.0223.1522
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: DQ45CB
dmi.board.vendor: Intel Corporation
dmi.board.version: AAE30148-301
dmi.chassis.type: 3
dmi.modalias: dmi:bvnIntelCorp.:bvrCBQ4510H.86A.0119.2010.0223.1522:bd02/23/2010:svn:pn:pvr:rvnIntelCorporation:rnDQ45CB:rvrAAE30148-301:cvn:ct3:cvr:

** Affects: qemu-kvm (Ubuntu)
     Importance: Undecided
         Status: New

** Tags: amd64 apport-bug lucid

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https://bugs.launchpad.net/bugs/712392

Title:
  qemu-img convert blocks other tasks