Hi!,
On Sat, 23 May 2009 22:11:20 +0200, "Dipl.-Ing. Michael Niederle" wrote:
> Hi!
> 
> I continue testing nilfs as a root file system. Until now I have no script to
> cleanly unmount the root file system. (In the layered approach (aufs) I used
> before this was not necessary.) So I just called sync and then shut down the
> system.

I made a Debian lenny on my pendrive.  It looks remount my root nilfs
partition readonly on shutdown, and no trouble so far.

> The next boot took some time, because the superblock was "broken". Here an
> extract from the kernel log:
> 
> [    1.407323] NILFS warning: broken superblock. using spare superblock.
> [    1.408569] NILFS warning: broken superblock. using spare superblock.
> [  461.587031] segctord starting. Construction interval = 5 seconds, CP
> frequency < 30 seconds [  461.591873] NILFS warning: mounting unchecked fs
> [  461.629865] NILFS: recovery complete.
> 
> Is nilfs doing a sequential scan over the whole partition to find its spare
> superblock?

No, the location of spare superblock is determined by size of the divice.
It's in tail of the partition.

I think the spare superblock pointed to a certain old segment and it
took some time to scan forward from the old segment to the latest
segment.

It may take about a minute, but something is wrong if it took several
minutes.

> Then I wanted to remove some snapshots:
> 
> > lscp -s
>                  CNO        DATE     TIME  MODE  FLG   NBLKINC       ICNT
>                  685  2009-05-13 09:38:20   ss    -         35     568722
>                 1330  2009-05-13 10:59:41   ss    i       7629     579584
>                 4466  2009-05-14 19:15:28   ss    -         23     589270
>                 8250  2009-05-16 03:40:42   ss    i       6202     597141
>                 9910  2009-05-17 19:14:54   ss    -         49     626715
>                10380  2009-05-17 20:21:53   ss    -         18     647228
>                10620  2009-05-23 21:45:41   ss    i       6054     646978
> 
> >rmcp 685
> rmcp: 685: operation not permitted
> 
> What's the cause of this message? (rmcp also failed for all other snapshots;
> the failed rmcp did not produce any kernel message)

rmcp is allowed only for plain checkpoints.
So, you have to change it to the plain checkpoint like

 # chcp cp 685 1330 ...
 # rmcp 685 ...

Actually, you don't have to do the rmcp because the garbage collection
will delete plain checkpoints.

I remember someone asked a simliar question before.

I think we should make the error message more user-friendly.  And we
should allow force option of rmcp to remove snapshots; the current
force option does not have this meaning.

Cheers,
Ryusuke Konishi
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