Subject: Re: stat64 for over 2TB file returned invalid st_blocks
From: Dave Kleikamp <shaggy@austin.ibm.com>
To: Takashi Sato <sho@bsd.tnes.nec.co.jp>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
In-Reply-To: <041701c5f742$d6b0a450$4168010a@bsd.tnes.nec.co.jp>
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Date: Fri, 02 Dec 2005 08:11:50 -0600
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On Fri, 2005-12-02 at 22:18 +0900, Takashi Sato wrote:
> >> 2. Change the type of architecture dependent stat64.st_blocks in
> >>    include/asm/asm-*/stat.h from unsigned long to unsigned long long.
> >>    I tried modifying only stat64 of 32bit architecture
> >>    (include/asm-i386/stat.h).
> >
> >This changes the API, but the structure does suggest that the 4-byte pad
> >should be used for the high-order bytes of st_blocks, so that's not
> >really a problem.  A correct fix would replace __pad4 with
> >st_blocks_high (or something like that) and ensure that the high-order
> >word was stored there.  Your proposed fix would only be correct on
> >little-endian hardware, as J?rn pointed out.
> 
> Thank you for your advice.  I'll research for glibc and consider
> how to implement.
> By the way I think, as Avi Kivity said, it's always little-endian on i386,
> is it correct?

That's true.  The patch does fix i386 without any bad side-effects.  A
generic fix that would fix all architectures would be a little more
complicated, since the size of st_blocks varies.  32-bit big-endian
would have to explicitly copy the high and low words.  (The first time I
looked at this, I ignored the fact that the change was in asm-i386.)

Shaggy
-- 
David Kleikamp
IBM Linux Technology Center

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