Re: resizing file system

[Matteo Frigo <athena-/JWCw35jmeM@public.gmane.org>]

Ryusuke Konishi <ryusuke-sG5X7nlA6pw@public.gmane.org> writes:

> An experimental resize feature did exist, but it's not applicable to
> the current version.  And, it didn't support shrinking.
> So the feature you want is not available now.  (Sorry for inconvenience)

Ryusuke,

Thanks for developing nilfs2, it is a superb piece of work.

I am interested in the resize feature and willing to implement it, but I
need a little help.  My understanding of the nilfs2 source code in
2.6.35.4 is that in order to grow a file system it should be sufficient
to change s_nsegments in both superblocks while the file system is
unmounted.  If I understand correctly, the sufile grows automatically to
accomodate the additional segments because nilfs_sufile_alloc() calls
nilfs_sufile_get_segment_usage_block() with create=1, which grows the
sufile as necessary.

Is this interpretation correct?  If so, it should not be too hard to
code a little utility that grows an unmounted file system.  (Later we'll
worry about shrinking and online resize.)

You allude to an experimental resize feature.  Do you have code that I
can adapt to the current version?

Thanks,
Matteo Frigo

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