Re: [PATCH 011/119] xfs: refactor btree maxlevels computation

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On Mon, Jun 20, 2016 at 10:31:59AM -0400, Brian Foster wrote:
> On Thu, Jun 16, 2016 at 06:19:02PM -0700, Darrick J. Wong wrote:
> > Create a common function to calculate the maximum height of a per-AG
> > btree.  This will eventually be used by the rmapbt and refcountbt code
> > to calculate appropriate maxlevels values for each.  This is important
> > because the verifiers and the transaction block reservations depend on
> > accurate estimates of many blocks are needed to satisfy a btree split.
> 
> 			how many

Got it, will change for the next posting.

--D

> 
> > 
> > We were mistakenly using the max bnobt height for all the btrees,
> > which creates a dangerous situation since the larger records and keys
> > in an rmapbt make it very possible that the rmapbt will be taller than
> > the bnobt and so we can run out of transaction block reservation.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > ---
> 
> Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
> 
> >  fs/xfs/libxfs/xfs_alloc.c  |   15 ++-------------
> >  fs/xfs/libxfs/xfs_btree.c  |   19 +++++++++++++++++++
> >  fs/xfs/libxfs/xfs_btree.h  |    2 ++
> >  fs/xfs/libxfs/xfs_ialloc.c |   19 +++++--------------
> >  4 files changed, 28 insertions(+), 27 deletions(-)
> > 
> > 
> > diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> > index 1c76a0e..c366889 100644
> > --- a/fs/xfs/libxfs/xfs_alloc.c
> > +++ b/fs/xfs/libxfs/xfs_alloc.c
> > @@ -1839,19 +1839,8 @@ void
> >  xfs_alloc_compute_maxlevels(
> >  	xfs_mount_t	*mp)	/* file system mount structure */
> >  {
> > -	int		level;
> > -	uint		maxblocks;
> > -	uint		maxleafents;
> > -	int		minleafrecs;
> > -	int		minnoderecs;
> > -
> > -	maxleafents = (mp->m_sb.sb_agblocks + 1) / 2;
> > -	minleafrecs = mp->m_alloc_mnr[0];
> > -	minnoderecs = mp->m_alloc_mnr[1];
> > -	maxblocks = (maxleafents + minleafrecs - 1) / minleafrecs;
> > -	for (level = 1; maxblocks > 1; level++)
> > -		maxblocks = (maxblocks + minnoderecs - 1) / minnoderecs;
> > -	mp->m_ag_maxlevels = level;
> > +	mp->m_ag_maxlevels = xfs_btree_compute_maxlevels(mp, mp->m_alloc_mnr,
> > +			(mp->m_sb.sb_agblocks + 1) / 2);
> >  }
> >  
> >  /*
> > diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
> > index 5eb4e40..046fbcf 100644
> > --- a/fs/xfs/libxfs/xfs_btree.c
> > +++ b/fs/xfs/libxfs/xfs_btree.c
> > @@ -4158,6 +4158,25 @@ xfs_btree_sblock_verify(
> >  }
> >  
> >  /*
> > + * Calculate the number of btree levels needed to store a given number of
> > + * records in a short-format btree.
> > + */
> > +uint
> > +xfs_btree_compute_maxlevels(
> > +	struct xfs_mount	*mp,
> > +	uint			*limits,
> > +	unsigned long		len)
> > +{
> > +	uint			level;
> > +	unsigned long		maxblocks;
> > +
> > +	maxblocks = (len + limits[0] - 1) / limits[0];
> > +	for (level = 1; maxblocks > 1; level++)
> > +		maxblocks = (maxblocks + limits[1] - 1) / limits[1];
> > +	return level;
> > +}
> > +
> > +/*
> >   * Calculate the number of blocks needed to store a given number of records
> >   * in a short-format (per-AG metadata) btree.
> >   */
> > diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h
> > index b330f19..b955e5d 100644
> > --- a/fs/xfs/libxfs/xfs_btree.h
> > +++ b/fs/xfs/libxfs/xfs_btree.h
> > @@ -477,5 +477,7 @@ bool xfs_btree_sblock_verify(struct xfs_buf *bp, unsigned int max_recs);
> >  
> >  xfs_extlen_t xfs_btree_calc_size(struct xfs_mount *mp, uint *limits,
> >  		unsigned long long len);
> > +uint xfs_btree_compute_maxlevels(struct xfs_mount *mp, uint *limits,
> > +		unsigned long len);
> >  
> >  #endif	/* __XFS_BTREE_H__ */
> > diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
> > index 9d0003c..cda7269 100644
> > --- a/fs/xfs/libxfs/xfs_ialloc.c
> > +++ b/fs/xfs/libxfs/xfs_ialloc.c
> > @@ -2394,20 +2394,11 @@ void
> >  xfs_ialloc_compute_maxlevels(
> >  	xfs_mount_t	*mp)		/* file system mount structure */
> >  {
> > -	int		level;
> > -	uint		maxblocks;
> > -	uint		maxleafents;
> > -	int		minleafrecs;
> > -	int		minnoderecs;
> > -
> > -	maxleafents = (1LL << XFS_INO_AGINO_BITS(mp)) >>
> > -		XFS_INODES_PER_CHUNK_LOG;
> > -	minleafrecs = mp->m_inobt_mnr[0];
> > -	minnoderecs = mp->m_inobt_mnr[1];
> > -	maxblocks = (maxleafents + minleafrecs - 1) / minleafrecs;
> > -	for (level = 1; maxblocks > 1; level++)
> > -		maxblocks = (maxblocks + minnoderecs - 1) / minnoderecs;
> > -	mp->m_in_maxlevels = level;
> > +	uint		inodes;
> > +
> > +	inodes = (1LL << XFS_INO_AGINO_BITS(mp)) >> XFS_INODES_PER_CHUNK_LOG;
> > +	mp->m_in_maxlevels = xfs_btree_compute_maxlevels(mp, mp->m_inobt_mnr,
> > +							 inodes);
> >  }
> >  
> >  /*
> > 
> > _______________________________________________
> > xfs mailing list
> > xfs@xxxxxxxxxxx
> > http://oss.sgi.com/mailman/listinfo/xfs
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