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Re: [dm-devel] [PATCH v8 01/16] hashtable: introduce a small and naive hashtable



On Tue, Oct 30, 2012 at 8:51 PM, Jim Rees <rees umich edu> wrote:
> Sasha Levin wrote:
>
>   On Tue, Oct 30, 2012 at 5:42 PM, Tejun Heo <tj kernel org> wrote:
>   > Hello,
>   >
>   > Just some nitpicks.
>   >
>   > On Tue, Oct 30, 2012 at 02:45:57PM -0400, Sasha Levin wrote:
>   >> +/* Use hash_32 when possible to allow for fast 32bit hashing in 64bit kernels. */
>   >> +#define hash_min(val, bits)                                                  \
>   >> +({                                                                           \
>   >> +     sizeof(val) <= 4 ?                                                      \
>   >> +     hash_32(val, bits) :                                                    \
>   >> +     hash_long(val, bits);                                                   \
>   >> +})
>   >
>   > Doesn't the above fit in 80 column.  Why is it broken into multiple
>   > lines?  Also, you probably want () around at least @val.  In general,
>   > it's a good idea to add () around any macro argument to avoid nasty
>   > surprises.
>
>   It was broken to multiple lines because it looks nicer that way (IMO).
>
>   If we wrap it with () it's going to go over 80, so it's going to stay
>   broken down either way :)
>
> I would prefer the body be all on one line too. But shouldn't this be a
> static inline function?

We want sizeof(val), which wouldn't work in a static inline. We can
either wrap a static inline __hash_min() with a macro and pass that
size to it, but that's quite an overkill here, or we can add a size
parameter to hash_min(), but it would look awkward considering how
hash_32()/hash_64()/hash_long() look like.


Thanks,
Sasha


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