Re: generic name for volume and subvolume root?

[Hugo Mills <hugo@carfax.org.uk>]

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On Sat, Sep 09, 2017 at 06:58:38PM +0800, Qu Wenruo wrote:
> 
> 
> On 2017年09月09日 18:48, Ulli Horlacher wrote:
> >On Sat 2017-09-09 (18:40), Qu Wenruo wrote:
> >
> >>>Is there a generic name for both volume and subvolume root?
> >>
> >>Nope, subvolume (including snapshot) is not distinguished by its
> >>filename/path/directory name.
> >>
> >>And you can only do snapshot on subvolume (snapshot is one kind of
> >>subvolume) boundary.
> >
> >So, I can name a btrfs root volume also btrfs subvolume?
> 
> Yes, root volume is also a subvolume, so just call "btrfs root volume"
> a "subvolume".

   I find it's best to avoid the word "root" entirely, as it's got
several meanings, and it tends to get confusing in conversation.
Instead, we have:

 - "the top level" (subvolid=5)
 - "/"             (what you see at / in your running system)
 - "<top-level>/@" or similar names
                   (the subvolume that's mounted at /)

> >I am talking about documentation, not coding!
> >
> >I just want yo use the correct terms.
> 
> If you're referring to the term, I think subvolume is good enough.
> Which represents your original term, "directories one can snapshot".
> 
> 
> For the whole btrfs "volume", I would just call it "filesystem" to
> avoid the name "volume" or "subvolume" at all.

   Yes, it's a filesystem. (Although that does occasionally cause
confusion between "the conceptual filesystem implemented by btrfs.ko"
and "the concrete filesystem stored on /dev/sda1", but it's generally
far less confusing than the overloading of "root").

   Hugo.

-- 
Hugo Mills             | Well, you don't get to be a kernel hacker simply by
hugo@... carfax.org.uk | looking good in Speedos.
http://carfax.org.uk/  |
PGP: E2AB1DE4          |                                         Rusty Russell

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