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Path: utzoo!utgpu!water!watnot!watmath!clyde!cbatt!cwruecmp!hal!ncoast!allbery
From: allbery@ncoast.UUCP
Newsgroups: comp.bugs.sys5
Subject: Re: Unlinking "."
Message-ID: <2326@ncoast.UUCP>
Date: Tue, 7-Apr-87 22:00:06 EST
Article-I.D.: ncoast.2326
Posted: Tue Apr  7 22:00:06 1987
Date-Received: Sat, 11-Apr-87 05:21:14 EST
References: <1059@cci632.UUCP> <5715@brl-smoke.ARPA> <736@killer.UUCP>
Reply-To: allbery@ncoast.UUCP (Brandon Allbery)
Followup-To: comp.bugs.sys5
Organization: Cleveland Public Access UN*X, Cleveland, Oh
Lines: 36

As quoted from <736@killer.UUCP> by jfh@killer.UUCP (John Haugh):
+---------------
| > In article <1059@cci632.UUCP> rrw@cci632.UUCP (Rick Wessman) writes:
| > >In our version of Unix*, PERPOS**, it is legal to remove ".", and there
| > >is a raging controversy about whether it should be.
|
| Doug is right about the races, but if you start moving all of the utilities
| into the kernel, Sys5 will wind up looking a little fat.  There are plenty
| of good reasons to let people unlink "." and "..".  Fix the races instead.
+---------------

No, there aren't.  When it was decided to go with a directed graph rather
than an arbitrary linked mishmash, "." and ".." became sources of trouble.
Unless you want to go back to the old format (and Ghod help fsck!), it's
best to make the kernel force "." and ".." to be correct via mkdir()/rmdir()/
rename().  Otherwise you're asking for trouble.

System V ld unlinks the destination if it encounters an error.  I once tried
to relink the sysV kernel (as root, due to file permissions) and did it wrong;
ld tried to write ./.., failed for the obvious reasons, and unlinked the
destination.  Worse, fsck didn't let out a peep; I had to use /etc/link to
fix it.

This is a VERY good reason to make "." and ".." only linkable internal to the
kernel and force mkdir()/rmdir()/rename() outside it.

++Brando
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