If any devices are marked with 'SYSTEMD_READY=0' then we shouldn't run any
btrfs check on them.
Indeed there's no point in running "btrfs ready" on devices that already have
SYSTEMD_READY=0 set. Most probably such devices are members of a higher layer
aggregate device such as dm-multipath or software RAID. Doing IO on them wastes
time at best, and may cause delays, timeouts, or even hangs at worst (think
active-passive multipath or degraded RAID, for example).
It was initially reported at:
https://bugzilla.opensuse.org/show_bug.cgi?id=872929
Commit 0e8856d2 (assemble multidevice btrfs volumes without external
tools (#6607)) introduced a call to udevadm. That lives in @rootbindir@,
not @rootlibexecdir@. So fix the path.
assemble multidevice btrfs volumes without external tools
This self-contained approach introduce very little overhead, unless
someone has a large number of devices composing many btrfs volumes,
in which case btrfs device scan would be faster. Still, having robust
implementation is a nice to have alternative for btrfs-progs.
Franck Bui