Re: booting btrfs

[Chris Murphy]

On Oct 14, 2013, at 3:01 PM, Vladimir 'φ-coder/phcoder' Serbinenko 
<address@hidden> wrote:

> On 14.10.2013 22:45, Chris Murphy wrote:
>> 
>> 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.
>>> Is there a way to detect that mountinfo gives garbage and somehow get
>>> where the real root points?
>> 
>> Here's the response. It seems similar but not identical to what you 
>> described above.
>> 
>> http://www.mail-archive.com/address@hidden/msg27955.html
>> 
> Possibly this is the answer:
> === modified file 'grub-core/fs/btrfs.c'
> --- grub-core/fs/btrfs.c      2013-01-21 01:33:46 +0000
> +++ grub-core/fs/btrfs.c      2013-10-14 21:00:53 +0000
> @@ -1217,7 +1217,7 @@
> 
>   *type = GRUB_BTRFS_DIR_ITEM_TYPE_DIRECTORY;
>   *tree = data->sblock.root_tree;
> -  key->object_id = data->sblock.root_dir_objectid;
> +  key->object_id = grub_cpu_to_le64_compile_time (5);
>   key->type = GRUB_BTRFS_ITEM_TYPE_DIR_ITEM;
>   key->offset = 0;
>   skip_default = 1;
> 

I applied this to current bzr and built it. With the default default subvolume, 
i.e set-default is ID 5, I get:

GRUB loading ..
Welcome to GRUB!

error: file '/' not found.
Entering rescue mode…
grub rescue>


Chris Murphy