ZFS crash -- zvol_geom_bio_getattr called when volmode=dev

[Eric van Gyzen]

On 10/9/20 7:54 PM, Eric van Gyzen wrote:
> On 10/9/20 6:27 PM, Ryan Moeller wrote:
>>
>> On 10/9/20 6:22 PM, Alan Somers wrote:
>>> This sounds like it might be a regression introduced by the OpenZFS 
>>> merge.
>>> Have you compared vdev_geom.c in OpenZFS vs the old version?
>>> -Alan
>>
>>
>> I don't think vdev_geom.c is involved, we're taking a wrong path in 
>> zvol_os.c because
>> it seems the volume is created using the default volmode and later 
>> changed to volmode=dev.
> 
> Yes, you're on the right track.  I tried this several times on a VM and 
> it eventually hit the window:
> 
> # zfs create -s -V 20G -o primarycache=none -o volmode=dev 
> head_root/testvol
> zvol_create_minor_impl:1250[1]: Creating ZVOL head_root/testvol...
> zvol_create_minor_impl:1371[1]: ZVOL head_root/testvol created.
> 
> 
> Fatal trap 12: page fault while in kernel mode

Let's track this in

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=250297

Eric