mkfs.ext4 on flashcache device failed

[brucewanght]

Hi, I modified some codes of bio in flashcache in order to use it in a archlinux with linux kernel 4.14, and when I did these following steps, I failed to make a ext4 filesystem on the flashcache device. Below is my experiment, can anyone help me out?

steps：

1. I create 2 loop devices to serve as HDD(/dev/loop2) and SSD(/dev/loop1).

2. sudo flashcache_create -p around cachedev /dev/loop1 /dev/loop2

3. sudo mkfs.ext4 /dev/mapper/cachedev

   Then, problem shows like this:

mke2fs 1.43.7 (16-Oct-2017)
Warning: could not erase sector 2: Input/output error
Creating filesystem with 1310720 4k blocks and 327680 inodes
Filesystem UUID: 1cb0462c-9bb1-4c62-a101-5d98a9d98b77
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736

Allocating group tables: done
Warning: could not read block 0: Input/output error
Warning: could not erase sector 0: Input/output error
Writing inode tables: done
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: 0/40
Warning, had trouble writing out superblocks.

And the dmesg shows many errors like these:

device-mapper: flashcache: flashcache uncached disk IO error: io error -5 block 4579304 R/w WRITE