Comment 32 for bug 1423672

I'm on Debian, but it's happening to me as well.
KVM with virtual disks backed by LVM volumes on the host.

Both the VM and the host are running
Linux version 3.16.0-4-amd64 (<email address hidden>) (gcc version 4.8.4 (Debian 4.8.4-1) ) #1 SMP Debian 3.16.7-ckt11-1+deb8u2 (2015-07-17)

First occurred on August 24th. Manual fsck required, lots of files converted to lost-inodes.
[1992712.418275] EXT4-fs error (device vda2): ext4_mb_generate_buddy:757: group 96, block bitmap and bg descriptor inconsistent: 24017 vs 24015 free clusters
[1992712.513438] Aborting journal on device vda2-8.
[1992712.514007] EXT4-fs (vda2): Remounting filesystem read-only
[1992712.514205] EXT4-fs error (device vda2) in ext4_evict_inode:243: Journal has aborted

Happened again today September 14th in the same VM.
[1489393.753098] EXT4-fs error (device vda2): ext4_mb_generate_buddy:757: group 144, block bitmap and bg descriptor inconsistent: 23914 vs 23913 free clusters
[1489393.803865] Aborting journal on device vda2-8.
[1489393.804439] EXT4-fs (vda2): Remounting filesystem read-only

This is the first syslog activity since I rebooted in August, no block IO errors on the guest or host.

Manual fsck required, files were lost, but everything is running again.

It has not happened in other VMs running older kernels. It also has not happened on the host, however there's very little file system activity on the host. The fact that it hasn't happened on other VMs leads me to believe the bug is inside the guest rather than with KVM - perhaps ext4 or the virtual disk driver.