From 4cc987eaff9144182cde88d6d132420c28d3f81b Mon Sep 17 00:00:00 2001 From: Nicholas Bellinger Date: Tue, 19 May 2015 00:03:07 -0700 Subject: [PATCH 11/12] target: Drop lun_sep_lock for se_lun->lun_se_dev RCU usage With se_port and t10_alua_tg_pt_gp_member being absored into se_lun, there is no need for an extra lock to protect se_lun->lun_se_dev assignment. This patch also converts backend drivers to use call_rcu() release to allow any se_device readers to complete. The call_rcu() instead of kfree_rcu() is required here because se_device is embedded into the backend driver specific structure. Also, convert se_lun->lun_stats to use atomic_long_t within the target_complete_ok_work() completion callback, and add FIXME for transport_lookup_tmr_lun() with se_lun->lun_ref. Finally, update sbp_update_unit_directory() special case usage with proper rcu_dereference_raw() and configfs symlink comment. Reported-by: Christoph Hellwig Reviewed-by: Hannes Reinecke Cc: Paul E. McKenney Cc: Chris Boot Signed-off-by: Nicholas Bellinger [[ stefanr: only sbp part included here ]] --- drivers/target/sbp/sbp_target.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/target/sbp/sbp_target.c b/drivers/target/sbp/sbp_target.c index 47fb12fbaf47..28e3adf1eb85 100644 --- a/drivers/target/sbp/sbp_target.c +++ b/drivers/target/sbp/sbp_target.c @@ -1905,8 +1905,11 @@ static int sbp_update_unit_directory(struct sbp_tport *tport) hlist_for_each_entry_rcu(lun, &tport->tpg->se_tpg.tpg_lun_hlist, link) { struct se_device *dev; int type; - - dev = lun->lun_se_dev; + /* + * rcu_dereference_raw protected by se_lun->lun_group symlink + * reference to se_device->dev_group. + */ + dev = rcu_dereference_raw(lun->lun_se_dev); type = dev->transport->get_device_type(dev); /* logical_unit_number */ -- 2.3.6