Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!njin!princeton!notecnirp!nfs
From: nfs@notecnirp.Princeton.EDU (Norbert Schlenker)
Newsgroups: comp.os.minix
Subject: Re: Large Disks
Keywords: POSIX stat inode
Message-ID: <19846@princeton.Princeton.EDU>
Date: 4 Oct 89 11:02:50 GMT
References: <233@vsserv.scri.fsu.edu> <3463@ast.cs.vu.nl> <275@nikhefh.nikhef.nl>
Sender: news@princeton.Princeton.EDU
Reply-To: nfs@notecnirp.UUCP (Norbert Schlenker)
Organization: Dept. of Computer Science, Princeton University
Lines: 46

In article <275@nikhefh.nikhef.nl> Schutte@nikhefh.nikhef.nl (Klamer Schutte) writes:
]In article <3463@ast.cs.vu.nl> ast@cs.vu.nl (Andy Tanenbaum) writes:
]#>The MINIX i-node is 32 bytes.  This was designed to be frugal on a floppy
]#>based system.  The 32 bytes contain 9 16-bit disk addresses and a few other
]#>goodies.  Going to 9 24-bit addresses (like UNIX) takes up 27 bytes.
]	24 bit addresses are not to efficient on a 68000: needs a lot of
]	shift operations to come a decent integer type (long/short).
]#>Since we also need the mode, at least one time (a long), a gid, uid, etc,
]#>it is not going to fit.  Furthermore, POSIX really requires three distinct
]#>times in the i-node, not 1 like MINIX has.  The implication of all this is
]	Where is that in the standard? In my version (1986) paragraph
]	5.6.1.2 says: 
]	Only st_mode, st_ino, st_dev, st_uid, st_gid, st_size and st_mtime
]	are requiered data elements in the stat structure. All other
]	elements are optional, ... (etc.)
]	So reading this whole section i think we are POSIX-compatible if
]	we delete the fields st_atime & st_ctime from stat.h!

The 1988 standard says, in 5.6.1, that all of the following are required
and must have meaningful values:

st_mode, st_ino, st_dev, st_uid, st_gid, st_atime, st_ctime, st_mtime

I count that to use at least 20 bytes.  Adding other useful information
(like disk addresses!), 32 bytes is not going to be enough.

]#>that we have to go to a 64-byte i-node.  Not that this is so awful, and
]#>technically it is not a problem, but it does mean that the V2.0 file
]#>system will not be compatible with the 1.x file system (choke!).  I have
]#>been aware of this since I read the POSIX standard and saw that one must
]#>have three times in the i-node, since the standard tells exactly when each
]#>time is updated, and test suites can easily verify this.
]	where can i find this?

In the 1988 standard, there is additional discussion in 2.4 under "file
times update".  There is no getting away from this.

]#>
]#>Andy Tanenbaum (ast@cs.vu.nl)
]
]Klamer.
]-- 
]____________________Yes, mail address changed again :-(_________________________
]Klamer Schutte        mcvax!nikhefh!{n62,Schutte}        {Schutte,n62}@nikhef.nl

Norbert