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Date: Sat, 27 Jul 2002 10:23:18 -0700
From: Andrew Morton <akpm@zip.com.au>
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To: Anton Altaparmakov <aia21@cantab.net>
CC: Linus Torvalds <torvalds@transmeta.com>,
       Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [BK PATCH 2.5] Introduce 64-bit versions of 
 PAGE_{CACHE_,}{MASK,ALIGN}
References: <E17YRp5-0006H6-00@storm.christs.cam.ac.uk>
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Anton Altaparmakov wrote:
> 
> Linus,
> 
> This patch introduces 64-bit versions of PAGE_{CACHE_,}MASK and
> PAGE_{CACHE_,}ALIGN:
>         PAGE_{CACHE_,}MASK_LL and PAGE_{CACHE_,}ALIGN_LL.
> 
> These are needed when 64-bit values are worked with on 32-bit
> architectures, otherwise the high 32-bits are destroyed.
> 
> ...
>  #define PAGE_SIZE      (1UL << PAGE_SHIFT)
>  #define PAGE_MASK      (~(PAGE_SIZE-1))
> +#define PAGE_MASK_LL   (~(u64)(PAGE_SIZE-1))

The problem here is that we've explicitly forced the
PAGE_foo type to unsigned long.

If we instead take the "UL" out of PAGE_SIZE altogether,
the compiler can then promote the type of PAGE_SIZE and PAGE_MASK
to the widest type being used in the expression (ie: long long)
and everything should work.

Which seems to be a much cleaner solution, if it works.

Will it work?

-