linux-kernel - Re: [Patch 5/8] ia64: implement crashkernel=auto

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Date:	Fri, 21 Aug 2009 17:24:07 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Amerigo Wang <amwang@...hat.com>
Cc:	linux-kernel@...r.kernel.org, tony.luck@...el.com,
	linux-ia64@...r.kernel.org, nhorman@...hat.com,
	ebiederm@...ssion.com, andi@...stfloor.org, mingo@...e.hu,
	amwang@...hat.com, bernhard.walle@....de, fenghua.yu@...el.com,
	kamezawa.hiroyu@...fujitsu.com, avorontsov@...mvista.com
Subject: Re: [Patch 5/8] ia64: implement crashkernel=auto

On Fri, 21 Aug 2009 02:55:04 -0400
Amerigo Wang <amwang@...hat.com> wrote:

> +#ifdef CONFIG_KEXEC_AUTO_RESERVE
> +#define ARCH_HAS_DEFAULT_CRASH_SIZE
> +static inline
> +unsigned long long arch_default_crash_size(unsigned long long total_size)
> +{
> +	if (total_size >= 4ULL<<30 && total_size < 12ULL<<30)
> +		return 1ULL<<28;
> +	else if (total_size >= 12ULL<<30 && total_size < 128ULL<<30)
> +		return 1ULL<<29;
> +	else if (total_size >= 128ULL<<30 && total_size < 256ULL<<30)
> +		return 3ULL<<28;
> +	else if (total_size >= 256ULL<<30 && total_size < 378ULL<<30)
> +		return 1ULL<<30;
> +	else if (total_size >= 318ULL<<30 && total_size < 512ULL<<30)
> +		return 3ULL<<29;
> +	else if (total_size >= 512ULL<<30 && total_size < 768ULL<<30)
> +		return 2ULL<<30;
> +	else if (total_size >= 768ULL<<30)
> +		return 3ULL<<30;
> +}
> +#include <asm-generic/kexec.h>
> +#endif

a) Why on earth is this inlined?

b) Please consider making arch_default_crash_size() a __weak
   function.  You'll probably find the result to be pleasing.

c) If we can't use __weak then please don't add
   ARCH_HAS_DEFAULT_CRASH_SIZE.  Instead do this trick:


	#ifndef arch_default_crash_size
	static inline unsigned long long arch_default_crash_size(unsigned long long total_size)
	{
		...
	}
	#define arch_default_crash_size arch_default_crash_size
	#endif

	because i) it's good to standardise on something and ii) one less
	symbol gets added to the kernel.

d) why is asm-generic/kexec.h only included in asm/kexec.h if
   CONFIG_KEXEC_AUTO_RESERVE happened to be defined?  That makes no
   sense - there may be a multitude of reasons why asm/kexec.h wants
   to include asm-generic/kexec.h.

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