leases: when unlocking, skip locking-related steps

In generic_setlease(), we don't need to allocate a new struct file_lock
or check for readers or writers when called with F_UNLCK.
Signed-off-by: David M. Richter <richterd@citi.umich.edu>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

fs/locks.c

@@ -1367,6 +1367,7 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
 
 	lease = *flp;
 
+	if (arg != F_UNLCK) {
 		error = -EAGAIN;
 		if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
 			goto out;
@@ -1379,6 +1380,7 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
 		new_fl = locks_alloc_lock();
 		if (new_fl == NULL)
 			goto out;
+	}
 
 	/*
 	 * At this point, we know that if there is an exclusive