1 files changed, 15 insertions, 7 deletions

diff --git a/fs/xfs/xfs_trans_resv.c b/fs/xfs/xfs_trans_resv.c
index 2ffd3e331b49..c486e4b9f2a7 100644
--- a/fs/xfs/xfs_trans_resv.c
+++ b/fs/xfs/xfs_trans_resv.c
@@ -81,20 +81,28 @@ xfs_calc_buf_res(
  * on disk. Hence we need an inode reservation function that calculates all this
  * correctly. So, we log:
  *
- * - log op headers for object
+ * - 4 log op headers for object
+ *      - for the ilf, the inode core and 2 forks
  * - inode log format object
- * - the entire inode contents (core + 2 forks)
- * - two bmap btree block headers
+ * - the inode core
+ * - two inode forks containing bmap btree root blocks.
+ *      - the btree data contained by both forks will fit into the inode size,
+ *        hence when combined with the inode core above, we have a total of the
+ *        actual inode size.
+ *      - the BMBT headers need to be accounted separately, as they are
+ *        additional to the records and pointers that fit inside the inode
+ *        forks.
  */
 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));
+        return ninodes *
+                (4 * sizeof(struct xlog_op_header) +
+                 sizeof(struct xfs_inode_log_format) +
+                 mp->m_sb.sb_inodesize +
+                 2 * XFS_BMBT_BLOCK_LEN(mp));
 }
 
 /*