Re: booting btrfs

[Chris Murphy]

On Oct 14, 2013, at 1:29 PM, Vladimir 'φ-coder/phcoder' Serbinenko 
<address@hidden> wrote:

>> So it seems that GRUB is using relative pathnames to the default subvolume.
> This is not intentional. When this part of code was written there was no
> set-default available at all so this couldn't be tested and I simply
> followed the specification. It told to take root_tree and
> root_dir_objectid from superblock then go to "default" directory. What
> of this needs to be changed? Just remove "default" and make it part of
> path? We would need to change grub-mkrelpath to match runtime behaviour.

Somehow the default subvolume needs to be ignored and always start from top 
level 5 subvolume for full pathnames, which is what GRUB already seems to try 
to use for prefix. I'll inquire and hopefully get someone more knowledgable to 
reply here.


> Is there a way to detect that mountinfo gives garbage and somehow get
> where the real root points?

I don't know. I've asked on address@hidden Instead of rebooting, I merely tried 
mounting without options after changing the default subvolume to a nested 
subvolume (one attempt subvolume in a subvolume, another a subvolume in a 
directory): in both cases /proc/self/mountinfo reports / as the root, not the 
full path or ID of the subvolume actually mounted.

Somehow it seems like the mountinfo root field should return a block device and 
full path to the mounted subvolume or its ID. Currently it seems like a problem.


Chris Murphy