Quiz: what a process is doing

Read the output

Why does touch in /mnt/archive print Input/output error, although findmnt shows rw?

$ sudo dmesg -T | tail -n 3
[Tue Oct 20 23:49:21 2026] EXT4-fs error (device loop0): ext4_lookup:1864: inode #19: comm cat: iget: checksum invalid
[Tue Oct 20 23:49:21 2026] Aborting journal on device loop0-8.
[Tue Oct 20 23:49:21 2026] EXT4-fs (loop0): Remounting filesystem read-only
$ findmnt -n -o OPTIONS /mnt/archive
rw,relatime

• A The loop0 disk was detached from the machine.
• B The kernel found damage in ext4 and switched writing off inside the filesystem without changing the mount options.
• C The cat process holds the file and blocks writing.