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

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Date:	Tue, 25 Jul 2006 21:00:48 -0400
From:	"Horst H. von Brand" <vonbrand@....utfsm.cl>
To:	7eggert@....de
cc:	"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 

Bodo Eggert <7eggert@...tempel.de> wrote:
> 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.

This is a serious restriction...

> 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.

And allow loops there? I don't see how that solves anything...

> 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.

Argh... even /more/ illogical restrictions!

> You can also use the generic solution: Allow root to shoot his feet, and
> make sure the gun works correctly.

;-)
-- 
Dr. Horst H. von Brand                   User #22616 counter.li.org
Departamento de Informatica                     Fono: +56 32 654431
Universidad Tecnica Federico Santa Maria              +56 32 654239
Casilla 110-V, Valparaiso, Chile                Fax:  +56 32 797513
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