systemctl: restore "systemctl reboot ARG" functionality

Commit d85515edcf9700dc068201ab9f7103f04f3b25b2 changed logic how reboot is
executed. That commit changed behavior to use emergency action reboot code path
to perform the reboot.

This inadvertently broke rebooting with argument:
$ systemctl reboot custom-reason

Restore original behavior so that if reboot service unit similar to
systemd-reboot.service is executed it is possible to override reboot reason
with "systemctl reboot ARG".

When "systemctl reboot ARG" is executed ARG is placed in file
/run/systemd/reboot-param and reboot is issued using logind's Reboot
dbus-service.

If RebootArgument is specified in systemd-reboot.service it takes precedence
over what systemctl sets.

Fixes: #11828

4 files changed, 9 insertions, 6 deletions

diff --git a/src/core/emergency-action.c b/src/core/emergency-action.c
index 9731aef5c44..09f8d740927 100644
--- a/src/core/emergency-action.c
+++ b/src/core/emergency-action.c
@@ -47,7 +47,7 @@ void emergency_action(
         case EMERGENCY_ACTION_REBOOT:
                 log_and_status(m, warn, "Rebooting", reason);
 
-                (void) update_reboot_parameter_and_warn(reboot_arg);
+                (void) update_reboot_parameter_and_warn(reboot_arg, true);
                 (void) manager_add_job_by_name_and_warn(m, JOB_START, SPECIAL_REBOOT_TARGET, JOB_REPLACE_IRREVERSIBLY, NULL);
 
                 break;
@@ -55,7 +55,7 @@ void emergency_action(
         case EMERGENCY_ACTION_REBOOT_FORCE:
                 log_and_status(m, warn, "Forcibly rebooting", reason);
 
-                (void) update_reboot_parameter_and_warn(reboot_arg);
+                (void) update_reboot_parameter_and_warn(reboot_arg, true);
                 m->objective = MANAGER_REBOOT;
 
                 break;
diff --git a/src/shared/reboot-util.c b/src/shared/reboot-util.c
index ca40159b966..6d5eee03173 100644
--- a/src/shared/reboot-util.c
+++ b/src/shared/reboot-util.c
@@ -12,10 +12,13 @@
 #include "umask-util.h"
 #include "virt.h"
 
-int update_reboot_parameter_and_warn(const char *parameter) {
+int update_reboot_parameter_and_warn(const char *parameter, bool keep) {
         int r;
 
         if (isempty(parameter)) {
+                if (keep)
+                        return 0;
+
                 if (unlink("/run/systemd/reboot-param") < 0) {
                         if (errno == ENOENT)
                                 return 0;
diff --git a/src/shared/reboot-util.h b/src/shared/reboot-util.h
index d459333efcc..ac59b7d79c6 100644
--- a/src/shared/reboot-util.h
+++ b/src/shared/reboot-util.h
@@ -1,7 +1,7 @@
 /* SPDX-License-Identifier: LGPL-2.1+ */
 #pragma once
 
-int update_reboot_parameter_and_warn(const char *parameter);
+int update_reboot_parameter_and_warn(const char *parameter, bool keep);
 
 typedef enum RebootFlags {
         REBOOT_LOG      = 1 << 0, /* log about what we are going to do and all errors */
diff --git a/src/systemctl/systemctl.c b/src/systemctl/systemctl.c
index afe6f84f774..d49d3878a9f 100644
--- a/src/systemctl/systemctl.c
+++ b/src/systemctl/systemctl.c
@@ -3735,7 +3735,7 @@ static int start_special(int argc, char *argv[], void *userdata) {
                 return r;
 
         if (a == ACTION_REBOOT && argc > 1) {
-                r = update_reboot_parameter_and_warn(argv[1]);
+                r = update_reboot_parameter_and_warn(argv[1], false);
                 if (r < 0)
                         return r;
 
@@ -8444,7 +8444,7 @@ static int halt_parse_argv(int argc, char *argv[]) {
                 }
 
         if (arg_action == ACTION_REBOOT && (argc == optind || argc == optind + 1)) {
-                r = update_reboot_parameter_and_warn(argc == optind + 1 ? argv[optind] : NULL);
+                r = update_reboot_parameter_and_warn(argc == optind + 1 ? argv[optind] : NULL, false);
                 if (r < 0)
                         return r;
         } else if (optind < argc)