Re: Persistent Reservation API

[David Disseldorp <ddiss@suse.de>]

Hi Christoph,

On Tue,  4 Aug 2015 09:11:05 +0200, Christoph Hellwig wrote:

> This series adds support for a simplified persistent reservation API
> to the block layer.  The intent is that both in-kernel and userspace
> consumers can use the API instead of having to hand craft SCSI or NVMe
> command through the various pass through interfaces.  It also adds
> DM support as getting reservations through dm-multipath is a major
> pain with the current scheme.
> 
> NVMe support currently isn't included as I don't have a multihost
> NVMe setup to test on, but if I can find a volunteer to test it I'm
> happy to write the code for it.
> 
> The ioctl API is documented in Documentation/block/pr.txt, but to
> fully understand the concept you'll have to read up the SPC spec,
> PRs are too complicated that trying to rephrase them into different
> terminology is just going to create confusion.

Do you have any thoughts on where SCSI-2 RESERVE/RELEASE should fit into
this API, if at all? I.e. as a new enum pr_type members for
pr_reserve()/pr_release(), as separate pr_ops hooks, etc?
Similarly for PR_IN - IIUC, if LIO is to handle cluster wide PRs
for Ceph rbd via the block layer, these will all need to be supported
by block layer (and LIO backend) APIs.

Cheers, David