> reading a raw device node (e.g. /dev/rdisk*)

That's... not bypassing the kernel. Time to integrate SPDK so it actually bypasses the kernel :)

https://spdk.io

supports ext4, btrfs, and apfs. Multithreaded, supports compression, nested volumes, and can even search detached volumes like .iso and .dmg without mounting

An interesting bonus point: you can't really vibe code it cause clankers can not run sudo commands

It works by reading the block device in /dev directly, wouldn't it also work on an HDD, flash drive or a memory card?

I don't think I'd ever trust or use this, but still, good job OP :)

In particular, can it be certain that a flush is really a flush?

  sudo setfacl -m u:$USER:r-- /dev/nvmen01p2 # or whatever

Or if you want to only give fff access,

  sudo groupadd diskreaders
  sudo setfacl -m g:diskreaders:r-- /dev/nvmen01p2
  sudo chown :diskreaders /path/to/fff
  sudo chmod g+s /path/to/fff

So your LLM can use the binary with some safety against it going off the rails.

Is it really faster than normal filesystem? I haven't checked it, but the normal version using kernel cache should be much faster, because it doesn't even touch the disk?