linux-kernel - Re: what is necessary for directory hard links

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Message-Id: <E1G5USP-0000fF-Sp@be1.lrz>
Date:	Tue, 25 Jul 2006 23:28:29 +0200
From:	Bodo Eggert <7eggert@...tempel.de>
To:	"Horst H. von Brand" <vonbrand@....utfsm.cl>,
	Joshua Hudson <joshudson@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: what is necessary for directory hard links

Horst H. von Brand <vonbrand@....utfsm.cl> wrote:
> Joshua Hudson <joshudson@...il.com> wrote:

> [...]
> 
>> Maybe someday I'll work out a system by which much less is locked.
>> Conceptually, all that is requred to lock for the algorithm
>> to work is creating hard-links to directories and renaming directories
>> cross-directory.
> 
> Some 40 years of filesystem development without finding a solution to that
> conundrum would make that quite unlikely, but you are certainly welcome to
> try.

There is a simple solution against loops: No directory may contain a directory
with a lower inode number.

Off cause this would interfere with normal operations, so you'll allocate all
normal inodes above e.g. 0x800000 and don't test between those inodes.

If you want to hardlink, you'll use a different (privileged) mkdir call
that will allocate a choosen low inode number. This is also required for
the parents of the hardlinked directories.

You can also use the generic solution: Allow root to shoot his feet, and
make sure the gun works correctly.
-- 
Ich danke GMX dafür, die Verwendung meiner Adressen mittels per SPF
verbreiteten Lügen zu sabotieren.

http://david.woodhou.se/why-not-spf.html
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