On Wed, Dec 03, 2025 at 08:54:31PM +0900, Alexandre Courbot wrote: > On Tue Dec 2, 2025 at 8:25 AM JST, Timur Tabi wrote: > > On Wed, 2025-11-19 at 12:36 +0900, Alexandre Courbot wrote: > >> You can use the `Alignment` type here, as the rest of the code does: > >> > >> let size = num::usize_as_u64(obj.size()) > >> .align_up(Alignment::new::<GSP_PAGE_SIZE>())?; > >> > >> Now `align_up` returns an error in case of overflow, that we will need > >> to pass down to the caller by changing the return type of `new`. It is a > >> bit annoying, but better than the behavior of `next_mutiple_of` in such > >> a case, which is to panic. :) > > > > I see your point, but these are u64s that we're talking about. The only > > way next_mutiple_of() can > > panic is if obj.size() is greater than 0xFFFFFFFFFFFFF000, which is not > > possible. > > > > I would say in this case, a panic is preferable to a convoluted error > > return that will never be > > exercised, because failure here indicates a coding error, not an input > > error. > > The input data is a usize, so technically we could get an input that > triggers that error. > > I know it's a very edge case, and clearly indicates a bug, but the > general rule is: don't panic the kernel. And in Rust, if possible, don't > even let me compiler insert panic-handling code. If you don't want to > change the return type of the method, then maybe use `unwrap_or` and > `inspect_err` to print an error before returning e.g. `0`. > > But others have already thought "naah, that's never gonna happen" and > got burnt very publicly [1], so let's learn from that. :P > > [1] https://blog.cloudflare.com/18-november-2025-outage/
For what it's worth, my friend at Cloudflare tells me they would have failed in the same way had they used ? instead of unwrap. Alice
