Non-default root subvolume reset on hook if not top-level

[rbellamy]

I have the following:

__system
__system/ROOT
__system/home
__system_snapshots

With __system/ROOT set as the default subvolume.

I then boot, and the default subvolume is set to __system, regardless of the value of BTRFS_DIR_ACTIVE in /etc/defaults/btrfs_advanced

I realize now after reading some more and looking at the code, that this is by design. But thought someone else might find it useful if it were mentioned here.

[visit1985]

Hi @rbellamy,

I've tested it, and can't get whats wrong with your setup. In my opinion it should work. Check out the following.

Setup a test partition, like your's:

$ cd /tmp
$ sudo su
# dd if=/dev/urandom of=./drive count=100 bs=1M
# losetup /dev/loop0 ./drive
# mkfs.btrfs -L test /dev/loop0
# mkdir ./test
# mount /dev/loop0 ./test
# cd ./test
# btrfs su cr __system
# btrfs su cr __system/root
# btrfs su cr __system/home
# btrfs su cr __snapshot
# btrfs subvolume list . --sort=gen | awk '{print $2 ",/" $9}'
257,/__system/root
256,/__system
258,/__system/home
259,/__snapshot

Now use some code from mkinitcpio-btrfs:

# work="."
# BTRFS_DIR_ACTIVE="/__system/root"
# x="$(btrfs subvolume list ${work} | awk '{print $2 ",/" $9}' | grep -E "^[0-9]*,${BTRFS_DIR_ACTIVE}$")"
# BTRFS_BOOT_SUBVOL=${x#*,}
# BTRFS_BOOT_SUBVOLID=${x%,*}
# btrfs subvolume set-default ${BTRFS_BOOT_SUBVOLID} ${work}

And here comes the result:

# btrfs subvolume get-default ${work}
ID 257 gen 7 top level 5 path __system/root

Finally cleanup:

# cd ..
# umount ./test
# losetup -d /dev/loop0
# rm ./drive
# exit

I don't understand it, can you give me a hint?

[rbellamy]

Oh wow... sorry just noticed your request for more info. I've tried to reproduce, and haven't been able to... so closing this is the right thing. Sorry for the late response.

[visit1985]

This was not meant to be offense. And I had a long response time too :) If you are able to provide the requested infos, please reopen it any time.