[Ocfs2-tools-devel] Add compress dirs option in fsck.ocfs2

[Goldwyn Rodrigues]

On Tue, Oct 13, 2009 at 03:46:46PM -0700, Joel Becker wrote:
> [Hi Goldwyn.  Sorry it took me so long to get back on this]

No problem.

> 
> On Thu, Sep 03, 2009 at 10:49:44AM -0500, Goldwyn Rodrigues wrote:
> > >> No, I do not skip the dirent record if dirent->inode==0. I still
> > >> memmove() it and set prev to dirent (the empty one).
> > >>
> > >> prev is responsible for skipping empty records (by not updating write_off)
> 
> 	I think I see what you are doing.  You slide things over those
> empty records.
> 	Here's an example in ascii-art:
> 
> d - dirent pointer
> p - prev pointer
> o - offset
> w - write offset
> N - inode number
> 
> --------
> 
> Start:
>     w
>     d
> p   o
>     [100     |0       |101     |0       |102     |0        ] 
> 
> Looped past 100:
>              w
>              d
>     p        o
>     [100     |0       |101     |0       |102     |0        ] 
> 
> Looped past 0:
>              w
>                       d
>              p        o
>     [100     |0       |101     |0       |102     |0        ] 
> 
> Shifted 101 down:
>              w
>              d
>              p        o
>     [100     |101              |0       |102     |0        ] 
> 
> Looped past 101:
>              w
>                                d
>              p                 o
>     [100     |101              |0       |102     |0        ] 
> 
> Adjust 101:
>                       w
>                                d
>              p                 o
>     [100     |101     |        |0       |102     |0        ] 
> 
> Shift 0 down:
>                       w
>                       d
>              p                 o
>     [100     |101     |0                |102     |0        ] 
> 
> Looped past 0:
>                       w
>                                         d
>                       p                 o
>     [100     |101     |0                |102     |0        ] 
> 
> Shift 102 down:
>                       w
>                       d
>                       p                 o
>     [100     |101     |102                       |0        ] 
> 
> Looped past 102:
>                       w
>                                                  d
>                       p                          o
>     [100     |101     |102                       |0        ] 
> 
> Adjust 102:
>                                w
>                                                  d
>                       p                          o
>     [100     |101     |102     |                 |0        ] 
> 
> Shift 0 down:
>                                w
>                                d
>                       p                          o
>     [100     |101     |102     |0                          ] 
> 
> --------
> 
> 	So there you have a valid compressed dirblock.  Every state that
> is after going around the loop - a place where we can potentially write
> - is safe.  The only squirrelly thing is that last empty dirent.  It
> doesn't get squished with 102.  But it is still valid, so it's fine.
> 	Do I have it correct?  Let me know if I've misunderstood
> anything.  I'm going to go back and look at the patch in its entirety to
> give a final once-over.
> 

Yes. you have it correct.

However, I am not aware of a situation which would get a block like the
one you have shown (with 0 as the last entry in the dirblock). In any
case, it is valid, and the "dirent hole" is at the end of the block.

Thanks,
-- 
Goldwyn