[PATCH] dma-debug: Fix the overlap() function to be correct andreadable

[Ingo Molnar]

* Ingo Molnar <mingo@xxxxxxx> wrote:

> > IOW, I think this whole function is just total crap, apparently 
> > put together by randomly assembling characters until it 
> > compiles. Somebody should put more effort into looking at it, 
> > but I think it should be something like
> > 
> > 	static inline int overlap(void *addr, unsigned long len, void *start, void *end)
> > 	{
> > 		unsigned long a1 = (unsigned long) addr;
> > 		unsigned long b1 = a1 + len;
> > 		unsigned long a2 = (unsigned long) start;
> > 		unsigned long b2 = (unsigned long) end;
> 
> At least some arguments have unsigned long natural types (they come 
> out of page_address() for example) so the function parameters could 
> perhaps be changed to unsigned long too as well.
> 
> > 	#ifdef WE_CARE_DEEPLY
> > 		/* Overflow? */
> > 		if (b1 < a1)
> > 			return 1;
> > 	#ifdef AND_ARE_ANAL
> > 		if (b2 < a2)
> > 			return 1;
> > 	#endif
> > 	#endif
> > 		return !(b1 <= a2 || a1 >= b2);
> > 	}
> > 
> > but I really migth have done soemthing wrong there. It's a 
> > simple function, but somebody needs to double-check that I 
> > haven't made it worse.
> 
> Looks correct to me.

How about the patch below? Lightly tested.

	Ingo

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