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

Darrick J. Wong
2016-06-17T01:19:09Z

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.

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>
---
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);
}

/*