Re: linux capabilities and ACLs

Jakub Jelinek (jj@sunsite.ms.mff.cuni.cz)
Wed, 3 Feb 1999 10:51:06 +0100 (CET)

>
> According to David Watson <david@cs.ucsb.edu>:
> > I'm also interested in knowing the status on ACL support. Is support
> > being worked on? Can it be added to ext2, or is something new needed?
>
> As far as I know, the ACL support for ext2 was planned, but never
> achieved, and now dropped, because an ACL field in the indode
> structure has been used to allow files bigger than 4GB. See the file:
> linux/include/linux/ext2_fs.h. It contains the following line:
>
> #define i_size_high i_dir_acl
>
> Which means that you cannot have ACL and +4GB files in the same time.
> This second feature has been considered more useful than ACL. I think
> that it is not feasible to keep backward compatibility with older ext2
> filesystems and get ACL and big files in the same time. Maybe it is time
> for an ext3 filesystem ?

i_dir_acl is for directories only, whereas
i_size_high is for other inodes, thus you cannot have +4GB directories (and
you generally don't even want that, even with btrees), otherwise you can
well have acls and +4GB files at the same time. See discussion on this topic
on l-k several months ago.
This is the same as it there was a union...
I hope ACL will make it into 2.3, as well as journalling, btrees, so IMHO
you don't need to start thinking about ext3, ext2 is extensible enough to
cope with that. There is even space for 32bit uid/gids and large devices,
AFAIK.

Cheers,
Jakub
___________________________________________________________________
Jakub Jelinek | jj@sunsite.mff.cuni.cz | http://sunsite.mff.cuni.cz
Administrator of SunSITE Czech Republic, MFF, Charles University
___________________________________________________________________
UltraLinux | http://ultra.linux.cz/ | http://ultra.penguin.cz/
Linux version 2.2.1 on a sparc64 machine (3958.37 BogoMips)
___________________________________________________________________

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