./move.sh

1 files changed, 878 insertions, 0 deletions

diff --git a/src/libcore/device.c b/src/libcore/device.c
new file mode 100644
index 0000000000..d201dc5e4b
--- /dev/null
+++ b/src/libcore/device.c
@@ -0,0 +1,878 @@
+/***
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <errno.h>
+#include <sys/epoll.h>
+
+#include "libudev.h"
+
+#include "alloc-util.h"
+#include "dbus-device.h"
+#include "device.h"
+#include "log.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "stat-util.h"
+#include "string-util.h"
+#include "swap.h"
+#include "udev-util.h"
+#include "unit-name.h"
+#include "unit.h"
+
+static const UnitActiveState state_translation_table[_DEVICE_STATE_MAX] = {
+        [DEVICE_DEAD] = UNIT_INACTIVE,
+        [DEVICE_TENTATIVE] = UNIT_ACTIVATING,
+        [DEVICE_PLUGGED] = UNIT_ACTIVE,
+};
+
+static int device_dispatch_io(sd_event_source *source, int fd, uint32_t revents, void *userdata);
+
+static void device_unset_sysfs(Device *d) {
+        Hashmap *devices;
+        Device *first;
+
+        assert(d);
+
+        if (!d->sysfs)
+                return;
+
+        /* Remove this unit from the chain of devices which share the
+         * same sysfs path. */
+        devices = UNIT(d)->manager->devices_by_sysfs;
+        first = hashmap_get(devices, d->sysfs);
+        LIST_REMOVE(same_sysfs, first, d);
+
+        if (first)
+                hashmap_remove_and_replace(devices, d->sysfs, first->sysfs, first);
+        else
+                hashmap_remove(devices, d->sysfs);
+
+        d->sysfs = mfree(d->sysfs);
+}
+
+static int device_set_sysfs(Device *d, const char *sysfs) {
+        Device *first;
+        char *copy;
+        int r;
+
+        assert(d);
+
+        if (streq_ptr(d->sysfs, sysfs))
+                return 0;
+
+        r = hashmap_ensure_allocated(&UNIT(d)->manager->devices_by_sysfs, &string_hash_ops);
+        if (r < 0)
+                return r;
+
+        copy = strdup(sysfs);
+        if (!copy)
+                return -ENOMEM;
+
+        device_unset_sysfs(d);
+
+        first = hashmap_get(UNIT(d)->manager->devices_by_sysfs, sysfs);
+        LIST_PREPEND(same_sysfs, first, d);
+
+        r = hashmap_replace(UNIT(d)->manager->devices_by_sysfs, copy, first);
+        if (r < 0) {
+                LIST_REMOVE(same_sysfs, first, d);
+                free(copy);
+                return r;
+        }
+
+        d->sysfs = copy;
+
+        return 0;
+}
+
+static void device_init(Unit *u) {
+        Device *d = DEVICE(u);
+
+        assert(d);
+        assert(UNIT(d)->load_state == UNIT_STUB);
+
+        /* In contrast to all other unit types we timeout jobs waiting
+         * for devices by default. This is because they otherwise wait
+         * indefinitely for plugged in devices, something which cannot
+         * happen for the other units since their operations time out
+         * anyway. */
+        u->job_timeout = u->manager->default_timeout_start_usec;
+
+        u->ignore_on_isolate = true;
+}
+
+static void device_done(Unit *u) {
+        Device *d = DEVICE(u);
+
+        assert(d);
+
+        device_unset_sysfs(d);
+}
+
+static void device_set_state(Device *d, DeviceState state) {
+        DeviceState old_state;
+        assert(d);
+
+        old_state = d->state;
+        d->state = state;
+
+        if (state != old_state)
+                log_unit_debug(UNIT(d), "Changed %s -> %s", device_state_to_string(old_state), device_state_to_string(state));
+
+        unit_notify(UNIT(d), state_translation_table[old_state], state_translation_table[state], true);
+}
+
+static int device_coldplug(Unit *u) {
+        Device *d = DEVICE(u);
+
+        assert(d);
+        assert(d->state == DEVICE_DEAD);
+
+        if (d->found & DEVICE_FOUND_UDEV)
+                /* If udev says the device is around, it's around */
+                device_set_state(d, DEVICE_PLUGGED);
+        else if (d->found != DEVICE_NOT_FOUND && d->deserialized_state != DEVICE_PLUGGED)
+                /* If a device is found in /proc/self/mountinfo or
+                 * /proc/swaps, and was not yet announced via udev,
+                 * it's "tentatively" around. */
+                device_set_state(d, DEVICE_TENTATIVE);
+
+        return 0;
+}
+
+static int device_serialize(Unit *u, FILE *f, FDSet *fds) {
+        Device *d = DEVICE(u);
+
+        assert(u);
+        assert(f);
+        assert(fds);
+
+        unit_serialize_item(u, f, "state", device_state_to_string(d->state));
+
+        return 0;
+}
+
+static int device_deserialize_item(Unit *u, const char *key, const char *value, FDSet *fds) {
+        Device *d = DEVICE(u);
+
+        assert(u);
+        assert(key);
+        assert(value);
+        assert(fds);
+
+        if (streq(key, "state")) {
+                DeviceState state;
+
+                state = device_state_from_string(value);
+                if (state < 0)
+                        log_unit_debug(u, "Failed to parse state value: %s", value);
+                else
+                        d->deserialized_state = state;
+        } else
+                log_unit_debug(u, "Unknown serialization key: %s", key);
+
+        return 0;
+}
+
+static void device_dump(Unit *u, FILE *f, const char *prefix) {
+        Device *d = DEVICE(u);
+
+        assert(d);
+
+        fprintf(f,
+                "%sDevice State: %s\n"
+                "%sSysfs Path: %s\n",
+                prefix, device_state_to_string(d->state),
+                prefix, strna(d->sysfs));
+}
+
+_pure_ static UnitActiveState device_active_state(Unit *u) {
+        assert(u);
+
+        return state_translation_table[DEVICE(u)->state];
+}
+
+_pure_ static const char *device_sub_state_to_string(Unit *u) {
+        assert(u);
+
+        return device_state_to_string(DEVICE(u)->state);
+}
+
+static int device_update_description(Unit *u, struct udev_device *dev, const char *path) {
+        const char *model;
+        int r;
+
+        assert(u);
+        assert(dev);
+        assert(path);
+
+        model = udev_device_get_property_value(dev, "ID_MODEL_FROM_DATABASE");
+        if (!model)
+                model = udev_device_get_property_value(dev, "ID_MODEL");
+
+        if (model) {
+                const char *label;
+
+                /* Try to concatenate the device model string with a label, if there is one */
+                label = udev_device_get_property_value(dev, "ID_FS_LABEL");
+                if (!label)
+                        label = udev_device_get_property_value(dev, "ID_PART_ENTRY_NAME");
+                if (!label)
+                        label = udev_device_get_property_value(dev, "ID_PART_ENTRY_NUMBER");
+
+                if (label) {
+                        _cleanup_free_ char *j;
+
+                        j = strjoin(model, " ", label, NULL);
+                        if (j)
+                                r = unit_set_description(u, j);
+                        else
+                                r = -ENOMEM;
+                } else
+                        r = unit_set_description(u, model);
+        } else
+                r = unit_set_description(u, path);
+
+        if (r < 0)
+                log_unit_error_errno(u, r, "Failed to set device description: %m");
+
+        return r;
+}
+
+static int device_add_udev_wants(Unit *u, struct udev_device *dev) {
+        const char *wants;
+        const char *word, *state;
+        size_t l;
+        int r;
+        const char *property;
+
+        assert(u);
+        assert(dev);
+
+        property = u->manager->running_as == MANAGER_USER ? "SYSTEMD_USER_WANTS" : "SYSTEMD_WANTS";
+        wants = udev_device_get_property_value(dev, property);
+        if (!wants)
+                return 0;
+
+        FOREACH_WORD_QUOTED(word, l, wants, state) {
+                _cleanup_free_ char *n = NULL;
+                char e[l+1];
+
+                memcpy(e, word, l);
+                e[l] = 0;
+
+                r = unit_name_mangle(e, UNIT_NAME_NOGLOB, &n);
+                if (r < 0)
+                        return log_unit_error_errno(u, r, "Failed to mangle unit name: %m");
+
+                r = unit_add_dependency_by_name(u, UNIT_WANTS, n, NULL, true);
+                if (r < 0)
+                        return log_unit_error_errno(u, r, "Failed to add wants dependency: %m");
+        }
+        if (!isempty(state))
+                log_unit_warning(u, "Property %s on %s has trailing garbage, ignoring.", property, strna(udev_device_get_syspath(dev)));
+
+        return 0;
+}
+
+static int device_setup_unit(Manager *m, struct udev_device *dev, const char *path, bool main) {
+        _cleanup_free_ char *e = NULL;
+        const char *sysfs = NULL;
+        Unit *u = NULL;
+        bool delete;
+        int r;
+
+        assert(m);
+        assert(path);
+
+        if (dev) {
+                sysfs = udev_device_get_syspath(dev);
+                if (!sysfs)
+                        return 0;
+        }
+
+        r = unit_name_from_path(path, ".device", &e);
+        if (r < 0)
+                return log_error_errno(r, "Failed to generate unit name from device path: %m");
+
+        u = manager_get_unit(m, e);
+
+        /* The device unit can still be present even if the device was
+         * unplugged: a mount unit can reference it hence preventing
+         * the GC to have garbaged it. That's desired since the device
+         * unit may have a dependency on the mount unit which was
+         * added during the loading of the later. */
+        if (u && DEVICE(u)->state == DEVICE_PLUGGED) {
+                /* This unit is in plugged state: we're sure it's
+                 * attached to a device. */
+                if (!path_equal(DEVICE(u)->sysfs, sysfs)) {
+                        log_unit_error(u, "Dev %s appeared twice with different sysfs paths %s and %s",
+                                       e, DEVICE(u)->sysfs, sysfs);
+                        return -EEXIST;
+                }
+        }
+
+        if (!u) {
+                delete = true;
+
+                u = unit_new(m, sizeof(Device));
+                if (!u)
+                        return log_oom();
+
+                r = unit_add_name(u, e);
+                if (r < 0)
+                        goto fail;
+
+                unit_add_to_load_queue(u);
+        } else
+                delete = false;
+
+        /* If this was created via some dependency and has not
+         * actually been seen yet ->sysfs will not be
+         * initialized. Hence initialize it if necessary. */
+        if (sysfs) {
+                r = device_set_sysfs(DEVICE(u), sysfs);
+                if (r < 0)
+                        goto fail;
+
+                (void) device_update_description(u, dev, path);
+
+                /* The additional systemd udev properties we only interpret
+                 * for the main object */
+                if (main)
+                        (void) device_add_udev_wants(u, dev);
+        }
+
+
+        /* Note that this won't dispatch the load queue, the caller
+         * has to do that if needed and appropriate */
+
+        unit_add_to_dbus_queue(u);
+        return 0;
+
+fail:
+        log_unit_warning_errno(u, r, "Failed to set up device unit: %m");
+
+        if (delete)
+                unit_free(u);
+
+        return r;
+}
+
+static int device_process_new(Manager *m, struct udev_device *dev) {
+        const char *sysfs, *dn, *alias;
+        struct udev_list_entry *item = NULL, *first = NULL;
+        int r;
+
+        assert(m);
+
+        sysfs = udev_device_get_syspath(dev);
+        if (!sysfs)
+                return 0;
+
+        /* Add the main unit named after the sysfs path */
+        r = device_setup_unit(m, dev, sysfs, true);
+        if (r < 0)
+                return r;
+
+        /* Add an additional unit for the device node */
+        dn = udev_device_get_devnode(dev);
+        if (dn)
+                (void) device_setup_unit(m, dev, dn, false);
+
+        /* Add additional units for all symlinks */
+        first = udev_device_get_devlinks_list_entry(dev);
+        udev_list_entry_foreach(item, first) {
+                const char *p;
+                struct stat st;
+
+                /* Don't bother with the /dev/block links */
+                p = udev_list_entry_get_name(item);
+
+                if (path_startswith(p, "/dev/block/") ||
+                    path_startswith(p, "/dev/char/"))
+                        continue;
+
+                /* Verify that the symlink in the FS actually belongs
+                 * to this device. This is useful to deal with
+                 * conflicting devices, e.g. when two disks want the
+                 * same /dev/disk/by-label/xxx link because they have
+                 * the same label. We want to make sure that the same
+                 * device that won the symlink wins in systemd, so we
+                 * check the device node major/minor */
+                if (stat(p, &st) >= 0)
+                        if ((!S_ISBLK(st.st_mode) && !S_ISCHR(st.st_mode)) ||
+                            st.st_rdev != udev_device_get_devnum(dev))
+                                continue;
+
+                (void) device_setup_unit(m, dev, p, false);
+        }
+
+        /* Add additional units for all explicitly configured
+         * aliases */
+        alias = udev_device_get_property_value(dev, "SYSTEMD_ALIAS");
+        if (alias) {
+                const char *word, *state;
+                size_t l;
+
+                FOREACH_WORD_QUOTED(word, l, alias, state) {
+                        char e[l+1];
+
+                        memcpy(e, word, l);
+                        e[l] = 0;
+
+                        if (path_is_absolute(e))
+                                (void) device_setup_unit(m, dev, e, false);
+                        else
+                                log_warning("SYSTEMD_ALIAS for %s is not an absolute path, ignoring: %s", sysfs, e);
+                }
+                if (!isempty(state))
+                        log_warning("SYSTEMD_ALIAS for %s has trailing garbage, ignoring.", sysfs);
+        }
+
+        return 0;
+}
+
+static void device_update_found_one(Device *d, bool add, DeviceFound found, bool now) {
+        DeviceFound n, previous;
+
+        assert(d);
+
+        n = add ? (d->found | found) : (d->found & ~found);
+        if (n == d->found)
+                return;
+
+        previous = d->found;
+        d->found = n;
+
+        if (!now)
+                return;
+
+        if (d->found & DEVICE_FOUND_UDEV)
+                /* When the device is known to udev we consider it
+                 * plugged. */
+                device_set_state(d, DEVICE_PLUGGED);
+        else if (d->found != DEVICE_NOT_FOUND && (previous & DEVICE_FOUND_UDEV) == 0)
+                /* If the device has not been seen by udev yet, but is
+                 * now referenced by the kernel, then we assume the
+                 * kernel knows it now, and udev might soon too. */
+                device_set_state(d, DEVICE_TENTATIVE);
+        else
+                /* If nobody sees the device, or if the device was
+                 * previously seen by udev and now is only referenced
+                 * from the kernel, then we consider the device is
+                 * gone, the kernel just hasn't noticed it yet. */
+                device_set_state(d, DEVICE_DEAD);
+}
+
+static int device_update_found_by_sysfs(Manager *m, const char *sysfs, bool add, DeviceFound found, bool now) {
+        Device *d, *l;
+
+        assert(m);
+        assert(sysfs);
+
+        if (found == DEVICE_NOT_FOUND)
+                return 0;
+
+        l = hashmap_get(m->devices_by_sysfs, sysfs);
+        LIST_FOREACH(same_sysfs, d, l)
+                device_update_found_one(d, add, found, now);
+
+        return 0;
+}
+
+static int device_update_found_by_name(Manager *m, const char *path, bool add, DeviceFound found, bool now) {
+        _cleanup_free_ char *e = NULL;
+        Unit *u;
+        int r;
+
+        assert(m);
+        assert(path);
+
+        if (found == DEVICE_NOT_FOUND)
+                return 0;
+
+        r = unit_name_from_path(path, ".device", &e);
+        if (r < 0)
+                return log_error_errno(r, "Failed to generate unit name from device path: %m");
+
+        u = manager_get_unit(m, e);
+        if (!u)
+                return 0;
+
+        device_update_found_one(DEVICE(u), add, found, now);
+        return 0;
+}
+
+static bool device_is_ready(struct udev_device *dev) {
+        const char *ready;
+
+        assert(dev);
+
+        ready = udev_device_get_property_value(dev, "SYSTEMD_READY");
+        if (!ready)
+                return true;
+
+        return parse_boolean(ready) != 0;
+}
+
+static Unit *device_following(Unit *u) {
+        Device *d = DEVICE(u);
+        Device *other, *first = NULL;
+
+        assert(d);
+
+        if (startswith(u->id, "sys-"))
+                return NULL;
+
+        /* Make everybody follow the unit that's named after the sysfs path */
+        for (other = d->same_sysfs_next; other; other = other->same_sysfs_next)
+                if (startswith(UNIT(other)->id, "sys-"))
+                        return UNIT(other);
+
+        for (other = d->same_sysfs_prev; other; other = other->same_sysfs_prev) {
+                if (startswith(UNIT(other)->id, "sys-"))
+                        return UNIT(other);
+
+                first = other;
+        }
+
+        return UNIT(first);
+}
+
+static int device_following_set(Unit *u, Set **_set) {
+        Device *d = DEVICE(u), *other;
+        Set *set;
+        int r;
+
+        assert(d);
+        assert(_set);
+
+        if (LIST_JUST_US(same_sysfs, d)) {
+                *_set = NULL;
+                return 0;
+        }
+
+        set = set_new(NULL);
+        if (!set)
+                return -ENOMEM;
+
+        LIST_FOREACH_AFTER(same_sysfs, other, d) {
+                r = set_put(set, other);
+                if (r < 0)
+                        goto fail;
+        }
+
+        LIST_FOREACH_BEFORE(same_sysfs, other, d) {
+                r = set_put(set, other);
+                if (r < 0)
+                        goto fail;
+        }
+
+        *_set = set;
+        return 1;
+
+fail:
+        set_free(set);
+        return r;
+}
+
+static void device_shutdown(Manager *m) {
+        assert(m);
+
+        m->udev_event_source = sd_event_source_unref(m->udev_event_source);
+
+        if (m->udev_monitor) {
+                udev_monitor_unref(m->udev_monitor);
+                m->udev_monitor = NULL;
+        }
+
+        m->devices_by_sysfs = hashmap_free(m->devices_by_sysfs);
+}
+
+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;
+
+        assert(m);
+
+        if (!m->udev_monitor) {
+                m->udev_monitor = udev_monitor_new_from_netlink(m->udev, "udev");
+                if (!m->udev_monitor) {
+                        log_oom();
+                        goto fail;
+                }
+
+                /* This will fail if we are unprivileged, but that
+                 * should not matter much, as user instances won't run
+                 * during boot. */
+                (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) {
+                        log_error_errno(r, "Failed to add udev tag match: %m");
+                        goto fail;
+                }
+
+                r = udev_monitor_enable_receiving(m->udev_monitor);
+                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) {
+                        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) {
+                log_oom();
+                goto fail;
+        }
+
+        r = udev_enumerate_add_match_tag(e, "systemd");
+        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) {
+                log_error_errno(r, "Failed to install initialization match into enumeration: %m");
+                goto fail;
+        }
+
+        r = udev_enumerate_scan_devices(e);
+        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) {
+                _cleanup_udev_device_unref_ struct udev_device *dev = NULL;
+                const char *sysfs;
+
+                sysfs = udev_list_entry_get_name(item);
+
+                dev = udev_device_new_from_syspath(m->udev, sysfs);
+                if (!dev) {
+                        log_oom();
+                        continue;
+                }
+
+                if (!device_is_ready(dev))
+                        continue;
+
+                (void) device_process_new(m, dev);
+
+                device_update_found_by_sysfs(m, sysfs, true, DEVICE_FOUND_UDEV, false);
+        }
+
+        return;
+
+fail:
+        device_shutdown(m);
+}
+
+static int device_dispatch_io(sd_event_source *source, int fd, uint32_t revents, void *userdata) {
+        _cleanup_udev_device_unref_ struct udev_device *dev = NULL;
+        Manager *m = userdata;
+        const char *action, *sysfs;
+        int r;
+
+        assert(m);
+
+        if (revents != EPOLLIN) {
+                static RATELIMIT_DEFINE(limit, 10*USEC_PER_SEC, 5);
+
+                if (!ratelimit_test(&limit))
+                        log_error_errno(errno, "Failed to get udev event: %m");
+                if (!(revents & EPOLLIN))
+                        return 0;
+        }
+
+        /*
+         * libudev might filter-out devices which pass the bloom
+         * filter, so getting NULL here is not necessarily an error.
+         */
+        dev = udev_monitor_receive_device(m->udev_monitor);
+        if (!dev)
+                return 0;
+
+        sysfs = udev_device_get_syspath(dev);
+        if (!sysfs) {
+                log_error("Failed to get udev sys path.");
+                return 0;
+        }
+
+        action = udev_device_get_action(dev);
+        if (!action) {
+                log_error("Failed to get udev action string.");
+                return 0;
+        }
+
+        if (streq(action, "remove"))  {
+                r = swap_process_device_remove(m, dev);
+                if (r < 0)
+                        log_error_errno(r, "Failed to process swap device remove event: %m");
+
+                /* If we get notified that a device was removed by
+                 * udev, then it's completely gone, hence unset all
+                 * found bits */
+                device_update_found_by_sysfs(m, sysfs, false, DEVICE_FOUND_UDEV|DEVICE_FOUND_MOUNT|DEVICE_FOUND_SWAP, true);
+
+        } else if (device_is_ready(dev)) {
+
+                (void) device_process_new(m, dev);
+
+                r = swap_process_device_new(m, dev);
+                if (r < 0)
+                        log_error_errno(r, "Failed to process swap device new event: %m");
+
+                manager_dispatch_load_queue(m);
+
+                /* The device is found now, set the udev found bit */
+                device_update_found_by_sysfs(m, sysfs, true, DEVICE_FOUND_UDEV, true);
+
+        } else {
+                /* The device is nominally around, but not ready for
+                 * us. Hence unset the udev bit, but leave the rest
+                 * around. */
+
+                device_update_found_by_sysfs(m, sysfs, false, DEVICE_FOUND_UDEV, true);
+        }
+
+        return 0;
+}
+
+static bool device_supported(void) {
+        static int read_only = -1;
+
+        /* If /sys is read-only we don't support device units, and any
+         * attempts to start one should fail immediately. */
+
+        if (read_only < 0)
+                read_only = path_is_read_only_fs("/sys");
+
+        return read_only <= 0;
+}
+
+int device_found_node(Manager *m, const char *node, bool add, DeviceFound found, bool now) {
+        _cleanup_udev_device_unref_ struct udev_device *dev = NULL;
+        struct stat st;
+
+        assert(m);
+        assert(node);
+
+        if (!device_supported())
+                return 0;
+
+        /* This is called whenever we find a device referenced in
+         * /proc/swaps or /proc/self/mounts. Such a device might be
+         * mounted/enabled at a time where udev has not finished
+         * probing it yet, and we thus haven't learned about it
+         * yet. In this case we will set the device unit to
+         * "tentative" state. */
+
+        if (add) {
+                if (!path_startswith(node, "/dev"))
+                        return 0;
+
+                /* We make an extra check here, if the device node
+                 * actually exists. If it's missing, then this is an
+                 * indication that device was unplugged but is still
+                 * referenced in /proc/swaps or
+                 * /proc/self/mountinfo. Note that this check doesn't
+                 * really cover all cases where a device might be gone
+                 * away, since drives that can have a medium inserted
+                 * will still have a device node even when the medium
+                 * is not there... */
+
+                if (stat(node, &st) >= 0) {
+                        if (!S_ISBLK(st.st_mode) && !S_ISCHR(st.st_mode))
+                                return 0;
+
+                        dev = udev_device_new_from_devnum(m->udev, S_ISBLK(st.st_mode) ? 'b' : 'c', st.st_rdev);
+                        if (!dev && errno != ENOENT)
+                                return log_error_errno(errno, "Failed to get udev device from devnum %u:%u: %m", major(st.st_rdev), minor(st.st_rdev));
+
+                } else if (errno != ENOENT)
+                        return log_error_errno(errno, "Failed to stat device node file %s: %m", node);
+
+                /* If the device is known in the kernel and newly
+                 * appeared, then we'll create a device unit for it,
+                 * under the name referenced in /proc/swaps or
+                 * /proc/self/mountinfo. */
+
+                (void) device_setup_unit(m, dev, node, false);
+        }
+
+        /* Update the device unit's state, should it exist */
+        return device_update_found_by_name(m, node, add, found, now);
+}
+
+const UnitVTable device_vtable = {
+        .object_size = sizeof(Device),
+        .sections =
+                "Unit\0"
+                "Device\0"
+                "Install\0",
+
+        .no_instances = true,
+
+        .init = device_init,
+        .done = device_done,
+        .load = unit_load_fragment_and_dropin_optional,
+
+        .coldplug = device_coldplug,
+
+        .serialize = device_serialize,
+        .deserialize_item = device_deserialize_item,
+
+        .dump = device_dump,
+
+        .active_state = device_active_state,
+        .sub_state_to_string = device_sub_state_to_string,
+
+        .bus_vtable = bus_device_vtable,
+
+        .following = device_following,
+        .following_set = device_following_set,
+
+        .enumerate = device_enumerate,
+        .shutdown = device_shutdown,
+        .supported = device_supported,
+
+        .status_message_formats = {
+                .starting_stopping = {
+                        [0] = "Expecting device %s...",
+                },
+                .finished_start_job = {
+                        [JOB_DONE]       = "Found device %s.",
+                        [JOB_TIMEOUT]    = "Timed out waiting for device %s.",
+                },
+        },
+};