On Wed, Dec 03, 2014 at 08:02:31AM +0530, Shriramana Sharma wrote:
> On Tue, Dec 2, 2014 at 2:04 PM, Hugo Mills <hugo@carfax.org.uk> wrote:
> >
> >> Is that correct: what btr sub list shows as "top level" is indeed the
> >> parent subvolume?
> >
> >    No, it's the top-level subvolume. (See my earlier mail about
> > nomenclature). "Parent subvolume" has a number of meanings, none of
> > which should be "the subvolume with subvolid 5".
> 
> Um I searched my inbox but didn't find a specific definition from you
> for "top-level". You only said it's better to avoid calling it "root"
> to avoid confounding it with the subvol that may be mounted at root
> i.e. /.

   It was the first line I wrote in my first reply to your thread
about subvol 5 vs subvol 0. I had hoped to be both definitive and
comprehensive.

> IIUC the "top-level subvolume" can only be subvolid 5 which accords
> with your later comment:
> 
> > that putting files in the top-level subvol can't do what most people
> > want to do with it. Hence the recommended subvol management layout at
> > [1] https://btrfs.wiki.kernel.org/index.php/SysadminGuide#Subvolumes
> 
> ... which means that I am not able to understand the output of btr sub
> list which gives the subvolid of whichever subvol is currently the
> "parent" (as in outer nesting) subvol. Observe:
> 
> $ btr sub list .
> ID 257 gen 10 top level 5 path test1
> ID 258 gen 10 top level 5 path test2
> ID 259 gen 9 top level 258 path test2/foo
> $ sudo mv test2/foo test1/
> $ btr sub list .
> ID 257 gen 10 top level 5 path test1
> ID 258 gen 10 top level 5 path test2
> ID 259 gen 9 top level 257 path test1/foo
> $
> 
> So now what is the meaning of "top level"?

   Urgh. I haven't seriously looked at that piece of output in a
while. That's broken, in my opinion. Here, "top level" means
"containing subvolume ID".

   Hugo.

-- 
Hugo Mills             | "I don't like the look of it, I tell you." "Well,
hugo@... carfax.org.uk | stop looking at it, then."
http://carfax.org.uk/  |
PGP: 65E74AC0          |                                             The Goons