Re: PAGE_ALIGN() compile breakage

Adrian Bunk
2008-07-25T09:15:30Z

On Fri, Jul 25, 2008 at 01:55:37AM -0700, Andrew Morton wrote:
> On Fri, 25 Jul 2008 11:39:43 +0300 Adrian Bunk <bunk@kernel.org> wrote:
>
> > Commit 27ac792ca0b0a1e7e65f20342260650516c95864
> > (PAGE_ALIGN(): correctly handle 64-bit values on 32-bit architectures)
> > causes on some architectures (e.g. avr32 and mips) compile errors
> > like the following in some configurations starting with:
> >
> > <-- snip -->
> >
> > ...
> > CC init/main.o
> > In file included from
> > /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/utsname.h:35,
> > from /home/bunk/linux/kernel-2.6/git/linux-2.6/init/main.c:20:
> > /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/sched.h: In function 'arch_pick_mmap_layout':
> > /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/sched.h:2149: error: implicit declaration of function 'PAGE_ALIGN'
> > make[2]: *** [init/main.o] Error 1
> >
>
> pls test:
>
> diff -puN include/linux/sched.h~a include/linux/sched.h
> --- a/include/linux/sched.h~a
> +++ a/include/linux/sched.h
> @@ -2139,16 +2139,7 @@ static inline void set_task_cpu(struct t
>
> #endif /* CONFIG_SMP */
>
> -#ifdef HAVE_ARCH_PICK_MMAP_LAYOUT
> extern void arch_pick_mmap_layout(struct mm_struct *mm);
> -#else
> -static inline void arch_pick_mmap_layout(struct mm_struct *mm)
> -{
> - mm->mmap_base = TASK_UNMAPPED_BASE;
> - mm->get_unmapped_area = arch_get_unmapped_area;
> - mm->unmap_area = arch_unmap_area;
> -}
> -#endif
>
> #ifdef CONFIG_TRACING
> extern void
> diff -puN mm/mmap.c~a mm/mmap.c
> --- a/mm/mmap.c~a
> +++ a/mm/mmap.c
> @@ -2268,3 +2268,12 @@ int install_special_mapping(struct mm_st
>
> return 0;
> }
> +
> +#ifndef HAVE_ARCH_PICK_MMAP_LAYOUT
> +void arch_pick_mmap_layout(struct mm_struct *mm)
> +{
> + mm->mmap_base = TASK_UNMAPPED_BASE;
> + mm->get_unmapped_area = arch_get_unmapped_area;
> + mm->unmap_area = arch_unmap_area;
> +}
> +#endif

Nice, this seems to fix the problem.

> > and more nasty problems follow later.
> >
> > My suggestion is to:
> > - revert commit 27ac792ca0b0a1e7e65f20342260650516c95864 and then
> > - fix all PAGE_ALIGN() instances without moving them.
>
> Every time this patch blew up (and it did it often), fixing it resulted
> in overall improvements.
>
> > Unifying code is a good thing, but in this case it is not worth the
> > trouble it causes by poking into the heart of our headers mess.
>
> Well. If we leave it a mess, it'll stay a mess.

An interesting question is whether the PAGE_ALIGN() move makes the mess
bigger or smaller.

Ideally, all headers should be self-contained. IOW, they should #include
everything they use.

But TASK_UNMAPPED_BASE in asm/processor.h on some architectures uses
PAGE_ALIGN() that got moved from asm/page.h to linux/mm.h .

cu
Adrian

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