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 <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Chris Boot <bootc@bootc.net>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index 1927dd5947a7..b82a989a4d3b 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -690,9 +690,9 @@ struct se_port_stat_grps {
 };
 
 struct scsi_port_stats {
-        u32             cmd_pdus;
-        u64             tx_data_octets;
-        u64             rx_data_octets;
+        atomic_long_t   cmd_pdus;
+        atomic_long_t   tx_data_octets;
+        atomic_long_t   rx_data_octets;
 };
 
 struct se_lun {
@@ -705,7 +705,6 @@ struct se_lun {
         u32                     unpacked_lun;
         u32                     lun_index;
         atomic_t                lun_acl_count;
-        spinlock_t              lun_sep_lock;
         struct se_device __rcu  *lun_se_dev;
 
         struct list_head        lun_deve_list;
@@ -818,6 +817,9 @@ struct se_device {
         struct se_lun           xcopy_lun;
         /* Protection Information */
         int                     prot_length;
+        /* For se_lun->lun_se_dev RCU read-side critical access */
+        u32                     hba_index;
+        struct rcu_head         rcu_head;
 };
 
 struct se_hba {