[PATCH 010/119] xfs: create a standard btree size calculator code

Darrick J. Wong
2016-06-17T01:19:02Z

Create a helper to generate AG btree height calculator functions.
This will be used (much) later when we get to the refcount btree.

v2: Use a helper function instead of a macro.
v3: We can (theoretically) store more than 2^32 records in a btree, so
widen the fields to accept that.
v4: Don't modify xfs_bmap_worst_indlen; the purpose of /that/ function
is to estimate the worst-case number of blocks needed for a bmbt
expansion, not to calculate the space required to store nr records.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
fs/xfs/libxfs/xfs_btree.c | 27 +++++++++++++++++++++++++++
fs/xfs/libxfs/xfs_btree.h | 3 +++
2 files changed, 30 insertions(+)

diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
index 105979d..5eb4e40 100644
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -4156,3 +4156,30 @@ xfs_btree_sblock_verify(

return true;
}
+
+/*
+ * Calculate the number of blocks needed to store a given number of records
+ * in a short-format (per-AG metadata) btree.
+ */
+xfs_extlen_t
+xfs_btree_calc_size(
+ struct xfs_mount *mp,
+ uint *limits,
+ unsigned long long len)
+{
+ int level;
+ int maxrecs;
+ xfs_extlen_t rval;
+
+ maxrecs = limits[0];
+ for (level = 0, rval = 0; len > 0; level++) {
+ len += maxrecs - 1;
+ do_div(len, maxrecs);
+ rval += len;
+ if (len == 1)
+ return rval;
+ if (level == 0)
+ maxrecs = limits[1];
+ }
+ return rval;
+}
diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h
index 9a88839..b330f19 100644
--- a/fs/xfs/libxfs/xfs_btree.h
+++ b/fs/xfs/libxfs/xfs_btree.h
@@ -475,4 +475,7 @@ 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);

+xfs_extlen_t xfs_btree_calc_size(struct xfs_mount *mp, uint *limits,
+ unsigned long long len);
+
#endif /* __XFS_BTREE_H__ */