core: skip deps on oomd if v2 or memory unavailable

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2055664
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2172146
User report that systemd repeatedly logs about not being able to start oomd
when booted with v1:

Feb 20 16:52:33   systemd[1]: systemd-oomd.service - Userspace Out-Of-Memory (OOM) Killer was skipped because of a failed condition check (ConditionControlGroupController=v2).
Feb 20 16:52:34   systemd[1]: systemd-oomd.service - Userspace Out-Of-Memory (OOM) Killer was skipped because of a failed condition check (ConditionControlGroupController=v2).
Feb 20 16:52:34   systemd[1]: systemd-oomd.service - Userspace Out-Of-Memory (OOM) Killer was skipped because of a failed condition check (ConditionControlGroupController=v2).
Feb 20 16:52:34   systemd[1]: systemd-oomd.service - Userspace Out-Of-Memory (OOM) Killer was skipped because of a failed condition check (ConditionControlGroupController=v2).
Feb 20 16:52:34   systemd[1]: systemd-oomd.service - Userspace Out-Of-Memory (OOM) Killer was skipped because of a failed condition check (ConditionControlGroupController=v2).
Feb 20 16:52:34   systemd[1]: systemd-oomd.service - Userspace Out-Of-Memory (OOM) Killer was skipped because of a failed condition check (ConditionControlGroupController=v2).
Feb 20 16:52:34   systemd[2067491]: Queued start job for default target default.target.
Feb 20 16:52:34   systemd[1]: systemd-oomd.service - Userspace Out-Of-Memory (OOM) Killer was skipped because of a failed condition check (ConditionControlGroupController=v2).
Feb 20 16:52:34   systemd[2067491]: Created slice app.slice - User Application Slice.
Feb 20 16:52:34   systemd[1]: systemd-oomd.service - Userspace Out-Of-Memory (OOM) Killer was skipped because of a failed condition check (ConditionControlGroupController=v2).

systemd-oomd.service that pulls systemd-oomd.socket in (because it requires
it); systemd-oomd.service itself is pulled by user@.service because
systemd-oomd package installs an override config file that sets
ManagedOOMMemoryPressure=kill.

Add a check to the code that adds the implicit dependency to skip the
dep if we cannot start it. The check is done exactly the same as in oomd
itself.

diff --git a/src/core/unit.c b/src/core/unit.c
index e3a57e3b843538d35f3b06b33c12c145c83a2af5..642db41e41b6c900a25e8fee2e4c14412714f1c2 100644 (file)
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -1546,7 +1546,8 @@ static int unit_add_mount_dependencies(Unit *u) {
 
 static int unit_add_oomd_dependencies(Unit *u) {
         CGroupContext *c;
-        bool wants_oomd;
+        CGroupMask mask;
+        int r;
 
         assert(u);
 
@@ -1557,10 +1558,20 @@ static int unit_add_oomd_dependencies(Unit *u) {
         if (!c)
                 return 0;
 
-        wants_oomd = (c->moom_swap == MANAGED_OOM_KILL || c->moom_mem_pressure == MANAGED_OOM_KILL);
+        bool wants_oomd = c->moom_swap == MANAGED_OOM_KILL || c->moom_mem_pressure == MANAGED_OOM_KILL;
         if (!wants_oomd)
                 return 0;
 
+        if (!cg_all_unified())
+                return 0;
+
+        r = cg_mask_supported(&mask);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to determine supported controllers: %m");
+
+        if (!FLAGS_SET(mask, CGROUP_MASK_MEMORY))
+                return 0;
+
         return unit_add_two_dependencies_by_name(u, UNIT_AFTER, UNIT_WANTS, "systemd-oomd.service", true, UNIT_DEPENDENCY_FILE);
 }