Re: [PATCH] 2/11 Ext2/3 Updates: Extended attributes, ACL, etc.

[Jeff Garzik <jgarzik@pobox.com>]

Theodore Ts'o wrote:

>I'm not sure ext2meta will be sufficient.  It's not just a matter of
>modifying the on-disk metadata, as would be needed for defrag, but I
>would also need to modify some of the in-core data structions in the
>ext2/3 filesystem data structures.  For example, when you resize the
>filesystem, you need to increase the number of group descriptors,
>which means you need to kmalloc, copy, and then kfree sbi->group_desc
>out from under the mounted filesystem.
>
>No doubt ext2meta could be modified so it could "reach out and touch"
>internal ext2/3 fileststem data structures in core.  But the locking
>issues involved get really messy.
>  
>

Like Al mentioned... any merge of ext[23]meta would be inside ext[23].o, 
so it would be a first class object and not some random module sticking 
its fingers in there.  I looked at the locking issue too (though 
admittedly not in-depth for filesystem resize), and it's not different 
at all from existing locking, both in 2.4.x and 2.5.x.  It's 
intentionally pretty darn compatible with existing locking :)

I'll post a patch in the next couple weeks...

    Jeff