Re: [PATCH v3 4/4] xfs: support shrinking unused space in the last AG

[Gao Xiang <hsiangkao@redhat.com>]

Hi Darrick,

On Fri, Jan 08, 2021 at 01:19:42PM -0800, Darrick J. Wong wrote:
> On Sat, Jan 09, 2021 at 03:09:19AM +0800, Gao Xiang wrote:

...

> >  	delta = nb;	/* use delta as a temporary here */
> 
> Yikes, can this become a separate variable please?

Ok.

> 
> >  	nb_mod = do_div(delta, mp->m_sb.sb_agblocks);
> > @@ -99,10 +102,18 @@ xfs_growfs_data_private(
> >  	if (nb_mod && nb_mod < XFS_MIN_AG_BLOCKS) {
> >  		nagcount--;
> >  		nb = (xfs_rfsblock_t)nagcount * mp->m_sb.sb_agblocks;
> > -		if (nb < mp->m_sb.sb_dblocks)
> > +		if (nagcount < 2)
> >  			return -EINVAL;
> >  	}
> > -	delta = nb - mp->m_sb.sb_dblocks;
> > +
> > +	if (nb > mp->m_sb.sb_dblocks) {
> > +		delta = nb - mp->m_sb.sb_dblocks;
> > +		extend = true;
> > +	} else {
> > +		delta = mp->m_sb.sb_dblocks - nb;
> > +		extend = false;
> 
> /me wonders why delta isn't simply int64_t, and then you can do things
> like:
> 
> if (delta > 0)
> 	growfs
> else if (delta < 0)
> 	shrinkfs
> 
> ?

Yeah, delta changed into a signed variable in mycurrent experimental
shrinking entire AG hack as well. Will update this here in advance.

Thanks,
Gao Xiang