Hello. I'm currently working on improving disko's support for bcachefs. So far, I have made a PR to add encryption support. Currently, I am working on adding subvolume support. However, I am having trouble getting this to work. This is the output when I run nix build --no-link .#checks.x86_64-linux.bcachefs-subvolumes --show-trace -L -v.

I suspect that a reason that this could happening might be due the order in which mountpoints are mounted. My theory is that descendant mountpoints (e.g., /ancestor/descendant) could be being mounted before ancestor mountpoints (e.g., /ancestor) have been created/mounted.

Does disko mount filesystems such that ancestor mountpoints are mounted before descendants, or is this behaviour dependent on how the _mount option (made with diskoLib.mkMountOption) for the relevant filesystem type is implemented?

I have tried to debug my implementation using nix build .#checks.x86_64-linux.bcachefs-subvolumes.driverInteractive; result/bin/nixos-test-driver --keep-vm-state, but this doesn't seem to be working properly, as it doesn't show the bcachefs filesystem that should have been created:

$ lsblk -f
NAME FSTYPE FSVER LABEL UUID                                 FSAVAIL FSUSE% MOUNTPOINTS
fd0                                                                         
sr0                                                                         
vda  ext4   1.0   nixos a7ac900e-9d30-45da-b745-56d7d190aedd  888.3M     2% /
vdb  

In fact, it shows that same lsblk output for various other examples I tried it with (I also tried it with btrfs-subvolumes and simple-efi).

Is there another way I can go about debugging this?

I am having (skill) issues resizing my .swapvol after I have mistakenly put it to 20M instead of 16G,
I've tried to do

% sudo btrfs filesystem resize "+16G" "/.swapvol"
Resize device id 1 (/dev/mapper/crypted) from 476.42GiB to 492.42GiB
ERROR: unable to resize '/.swapvol': no enough free space

but

% df -h | \grep -E 'Avail|.swapvol'
Filesystem           Size  Used Avail Use% Mounted on
/dev/mapper/crypted  477G   88G  389G  19% /.swapvol

% sudo btrfs filesystem df /.swapvol
Data, single: total=80.00GiB, used=77.80GiB
System, DUP: total=32.00MiB, used=16.00KiB
Metadata, DUP: total=5.00GiB, used=4.52GiB
GlobalReserve, single: total=243.62MiB, used=0.00B

Is there a way to get Disko to just resize a subvolume?

In reply to @projectinitiative:matrix.org

Hey! I was working on adding advanced options for Bcachefs a few months ago. May want to poke around here: https://github.com/nix-community/disko/pull/961

There are some current gotchas that cause some of the issues you are facing. Using the bcachesfs fs formatter is limited which is why I went the route of creating a custom type similar to mdadm and zfs.

There are some systemd bugs that prevent the FS ground getting mounted properly/consistently during reboots

Oh cool! Thanks for sharing that, I didn't see it. It's good to see someone else working on this too. Maybe we can work together on this, so that work isn't duplicated?

What's your progress so far and what still needs to be done? I can see that you left a comment last month about trying to get encryption to work. Is that still the case? I believe I've got encryption working in my other PR, so if you like, I can try to adapt it to work with yours and submit a PR against yours?

I am having (skill) issues resizing my .swapvol after I have mistakenly put it to 20M instead of 16G,
I've tried to do

% sudo btrfs filesystem resize "+16G" "/.swapvol"
Resize device id 1 (/dev/mapper/crypted) from 476.42GiB to 492.42GiB
ERROR: unable to resize '/.swapvol': no enough free space

but

% df -h | \grep -E 'Avail|.swapvol'
Filesystem           Size  Used Avail Use% Mounted on
/dev/mapper/crypted  477G   88G  389G  19% /.swapvol

% sudo btrfs filesystem df /.swapvol
Data, single: total=80.00GiB, used=77.80GiB
System, DUP: total=32.00MiB, used=16.00KiB
Metadata, DUP: total=5.00GiB, used=4.52GiB
GlobalReserve, single: total=243.62MiB, used=0.00B

Is there a way to get Disko to just resize a subvolume?
I am tired of having my laptop fall over instead of just going slow if I try to compile something big or something else

I am having (skill) issues resizing my .swapvol after I have mistakenly put it to 20M instead of 16G,
I've tried to do

% sudo btrfs filesystem resize "+16G" "/.swapvol"
Resize device id 1 (/dev/mapper/crypted) from 476.42GiB to 492.42GiB
ERROR: unable to resize '/.swapvol': no enough free space

but

% df -h | \grep -E 'Avail|.swapvol'
Filesystem           Size  Used Avail Use% Mounted on
/dev/mapper/crypted  477G   88G  389G  19% /.swapvol

% sudo btrfs filesystem df /.swapvol
Data, single: total=80.00GiB, used=77.80GiB
System, DUP: total=32.00MiB, used=16.00KiB
Metadata, DUP: total=5.00GiB, used=4.52GiB
GlobalReserve, single: total=243.62MiB, used=0.00B

Is there a way to get Disko to just resize a subvolume?
I am tired of having my laptop fall over instead of just going slow if I try to compile something big or something else
I also tried to balance my drive

I think I did something stupid now

% sudo btrfs filesystem resize 16G /.swapvol
[sudo] password for sigurdb: 
Resize device id 1 (/dev/mapper/crypted) from 476.42GiB to 16.00GiB

I ctrl+c on the operation, the laptop fan spun up, btop showed the disk usage went bananas, but memory and cpu stayed low

I figured this out!

of course disko doesn't set usage limits on the subvolumes

and apparently I can't manually make my own swapfile on btrfs because chattr doesn't work.

But btrfs has a subcommand to make swapfiles!

This fixed my issue!

sudo btrfs filesystem mkswapfile --size 16G /.swapvol/swapfile

Thank you, is there any consideration I have to take when making subvolumes? I'd like it to be consistent with how disko makes it

                  "/snapshots" = {
                    mountpoint = "/snapshots";
                    mountOptions = [ "compress=zstd" "noatime" ];
                  };

When I sudo btrfs subvolume list /home -t I notice that there are no slashes in the path name

ID	gen	top level	path	
--	---	---------	----	
256	87522	5		home
257	87348	5		nix
258	87522	5		persist
259	87283	5		swap

In reply to @phaer:matrix.org
Was that recently or a while ago?