received uuid not set btrfs send/receive

From: Anders Halman <anders.halman@gmail.com>
To: linux-btrfs@vger.kernel.org
Subject: received uuid not set btrfs send/receive
Date: Sun, 17 Jan 2021 10:49:26 -0800	[thread overview]
Message-ID: <95f9479d-2217-768e-f866-ae42509c3b2c@gmail.com> (raw)

Hello,

I try to backup my laptop over an unreliable slow internet connection to 
a even slower Raspberry Pi.

To bootstrap the backup I used the following:

# local
btrfs send root.send.ro | pigz | split --verbose -d -b 1G
rsync -aHAXxv --numeric-ids --partial --progress -e "ssh -T -o 
Compression=no -x" x* remote-host:/mnt/backup/btrfs-backup/

# remote
cat x* > split.gz
pigz -d split.gz
btrfs receive -f split

worked nicely. But I don't understand why the "received uuid" on the 
remote site in blank.
I tried it locally with smaller volumes and it worked.

The 'split' file contains the correct uuid, but it is not set (remote).

remote$ btrfs receive --dump -f split | head
subvol          ./root.send.ro uuid=99a34963-3506-7e4c-a82d-93e337191684 
transid=1232187

local$ sudo btrfs sub show root.send.ro| grep -i uuid:
     UUID:             99a34963-3506-7e4c-a82d-93e337191684

Questions:

- Is there a way to set the "received uuid"?
- Is it a matter of btrfs-progs version difference?
- What whould be a better approach?

Thank you

----

# local

root@fos ~$ uname -a
Linux fos 5.9.16-200.fc33.x86_64 #1 SMP Mon Dec 21 14:08:22 UTC 2020 
x86_64 x86_64 x86_64 GNU/Linux

root@fos ~$   btrfs --version
btrfs-progs v5.9

root@fos ~$   btrfs fi show
Label: 'DATA'  uuid: b6e675b3-84e3-4869-b858-218c5f0ac5ad
     Total devices 1 FS bytes used 402.17GiB
     devid    1 size 464.27GiB used 414.06GiB path 
/dev/mapper/luks-e4e69cfa-faae-4af8-93f5-7b21b25ab4e6

root@fos ~$   btrfs fi df /btrfs-root/
Data, single: total=404.00GiB, used=397.80GiB
System, DUP: total=32.00MiB, used=64.00KiB
Metadata, DUP: total=5.00GiB, used=4.38GiB
GlobalReserve, single: total=512.00MiB, used=0.00B

# remote
root@pih:~# uname -a
Linux pih 5.4.72+ #1356 Thu Oct 22 13:56:00 BST 2020 armv6l GNU/Linux

root@pih:~#   btrfs --version
btrfs-progs v4.20.1

root@pih:~#   btrfs fi show
Label: 'DATA'  uuid: 6be1e09c-d1a5-469d-932b-a8d1c339afae
     Total devices 1 FS bytes used 377.57GiB
     devid    2 size 931.51GiB used 383.06GiB path 
/dev/mapper/luks_open_backup0

root@pih:~#   btrfs fi df /mnt/backup
Data, single: total=375.00GiB, used=374.25GiB
System, DUP: total=32.00MiB, used=64.00KiB
Metadata, DUP: total=4.00GiB, used=3.32GiB
GlobalReserve, single: total=512.00MiB, used=0.00B

dmesg is empty for the time of import/btrfs receive.