mke2fs -F -b 4096 -o Linux -t ext4 -O ^metadata_csum,^uninit_bg -D $LOOP
Creating filesystem with 32768 4k blocks and 32768 inodes

Allocating group tables:    done                            
Writing inode tables:    done                            
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information:    done

debugfs -D -R stats $LOOP
Filesystem volume name:   <none>
Last mounted on:          <not available>
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file dir_nlink extra_isize
Default mount options:    (none)
Filesystem state:         clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              32768
Block count:              32768
Reserved block count:     1638
Overhead clusters:        6155
Free blocks:              26607
Free inodes:              32757
First block:              0
Block size:               4096
Fragment size:            4096
Reserved GDT blocks:      7
Blocks per group:         32768
Fragments per group:      32768
Inodes per group:         32768
Inode blocks per group:   2048
Flex block group size:    16
Mount count:              0
Check interval:           15552000 (6 months)
Reserved blocks uid:      0
Reserved blocks gid:      0
First inode:              11
Inode size:               256
Required extra isize:     32
Desired extra isize:      32
Journal inode:            8
Default directory hash:   half_md4
Journal backup:           inode blocks
Directories:              2
 Group  0: block bitmap at 9, inode bitmap at 25, inode table at 41
           26607 free blocks, 32757 free inodes, 2 used directories
e2fsck -fn -N test_filesys $LOOP
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
test_filesys: 11/32768 files (9.1% non-contiguous), 6161/32768 blocks
Exit status is 0
e2fsck -fn -N test_filesys $TMPFILE
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
test_filesys: 11/32768 files (9.1% non-contiguous), 6161/32768 blocks
Exit status is 0
