Re: [PATCH 2/2] xfs_db: calculate iext tree geometry in btheight command

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Sep 27, 2019 at 07:41:02AM +1000, Dave Chinner wrote:
> On Wed, Sep 25, 2019 at 02:40:59PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > (Ab)use the btheight command to calculate the geometry of the incore
> > extent tree.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> >  db/btheight.c |   87 +++++++++++++++++++++++++++++++++++++++------------------
> >  1 file changed, 60 insertions(+), 27 deletions(-)
> > 
> > 
> > diff --git a/db/btheight.c b/db/btheight.c
> > index e2c9759f..be604ebc 100644
> > --- a/db/btheight.c
> > +++ b/db/btheight.c
> > @@ -22,18 +22,37 @@ static int rmap_maxrecs(struct xfs_mount *mp, int blocklen, int leaf)
> >  	return libxfs_rmapbt_maxrecs(blocklen, leaf);
> >  }
> >  
> > +static int iext_maxrecs(struct xfs_mount *mp, int blocklen, int leaf)
> > +{
> > +	blocklen -= 2 * sizeof(void *);
> > +
> > +	return blocklen / sizeof(struct xfs_bmbt_rec);
> > +}
> 
> This isn't correct for the iext nodes. They hold 16 key/ptr pairs,
> not 15.
> 
> I suspect you should be lifting the iext btree format definitions
> like this one:
> 
> enum {                                                                           
>         NODE_SIZE       = 256,                                                   
>         KEYS_PER_NODE   = NODE_SIZE / (sizeof(uint64_t) + sizeof(void *)),       
>         RECS_PER_LEAF   = (NODE_SIZE - (2 * sizeof(struct xfs_iext_leaf *))) /   
>                                 sizeof(struct xfs_iext_rec),                     
> };                                                                               
> 
> from libxfs/xfs_iext_tree.c to a libxfs header file and then using
> KEYS_PER_NODE and RECS_PER_LEAF here. See the patch below, lifted
> from a varaint of my range locking prototypes...
> 
> However, these are not on-disk values and so are subject to change,
> hence it may be that a warning might be needed when xfs_db is used
> to calculate the height of this tree.

Er... I don't mind lifting the iext values, but I don't see a patch?

--D

> > +static int disk_blocksize(struct xfs_mount *mp)
> > +{
> > +	return mp->m_sb.sb_blocksize;
> > +}
> > +
> > +static int iext_blocksize(struct xfs_mount *mp)
> > +{
> > +	return 256;
> > +}
> 
> NODE_SIZE....
> 
> Cheers,
> 
> Dave.
> -- 
> Dave Chinner
> david@fromorbit.com