btrfs subvolume list: what is the meaning of "top level"

[Goffredo Baroncelli <kreijack@inwind.it>]

Hi all,

in "btrfs subvolume list" I supposed that "top level" is the subvolume
"father" tree id. But the example below shows that I am wrong.


ghigo@venice:/tmp$ uname -a
Linux venice 3.11.7 #142 SMP Wed Nov 6 19:25:46 CET 2013 x86_64 GNU/Linux
ghigo@venice:/tmp$ sudo mkfs.btrfs /dev/loop0

WARNING! - Btrfs v0.20-rc1 IS EXPERIMENTAL
WARNING! - see http://btrfs.wiki.kernel.org before using

SMALL VOLUME: forcing mixed metadata/data groups
Created a data/metadata chunk of size 8388608
fs created label (null) on /dev/loop0
	nodesize 4096 leafsize 4096 sectorsize 4096 size 1001.00MB
Btrfs v0.20-rc1
ghigo@venice:/tmp$ sudo mount /dev/loop0 t/
ghigo@venice:/tmp$ sudo mkdir t/dir
ghigo@venice:/tmp$ sudo btrfs sub create t/sub1
Create subvolume 't/sub1'
ghigo@venice:/tmp$ sudo btrfs sub create t/dir/sub2
Create subvolume 't/dir/sub2'
ghigo@venice:/tmp$ sudo btrfs sub create t/dir/sub3
Create subvolume 't/dir/sub3'
ghigo@venice:/tmp$ sudo btrfs sub create t/dir/sub3/sub4
Create subvolume 't/dir/sub3/sub4'
ghigo@venice:/tmp$ sudo btrfs sub create t/sub5
Create subvolume 't/sub5'
ghigo@venice:/tmp$ sudo btrfs sub create t/sub5/sub6
Create subvolume 't/sub5/sub6'
ghigo@venice:/tmp$ sudo btrfs sub list t/ | nl
     1	ID 256 gen 5 top level 5 path sub1
     2	ID 257 gen 6 top level 5 path dir/sub2
     3	ID 258 gen 8 top level 5 path dir/sub3
     4	ID 259 gen 8 top level 5 path dir/sub3/sub4
     5	ID 260 gen 10 top level 5 path sub5
     6	ID 261 gen 10 top level 5 path sub5/sub6


I expected that in the line 4, the top level should be 258; the same for
the line 6: top level should be 260. So my question is: what is the
meaning of the "top level" value ?

Thanks.

BR
G.Baroncelli
-- 
gpg @keyserver.linux.it: Goffredo Baroncelli (kreijackATinwind.it>
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