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To: linux-kernel@vger.kernel.org
From: "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: New nanosecond stat patch for 2.5.44
Date: 27 Oct 2002 14:54:16 -0800
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References: <20021027121318.GA2249@averell> <20021027214913.GA17533@clusterfs.com>
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Followup to:  <20021027214913.GA17533@clusterfs.com>
By author:    Andreas Dilger <adilger@clusterfs.com>
In newsgroup: linux.dev.kernel
> 
> 3) The fields you are usurping in struct stat are actually there for the
>    Y2038 problem (when time_t wraps).  At least that's what Ted said when
>    we were looking into nsec times for ext2/3.  Granted, we may all be
>    using 64-bit systems by 2038...  I've always thought 64 bits is much
>    to large for time_t, so we could always use 20 or 30 bits for sub-second
>    times, and the remaining bits for extending time_t at the high end,
>    and mask those off for now, but that is a separate issue...
> 

64-bit time_t is nice because you don't *ever* need to worry about
overflow; it's capable of handling times on a galactic lifespan
scale.  It's overkill, of course, but it's the *right* kind of
overkill.

We probably need to revamp struct stat anyway, to support a larger
dev_t, and possibly a larger ino_t (we should account for 64-bit ino_t
at least if we have to redesign the structure.)  At that point I would
really like to advocate for int64_t ts_sec and uint32_t ts_nsec and
quite possibly a int32_t ts_taidelta to deal with leap seconds... I'd
personally like struct timespec to look like the above everywhere.

	-hpa


-- 
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"Unix gives you enough rope to shoot yourself in the foot."
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