root[249] ~
# mkfs.xfs -V
mkfs.xfs version 3.2.1
root[250] ~
# mkfs.xfs /dev/mmcblk0p6
mkfs.xfs: /dev/mmcblk0p6 appears to contain an existing filesystem (xfs).
mkfs.xfs: Use the -f option to force overwrite.
root[251] ~
# mkfs.xfs -f /dev/mmcblk0p6
meta-data=/dev/mmcblk0p6         isize=256    agcount=4, agsize=551008 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=0        finobt=0
data     =                       bsize=4096   blocks=2204032, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=0
log      =internal log           bsize=4096   blocks=2560, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
root[252] ~
# mount /dev/mmcblk0p6 /media/p6                
[38946.599770] XFS (mmcblk0p6): Mounting V4 Filesystem
[38946.800708] XFS (mmcblk0p6): Ending clean mount

# xfs_io -f -c "pwrite 0 64k" -c sync \
                       -c "bmap -vp" -c "fiemap -v" \
                       -c "falloc 1024k 256k" -c sync \
                       -c "pwrite 1088k 64k" -c sync \
                       -c "bmap -vp" -c "fiemap -v" \
                       /media/p6/testfile
wrote 65536/65536 bytes at offset 0
64 KiB, 16 ops; 0.0000 sec (96.154 MiB/sec and 24615.3846 ops/sec)
command "sync" not found
/media/p6/testfile:
 EXT: FILE-OFFSET      BLOCK-RANGE      AG AG-OFFSET        TOTAL FLAGS
   0: [0..127]:        96..223           0 (96..223)          128 00000
/media/p6/testfile:
 EXT: FILE-OFFSET      BLOCK-RANGE      TOTAL FLAGS
   0: [0..127]:        96..223            128   0x1
command "sync" not found
wrote 65536/65536 bytes at offset 1114112
64 KiB, 16 ops; 0.0000 sec (112.208 MiB/sec and 28725.3142 ops/sec)
command "sync" not found
/media/p6/testfile:
 EXT: FILE-OFFSET      BLOCK-RANGE      AG AG-OFFSET        TOTAL FLAGS
   0: [0..127]:        96..223           0 (96..223)          128 00000
   1: [128..2047]:     hole                                  1920
   2: [2048..2559]:    2144..2655        0 (2144..2655)       512 10000
/media/p6/testfile:
 EXT: FILE-OFFSET      BLOCK-RANGE      TOTAL FLAGS
   0: [0..127]:        96..223            128   0x0
   1: [128..2047]:     hole              1920
   2: [2048..2175]:    2144..2271         128 0x800
   3: [2176..2303]:    2272..2399         128   0x0
   4: [2304..2559]:    2400..2655         256 0x801

Step by step xfs_io
-------------------

Due to the "sync" is missing, i tried also command by command with
shell "sync" after each command. Output is exactly the same.