unit: don't bother determining unit install state for transient or perpetual units (systemd#36504)

Author: yuwata

src/core/unit.c

@@ -107,7 +107,7 @@ Unit* unit_new(Manager *m, size_t size) {
         u->type = _UNIT_TYPE_INVALID;
         u->default_dependencies = true;
         u->unit_file_state = _UNIT_FILE_STATE_INVALID;
-        u->unit_file_preset = -1;
+        u->unit_file_preset = _PRESET_ACTION_INVALID;
         u->on_failure_job_mode = JOB_REPLACE;
         u->on_success_job_mode = JOB_FAIL;
         u->job_timeout = USEC_INFINITY;
@@ -4149,15 +4149,21 @@ UnitFileState unit_get_unit_file_state(Unit *u) {
 
         assert(u);
 
-        if (u->unit_file_state < 0 && u->fragment_path) {
-                r = unit_file_get_state(
-                                u->manager->runtime_scope,
-                                NULL,
-                                u->id,
-                                &u->unit_file_state);
-                if (r < 0)
-                        u->unit_file_state = UNIT_FILE_BAD;
-        }
+        if (u->unit_file_state >= 0 || !u->fragment_path)
+                return u->unit_file_state;
+
+        /* If we know this is a transient unit no need to ask the unit file state for details. Let's bypass
+         * the more expensive on-disk check. */
+        if (u->transient)
+                return (u->unit_file_state = UNIT_FILE_TRANSIENT);
+
+        r = unit_file_get_state(
+                        u->manager->runtime_scope,
+                        /* root_dir= */ NULL,
+                        u->id,
+                        &u->unit_file_state);
+        if (r < 0)
+                u->unit_file_state = UNIT_FILE_BAD;
 
         return u->unit_file_state;
 }
@@ -4167,24 +4173,26 @@ PresetAction unit_get_unit_file_preset(Unit *u) {
 
         assert(u);
 
-        if (u->unit_file_preset < 0 && u->fragment_path) {
-                _cleanup_free_ char *bn = NULL;
+        if (u->unit_file_preset >= 0)
+                return u->unit_file_preset;
 
-                r = path_extract_filename(u->fragment_path, &bn);
-                if (r < 0)
-                        return (u->unit_file_preset = r);
+        /* If this is a transient or perpetual unit file it doesn't make much sense to ask the preset
+         * database about this, because enabling/disabling makes no sense for either. Hence don't. */
+        if (!u->fragment_path || u->transient || u->perpetual)
+                return (u->unit_file_preset = -ENOEXEC);
 
-                if (r == O_DIRECTORY)
-                        return (u->unit_file_preset = -EISDIR);
+        _cleanup_free_ char *bn = NULL;
+        r = path_extract_filename(u->fragment_path, &bn);
+        if (r < 0)
+                return (u->unit_file_preset = r);
+        if (r == O_DIRECTORY)
+                return (u->unit_file_preset = -EISDIR);
 
-                u->unit_file_preset = unit_file_query_preset(
+        return (u->unit_file_preset = unit_file_query_preset(
                                 u->manager->runtime_scope,
-                                NULL,
+                                /* root_dir= */ NULL,
                                 bn,
-                                NULL);
-        }
-
-        return u->unit_file_preset;
+                                /* cache= */ NULL));
 }
 
 Unit* unit_ref_set(UnitRef *ref, Unit *source, Unit *target) {