From mboxrd@z Thu Jan  1 00:00:00 1970
From: ralph@inputplus.co.uk (Ralph Corderoy)
Date: Sat, 16 Dec 2017 17:11:32 +0000
Subject: [TUHS] Date madness
In-Reply-To: <1513440719.1943285.1207178784.050ABA15@webmail.messagingengine.com>
References: <201712161050.vBGAojbd027976@coolidge.cs.Dartmouth.EDU>
 <1513440719.1943285.1207178784.050ABA15@webmail.messagingengine.com>
Message-ID: <20171216171132.4D5ED21CB8@orac.inputplus.co.uk>

Hi Randy,

> One way the kernel could tell old from new inodes is by reserving the
> high bit of one of the current 32-bit fields

When Doug mentioned the high bit being an escape I assumed something
like, using eight bits for ease,

    00-7f  existing positive meaning
    80-df  new meaning as if unsigned
    e0-ff  existing negative meaning

    existing  80 81...df e0...fe ff 00 01...7f
    new                  e0...fe ff 00 01...7f 80 81..df

This would extend the positive range beyond 2038, but keep a small range
of negatives for their existing pre-1970 meaning.  This is storage
representation.  Calculations can be done in a wider int, with
intermediate values simply being signed, as before.

-- 
Cheers, Ralph.
https://plus.google.com/+RalphCorderoy