Storing additional Information to a file (eg. ACLs) -> a solution?

Storing additional Information to a file (eg. ACLs) -> a solution?

[Heinz-Josef Claes]

Hi,

I just read the article from the first side of namesys.com. I have an
idea about how to generally store security related attributes in a fast
way which uses only a minimum of storage.

First of all, I have absolutely now idea about filesystem layout; so
don't hesitate to blame me that it's nonsense what I'm writing here, but
perhaps it's not ...


assumptions for my suggestion to make sense:
1. securtity related attributes for files can be stored in (small)
files.
2. lots of files will probably have the same security related attributes
3. you don't want to store security related attributes in lots of little
files (eg. bad perforance)
4. it's fast to calc an md5sum (or something similar) for a short series
of bytes (a short file)


the solution:
1. take the first security related attribute and store it in a special
(hidden) directory. The name of the file is the md5sum of it. The file
which "points" to these permissions stores the md5sum or some kind of
sequence number (which can be smaller the the 16 byte of the md5sum) of
that little security related attribute file (sraf). This sraf counts the
number of "links" to it by the normal link counter of the filesystem.
2. take the second security related attribute and calc the md5sum. If
it's new, do the same as described in 1. If it's same the md5sum of an
existing sraf, make a "link" to it.
3. If you delete a file, decrease the "link" count in the sraf. If the
link count is zero, delete the sraf.


This should be easy to implement, space efficient, fast and very
flexible. (Reiserfs has no problems with lots of files in one
directory.) You only have to think about what to do if the link count of
an sraf is exceeded. This should be solvable in an easy way. I do not
make any suggestion about this because I do not know anything about the
internals of reiserfs (my solution would be stupid).


Regards,
and apologize my bad english

Heinz-Josef Claes

PS: This is basically the same idea as in storebackup ;-)

-- 
Heinz-Josef Claes                     hjclaes@web.de
project: http://sourceforge.net/projects/storebackup
      -> snapshot-like backup to another disk

Re: Storing additional Information to a file (eg. ACLs) -> a solution?

[Hans Reiser]

Heinz-Josef Claes wrote:

>Hi,
>
>I just read the article from the first side of namesys.com. I have an
>idea about how to generally store security related attributes in a fast
>way which uses only a minimum of storage.
>
>First of all, I have absolutely now idea about filesystem layout; so
>don't hesitate to blame me that it's nonsense what I'm writing here, but
>perhaps it's not ...
>
>
>assumptions for my suggestion to make sense:
>1. securtity related attributes for files can be stored in (small)
>files.
>2. lots of files will probably have the same security related attributes
>3. you don't want to store security related attributes in lots of little
>files (eg. bad perforance)
>4. it's fast to calc an md5sum (or something similar) for a short series
>of bytes (a short file)
>
>
>the solution:
>1. take the first security related attribute and store it in a special
>(hidden) directory. The name of the file is the md5sum of it. The file
>which "points" to these permissions stores the md5sum or some kind of
>sequence number (which can be smaller the the 16 byte of the md5sum) of
>that little security related attribute file (sraf). This sraf counts the
>number of "links" to it by the normal link counter of the filesystem.
>2. take the second security related attribute and calc the md5sum. If
>it's new, do the same as described in 1. If it's same the md5sum of an
>existing sraf, make a "link" to it.
>3. If you delete a file, decrease the "link" count in the sraf. If the
>link count is zero, delete the sraf.
>
>
>This should be easy to implement, space efficient, fast and very
>flexible. (Reiserfs has no problems with lots of files in one
>directory.) You only have to think about what to do if the link count of
>an sraf is exceeded. This should be solvable in an easy way. I do not
>make any suggestion about this because I do not know anything about the
>internals of reiserfs (my solution would be stupid).
>
>
>Regards,
>and apologize my bad english
>
>Heinz-Josef Claes
>
>PS: This is basically the same idea as in storebackup ;-)
>
>  
>
Interesting.  Essentially, it is a form of compression.  If the unique 
values all easily fit into ram, it is a good thing.