Re: [PATCH 1/2] bitmap: new bitmap_copy_safe and bitmap_{from,to}_arr32

[Rasmus Villemoes]

On 28 December 2017 at 16:00, Yury Norov <ynorov@xxxxxxxxxxxxxxxxxx> wrote:
>
> In this patch, bitmap_copy_safe and bitmap_{from,to}_arr32 are introduced.
>
> 'Safe' in bitmap_copy_safe() stands for clearing unused bits in bitmap
> beyond last bit till the end of last word. It is useful for hardening
> API when bitmap is assumed to be exposed to userspace.

I agree completely with getting rid of the complexity of the u32array
functions, and also think they should simply be implemented as a
memcpy() when possible.

I'm not a fan of the _safe suffix, though. It doesn't say what it's
safe from. For example, one possible interpretation is that it allows
src or dst to be NULL (becoming a noop in such a case). Why not say
what it does? _clear_tail, _clear_rest, something like that. Or maybe,
can we simply make bitmap_copy behave that way? Hm, probably not, a
bit too many users to check they'd all be ok with that.

Rasmus