Re: XFS shrink functionality

[Ruben Porras <nahoo82@gmail.com>]

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> > I took a look at both items since this discussion started. And honestly,
> > I think 1) is harder that 4), so you're welcome to work on it :) The
> > points that make it harder is that, per David's suggestion, there needs
> > to be:
> >  - define two new transaction types
> 
> one new transaction type:
> 
> XFS_TRANS_AGF_FLAGS

done

> and and extension to xfs_alloc_log_agf(). Is about all that is
> needed there.

still to do. Will come after the ioctls.

> See the patch here:
> 
> http://oss.sgi.com/archives/xfs/2007-04/msg00103.html
> 
> For an example of a very simlar transaction to what is needed
> (look at xfs_log_sbcount()) and very similar addition to
> the AGF (xfs_btreeblks).
> 
> >  - define two new ioctls
> 
> XFS_IOC_ALLOC_ALLOW_AG, parameter xfsagnumber_t.
> XFS_IOC_ALLOC_DENY_AG, parameter xfsagnumber_t.

almost done. How I'm should I obtain a pointer to an xfs_agf_t from
inside the ioctls?

I guess that the first step is to get a *bp with xfs_getsb and then an *sbp,
but, which function/macro gives me the xfs_agf_t pointer? Sorry, I can't
find the way greeping through the code.

> >  - update the ondisk-format (!), if we want persistence of these flags;
> >    luckily, there are two spare fields in the AGF structure.
> 
> Better to expand, I think. The AGF is a sector in length - we can
> expand the structure as we need to this size without fear, esp. as
> the part of the sector outside the structure is guaranteed to be
> zero.  i.e. we can add a fields flag to the end of the AGF
> structure - old filesystems simple read as "no flags set" and
> old kernels never look at those bits....

done.

> >  - check the list of allocation functions that allocate space from the
> >    AG

still to be done.

Thaks again for the help.

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