Re: [PATCH] btrfs: Fix no space bug caused by removing bg

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

在 2015年09月23日 21:12, David Sterba 写道:
> On Tue, Sep 22, 2015 at 02:36:02PM +0000, Hugo Mills wrote:
>>> Yeah, right now there's no persistent default for the allocator. I'm
>>> still hoping that the object properties will magically solve that.
>>
>>     There's no obvious place that filesystem-wide properties can be
>> stored, though. There's a userspace tool to manipulate the few current
>> FS-wide properties, but that's all special-cased to use the
>> "historical" ioctls for those properties, with no generalisation of a
>> property store, or even (IIRC) any external API for them.
>
>  From the UI point, we proposed to add a specifier that would route the
> property to either subvolume or the filesystem:
>
> $ btrfs prop set -t filesystem bgtype raid0
> $ btrfs prop set -t subvolume bgtype raid1
>

BTW, is btrfs going to support different chunk/bg type for subvolume?!
I thought data/meta/system chunk types are all per filesystem level,
and was planning to use superblock to record it...

If really to support that, does it mean we will have different meta/data 
type for each subvolume?
That's a little too flex for me....

Thanks,
Qu

> How this will get stored in the xattrs is another question. As there's
> always only single instance of the filesystem properties, it coud be
> something like 'btrfs.fs.bgtype' and be stored as a xattr of the
> toplevel subvolume.
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