Re: [Xen-devel] Xen 4.8.0 dom0pvh=1 causes ext4 filesystem corruption

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Mar 09, 2017 at 05:13:38PM +0200, Valtteri Kiviniemi wrote:
> Hi,
> 
> Yesterday I decided to upgrade my Xen version from 4.6.0 to 4.8.0. I
> compiled it from source and at the same time I compiled the latest Linux
> kernel (4.10.1).
> 
> When rebooting I decided to try if dom0 PVH would work (with previous Xen
> version it just caused kernel panic). Seemed to boot fine until systemd
> started mounting the root filesystem and then the console was filled with
> ext4 errors. Couldn't even log in.
> 
> Booting with a systemrescuecd and running fsck just caused the whole
> filesystem to be re-attached in thousands of small pieces under lost+found.
> I was sure that this was a some kind of hardware failure, so I switched my
> hard drives and did a clean reinstall for dom0 and tried again. Again,
> after a reboot the whole rootfs was completely corrupted.
> 
> Second reinstall and this time I disabled dom0 PVH and the system booted
> just fine, and no ext4 errors. My root filesystem is just a simple Linux
> software raid1 with ext4 on top of it.
> 
> Now that I started thinking I have also had strange ext4 errors happening
> inside my guests, so I also disabled PVH from all the guests. With guests
> the ext4 error is always the same: "EXT4-fs error (device xvda1):
> ext4_iget:4665: inode #317: comm find: bogus i_mode (135206)"

As Andrew already pointed out, this implementation (PVHv1) is already removed
from Linux, and will be removed soon from Xen. FWIW, FreeBSD has been using
that for Dom0, and no one reported a single FS corruption issue, so it seems
like this was something specific to the Linux PVHv1 implementation.

Roger.

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