Hi Prasenjit Giri, and Reinoud,
On Thu, 10 Sep 2009 21:26:19 +0200, Reinoud Zandijk <wrote:
> Hi Prasenjit Giri,
>
> On Fri, Sep 11, 2009 at 12:46:04AM +0530, Prasenjit Giri wrote:
> > Even after looking through various sites, forums, mailing lists I could not
> > uncover the present directoy management of NILFS2.
> >
> > As I see a B-tree directory management in your long term to do list, it
> > would be really nice if someone would ought to share the information
> > regarding the present directory management of NILFS2
>
> Currently directories are recorded just as a sequential file but not filled
> with user data but with dirent entries in their blocks like ext2fs does.
> Nothing special about that :)
>
> I dont know if b+tree directory management would be preferable though. With
> some smart caching all directory operations can be made O(1) anyway.
>
> With regards,
> Reinoud Zandijk
Yes, directory is a file and it's already managed with b-tree like
other files. However, the current directory design is not O(log n),
and is actually slow especially for file creation.
So, it leaves room for considering the true "b-tree directory
management".
OTOH, the replacement has the following points to notice:
1) It may complicate the log writer.
The current log writer is designed on the basis that every data
and meta data is a file. In NILFS, inodes, segment usage state,
and checkpoints, are managed with correponding meta-data files.
The true "b-tree directory management" may break this uniformity.
2) A disk format change is required.
(We can deem this a trade-off at this stage)
This may be a -v3 material. But anyway, patch proposals are welcome.
Thank you,
Ryusuke Konishi
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