Re: [PATCH 09/12] target: Convert se_portal_group->tpg_lun_list[] to RCU hlist

[Christoph Hellwig <hch@lst.de>]

On Wed, May 13, 2015 at 09:22:04AM +0200, Juergen Gross wrote:
>> The Xen usage also looks really weird.  Maybe Juergen can explain what
>> scsiback_add_translation_entry is trying to do?
>
> scsiback_add_translation_entry() makes the connection between a pvSCSI
> LUN configured by the xen tools in xenstore and a xen-scsiback target.
>
> The xen tools specify the pvSCSI LUN via <device>:<lun>, with <device>
> being either the WWN of the target or an alias of that target specified
> in config_fs.
>
> scsiback_add_translation_entry() searches all it's targets until a match
> is found and links the found tpg to the device specification of the xen
> guest.
>
>> Note that I think both
>> sbp and xen really should be working on node ACLs.  Right now both
>> of them oly supported autogenerated ACLs, so in practice it doesn't
>> matter, but keeping the data structure use clean is a goal on it's own.
>
> I'd be fine with this, but I think I'll need some hints how to achieve
> this. I guess I have to specify .fabric_make_nodeacl and
> .fabric_drop_nodeacl like e.g. done in drivers/vhost/scsi.c ? Is there
> anything else I have to consider?

I don't think that model works to well for Xen, at it assumes
we get someone to mkdir/rmdir on configfs to create / delete ACLs,
while for Xen we get this through in-kernel through a management channel.

So I guess you need to export the raw core_tpg_add_initiator_node_acl
and core_tpg_del_initiator_node_acl functions again and call them
in response to the Xenbus events.