Assumption on fixed device numbers in Plasma's desktop search Baloo

[Martin Steigerwald <martin@lichtvoll.de>]

Hi!

I found repeatedly that Baloo indexes the same files twice or even more 
often after a while.

I reported this upstream in:

Bug 438434 - Baloo appears to be indexing twice the number of files than 
are actually in my home directory 

https://bugs.kde.org/show_bug.cgi?id=438434

And got back that if the device number changes, Baloo will think it has 
new files even tough the path is still the same. And found over time that 
the device number for the single BTRFS filesystem on a NVMe SSD in a 
ThinkPad T14 Gen1 AMD can change. It is not (maybe yet) RAID 1. I do 
have BTRFS RAID 1 in another laptop and there I also had this issue 
already.

I argued that a desktop application has no business to rely on a device 
number and got back that search/indexing is in the middle between an 
application and system software. And that Baloo needs an "invariant" for 
a file. See comment #11 of that bug report:

https://bugs.kde.org/show_bug.cgi?id=438434#c11

I got the suggestion to try to find a way to tell the kernel to use a 
fixed device number. 

I still think, an application or an infrastructure service for a desktop 
environment or even anything else in user space should not rely on a 
device number to be fixed and never change upon reboots.

But maybe you have a different idea about that and it is okay for an 
userspace component to do that. I would like to hear your idea about 
that.

Another question would be whether I could somehow make sure that the 
device number does not change, even if just as a work-around. I know for 
NFS there is a fsid= mount option, but it does not appear to be 
something generic, at least the mount man page seems to have nothing 
related to fsid.


Best,
-- 
Martin