systemd-tmpfiles prints weird errors when setting file attributes that conflict

[brainpower]

systemd version the issue has been seen with

Arch Linux's 246.6-1

Used distribution

Arch Linux

Linux kernel version used (uname -a)

5.9.9-arch1-1

CPU architecture issue was seen on

x86-64

Expected behaviour you didn't see

systemd-tmpfiles not printing any errors

Unexpected behaviour you saw

systemd-tempfiles prints the following errors:

(2/3) Creating temporary files...
Cannot set file attribute for '/var/log/journal', value=0x00800000, mask=0x00800000, ignoring: Invalid argument
Cannot set file attribute for '/var/log/journal/1cd5XXXXXXXXXXXXXXXX32420fa', value=0x00800000, mask=0x00800000, ignoring: Invalid argument
Cannot set file attribute for '/var/log/journal/remote', value=0x00800000, mask=0x00800000, ignoring: Invalid argument

My investigation showed that these errors are only printed when compression was enabled on the directories systemd-tmpfiles tries to set the +C attribute on. Running chattr -c on the directories listed in the error messages fixed the errors.
It seems to me that compression and no CoW cannot be enabled together on btrfs.

Maybe this can be fixed by also disabling compression in master/tmpfiles.d/journal-nocow.conf, if thats possible, sensible and does not hurt on other filesystems?

The other issue here is, maybe the error messages could be improved? It took me some googling to get to the root of the issue...

Steps to reproduce the problem

Enable compression on a btrfs filesystem before systemd-tmpfiles creates /var/log/journal

EDIT: It seems this only happens if the attributes are used via chattr +c or btrfs property set ./dir compression lzo, but not when using the mount option compress=.
Sounds like there could be a btrfs bug at play here, too, but I dont think thats the case since btrfs(5) states for the nodatacow mount option: Nodatacow implies nodatasum, and disables compression.

also, showing that +c and +C seem to conflict:

% mkdir dir                                             
% lsattr                                                
-------------------- ./dir
% chattr +C dir                                         
% lsattr                                                
---------------C---- ./dir
% chattr +c dir                                         
chattr: Invalid argument while setting flags on dir
% lsattr                                                
---------------C---- ./dir
% chattr -C dir                                         
% chattr +c dir                                         
% lsattr                                                
--------c----------- ./dir
% chattr +C dir                                         
chattr: Invalid argument while setting flags on dir
% lsattr                                                
--------c----------- ./dir

[yuwata]

Fix is waiting in #17693.