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: NDavid M. Richter <richterd@citi.umich.edu>
Signed-off-by: NJ. Bruce Fields <bfields@citi.umich.edu>

fs/locks.c

@@ -1367,18 +1367,20 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
 
 	lease = *flp;
 
-	error = -EAGAIN;
-	if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
-		goto out;
-	if ((arg == F_WRLCK)
-	    && ((atomic_read(&dentry->d_count) > 1)
-		|| (atomic_read(&inode->i_count) > 1)))
-		goto out;
+	if (arg != F_UNLCK) {
+		error = -EAGAIN;
+		if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
+			goto out;
+		if ((arg == F_WRLCK)
+		    && ((atomic_read(&dentry->d_count) > 1)
+			|| (atomic_read(&inode->i_count) > 1)))
+			goto out;
 
-	error = -ENOMEM;
-	new_fl = locks_alloc_lock();
-	if (new_fl == NULL)
-		goto out;
+		error = -ENOMEM;
+		new_fl = locks_alloc_lock();
+		if (new_fl == NULL)
+			goto out;
+	}
 
 	/*
 	 * At this point, we know that if there is an exclusive