xfs: refactor btree maxlevels computation

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 how 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 <[email protected]> Reviewed-by: Brian Foster <[email protected]> Signed-off-by: Dave Chinner <[email protected]>
berg · Jun 21, 2016 · 19b54ee · 19b54ee
1 parent e66a4c6
commit 19b54ee
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Showing 4 changed files with 28 additions and 27 deletions.
diff --git 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
@@ -4152,3 +4152,22 @@ xfs_btree_sblock_verify(
 
 	return true;
 }
+
+/*
+ * 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;
+}
diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h
@@ -474,5 +474,7 @@ static inline int xfs_btree_get_level(struct xfs_btree_block *block)
 
 bool xfs_btree_sblock_v5hdr_verify(struct xfs_buf *bp);
 bool xfs_btree_sblock_verify(struct xfs_buf *bp, unsigned int max_recs);
+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
@@ -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);
 }
 
 /*