target: Fix ALUA transition state race between multiple initiators

Multiple threads could be writing to alua_access_state at
the same time, or there could be multiple STPGs in flight
(different initiators sending them or one initiator sending
them to different ports), or a combo of both and the
core_alua_do_transition_tg_pt calls will race with each other.

Because from the last patches we no longer delay running
core_alua_do_transition_tg_pt_work, there does not seem to be
any point in running that in a workqueue. And, we always
wait for it to complete one way or another, so we can sleep
in this code path. So, this patch made over target-pending just adds a
mutex and does the work core_alua_do_transition_tg_pt_work was doing in
core_alua_do_transition_tg_pt.

There is also no need to use an atomic for the
tg_pt_gp_alua_access_state. In core_alua_do_transition_tg_pt we will
test and set it under the transition mutex. And, it is a int/32 bits
so in the other places where it is read, we will never see it partially
updated.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 2 insertions, 6 deletions

diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index 730ed3055336..ccfad0e9c2cd 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -280,8 +280,6 @@ struct t10_alua_tg_pt_gp {
 	u16	tg_pt_gp_id;
 	int	tg_pt_gp_valid_id;
 	int	tg_pt_gp_alua_supported_states;
-	int	tg_pt_gp_alua_pending_state;
-	int	tg_pt_gp_alua_previous_state;
 	int	tg_pt_gp_alua_access_status;
 	int	tg_pt_gp_alua_access_type;
 	int	tg_pt_gp_nonop_delay_msecs;
@@ -290,18 +288,16 @@ struct t10_alua_tg_pt_gp {
 	int	tg_pt_gp_pref;
 	int	tg_pt_gp_write_metadata;
 	u32	tg_pt_gp_members;
-	atomic_t tg_pt_gp_alua_access_state;
+	int	tg_pt_gp_alua_access_state;
 	atomic_t tg_pt_gp_ref_cnt;
 	spinlock_t tg_pt_gp_lock;
-	struct mutex tg_pt_gp_md_mutex;
+	struct mutex tg_pt_gp_transition_mutex;
 	struct se_device *tg_pt_gp_dev;
 	struct config_group tg_pt_gp_group;
 	struct list_head tg_pt_gp_list;
 	struct list_head tg_pt_gp_lun_list;
 	struct se_lun *tg_pt_gp_alua_lun;
 	struct se_node_acl *tg_pt_gp_alua_nacl;
-	struct work_struct tg_pt_gp_transition_work;
-	struct completion *tg_pt_gp_transition_complete;
 };
 
 struct t10_vpd {