Re: Reduce struct page by 8 bytes on 64bit

[Jakub Jelinek]

On Wed, Apr 16, 2003 at 05:45:21AM -0700, David S. Miller wrote:
>    From: Andi Kleen <[e-mail]>
>    Date: Tue, 15 Apr 2003 13:24:30 +0200
>    
>    I worked around this by declaring a new data type atomic_bitmask32
>    with matching set_bit32/clear_bit32 etc. interfaces. Currently only 
>    on x86-64 aomitc_bitmask32 is defined to unsigned, everybody else
>    still uses unsigned long. The other 64bit architectures can define it to
>    unsigned too if they can confirm that it's ok to do.
> 
> I have no problem with this.
> 
> If you are clever, you can define a generic version even for the
> "unsigned long" 64-bit platforms.  It's left as an exercise to
> the reader :-)

Why is any new macro needed?

struct page
{
#if BITS_PER_LONG == 64 && defined __BIG_ENDIAN
  union {
    unsigned long flags;
    atomic_t count;
  };
#elif BITS_PER_LONG == 64 && defined __LITTLE_ENDIAN
  union {
    unsigned long flags;
    struct {
      int : 32;
      atomic_t count;
    };
  };
#else
  unsigned long flags;
  atomic_t count;
#endif
...
};

should do the job.

	Jakub