xfs: create a standard btree size calculator code
Create a helper to generate AG btree height calculator functions.
This will be used (much) later when we get to the refcount btree.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
index 7be8d9c..50cfb98 100644
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -4797,3 +4797,27 @@
return xfs_btree_overlapped_query_range(cur, &low_key, &high_key,
fn, priv);
}
+
+/*
+ * 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 > 1; level++) {
+ len += maxrecs - 1;
+ do_div(len, maxrecs);
+ maxrecs = limits[1];
+ rval += len;
+ }
+ return rval;
+}