Comment 24 for bug 1950321

Hi Łukasz,
thanks for having a look - sure let me try to summarize an answer to your question.

# General

Yes - Debian has this enabled in both for what feels like ages.
It was the supportability in main which blocked us from following that, but we had plenty of requests and are happy to finally do so.

# qemu

This support has only effect if you call qemu with it enabled, that would be:
--drive file=gluster...
driver":"qcow2","file":{"driver":"gluster",
...

The important thing here is that so far this never worked, it would just tell you "Unknown protocol 'gluster'", but if not enabled it won't be used -> no regression for existing cases.

Not even the .so file will be loaded without calling it on the commandline:
$ strace -rtf -o q.strace qemu-system-x86_64
$ grep gluster.so q.strace
$ strace -rtf -o qg.strace qemu-system-x86_64 --drive file=gluster://192.0.2.1/testvol/a.img
$ grep gluster.so qg.strace
43900 12:49:01 (+ 0.000258) access("/usr/lib/x86_64-linux-gnu/qemu/block-gluster.so", F_OK) = 0
43900 12:49:01 (+ 0.000097) newfstatat(AT_FDCWD, "/usr/lib/x86_64-linux-gnu/qemu/block-gluster.so", {st_mode=S_IFREG|0644, st_size=39240, ...}, 0) = 0
43900 12:49:01 (+ 0.000103) openat(AT_FDCWD, "/usr/lib/x86_64-linux-gnu/qemu/block-gluster.so", O_RDONLY|O_CLOEXEC) = 3

Furthermore it is packaged in qemu-block-extra which is only a recommends. So someone that wants not even a bit to be present can remove that (also includes other less common block drivers like isci, ceph, ...)

# samba

Here it also is packaged separately in samba-vfs-modules which contains various optional samba extra features. People scared of gluster or any else can remove it.

Also does is it only active if configured in the samba config.
Details are here: https://www.samba.org/samba/docs/current/man-html/vfs_glusterfs.8.html
The TL;DR is (again as with qemu) that former users can't have it enabled yet (it would have failed always) and new users still need to enable it so that anything happens.