Fix last blocknr calculation in nova_truncate_file_blocks

A truncate following fallocate (file size 0) does not really truncate
the file blocks allocated, and a write after that will write to old blocks.
Fix last blocknr calculation so the blocks will be truncated.

Author: Andiry

fs/nova/inode.c

@@ -410,8 +410,9 @@ static void nova_truncate_file_blocks(struct inode *inode, loff_t start,
 	first_blocknr = (start + (1UL << data_bits) - 1) >> data_bits;
 
 	if (end == 0)
-		return;
-	last_blocknr = (end - 1) >> data_bits;
+		last_blocknr = 0;
+	else
+		last_blocknr = (end - 1) >> data_bits;
 
 	if (first_blocknr > last_blocknr)
 		return;