target: Invoke release_cmd() callback without holding a spinlock

This patch fixes the following kernel warning because it avoids that
IRQs are disabled while ft_release_cmd() is invoked (fc_seq_set_resp()
invokes spin_unlock_bh()):

WARNING: CPU: 3 PID: 117 at kernel/softirq.c:150 __local_bh_enable_ip+0xaa/0x110()
Call Trace:
 [<ffffffff814f71eb>] dump_stack+0x4f/0x7b
 [<ffffffff8105e56a>] warn_slowpath_common+0x8a/0xc0
 [<ffffffff8105e65a>] warn_slowpath_null+0x1a/0x20
 [<ffffffff81062b2a>] __local_bh_enable_ip+0xaa/0x110
 [<ffffffff814ff229>] _raw_spin_unlock_bh+0x39/0x40
 [<ffffffffa03a7f94>] fc_seq_set_resp+0xe4/0x100 [libfc]
 [<ffffffffa02e604a>] ft_free_cmd+0x4a/0x90 [tcm_fc]
 [<ffffffffa02e6972>] ft_release_cmd+0x12/0x20 [tcm_fc]
 [<ffffffffa042bd66>] target_release_cmd_kref+0x56/0x90 [target_core_mod]
 [<ffffffffa042caf0>] target_put_sess_cmd+0xc0/0x110 [target_core_mod]
 [<ffffffffa042cb81>] transport_release_cmd+0x41/0x70 [target_core_mod]
 [<ffffffffa042d975>] transport_generic_free_cmd+0x35/0x420 [target_core_mod]

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Acked-by: Joern Engel <joern@logfs.org>
Reviewed-by: Andy Grover <agrover@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_tmr.c

@@ -130,6 +130,9 @@ void core_tmr_abort_task(
 		if (tmr->ref_task_tag != ref_tag)
 			continue;
 
+		if (!kref_get_unless_zero(&se_cmd->cmd_kref))
+			continue;
+
 		printk("ABORT_TASK: Found referenced %s task_tag: %llu\n",
 			se_cmd->se_tfo->get_fabric_name(), ref_tag);
 
@@ -139,13 +142,15 @@ void core_tmr_abort_task(
 			       " skipping\n", ref_tag);
 			spin_unlock(&se_cmd->t_state_lock);
 			spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
+
+			target_put_sess_cmd(se_cmd);
+
 			goto out;
 		}
 		se_cmd->transport_state |= CMD_T_ABORTED;
 		spin_unlock(&se_cmd->t_state_lock);
 
 		list_del_init(&se_cmd->se_cmd_list);
-		kref_get(&se_cmd->cmd_kref);
 		spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
 
 		cancel_work_sync(&se_cmd->work);

drivers/target/target_core_transport.c

@@ -2509,23 +2509,24 @@ out:
 EXPORT_SYMBOL(target_get_sess_cmd);
 
 static void target_release_cmd_kref(struct kref *kref)
-		__releases(&se_cmd->se_sess->sess_cmd_lock)
 {
 	struct se_cmd *se_cmd = container_of(kref, struct se_cmd, cmd_kref);
 	struct se_session *se_sess = se_cmd->se_sess;
+	unsigned long flags;
 
+	spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
 	if (list_empty(&se_cmd->se_cmd_list)) {
-		spin_unlock(&se_sess->sess_cmd_lock);
+		spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
 		se_cmd->se_tfo->release_cmd(se_cmd);
 		return;
 	}
 	if (se_sess->sess_tearing_down && se_cmd->cmd_wait_set) {
-		spin_unlock(&se_sess->sess_cmd_lock);
+		spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
 		complete(&se_cmd->cmd_wait_comp);
 		return;
 	}
 	list_del(&se_cmd->se_cmd_list);
-	spin_unlock(&se_sess->sess_cmd_lock);
+	spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
 
 	se_cmd->se_tfo->release_cmd(se_cmd);
 }
@@ -2541,8 +2542,7 @@ int target_put_sess_cmd(struct se_cmd *se_cmd)
 		se_cmd->se_tfo->release_cmd(se_cmd);
 		return 1;
 	}
-	return kref_put_spinlock_irqsave(&se_cmd->cmd_kref, target_release_cmd_kref,
-			&se_sess->sess_cmd_lock);
+	return kref_put(&se_cmd->cmd_kref, target_release_cmd_kref);
 }
 EXPORT_SYMBOL(target_put_sess_cmd);