cannot mount bcachefs from lvm raid0 device

[jezcope]

Describe the bug

I have an LVM setup, and I've been trying out bcachefs by using it as scratch space (since it's stuff I don't mind losing) on an LVM RAID0 volume with 4 stripes. Since #304761 updated bcachefs-tools to 1.7.0 I can't mount this, but switching back to a previous generation with bcachefs-tools 1.4.1 or using bcachefs-tools 1.3.3 from nixos-23.11 lets me mount it just fine. Using a linear volume instead also works fine.

Steps To Reproduce

Steps to reproduce the behavior:

1. Create an LV with -t raid0 --stripes 2
2. Create a bcachefs filesystem on the new LV
3. Try to mount the new filesystem

Running bcachefs mount with -v results in:

INFO - bcachefs::commands::cmd_mount: mounting with params: device: /dev/dm-38:/dev/dm-40, target: /mnt, options: 
DEBUG - bcachefs::commands::cmd_mount: parsing mount options: 
INFO - bcachefs::commands::cmd_mount: mounting bcachefs filesystem, /mnt
INFO - bcachefs::commands::cmd_mount: mounting filesystem
ERROR - bcachefs::commands::cmd_mount: Fatal error: Device or resource busy

Expected behavior

Should mount correctly. Output from bcachefs-tools 1.3.3:

INFO - bcachefs_rust::cmd_mount: mounting with params: device: /dev/vg/test, target: /mnt, options: 
DEBUG - bcachefs_rust::cmd_mount: parsing mount options: 
INFO - bcachefs_rust::cmd_mount: mounting bcachefs filesystem, /mnt
INFO - bcachefs_rust::cmd_mount: mounting filesystem
INFO - bcachefs_rust::cmd_mount: Successfully mounted

Additional context

I don't know enough about Linux FS implementations, but suspect it might be an instance of koverstreet/bcachefs-tools#260

Notify maintainers

@davidak @JohnRTitor @Madouura

Metadata

Please run nix-shell -p nix-info --run "nix-info -m" and paste the result.

[user@system:~]$ nix-shell -p nix-info --run "nix-info -m"
 - system: `"x86_64-linux"`
 - host os: `Linux 6.9.1, NixOS, 24.05 (Uakari), 24.05.20240519.6c0b7a9`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Lix, like Nix) 2.90.0-beta.1-lixpre20240506-b6799ab`
 - channels(jez): `""`
 - channels(root): `"home-manager, nixos"`
 - nixpkgs: `/nix/store/r8nhgnkxacbnf4kv8kdi8b6ks3k9b16i-source`

---

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[JohnRTitor]

Is it an encrypted setup?

Can you try it with the updated upstream patch?

Test for both master and 1.7.0 branch

[jezcope]

No, unencrypted. Will give the patch a try... Thanks!

[jezcope]

Well, the patch doesn't make a difference, but that's ok because just building it from master at kentoverstreet/bcachefs-tools works fine. If I was a betting man I'd guess the issue is fixed by one of the udev-related commits from 7 May. It also gets rid of all the annoying warnings about not finding bcachefs superblocks as it walks the device tree.

Thanks for the pointers, I guess this will be fixed once nixpkgs gets bcachefs-tools 1.7.1?

[JohnRTitor]

So as I understand it, it is working on the bcachefs master branch, with or without the patch?

[jezcope]

Yes, that's correct. Using the following overlay to my nixpkgs causes everything to work as expected:

final: prev: { bcachefs-tools = inputs.bcachefs-tools.packages.${prev.system}.bcachefs; }

with:

inputs.bcachefs-tools.url = "github:koverstreet/bcachefs-tools";

and this in my flake.lock:

    "bcachefs-tools": {
      "inputs": {
        "flake-compat": "flake-compat",
        "nixpkgs": "nixpkgs",
        "utils": "utils"
      },
      "locked": {
        "lastModified": 1715290148,
        "narHash": "sha256-ZmkeYPiCy7vkXnMFbtUF4761K+I+Ef7UbmSY7dJG09U=",
        "owner": "koverstreet",
        "repo": "bcachefs-tools",
        "rev": "3ac510f6a41feb1b695381fa30869d557c00b822",
        "type": "github"
      },
      "original": {
        "owner": "koverstreet",
        "repo": "bcachefs-tools",
        "type": "github"
      }
    },

[JohnRTitor]

I am motivated to open #313424, as we don't want to ship a broken bcachefs-tools on 24.05. Please do test the PR.