Re: [PATCHv3] a new filesystem module for nilfs2

[Jiro SEKIBA]

Hi,

At Sat, 24 Apr 2010 22:12:52 +0200,
Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> 
> Committed. One question:

Thank you!

> +  .reserved_first_sector = 1,
> 
> This line claims that overwriting first sector of nilfs won't destroy any 
> data or metadata. Is it so?
> 

Oh, that is the one I copied from fs/ext2.c without any doubt.
But I think it's ok, since nilfs2 super block resides at 1K from
begining of the parition.  So any data within 1K will ignored.

I believe sector is assumed 512bytes, so first sector would be within 1K
which is not used in nilfs2.

I checked with loop back device and write random data in first 1K,
partion is healthy and mountable.  And the range 0-1K is unchanged.

thanks

regards,

> Jiro SEKIBA wrote:
> > Hi,
> >
> > Thank you very much for the comments!
> > I revised the patch to reflect the comments.
> >
> >   
> >> +  {
> >> +    grub_error(GRUB_ERR_BAD_FS,"btree corruption\n");
> >> +    return -1;
> >> +  }
> >> What do you think about possible fallback to iterate over all nodes in 
> >> case of fs corruption?
> >>     
> >
> > The case that btree is corrupted, it's very hard to take any action to 
> > recover
> > because it is not possible to distinguish which block has meta data
> > or which block has data without btree information.
> >
> > nilfs2 has ability to mount old checkpoint by specifying checkpoint number.
> > So using old checkpoint is one of the possible fallback if all the blocks
> > belonging to the old checkpoint is healthy. But it requires some more work.
> >
> > thanks,
> >
> > regards
> >   
> > ------------------------------------------------------------------------
> >
> >
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> >
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> 
> 
> -- 
> Regards
> Vladimir 'φ-coder/phcoder' Serbinenko
> 
> 


-- 
Jiro SEKIBA <address@hidden>