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

Darrick J. Wong
2016-06-20T18:23:29Z

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@oracle.com>
> > ---
>
> Reviewed-by: Brian Foster <bfoster@redhat.com>
>
> > 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);
> > }
> >
> > /*
> >
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