+/*
+ * Logging inodes is really tricksy. They are logged in memory format,
+ * which means that what we write into the log doesn't directly translate into
+ * the amount of space they use on disk.
+ *
+ * Case in point - btree format forks in memory format use more space than the
+ * on-disk format. In memory, the buffer contains a normal btree block header so
+ * the btree code can treat it as though it is just another generic buffer.
+ * However, when we write it to the inode fork, we don't write all of this
+ * header as it isn't needed. e.g. the root is only ever in the inode, so
+ * there's no need for sibling pointers which would waste 16 bytes of space.
+ *
+ * Hence when we have an inode with a maximally sized btree format fork, then
+ * amount of information we actually log is greater than the size of the inode
+ * on disk. Hence we need an inode reservation function that calculates all this
+ * correctly. So, we log:
+ *
+ * - log op headers for object
+ * - inode log format object
+ * - the entire inode contents (core + 2 forks)
+ * - two bmap btree block headers
+ */
+STATIC uint
+xfs_calc_inode_res(
+ struct xfs_mount *mp,
+ uint ninodes)
+{
+ return ninodes * (sizeof(struct xlog_op_header) +
+ sizeof(struct xfs_inode_log_format) +
+ mp->m_sb.sb_inodesize +
+ 2 * XFS_BMBT_BLOCK_LEN(mp));
+}
+