Re: [PATCH v2 2/3] Generic handling of multi-page exclusions

[Petr Tesarik <ptesarik@suse.cz>]

V Tue, 15 Apr 2014 01:20:46 +0000
Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp> napsáno:

> >From: Petr Tesarik <ptesarik@suse.cz>
> >Subject: Re: [PATCH v2 2/3] Generic handling of multi-page exclusions
> >Date: Thu, 10 Apr 2014 12:47:17 +0200
> >
> >> On Tue, 8 Apr 2014 07:06:34 +0000
> >> Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp> wrote:
> >>
> >>> [...]
> >>> > diff --git a/makedumpfile.h b/makedumpfile.h
> >>> >> index 951ed1b..dfad569 100644
> >>> >> --- a/makedumpfile.h
> >>> >> +++ b/makedumpfile.h
> >>> >> @@ -816,6 +816,13 @@ struct mem_map_data {
> >>> >>  	unsigned long long	pfn_start;
> >>> >>  	unsigned long long	pfn_end;
> >>> >>  	unsigned long	mem_map;
> >>> >> +
> >>> >> +	/*
> >>> >> +	 * for excluding multi-page regions
> >>> >> +	 */
> >>> >> +	unsigned long		exclude_pfn_start;
> >>> >> +	unsigned long		exclude_pfn_end;
> >>> >
> >>> >unsigned long long		exclude_pfn_start;
> >>> >unsigned long long		exclude_pfn_end;
> >>> >
> >>> >The integers representing page frame numbers need to be defined as
> >>> >unsigned long long for architectures where physical address can have
> >>> >64-bit length but unsigned long has 32-bit only, such as x86 PAE.
> >>> >
> >>> >Kumagai-san, I saw this sometimes in the past. How about introducing
> >>> >specific abstract type for page frame number like below?
> >>> >
> >>> >typedef unsigned long long pfn_t;
> >>>
> >>> Good idea! We should do it.
> >>
> >> Like the following patch?
> >>
> >> From 9f3f6876bf1e8c93690097c510dff9982651bfa5 Mon Sep 17 00:00:00 2001
> >> From: Petr Tesarik <ptesarik@suse.cz>
> >> Date: Thu, 10 Apr 2014 12:40:31 +0200
> >> Subject: [PATCH] Introduce the pfn_t type
> >>
> >> Replace unsigned long long with pfn_t where:
> >>
> >>   a. the variable denotes a PFN
> >>   b. the variable is a number of pages
> >>
> >> The number of pages is converted to a pfn_t, because it is a result of
> >> subtracting two PFNs or incremented in a loop over a range of PFNs, so
> >> it can get as large as a PFN.
> >>
> >> Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
> >
> >Thanks!
> >
> >Only concern is that pfn_t could be too generic; could collide with
> >symbols from any other libraries. On kernel, I found that kvm and um
> >defines pfn_t.
> >
> >So, it's better to prefix pfn_t with the letters indicating that this
> >is relevant to makedumpfile.
> >
> >But I don't come up with good prefix...
> 
> We don't need to be serious, just keeping identity is the important
> thing. So how about kdump_pfn_t or mdf_pfn_t?

I vote for mdf_pfn_t, because MDF is already used as an abbreviation
for makedumpfile in the crash utility source files.

My two cents,
Petr T

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