Re: CAM Shingled Disk support patches available

On 19 Nov, Kenneth D. Merry wrote:
> On Thu, Nov 19, 2015 at 12:48:41 -0600, Matthew D. Fuller wrote:
>> On Wed, Nov 18, 2015 at 12:13:09PM -0500 I heard the voice of
>> Kenneth D. Merry, and lo! it spake thus:
>> > 
>> > Testing and comments are welcome.
>> 
>> GELI does explicit handling of each BIO type, so will need to be
>> updated to pass it through (possibly in the form of inverting the
>> default handling?) or it'll just EOPNOTSUPP it, whether the underlying
>> layer does or not.  I wouldn't be surprised if there were other geom
>> layers that did similar things.
>> 
>> Not meant to be read as some kind of "you need to"; just a comment on
>> a possible [lack of] impact.
> 
> You're correct.  For GEOM classes like GELI that don't change the layout on
> disk, passing the BIO_ZONE bio through would be the right thing to do.
> 
> For those that change the layout (i.e. the lba you write on the virtual
> disk doesn't match what goes down to the physical disk), like graid or

partitioning or

> gstripe, I think all we really need to do is just make sure they return
> EOPNOTSUPP.  If someone wants to modify that code to handle shingled disks,
> they can certainly do that.
> 
> Ken