linux-kernel - Re: Size of sector_t in userspace [Was: fix 41 'make headers

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Date:	Wed, 21 Jan 2009 09:21:25 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Sam Ravnborg <sam@...nborg.org>
Cc:	Jaswinder Singh Rajput <jaswinder@...nel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Size of sector_t in userspace [Was: fix 41 'make headers_check' warnings]

On Wed, Jan 21 2009, Sam Ravnborg wrote:
> Hi Jens.
> 
> In an attempt to fix some of the issues in our exported Headers jsr
> encountered some strange stuff in types.h.
> 
> types.h is exported to userspace where we do not have access to CONFIG_*
> symbols.
> Despite this we use CONFGI_LBD to decide the size of sector_t like this:
> 
> #ifdef CONFIG_LBD
> typedef u64 sector_t;
> typedef u64 blkcnt_t;
> #else
> typedef unsigned long sector_t;
> typedef unsigned long blkcnt_t;
> #endif
> 
> But as CONFIG_LBD is never defined in userspace sector_t is now 32
> bit on 32 bit boxes and 64 bit on 64 bit boxes (in userspace).
> 
> Is sector:t (and the companion blkcnt_t) really used by userspace?
> If it is - what size is it expected to have?

I don't think it's used by userspace, at least it cannot be used in
userspace <-> kernelspace interactions, since the size isn't fixed.

-- 
Jens Axboe

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