Actually, this is not a regression.
The attached patch prevents the panic.
By default on IO errors reiser4 partition will be remounted as "readonly".

No ideas why accessing /dev/dm-X causes IO error.
Reiser4 is not the culprit ;) You can narrow down this, if interesting.
I think that something is wrong with LVM settings...

Thanks,
Edward.


On 09/04/2015 09:35 AM, Dušan Čolić wrote:
> Kernel: 4.1.6
> R4 patch: 4.1.5
> Test: xfstests/generic/081 "Test I/O error path by fully filling an dm
> snapshot."
>
> Test passes cleanly with ccreg40 but kernel panics with reg40 plugin.
> Picture of the panic, as I had no other means of capturing it, is in attachment.
>
> xfstests local.config section:
>
> [r4Hybrid]
> MKFS_OPTIONS="-o create=reg40"
> MOUNT_OPTIONS="-o noatime"
>
> Have a nice day.
>
> Dushan