# RE: \[PATCH\] block: create ioctl to discard-or-zeroout a range of blocks

- From: Seymour, Shane M \<hidden\>
- Date: 2015-11-12 00:56:02 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2015/11/101164
- Thread: https://ratatoskr.run/linux-fsdevel/2015/11/101169/t.md

```text
> which would make the other checks I suggested to ensure that neither start
> or end were more than (uint64_t)LLONG_MAX unnecessary.

My apologies I was wrong about what I said above - after thinking about it for longer you still need to make sure that at least len is not greater than (uint64_t)LLONG_MAX because in the calculation:

	if (start > (uint64_t)LLONG_MAX - len)
		return -EINVAL;

if len was more than (uint64_t)LLONG_MAX it would underflow and become a very large positive number and start would never be greater than that (and I said end when I should have said len).
```