1debugfs: ex /a
2Level Entries       Logical      Physical Length Flags
3 0/ 1   1/  2     0 -    16     9             17
4 1/ 1   1/  4     0 -     0    10 -    10      1
5 1/ 1   2/  4    11 -    11   100 -   100      1
6 1/ 1   3/  4    13 -    13   101 -   101      1
7 1/ 1   4/  4    15 -    15   102 -   102      1
8 0/ 1   2/  2    17 -    21    12              5
9 1/ 1   1/  3    17 -    17   103 -   103      1
10 1/ 1   2/  3    19 -    19   104 -   104      1
11 1/ 1   3/  3    21 -    21   105 -   105      1
12Pass 1: Checking inodes, blocks, and sizes
13Inode 12 extent tree (at level 1) could be narrower.  Optimize? yes
14
15Pass 1E: Optimizing extent trees
16Pass 2: Checking directory structure
17Pass 3: Checking directory connectivity
18Pass 4: Checking reference counts
19Pass 5: Checking group summary information
20
21test_filesys: ***** FILE SYSTEM WAS MODIFIED *****
22test_filesys: 12/128 files (8.3% non-contiguous), 26/512 blocks
23Exit status is 0
24