target: encapsulate smp_mb__after_atomic()
The target code has a rather generous helping of smp_mb__after_atomic()
throughout the code base. Most atomic operations were followed by one
and none were preceded by smp_mb__before_atomic(), nor accompanied by a
comment explaining the need for a barrier.
Instead of trying to prove for every case whether or not it is needed,
this patch introduces atomic_inc_mb() and atomic_dec_mb(), which
explicitly include the memory barriers before and after the atomic
operation. For now they are defined in a target header, although they
could be of general use.
Most of the existing atomic/mb combinations were replaced by the new
helpers. In a few cases the atomic was sandwiched in
spin_lock/spin_unlock and I simply removed the barrier.
I suspect that in most cases the correct conversion would have been to
drop the barrier. I also suspect that a few cases exist where a) the
barrier was necessary and b) a second barrier before the atomic would
have been necessary and got added by this patch.
Signed-off-by: Joern Engel <joern@logfs.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/target_core_alua.c b/drivers/target/target_core_alua.c
index fbc5ebb..fb87780 100644
--- a/drivers/target/target_core_alua.c
+++ b/drivers/target/target_core_alua.c
@@ -392,8 +392,7 @@
if (tg_pt_id != tg_pt_gp->tg_pt_gp_id)
continue;
- atomic_inc(&tg_pt_gp->tg_pt_gp_ref_cnt);
- smp_mb__after_atomic();
+ atomic_inc_mb(&tg_pt_gp->tg_pt_gp_ref_cnt);
spin_unlock(&dev->t10_alua.tg_pt_gps_lock);
@@ -403,8 +402,7 @@
found = true;
spin_lock(&dev->t10_alua.tg_pt_gps_lock);
- atomic_dec(&tg_pt_gp->tg_pt_gp_ref_cnt);
- smp_mb__after_atomic();
+ atomic_dec_mb(&tg_pt_gp->tg_pt_gp_ref_cnt);
break;
}
spin_unlock(&dev->t10_alua.tg_pt_gps_lock);
@@ -998,8 +996,7 @@
* every I_T nexus other than the I_T nexus on which the SET
* TARGET PORT GROUPS command
*/
- atomic_inc(&mem->tg_pt_gp_mem_ref_cnt);
- smp_mb__after_atomic();
+ atomic_inc_mb(&mem->tg_pt_gp_mem_ref_cnt);
spin_unlock(&tg_pt_gp->tg_pt_gp_lock);
spin_lock_bh(&port->sep_alua_lock);
@@ -1028,8 +1025,7 @@
spin_unlock_bh(&port->sep_alua_lock);
spin_lock(&tg_pt_gp->tg_pt_gp_lock);
- atomic_dec(&mem->tg_pt_gp_mem_ref_cnt);
- smp_mb__after_atomic();
+ atomic_dec_mb(&mem->tg_pt_gp_mem_ref_cnt);
}
spin_unlock(&tg_pt_gp->tg_pt_gp_lock);
/*
@@ -1063,7 +1059,6 @@
core_alua_dump_state(tg_pt_gp->tg_pt_gp_alua_pending_state));
spin_lock(&dev->t10_alua.tg_pt_gps_lock);
atomic_dec(&tg_pt_gp->tg_pt_gp_ref_cnt);
- smp_mb__after_atomic();
spin_unlock(&dev->t10_alua.tg_pt_gps_lock);
if (tg_pt_gp->tg_pt_gp_transition_complete)
@@ -1125,7 +1120,6 @@
*/
spin_lock(&dev->t10_alua.tg_pt_gps_lock);
atomic_inc(&tg_pt_gp->tg_pt_gp_ref_cnt);
- smp_mb__after_atomic();
spin_unlock(&dev->t10_alua.tg_pt_gps_lock);
if (!explicit && tg_pt_gp->tg_pt_gp_implicit_trans_secs) {
@@ -1168,7 +1162,6 @@
spin_lock(&local_lu_gp_mem->lu_gp_mem_lock);
lu_gp = local_lu_gp_mem->lu_gp;
atomic_inc(&lu_gp->lu_gp_ref_cnt);
- smp_mb__after_atomic();
spin_unlock(&local_lu_gp_mem->lu_gp_mem_lock);
/*
* For storage objects that are members of the 'default_lu_gp',
@@ -1184,8 +1177,7 @@
l_tg_pt_gp->tg_pt_gp_alua_nacl = l_nacl;
rc = core_alua_do_transition_tg_pt(l_tg_pt_gp,
new_state, explicit);
- atomic_dec(&lu_gp->lu_gp_ref_cnt);
- smp_mb__after_atomic();
+ atomic_dec_mb(&lu_gp->lu_gp_ref_cnt);
return rc;
}
/*
@@ -1198,8 +1190,7 @@
lu_gp_mem_list) {
dev = lu_gp_mem->lu_gp_mem_dev;
- atomic_inc(&lu_gp_mem->lu_gp_mem_ref_cnt);
- smp_mb__after_atomic();
+ atomic_inc_mb(&lu_gp_mem->lu_gp_mem_ref_cnt);
spin_unlock(&lu_gp->lu_gp_lock);
spin_lock(&dev->t10_alua.tg_pt_gps_lock);
@@ -1227,8 +1218,7 @@
tg_pt_gp->tg_pt_gp_alua_port = NULL;
tg_pt_gp->tg_pt_gp_alua_nacl = NULL;
}
- atomic_inc(&tg_pt_gp->tg_pt_gp_ref_cnt);
- smp_mb__after_atomic();
+ atomic_inc_mb(&tg_pt_gp->tg_pt_gp_ref_cnt);
spin_unlock(&dev->t10_alua.tg_pt_gps_lock);
/*
* core_alua_do_transition_tg_pt() will always return
@@ -1238,16 +1228,14 @@
new_state, explicit);
spin_lock(&dev->t10_alua.tg_pt_gps_lock);
- atomic_dec(&tg_pt_gp->tg_pt_gp_ref_cnt);
- smp_mb__after_atomic();
+ atomic_dec_mb(&tg_pt_gp->tg_pt_gp_ref_cnt);
if (rc)
break;
}
spin_unlock(&dev->t10_alua.tg_pt_gps_lock);
spin_lock(&lu_gp->lu_gp_lock);
- atomic_dec(&lu_gp_mem->lu_gp_mem_ref_cnt);
- smp_mb__after_atomic();
+ atomic_dec_mb(&lu_gp_mem->lu_gp_mem_ref_cnt);
}
spin_unlock(&lu_gp->lu_gp_lock);
@@ -1260,8 +1248,7 @@
core_alua_dump_state(new_state));
}
- atomic_dec(&lu_gp->lu_gp_ref_cnt);
- smp_mb__after_atomic();
+ atomic_dec_mb(&lu_gp->lu_gp_ref_cnt);
return rc;
}