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.
v5: More minor tweaks to the loop control; move down to reflink patches.
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
fs/xfs/libxfs/xfs_btree.c | 24 ++++++++++++++++++++++++
fs/xfs/libxfs/xfs_btree.h | 2 ++
2 files changed, 26 insertions(+)
diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
index d1155ca..1bc483b 100644
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -4801,3 +4801,27 @@ xfs_btree_query_range(
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;
+}
diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h
index 870a5ab..607463a 100644
--- a/fs/xfs/libxfs/xfs_btree.h
+++ b/fs/xfs/libxfs/xfs_btree.h
@@ -501,6 +501,8 @@ 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);
+xfs_extlen_t xfs_btree_calc_size(struct xfs_mount *mp, uint *limits,
+ unsigned long long len);
/* return codes */
#define XFS_BTREE_QUERY_RANGE_CONTINUE 0 /* keep iterating */
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