systemd/mdadm-last-resort: use ConditionPathExists instead of Conflicts

Commit cec72c071bbe ("systemd/mdadm-last-resort: add Conflicts to .service file.")

added a 'Conflicts' directive to the mdadm-last-resort@.service file in
the hope that this would make sure the service didn't run after the device
was active, even if the timer managed to get started, which is possible in
race conditions.

This seemed to work is testing, but it isn't clear why, and it is known
to cause problems.
If systemd happens to know that the mentioned device is a dependency of a
mount point, the Conflicts can unmount that mountpoint, which is certainly
not wanted.

So remove the "Conflicts" and instead use
 ConditionPathExists=!/sys/devices/virtual/block/%i/md/sync_action

The "sync_action" file exists for any array which requires last-resort
handling, and only appears when the array is activated.  So it is safe
to rely on it to determine if the last-resort is really needed.

Fixes: cec72c071bbe ("systemd/mdadm-last-resort: add Conflicts to .service file.")
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Jes Sorensen <jsorensen@fb.com>

diff --git a/systemd/mdadm-last-resort@.service b/systemd/mdadm-last-resort@.service
index e93d72b2b45e4eca6ad8146b71fd31dff19f8c79..f9d4d12738a3b776517c7cf0aa61f99a5296f397 100644 (file)
--- a/systemd/mdadm-last-resort@.service
+++ b/systemd/mdadm-last-resort@.service
@@ -1,7 +1,7 @@
 [Unit]
 Description=Activate md array even though degraded
 DefaultDependencies=no
-Conflicts=sys-devices-virtual-block-%i.device
+ConditionPathExists=!/sys/devices/virtual/block/%i/md/sync_action
 
 [Service]
 Type=oneshot