Non-UNIX permission models (resent)

[Andreas Gruenbacher]

Hello,

[resent -- the previous message probably was dropped by a list admin.]

I've thought about what we would need to change in the kernel in order to 
allow non-UNIX permission models on some filesystems/mounts, and I've 
discussed this with SUSE folks at the SUSE Labs conference in Prague 
yesterday. Surprisingly, nobody seemed to be strongly opposed to what I 
presented, rather the opposite. Samba is the most prominent potential user of 
non-UNIX permission models on Linux as far as I can see, so I would like to 
discuss the topic with you.

Very briefly put, I believe that we need a few small change at the VFS 
(virtual filesystem) layer, and with those, the CIFS and other permission 
models can be implemented at the low-level filesystem layer relatively 
easily. I'm thinking of allowing the user to choose a permission model per 
mount.

Attached are the slides that I used yesterday, and a first sketch how this 
could be implemented. Your comments are very welcome.

(It seems that the VFS could provide a CIFS permission model implementation 
that only uses extended attribute inode operations, so multiple filesystems 
could use the same implementation rather than having to duplicate the same 
code, even though logically it would be a filesystem-level feature. This is 
similar to how the current permission inode operation works.)

Cheers,
Andreas.
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