[Gluster-devel] regressions due to 64-bit ext4 directory cookies

[Dave Chinner]

On Wed, Feb 13, 2013 at 05:20:52PM -0500, Theodore Ts'o wrote:
> Telldir() and seekdir() are basically implementation horrors for any
> file system that is using anything other than a simple array of
> directory entries ala the V7 Unix file system or the BSD FFS.  For any
> file system which is using a more advanced data structure, like
> b-trees hash trees, etc, there **can't** possibly be a "offset" into a
> readdir stream. 

I'll just point you to this:

http://marc.info/?l=linux-ext4&m=136081996316453&w=2

so you can see that XFS implements what you say can't possibly be
done. ;)

FWIW, that post only talked about the data segment. I didn't mention
that XFS has 2 other segments in the directory file (both beyond
EOF) for the directory data indexes. One contains the name-hash btree
index used for name based lookups and the other contains a freespace
index for tracking free space in the data segment.

IOWs persistent, deterministic, low cost telldir/seekdir behaviour
was a problem solved in the 1990s. :)

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com