tree_len = be32_to_cpu(agf->agf_rmap_blocks);
xfs_trans_brelse(tp, agbp);
+ /*
+ * The log is permanently allocated, so the space it occupies will
+ * never be available for the kinds of things that would require btree
+ * expansion. We therefore can pretend the space isn't there.
+ */
+ if (mp->m_sb.sb_logstart &&
+ XFS_FSB_TO_AGNO(mp, mp->m_sb.sb_logstart) == agno)
+ agblocks -= mp->m_sb.sb_logblocks;
+
/* Reserve 1% of the AG or enough for 1 block per record. */
*ask += max(agblocks / 100, xfs_rmapbt_max_size(mp, agblocks));
*used += tree_len;