Re: [PATCH][next] afs: fix integer overflow when shifting 1 more than 32 places

From: David Howells
Date: Wed Apr 11 2018 - 10:10:24 EST


Colin Ian King <colin.king@xxxxxxxxxxxxx> wrote:

> >> - mask = (1 << nr_slots) - 1;
> >> + mask = (1ULL << nr_slots) - 1;
> >
> > nr_slots cannot be larger than 9, so what I wrote is actually fine and is
> > more efficient on a 32-bit machine.
>
> ok, sorry about the noise.

It would be possible to cast the value to u64 before assigning it, I suppose.
Would that help? E.g.:

mask = (u64)((1 << nr_slots) - 1);

It looks a bit odd, though, since the cast is made implicitly anyway.

David