ksmbd: fix WARNING "do not call blocking ops when !TASK_RUNNING"

wait_event_timeout() will set the state of the current
task to TASK_UNINTERRUPTIBLE, before doing the condition check. This
means that ksmbd_durable_scavenger_alive() will try to acquire the mutex
while already in a sleeping state. The scheduler warns us by giving
the following warning:

do not call blocking ops when !TASK_RUNNING; state=2 set at
 [<0000000061515a6f>] prepare_to_wait_event+0x9f/0x6c0
WARNING: CPU: 2 PID: 4147 at kernel/sched/core.c:10099 __might_sleep+0x12f/0x160

mutex lock is not needed in ksmbd_durable_scavenger_alive().

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: namjaejeon

fs/smb/server/vfs_cache.c

@@ -713,12 +713,8 @@ static bool tree_conn_fd_check(struct ksmbd_tree_connect *tcon,
 
 static bool ksmbd_durable_scavenger_alive(void)
 {
-	mutex_lock(&durable_scavenger_lock);
-	if (!durable_scavenger_running) {
-		mutex_unlock(&durable_scavenger_lock);
+	if (!durable_scavenger_running)
 		return false;
-	}
-	mutex_unlock(&durable_scavenger_lock);
 
 	if (kthread_should_stop())
 		return false;
@@ -799,9 +795,7 @@ static int ksmbd_durable_scavenger(void *dummy)
 			break;
 	}
 
-	mutex_lock(&durable_scavenger_lock);
 	durable_scavenger_running = false;
-	mutex_unlock(&durable_scavenger_lock);
 
 	module_put(THIS_MODULE);