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

Brian Foster
2016-06-20T14:32:05Z

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

>
> 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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