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Re: reiser4 (was Re: [PATCH] Revised extended attributes interface)

To: Andrew Pimlott <andrew@xxxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: reiser4 (was Re: [PATCH] Revised extended attributes interface)
From: Hans Reiser <reiser@xxxxxxxxxxx>
Date: Thu, 13 Dec 2001 12:23:46 +0300
Cc: Anton Altaparmakov <aia21@xxxxxxxxx>, Nathan Scott <nathans@xxxxxxx>, Andreas Gruenbacher <ag@xxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, linux-xfs@xxxxxxxxxxx
References: <20011205143209.C44610@xxxxxxxxxxxxxxxxxxxxxxxx> <20011207202036.J2274@xxxxxxxxxx> <20011208155841.A56289@xxxxxxxxxxxxxxxxxxxxxxxx> <3C127551.90305@xxxxxxxxxxx> <20011211134213.G70201@xxxxxxxxxxxxxxxxxxxxxxxx> <5.1.0.14.2.20011211184721.04adc9d0@xxxxxxxxxxxxxxxxx> <3C1678ED.8090805@xxxxxxxxxxx> <20011212204333.A4017@xxxxxxxxxxxxxxxxxxxxxxx>
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Andrew Pimlott wrote:

On Wed, Dec 12, 2001 at 12:21:49AM +0300, Hans Reiser wrote:

Naming conventions are easy.


Hans,

While I look forward to your work, I think Anton points out some
issues that you really should try to address now, only you have not
understood them.  Can I take a crack at posing some concrete
questions that manifest the issues?

Let's imagine that we have a Linux system with an NTFS filesystem
and a reiserfs4 filesystem.  You can make any tentative assumptions
about reiserfs4 and new API's that you like, I just want to have an
idea of how you envision the following working:

First, I write a desktop application that wants to save an HTML file
along with some other object that contains the name of the creating
application.  The latter can go anywhere you want, except in the
same stream as the HTML file.  The user has requested that the
filename be /home/user/foo.html , and expects to be able to FTP this
file to his ISP with a standard FTP program.  What calls does my
application make to store the HTML and the application name?  If the
answer is different depending on whether /home/user is NTFS or
reiserfs4, explain both ways.

Are you sure that standard ftp will be able to handle extended attributes without modification?

One approach is to create a plugin called ..archive that when read is a virtual file consisting of an archive of everything in the directory. It would be interesting I think to attach said plugin to standard directories by default along with several other standard plugins like ..cat, etc.



Second, I booted NT and created a directory in the NTFS filesystem
called /foo .  In the directory, I created a file called bar.  I
also created a named stream called bar, and an extended attribute
called bar.  Now I boot Linux.  What calls do I make to see each of
the three objects called bar?


You access /foo/bar, /foo/bar/,,bar, /foo/..bar by name.



The heart of Anton's argument is that the UNIX filesystem name space
is basically used up--there's just not much room to add new
semantics.  The only obvious avenue for extension is, if /foo is not
a directory, you can give some interpretation to /foo/bar .  But
this doesn't help if /foo is a directory.  So something has to give,
and we want to see what will give in reiserfs4.

Andrew


Naming conventions are easy, but teaching user space is hard no matter whose scheme is used.



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