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

Christoph Hellwig
2015-05-19T06:46:20Z

On Tue, May 12, 2015 at 09:25:33AM +0000, Nicholas A. Bellinger wrote:
> From: Nicholas Bellinger <nab@linux-iscsi.org>
>
> 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 call_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.

FYI, you can also kill ->lun_status with this as only allocated
se_lun structures will ever be on the list.