Re: Variable PTE_FILE_MAX_BITS

[Andrew Morton <akpm@digeo.com>]

Pete Zaitcev <zaitcev@redhat.com> wrote:
>
> Andrew,
> 
> would you be so kind to take this and forward to Linus?
> I think this segment of the code is your brainchild.

y'know, as I was writing that code I thought "no architecture could be dumb
enough to make PTE_FILE_MAX_BITS variable".

> On sparc

Ah.  That architecture.

> 
> --- linux-2.5.66-bk11/mm/fremap.c	2003-04-05 13:26:24.000000000 -0800
> +++ linux-2.5.66-bk11-sparc/mm/fremap.c	2003-04-05 13:28:22.000000000 -0800
> @@ -136,10 +136,10 @@
>  		return err;
>  
>  	/* Can we represent this offset inside this architecture's pte's? */
> -#if PTE_FILE_MAX_BITS < BITS_PER_LONG
> -	if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS))
> -		return err;
> -#endif
> +	/* This needs to be evaluated at runtime on some platforms */
> +	if (PTE_FILE_MAX_BITS < BITS_PER_LONG)
> +		if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS))
> +			return err;
>  

The reason I didn't do this in the first place is that if PTE_FILE_MAX_BITS
is 32 (as it is for ia32 PAE), the compiler generates a warning about the
(1<<32).  I guess it generates a bug, too.

Ho hum.  I shall make it "1ULL".