Re: [PATCH v2 1/1] eventfd: implementation of EFD_MASK flag

[Martin Sustrik]

On 14/02/13 23:54, Andrew Morton wrote:

> > +/*  On x86-64 keep the same binary layout as on i386. */
> > +#ifdef __x86_64__
> > +#define EVENTFD_MASK_PACKED __packed
> > +#else
> > +#define EVENTFD_MASK_PACKED
> > +#endif
> > +
> > +struct eventfd_mask {
> > +	__u32 events;
> > +	__u64 data;
> > +} EVENTFD_MASK_PACKED;
>
> The x86-64 specific thing is ugly.  I can find no explanation of why it
> was done, but it should go away.  You could make `events' a u64, or
> swap the order of the two fields and make the struct __packed on all
> architectures.
>
> Given that the size of the types is fixed, I see no compat issues here.

I've just copied how the definition is done for epoll_event. The comment 
there goes like this:

/*
 * On x86-64 make the 64bit structure have the same alignment as the
 * 32bit structure. This makes 32bit emulation easier.
 *
 * UML/x86_64 needs the same packing as x86_64
 */

If you still think I should remove the #ifdef, I am happy to do so.

Martin
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