Re: [PATCH 6/4] [-mm patch] use the existing offsetof().

[Satyam Sharma <satyam@infradead.org>]

On Thu, 20 Sep 2007, Ken'ichi Ohmichi wrote:
> 
> [PATCH 6/4] [-mm patch] use the existing offsetof().
>  It is better that offsetof() is used for VMCOREINFO_OFFSET().
>  This idea is Joe Perches's.
> 
> 
> 
> Thanks
> Ken'ichi Ohmichi 
> 
> ---
> Signed-off-by: Joe Perches <joe@perches.com>

Same deal here ...


> Signed-off-by: Ken'ichi Ohmichi <oomichi@mxs.nes.nec.co.jp>
> ---
> diff -rpuN a/include/linux/kexec.h b/include/linux/kexec.h
> --- a/include/linux/kexec.h	2007-09-18 15:23:22.000000000 +0900
> +++ b/include/linux/kexec.h	2007-09-18 15:27:29.000000000 +0900
> @@ -137,7 +137,7 @@ unsigned long paddr_vmcoreinfo_note(void
>  			      (unsigned long)sizeof(struct name))
>  #define VMCOREINFO_OFFSET(name, field) \
>  	vmcoreinfo_append_str("OFFSET(%s.%s)=%lu\n", #name, #field, \
> -			      (unsigned long)&(((struct name *)0)->field))
> +			      (unsigned long)offsetof(struct name, field))
>  #define VMCOREINFO_LENGTH(name, value) \
>  	vmcoreinfo_append_str("LENGTH(%s)=%lu\n", #name, (unsigned long)value)

... and here. Use %zu and lose the casts.

BTW I don't think these macros are such a big win in readability or
code clarity anyway. And I noticed that there are still some open
calls to vmcoreinfo_append_str() in kexec.c (such as for the OS_RELEASE
case) which you haven't macro-ized ... we end up having code that looks
like:

	vmcoreinfo_append_str(...);
	...

	...
	VMCOREINFO_OFFSET(...);
	...

and it's not even obvious (unless you follow on to the definition of the
later macro) that the above two are *exactly* the same. So you could also
consider just losing the macros altogether.


Satyam