Re: [GIT PULL] iscsi-target merge for v3.1-rc1

Linus Torvalds
2011-07-26T07:10:43Z

On Mon, Jul 25, 2011 at 11:51 PM, Nicholas A. Bellinger
<nab@linux-iscsi.org> wrote:
>
> How about the following to add a new DIV_ROUND_UP_ULL macro

Hmm.

>  #define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
> +#define DIV_ROUND_UP_ULL(n,d) (                                \
> +{                                                      \
> +       unsigned long long _tmp = n, _off;              \
> +       int _res;                                       \
> +       /* Round up using asm/div64.h:do_div */         \
> +       _off = do_div(_tmp, d);                         \
> +       if (_off != 0)                                  \
> +               _tmp++;                                 \
> +       _res = _tmp;                                    \
> +}                                                      \
> +)

That looks buggy. Why the "_res = _tmp" there? All that does is to
truncate the result to "int", which looks bogus.

And it just looks unnecessarily complicated. Just a simple

#define DIV_ROUND_UP_ULL(ll,d) \
({ unsigned long long _tmp = (ll)+(d)-1; do_div(_tmp, d); _tmp; })

looks like it would work and be simpler. Avoid the conditional, do the
same "add 'd-1' thing as the regular ROUND_UP().

Untested. And not much thinking involved.

Linus