homed: explicitly deactivate all home directories on shutdown

Let's explicitly deactivate all home dirs on shutdown, in order to
properly synchronizing unmounting and avoiding blocking devices.

Previously, we'd rely on automatic deactivation when home directories
become unused. However, that scheme is asynchronous, and ongoing
deactviations might conflicts with attempts to unmount /home. Let's fix
that by providing an explicit service systemd-homed-activate.service
whose only job is to have a ExecStop= line that explicitly deactivates
all home directories on shutdown. This service can the be ordered after
home.mount and similar, ensuring that we'll first deactivate all homes
before deactivating /home itself during shutdown.

This is kept separate from systemd-homed.service so that it is possible
to restart systemd-homed.service without deactivating all home
directories.

Fixes: #16842

1 files changed, 40 insertions, 1 deletions

diff --git a/src/home/homed-manager-bus.c b/src/home/homed-manager-bus.c
index fa3acb5244..a599c58297 100644
--- a/src/home/homed-manager-bus.c
+++ b/src/home/homed-manager-bus.c
@@ -591,7 +591,45 @@ static int method_lock_all_homes(sd_bus_message *message, void *userdata, sd_bus
         }
 
         if (waiting) /* At least one lock operation was enqeued, let's leave here without a reply: it will
-                        * be sent as soon as the last of the lock operations completed. */
+                      * be sent as soon as the last of the lock operations completed. */
+                return 1;
+
+        return sd_bus_reply_method_return(message, NULL);
+}
+
+static int method_deactivate_all_homes(sd_bus_message *message, void *userdata, sd_bus_error *error) {
+        _cleanup_(operation_unrefp) Operation *o = NULL;
+        bool waiting = false;
+        Manager *m = userdata;
+        Home *h;
+        int r;
+
+        assert(m);
+
+        /* This is called from systemd-homed-activate.service's ExecStop= command to ensure that all home
+         * directories are shutdown before the system goes down. Note that we don't do this from
+         * systemd-homed.service itself since we want to allow restarting of it without tearing down all home
+         * directories. */
+
+        HASHMAP_FOREACH(h, m->homes_by_name) {
+
+                if (!o) {
+                        o = operation_new(OPERATION_DEACTIVATE_ALL, message);
+                        if (!o)
+                                return -ENOMEM;
+                }
+
+                log_info("Automatically deactivating home of user %s.", h->user_name);
+
+                r = home_schedule_operation(h, o, error);
+                if (r < 0)
+                        return r;
+
+                waiting = true;
+        }
+
+        if (waiting) /* At least one lock operation was enqeued, let's leave here without a reply: it will be
+                      * sent as soon as the last of the deactivation operations completed. */
                 return 1;
 
         return sd_bus_reply_method_return(message, NULL);
@@ -804,6 +842,7 @@ static const sd_bus_vtable manager_vtable[] = {
 
         /* An operation that acts on all homes that allow it */
         SD_BUS_METHOD("LockAllHomes", NULL, NULL, method_lock_all_homes, 0),
+        SD_BUS_METHOD("DeactivateAllHomes", NULL, NULL, method_deactivate_all_homes, 0),
 
         SD_BUS_VTABLE_END
 };