Date: Wed, 21 Jan 2009 09:21:25 +0100
From: Jens Axboe <jens.axboe@oracle.com>
To: Sam Ravnborg <sam@ravnborg.org>
Cc: Jaswinder Singh Rajput <jaswinder@kernel.org>, Ingo Molnar <mingo@elte.hu>,
       Andrew Morton <akpm@linux-foundation.org>,
       x86 maintainers <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: Size of sector_t in userspace [Was: fix 41 'make headers_check' warnings]
Message-ID: <20090121082125.GW30821@kernel.dk>
References: <1232273454.23100.9.camel@localhost.localdomain> <20090118110221.GA29602@elte.hu> <1232501276.3123.49.camel@localhost.localdomain> <20090121055356.GA26731@uranus.ravnborg.org>
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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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