That doesn't really tell me much about the significance of the error, other than they've got a check to disable the error with a newer kernel. I'm using the stock 2.6.31-1 Mepis SMP Kernel, and VirtualBox is apparently going to give an error unless your kernel is >= 2.6.36-rc4 from what one of the links that thread points to implies (although I'm using a much newer VirtualBox version compared to when it looks like they started reporting the error).http://www.virtualbox.org/changeset/32593
So, I don't understand the significance of the error, and I've seen no problems with any virtual disks running from an ext4 partition with Mepis 11 as the host (at least not yet). Also, wouldn't some of the updates from Mepis and Debian have patched known bugs related to disk i/o?
I'm running VirtualBox 4.14 r74291 under Mepis 11 as the host.