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16 bit UIDs


From: Wolfgang Jährling
Subject: 16 bit UIDs
Date: Fri, 31 May 2002 15:43:23 +0200
User-agent: Mutt/1.0.1i

Hi!

The Minix file system uses 16 bit UIDs, which creates an obvious problem
for us.  Linux handles this by using a special "overflow UID":

#define fs_high2lowuid(uid) ((uid) > 65535 ? (uid16_t)fs_overflowuid : \
                                             (uid16_t)(uid))

This overflow UID can be set with sysctl(8) and defaults to the value
65534 (not 65535, as one might expect).  It seems to be good enough for
Linux, but I'm not sure if it is good enough for us, so how should we
handle this situation?  Storing the UID `(ushort) ~0' in the i_uid field
of the inode and using some trick (which shouldn't break anything, of
course) to store the real UID elsewhere?

Cheers,
GNU/Wolfgang

-- 
Wolfgang Jährling  <wolfgang@pro-linux.de>  \\  http://stdio.cjb.net/
Debian GNU/Hurd user && Debian GNU/Linux user \\  http://www.gnu.org/
The Hurd Hacking Guide: http://www.gnu.org/software/hurd/hacking-guide/
["We're way ahead of you here. The Hurd has always been on the    ]
[ cutting edge of not being good for anything." -- Roland McGrath ]



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