[PATCH 0/6] multipath-tools: udev rules and service improvements

[Martin Wilck <martin.wilck@suse.com>]

The first 3 patches and patch 5 are minor fixes for the udev rules.

Patch 4 fixes an issue that was observed in partner tests. Since we dropped
the dependency on systemd-udev-settle.service, it's more common that
multipath sees paths being added to existing maps during boot and reloads
the maps. If this happens while udev is executing rules for an uevent
related to the map in question (most importantly, a coldplug event),
the rules may see the map as suspended, and will refrain from scanning
the device content.

https://systemd.io/BLOCK_DEVICE_LOCKING/ doesn't help us here. We would need
to take an exclusive lock an lock_multipath() to achieve that, but since
5ec07b3 ("libmultipath: use a shared lock to co-operate with udev") we
don't. We _might_ consider re-introducing exclusive locking, because the main
reason we don't was that udev would discard events for which it couldn't
obtain the lock. Since systemd 250, udev has a retry logic for such events
which would avoid this problem. We would also need to implement similar retry
logic in multipathd, though. For now, and because we need to support systemd
< 250 anyway, I've come up with the workaround in patch 4 (first tests went
well, but more testing is still needed).

Patch 5 is a partial fix for the the problem that multipathd socket activation
starts multipathd also on systems that don't need it. See
https://github.com/opensvc/multipath-tools/issues/76. More far-reaching
approaches have been discussed to avoid that the user needs to enable
multipathd explicitly if multipath hardware is present
(https://github.com/opensvc/multipath-tools/pull/78) but no solid solution
for that has emerged yet.

Reviews and comments welcome.

Martin Wilck (6):
  11-dm-mpath.rules: don't import properties that are already set
  11-dm-mpath.rules: fix list of imported properties
  11-dm-mpath.rules: use import logic like 13-dm-disk.rules
  11-dm-mpath.rules: handle reloads during coldplug events
  multipath: udev rules: use configured $(bindir) in udev rules
  multipathd: don't activate socket activation by default

 .gitignore                                    |  1 +
 Makefile.inc                                  |  2 +-
 ...11-dm-mpath.rules => 11-dm-mpath.rules.in} | 49 ++++++++++++++-----
 multipath/Makefile                            |  2 +-
 multipath/multipath.rules.in                  |  5 +-
 multipathd/multipathd.socket                  |  4 +-
 6 files changed, 45 insertions(+), 18 deletions(-)
 rename multipath/{11-dm-mpath.rules => 11-dm-mpath.rules.in} (73%)

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2.43.0