core: change return value of the unit's enumerate() call to void

We cannot handle enumeration failures in a sensible way, hence let's try
hard to continue without making such failures fatal, and log about it
with precise error messages.

src/core/device.c

@@ -602,7 +602,7 @@ static void device_shutdown(Manager *m) {
         m->devices_by_sysfs = hashmap_free(m->devices_by_sysfs);
 }
 
-static int device_enumerate(Manager *m) {
+static void device_enumerate(Manager *m) {
         _cleanup_udev_enumerate_unref_ struct udev_enumerate *e = NULL;
         struct udev_list_entry *item = NULL, *first = NULL;
         int r;
@@ -612,7 +612,7 @@ static int device_enumerate(Manager *m) {
         if (!m->udev_monitor) {
                 m->udev_monitor = udev_monitor_new_from_netlink(m->udev, "udev");
                 if (!m->udev_monitor) {
-                        r = -ENOMEM;
+                        log_oom();
                         goto fail;
                 }
 
@@ -622,37 +622,49 @@ static int device_enumerate(Manager *m) {
                 (void) udev_monitor_set_receive_buffer_size(m->udev_monitor, 128*1024*1024);
 
                 r = udev_monitor_filter_add_match_tag(m->udev_monitor, "systemd");
-                if (r < 0)
+                if (r < 0) {
+                        log_error_errno(r, "Failed to add udev tag match: %m");
                         goto fail;
+                }
 
                 r = udev_monitor_enable_receiving(m->udev_monitor);
-                if (r < 0)
+                if (r < 0) {
+                        log_error_errno(r, "Failed to enable udev event reception: %m");
                         goto fail;
+                }
 
                 r = sd_event_add_io(m->event, &m->udev_event_source, udev_monitor_get_fd(m->udev_monitor), EPOLLIN, device_dispatch_io, m);
-                if (r < 0)
+                if (r < 0) {
+                        log_error_errno(r, "Failed to watch udev file descriptor: %m");
                         goto fail;
+                }
 
                 (void) sd_event_source_set_description(m->udev_event_source, "device");
         }
 
         e = udev_enumerate_new(m->udev);
         if (!e) {
-                r = -ENOMEM;
+                log_oom();
                 goto fail;
         }
 
         r = udev_enumerate_add_match_tag(e, "systemd");
-        if (r < 0)
+        if (r < 0) {
+                log_error_errno(r, "Failed to create udev tag enumeration: %m");
                 goto fail;
+        }
 
         r = udev_enumerate_add_match_is_initialized(e);
-        if (r < 0)
+        if (r < 0) {
+                log_error_errno(r, "Failed to install initialization match into enumeration: %m");
                 goto fail;
+        }
 
         r = udev_enumerate_scan_devices(e);
-        if (r < 0)
+        if (r < 0) {
+                log_error_errno(r, "Failed to enumerate devices: %m");
                 goto fail;
+        }
 
         first = udev_enumerate_get_list_entry(e);
         udev_list_entry_foreach(item, first) {
@@ -675,13 +687,10 @@ static int device_enumerate(Manager *m) {
                 device_update_found_by_sysfs(m, sysfs, true, DEVICE_FOUND_UDEV, false);
         }
 
-        return 0;
+        return;
 
 fail:
-        log_error_errno(r, "Failed to enumerate devices: %m");
-
         device_shutdown(m);
-        return r;
 }
 
 static int device_dispatch_io(sd_event_source *source, int fd, uint32_t revents, void *userdata) {

src/core/manager.c

@@ -993,8 +993,7 @@ Manager* manager_free(Manager *m) {
         return NULL;
 }
 
-int manager_enumerate(Manager *m) {
+void manager_enumerate(Manager *m) {
-        int r = 0;
         UnitType c;
 
         assert(m);
@@ -1002,8 +1001,6 @@ int manager_enumerate(Manager *m) {
         /* Let's ask every type to load all units from disk/kernel
          * that it might know */
         for (c = 0; c < _UNIT_TYPE_MAX; c++) {
-                int q;
-
                 if (!unit_type_supported(c)) {
                         log_debug("Unit type .%s is not supported on this system.", unit_type_to_string(c));
                         continue;
@@ -1012,13 +1009,10 @@ int manager_enumerate(Manager *m) {
                 if (!unit_vtable[c]->enumerate)
                         continue;
 
-                q = unit_vtable[c]->enumerate(m);
+                unit_vtable[c]->enumerate(m);
-                if (q < 0)
-                        r = q;
         }
 
         manager_dispatch_load_queue(m);
-        return r;
 }
 
 static void manager_coldplug(Manager *m) {
@@ -1152,7 +1146,7 @@ int manager_startup(Manager *m, FILE *serialization, FDSet *fds) {
 
         /* First, enumerate what we can from all config files */
         dual_timestamp_get(&m->units_load_start_timestamp);
-        r = manager_enumerate(m);
+        manager_enumerate(m);
         dual_timestamp_get(&m->units_load_finish_timestamp);
 
         /* Second, deserialize if there is something to deserialize */
@@ -2554,9 +2548,7 @@ int manager_reload(Manager *m) {
         manager_build_unit_path_cache(m);
 
         /* First, enumerate what we can from all config files */
-        q = manager_enumerate(m);
+        manager_enumerate(m);
-        if (q < 0 && r >= 0)
-                r = q;
 
         /* Second, deserialize our stored data */
         q = manager_deserialize(m, f, fds);

src/core/manager.h

@@ -316,7 +316,7 @@ struct Manager {
 int manager_new(ManagerRunningAs running_as, bool test_run, Manager **m);
 Manager* manager_free(Manager *m);
 
-int manager_enumerate(Manager *m);
+void manager_enumerate(Manager *m);
 int manager_startup(Manager *m, FILE *serialization, FDSet *fds);
 
 Job *manager_get_job(Manager *m, uint32_t id);

src/core/mount.c

@@ -1596,7 +1596,7 @@ static int mount_get_timeout(Unit *u, uint64_t *timeout) {
         return 1;
 }
 
-static int mount_enumerate(Manager *m) {
+static void mount_enumerate(Manager *m) {
         int r;
 
         assert(m);
@@ -1608,29 +1608,40 @@ static int mount_enumerate(Manager *m) {
 
                 m->mount_monitor = mnt_new_monitor();
                 if (!m->mount_monitor) {
-                        r = -ENOMEM;
+                        log_oom();
                         goto fail;
                 }
 
                 r = mnt_monitor_enable_kernel(m->mount_monitor, 1);
-                if (r < 0)
+                if (r < 0) {
+                        log_error_errno(r, "Failed to enable watching of kernel mount events: %m");
                         goto fail;
+                }
+
                 r = mnt_monitor_enable_userspace(m->mount_monitor, 1, NULL);
-                if (r < 0)
+                if (r < 0) {
+                        log_error_errno(r, "Failed to enable watching of userspace mount events: %m");
                         goto fail;
+                }
 
                 /* mnt_unref_monitor() will close the fd */
                 fd = r = mnt_monitor_get_fd(m->mount_monitor);
-                if (r < 0)
+                if (r < 0) {
+                        log_error_errno(r, "Failed to acquire watch file descriptor: %m");
                         goto fail;
+                }
 
                 r = sd_event_add_io(m->event, &m->mount_event_source, fd, EPOLLIN, mount_dispatch_io, m);
-                if (r < 0)
+                if (r < 0) {
+                        log_error_errno(r, "Failed to watch mount file descriptor: %m");
                         goto fail;
+                }
 
                 r = sd_event_source_set_priority(m->mount_event_source, -10);
-                if (r < 0)
+                if (r < 0) {
+                        log_error_errno(r, "Failed to adjust mount watch priority: %m");
                         goto fail;
+                }
 
                 (void) sd_event_source_set_description(m->mount_event_source, "mount-monitor-dispatch");
         }
@@ -1639,11 +1650,10 @@ static int mount_enumerate(Manager *m) {
         if (r < 0)
                 goto fail;
 
-        return 0;
+        return;
 
 fail:
         mount_shutdown(m);
-        return r;
 }
 
 static int mount_dispatch_io(sd_event_source *source, int fd, uint32_t revents, void *userdata) {

src/core/scope.c

@@ -510,7 +510,7 @@ _pure_ static const char *scope_sub_state_to_string(Unit *u) {
         return scope_state_to_string(SCOPE(u)->state);
 }
 
-static int scope_enumerate(Manager *m) {
+static void scope_enumerate(Manager *m) {
         Unit *u;
         int r;
 
@@ -524,13 +524,16 @@ static int scope_enumerate(Manager *m) {
         u = manager_get_unit(m, SPECIAL_INIT_SCOPE);
         if (!u) {
                 u = unit_new(m, sizeof(Scope));
-                if (!u)
+                if (!u) {
-                        return log_oom();
+                        log_oom();
+                        return;
+                }
 
                 r = unit_add_name(u, SPECIAL_INIT_SCOPE);
                 if (r < 0)  {
                         unit_free(u);
-                        return log_error_errno(r, "Failed to add init.scope name");
+                        log_error_errno(r, "Failed to add init.scope name");
+                        return;
                 }
         }
 
@@ -551,8 +554,6 @@ static int scope_enumerate(Manager *m) {
 
         unit_add_to_load_queue(u);
         unit_add_to_dbus_queue(u);
-
-        return 0;
 }
 
 static const char* const scope_result_table[_SCOPE_RESULT_MAX] = {

src/core/slice.c

@@ -255,7 +255,7 @@ _pure_ static const char *slice_sub_state_to_string(Unit *u) {
         return slice_state_to_string(SLICE(u)->state);
 }
 
-static int slice_enumerate(Manager *m) {
+static void slice_enumerate(Manager *m) {
         Unit *u;
         int r;
 
@@ -264,13 +264,16 @@ static int slice_enumerate(Manager *m) {
         u = manager_get_unit(m, SPECIAL_ROOT_SLICE);
         if (!u) {
                 u = unit_new(m, sizeof(Slice));
-                if (!u)
+                if (!u)  {
-                        return log_oom();
+                        log_oom();
+                        return;
+                }
 
                 r = unit_add_name(u, SPECIAL_ROOT_SLICE);
                 if (r < 0) {
                         unit_free(u);
-                        return log_error_errno(r, "Failed to add -.slice name");
+                        log_error_errno(r, "Failed to add -.slice name");
+                        return;
                 }
         }
 
@@ -288,8 +291,6 @@ static int slice_enumerate(Manager *m) {
 
         unit_add_to_load_queue(u);
         unit_add_to_dbus_queue(u);
-
-        return 0;
 }
 
 const UnitVTable slice_vtable = {

src/core/swap.c

@@ -1268,26 +1268,36 @@ static void swap_shutdown(Manager *m) {
         m->swaps_by_devnode = hashmap_free(m->swaps_by_devnode);
 }
 
-static int swap_enumerate(Manager *m) {
+static void swap_enumerate(Manager *m) {
         int r;
 
         assert(m);
 
         if (!m->proc_swaps) {
                 m->proc_swaps = fopen("/proc/swaps", "re");
-                if (!m->proc_swaps)
+                if (!m->proc_swaps) {
-                        return errno == ENOENT ? 0 : -errno;
+                        if (errno == ENOENT)
+                                log_debug("Not swap enabled, skipping enumeration");
+                        else
+                                log_error_errno(errno, "Failed to open /proc/swaps: %m");
+
+                        return;
+                }
 
                 r = sd_event_add_io(m->event, &m->swap_event_source, fileno(m->proc_swaps), EPOLLPRI, swap_dispatch_io, m);
-                if (r < 0)
+                if (r < 0) {
+                        log_error_errno(r, "Failed to watch /proc/swaps: %m");
                         goto fail;
+                }
 
                 /* Dispatch this before we dispatch SIGCHLD, so that
                  * we always get the events from /proc/swaps before
                  * the SIGCHLD of /sbin/swapon. */
                 r = sd_event_source_set_priority(m->swap_event_source, -10);
-                if (r < 0)
+                if (r < 0) {
+                        log_error_errno(r, "Failed to change /proc/swaps priority: %m");
                         goto fail;
+                }
 
                 (void) sd_event_source_set_description(m->swap_event_source, "swap-proc");
         }
@@ -1296,11 +1306,10 @@ static int swap_enumerate(Manager *m) {
         if (r < 0)
                 goto fail;
 
-        return 0;
+        return;
 
 fail:
         swap_shutdown(m);
-        return r;
 }
 
 int swap_process_device_new(Manager *m, struct udev_device *dev) {

src/core/unit.h

@@ -389,7 +389,7 @@ struct UnitVTable {
          * everything that is loaded here should still stay in
          * inactive state. It is the job of the coldplug() call above
          * to put the units into the initial state.  */
-        int (*enumerate)(Manager *m);
+        void (*enumerate)(Manager *m);
 
         /* Type specific cleanups. */
         void (*shutdown)(Manager *m);