Re: [PATCH-v2 5/9] target: Convert se_portal_group->tpg_lun_list[] to RCU hlist

Nicholas A. Bellinger
2015-05-22T08:48:23Z

On Fri, 2015-05-22 at 10:31 +0200, Christoph Hellwig wrote:
> > This patch converts the fixed size se_portal_group->tpg_lun_list[]
> > to use modern RCU with hlist_head in order to support an arbitary
> > number of se_lun ports per target endpoint.
> >
> > It includes dropping core_tpg_alloc_lun() from core_dev_add_lun(),
> > and calling it directly from target_fabric_make_lun() to allocate
> > a new se_lun.
> >
> > Also add a new target_fabric_port_release() configfs item callback
> > to invoke kfree_rcu() to release memory during se_lun->lun_group
> > shutdown.
> >
> > Also now that se_node_acl->lun_entry_hlist is using RCU, convert
> > existing tpg_lun_lock to struct mutex so core_tpg_add_node_to_devs()
> > can perform RCU updater logic without releasing ->tpg_lun_mutex.
>
> Still doesn't explain why core_tpg_clear_object_luns also disappears.

It's duplicate logic in iscsi-target to delete active TPG LUNs.

Adding a comment to clarify the removal.

>
> > + hlist_for_each_entry_rcu(lun, &tpg->tpg_lun_hlist, link) {
> > if (lun->lun_status != TRANSPORT_LUN_STATUS_ACTIVE)
> > continue;
>
> lun_status will always be active here as that's set and cleared at the
> same time as the list addition / removal. Which means that lun_status
> should go away in this patch.
>

Yes, thanks for the reminder. Dropping lun_status now.