linux-kernel - Re: [RFC 01/32] fs: introduce new 'struct inode

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Message-ID: <CAMuHMdVgch4REGcYWFZXVToX2b8iCinFVV10Bz3VoeiZy_yBtg@mail.gmail.com>
Date:	Sat, 31 May 2014 09:56:29 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux-Arch <linux-arch@...r.kernel.org>,
	"Joseph S. Myers" <joseph@...esourcery.com>,
	John Stultz <john.stultz@...aro.org>,
	Christoph Hellwig <hch@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ley Foon Tan <lftan@...era.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>
Subject: Re: [RFC 01/32] fs: introduce new 'struct inode_time'

Hi Arnd,

On Fri, May 30, 2014 at 10:01 PM, Arnd Bergmann <arnd@...db.de> wrote:
> + * The variant using bit fields is less efficient to access, but
> + * small and has a wider range as the 32-bit one, plus it keeps
> + * the signedness of the original timespec.
> + */
> +struct inode_time {
> +       long long       tv_sec  : 34;
> +       int             tv_nsec : 30;
> +};

Don't you need 31 bits for tv_nsec, to accommodate for the sign bit?
I know you won't really store negative numbers there, but storing a large
positive number will become negative on read out, won't it?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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