Adding upstream version 247.3.upstream/247.3upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1121 insertions, 0 deletions

diff --git a/src/core/device.c b/src/core/device.c
new file mode 100644
index 0000000..9a1d882
--- /dev/null
+++ b/src/core/device.c
@@ -0,0 +1,1121 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <sys/epoll.h>
+
+#include "alloc-util.h"
+#include "bus-error.h"
+#include "dbus-device.h"
+#include "dbus-unit.h"
+#include "device-private.h"
+#include "device-util.h"
+#include "device.h"
+#include "log.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "serialize.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_device_monitor *monitor, sd_device *dev, void *userdata);
+static void device_update_found_one(Device *d, DeviceFound found, DeviceFound mask);
+
+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) {
+        _cleanup_free_ char *copy = NULL;
+        Device *first;
+        int r;
+
+        assert(d);
+
+        if (streq_ptr(d->sysfs, sysfs))
+                return 0;
+
+        r = hashmap_ensure_allocated(&UNIT(d)->manager->devices_by_sysfs, &path_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);
+                return r;
+        }
+
+        d->sysfs = TAKE_PTR(copy);
+        unit_add_to_dbus_queue(UNIT(d));
+
+        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_running_timeout = u->manager->default_timeout_start_usec;
+
+        u->ignore_on_isolate = true;
+
+        d->deserialized_state = _DEVICE_STATE_INVALID;
+}
+
+static void device_done(Unit *u) {
+        Device *d = DEVICE(u);
+
+        assert(d);
+
+        device_unset_sysfs(d);
+        d->wants_property = strv_free(d->wants_property);
+}
+
+static int device_load(Unit *u) {
+        int r;
+
+        r = unit_load_fragment_and_dropin(u, false);
+        if (r < 0)
+                return r;
+
+        if (!u->description) {
+                /* Generate a description based on the path, to be used until the
+                   device is initialized properly */
+                r = unit_name_to_path(u->id, &u->description);
+                if (r < 0)
+                        log_unit_debug_errno(u, r, "Failed to unescape name: %m");
+        }
+
+        return 0;
+}
+
+static void device_set_state(Device *d, DeviceState state) {
+        DeviceState old_state;
+        assert(d);
+
+        if (d->state != state)
+                bus_unit_send_pending_change_signal(UNIT(d), false);
+
+        old_state = d->state;
+        d->state = state;
+
+        if (state == DEVICE_DEAD)
+                device_unset_sysfs(d);
+
+        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], 0);
+}
+
+static int device_coldplug(Unit *u) {
+        Device *d = DEVICE(u);
+
+        assert(d);
+        assert(d->state == DEVICE_DEAD);
+
+        /* First, let's put the deserialized state and found mask into effect, if we have it. */
+
+        if (d->deserialized_state < 0 ||
+            (d->deserialized_state == d->state &&
+             d->deserialized_found == d->found))
+                return 0;
+
+        d->found = d->deserialized_found;
+        device_set_state(d, d->deserialized_state);
+        return 0;
+}
+
+static void device_catchup(Unit *u) {
+        Device *d = DEVICE(u);
+
+        assert(d);
+
+        /* Second, let's update the state with the enumerated state if it's different */
+        if (d->enumerated_found == d->found)
+                return;
+
+        device_update_found_one(d, d->enumerated_found, DEVICE_FOUND_MASK);
+}
+
+static const struct {
+        DeviceFound flag;
+        const char *name;
+} device_found_map[] = {
+        { DEVICE_FOUND_UDEV,  "found-udev"  },
+        { DEVICE_FOUND_MOUNT, "found-mount" },
+        { DEVICE_FOUND_SWAP,  "found-swap"  },
+};
+
+static int device_found_to_string_many(DeviceFound flags, char **ret) {
+        _cleanup_free_ char *s = NULL;
+        unsigned i;
+
+        assert(ret);
+
+        for (i = 0; i < ELEMENTSOF(device_found_map); i++) {
+                if (!FLAGS_SET(flags, device_found_map[i].flag))
+                        continue;
+
+                if (!strextend_with_separator(&s, ",", device_found_map[i].name, NULL))
+                        return -ENOMEM;
+        }
+
+        *ret = TAKE_PTR(s);
+
+        return 0;
+}
+
+static int device_found_from_string_many(const char *name, DeviceFound *ret) {
+        DeviceFound flags = 0;
+        int r;
+
+        assert(ret);
+
+        for (;;) {
+                _cleanup_free_ char *word = NULL;
+                DeviceFound f = 0;
+                unsigned i;
+
+                r = extract_first_word(&name, &word, ",", 0);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        break;
+
+                for (i = 0; i < ELEMENTSOF(device_found_map); i++)
+                        if (streq(word, device_found_map[i].name)) {
+                                f = device_found_map[i].flag;
+                                break;
+                        }
+
+                if (f == 0)
+                        return -EINVAL;
+
+                flags |= f;
+        }
+
+        *ret = flags;
+        return 0;
+}
+
+static int device_serialize(Unit *u, FILE *f, FDSet *fds) {
+        _cleanup_free_ char *s = NULL;
+        Device *d = DEVICE(u);
+
+        assert(u);
+        assert(f);
+        assert(fds);
+
+        (void) serialize_item(f, "state", device_state_to_string(d->state));
+
+        if (device_found_to_string_many(d->found, &s) >= 0)
+                (void) serialize_item(f, "found", s);
+
+        return 0;
+}
+
+static int device_deserialize_item(Unit *u, const char *key, const char *value, FDSet *fds) {
+        Device *d = DEVICE(u);
+        int r;
+
+        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, ignoring: %s", value);
+                else
+                        d->deserialized_state = state;
+
+        } else if (streq(key, "found")) {
+                r = device_found_from_string_many(value, &d->deserialized_found);
+                if (r < 0)
+                        log_unit_debug_errno(u, r, "Failed to parse found value '%s', ignoring: %m", value);
+
+        } 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);
+        _cleanup_free_ char *s = NULL;
+
+        assert(d);
+
+        (void) device_found_to_string_many(d->found, &s);
+
+        fprintf(f,
+                "%sDevice State: %s\n"
+                "%sSysfs Path: %s\n"
+                "%sFound: %s\n",
+                prefix, device_state_to_string(d->state),
+                prefix, strna(d->sysfs),
+                prefix, strna(s));
+
+        if (!strv_isempty(d->wants_property)) {
+                char **i;
+
+                STRV_FOREACH(i, d->wants_property)
+                        fprintf(f, "%sudev SYSTEMD_WANTS: %s\n",
+                                prefix, *i);
+        }
+}
+
+_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, sd_device *dev, const char *path) {
+        _cleanup_free_ char *j = NULL;
+        const char *model, *label, *desc;
+        int r;
+
+        assert(u);
+        assert(path);
+
+        desc = path;
+
+        if (dev &&
+            (sd_device_get_property_value(dev, "ID_MODEL_FROM_DATABASE", &model) >= 0 ||
+             sd_device_get_property_value(dev, "ID_MODEL", &model) >= 0)) {
+                desc = model;
+
+                /* Try to concatenate the device model string with a label, if there is one */
+                if (sd_device_get_property_value(dev, "ID_FS_LABEL", &label) >= 0 ||
+                    sd_device_get_property_value(dev, "ID_PART_ENTRY_NAME", &label) >= 0 ||
+                    sd_device_get_property_value(dev, "ID_PART_ENTRY_NUMBER", &label) >= 0) {
+
+                        desc = j = strjoin(model, " ", label);
+                        if (!j)
+                                return log_oom();
+                }
+        }
+
+        r = unit_set_description(u, desc);
+        if (r < 0)
+                return log_unit_error_errno(u, r, "Failed to set device description: %m");
+
+        return 0;
+}
+
+static int device_add_udev_wants(Unit *u, sd_device *dev) {
+        _cleanup_strv_free_ char **added = NULL;
+        const char *wants, *property;
+        Device *d = DEVICE(u);
+        int r;
+
+        assert(d);
+        assert(dev);
+
+        property = MANAGER_IS_USER(u->manager) ? "SYSTEMD_USER_WANTS" : "SYSTEMD_WANTS";
+
+        r = sd_device_get_property_value(dev, property, &wants);
+        if (r < 0)
+                return 0;
+
+        for (;;) {
+                _cleanup_free_ char *word = NULL, *k = NULL;
+
+                r = extract_first_word(&wants, &word, NULL, EXTRACT_UNQUOTE);
+                if (r == 0)
+                        break;
+                if (r == -ENOMEM)
+                        return log_oom();
+                if (r < 0)
+                        return log_unit_error_errno(u, r, "Failed to parse property %s with value %s: %m", property, wants);
+
+                if (unit_name_is_valid(word, UNIT_NAME_TEMPLATE) && d->sysfs) {
+                        _cleanup_free_ char *escaped = NULL;
+
+                        /* If the unit name is specified as template, then automatically fill in the sysfs path of the
+                         * device as instance name, properly escaped. */
+
+                        r = unit_name_path_escape(d->sysfs, &escaped);
+                        if (r < 0)
+                                return log_unit_error_errno(u, r, "Failed to escape %s: %m", d->sysfs);
+
+                        r = unit_name_replace_instance(word, escaped, &k);
+                        if (r < 0)
+                                return log_unit_error_errno(u, r, "Failed to build %s instance of template %s: %m", escaped, word);
+                } else {
+                        /* If this is not a template, then let's mangle it so, that it becomes a valid unit name. */
+
+                        r = unit_name_mangle(word, UNIT_NAME_MANGLE_WARN, &k);
+                        if (r < 0)
+                                return log_unit_error_errno(u, r, "Failed to mangle unit name \"%s\": %m", word);
+                }
+
+                r = unit_add_dependency_by_name(u, UNIT_WANTS, k, true, UNIT_DEPENDENCY_UDEV);
+                if (r < 0)
+                        return log_unit_error_errno(u, r, "Failed to add Wants= dependency: %m");
+
+                r = strv_push(&added, k);
+                if (r < 0)
+                        return log_oom();
+
+                k = NULL;
+        }
+
+        if (d->state != DEVICE_DEAD) {
+                char **i;
+
+                /* So here's a special hack, to compensate for the fact that the udev database's reload cycles are not
+                 * synchronized with our own reload cycles: when we detect that the SYSTEMD_WANTS property of a device
+                 * changes while the device unit is already up, let's manually trigger any new units listed in it not
+                 * seen before. This typically happens during the boot-time switch root transition, as udev devices
+                 * will generally already be up in the initrd, but SYSTEMD_WANTS properties get then added through udev
+                 * rules only available on the host system, and thus only when the initial udev coldplug trigger runs.
+                 *
+                 * We do this only if the device has been up already when we parse this, as otherwise the usual
+                 * dependency logic that is run from the dead → plugged transition will trigger these deps. */
+
+                STRV_FOREACH(i, added) {
+                        _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+
+                        if (strv_contains(d->wants_property, *i)) /* Was this unit already listed before? */
+                                continue;
+
+                        r = manager_add_job_by_name(u->manager, JOB_START, *i, JOB_FAIL, NULL, &error, NULL);
+                        if (r < 0)
+                                log_unit_warning_errno(u, r, "Failed to enqueue SYSTEMD_WANTS= job, ignoring: %s", bus_error_message(&error, r));
+                }
+        }
+
+        return strv_free_and_replace(d->wants_property, added);
+}
+
+static bool device_is_bound_by_mounts(Device *d, sd_device *dev) {
+        const char *bound_by;
+        int r;
+
+        assert(d);
+        assert(dev);
+
+        if (sd_device_get_property_value(dev, "SYSTEMD_MOUNT_DEVICE_BOUND", &bound_by) >= 0) {
+                r = parse_boolean(bound_by);
+                if (r < 0)
+                        log_device_warning_errno(dev, r, "Failed to parse SYSTEMD_MOUNT_DEVICE_BOUND='%s' udev property, ignoring: %m", bound_by);
+
+                d->bind_mounts = r > 0;
+        } else
+                d->bind_mounts = false;
+
+        return d->bind_mounts;
+}
+
+static void device_upgrade_mount_deps(Unit *u) {
+        Unit *other;
+        void *v;
+        int r;
+
+        /* Let's upgrade Requires= to BindsTo= on us. (Used when SYSTEMD_MOUNT_DEVICE_BOUND is set) */
+
+        HASHMAP_FOREACH_KEY(v, other, u->dependencies[UNIT_REQUIRED_BY]) {
+                if (other->type != UNIT_MOUNT)
+                        continue;
+
+                r = unit_add_dependency(other, UNIT_BINDS_TO, u, true, UNIT_DEPENDENCY_UDEV);
+                if (r < 0)
+                        log_unit_warning_errno(u, r, "Failed to add BindsTo= dependency between device and mount unit, ignoring: %m");
+        }
+}
+
+static int device_setup_unit(Manager *m, sd_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) {
+                r = sd_device_get_syspath(dev, &sysfs);
+                if (r < 0) {
+                        log_device_debug_errno(dev, r, "Couldn't get syspath from device, ignoring: %m");
+                        return 0;
+                }
+        }
+
+        r = unit_name_from_path(path, ".device", &e);
+        if (r < 0)
+                return log_device_error_errno(dev, r, "Failed to generate unit name from device path: %m");
+
+        u = manager_get_unit(m, e);
+        if (u) {
+                /* 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. When the device is
+                 * plugged the sysfs might not be initialized yet, as we serialize the device's state but do not
+                 * serialize the sysfs path across reloads/reexecs. Hence, when coming back from a reload/restart we
+                 * might have the state valid, but not the sysfs path. Hence, let's filter out conflicting devices, but
+                 * let's accept devices in any state with no sysfs path set. */
+
+                if (DEVICE(u)->state == DEVICE_PLUGGED &&
+                    DEVICE(u)->sysfs &&
+                    sysfs &&
+                    !path_equal(DEVICE(u)->sysfs, sysfs)) {
+                        log_unit_debug(u, "Device %s appeared twice with different sysfs paths %s and %s, ignoring the latter.",
+                                       e, DEVICE(u)->sysfs, sysfs);
+                        return -EEXIST;
+                }
+
+                delete = false;
+
+                /* Let's remove all dependencies generated due to udev properties. We'll re-add whatever is configured
+                 * now below. */
+                unit_remove_dependencies(u, UNIT_DEPENDENCY_UDEV);
+        } else {
+                delete = true;
+
+                r = unit_new_for_name(m, sizeof(Device), e, &u);
+                if (r < 0) {
+                        log_device_error_errno(dev, r, "Failed to allocate device unit %s: %m", e);
+                        goto fail;
+                }
+
+                unit_add_to_load_queue(u);
+        }
+
+        /* 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) {
+                        log_unit_error_errno(u, r, "Failed to set sysfs path %s: %m", sysfs);
+                        goto fail;
+                }
+
+                /* The additional systemd udev properties we only interpret for the main object */
+                if (main)
+                        (void) device_add_udev_wants(u, dev);
+        }
+
+        (void) device_update_description(u, dev, path);
+
+        /* So the user wants the mount units to be bound to the device but a mount unit might has been seen by systemd
+         * before the device appears on its radar. In this case the device unit is partially initialized and includes
+         * the deps on the mount unit but at that time the "bind mounts" flag wasn't not present. Fix this up now. */
+        if (dev && device_is_bound_by_mounts(DEVICE(u), dev))
+                device_upgrade_mount_deps(u);
+
+        return 0;
+
+fail:
+        if (delete)
+                unit_free(u);
+
+        return r;
+}
+
+static int device_process_new(Manager *m, sd_device *dev) {
+        const char *sysfs, *dn, *alias;
+        dev_t devnum;
+        int r;
+
+        assert(m);
+
+        if (sd_device_get_syspath(dev, &sysfs) < 0)
+                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 */
+        if (sd_device_get_devname(dev, &dn) >= 0)
+                (void) device_setup_unit(m, dev, dn, false);
+
+        /* Add additional units for all symlinks */
+        if (sd_device_get_devnum(dev, &devnum) >= 0) {
+                const char *p;
+
+                FOREACH_DEVICE_DEVLINK(dev, p) {
+                        struct stat st;
+
+                        if (PATH_STARTSWITH_SET(p, "/dev/block/", "/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 &&
+                            ((!S_ISBLK(st.st_mode) && !S_ISCHR(st.st_mode)) ||
+                             st.st_rdev != devnum))
+                                continue;
+
+                        (void) device_setup_unit(m, dev, p, false);
+                }
+        }
+
+        /* Add additional units for all explicitly configured aliases */
+        if (sd_device_get_property_value(dev, "SYSTEMD_ALIAS", &alias) < 0)
+                return 0;
+
+        for (;;) {
+                _cleanup_free_ char *word = NULL;
+
+                r = extract_first_word(&alias, &word, NULL, EXTRACT_UNQUOTE);
+                if (r == 0)
+                        break;
+                if (r == -ENOMEM)
+                        return log_oom();
+                if (r < 0)
+                        return log_device_warning_errno(dev, r, "Failed to parse SYSTEMD_ALIAS property: %m");
+
+                if (!path_is_absolute(word))
+                        log_device_warning(dev, "SYSTEMD_ALIAS is not an absolute path, ignoring: %s", word);
+                else if (!path_is_normalized(word))
+                        log_device_warning(dev, "SYSTEMD_ALIAS is not a normalized path, ignoring: %s", word);
+                else
+                        (void) device_setup_unit(m, dev, word, false);
+        }
+
+        return 0;
+}
+
+static void device_found_changed(Device *d, DeviceFound previous, DeviceFound now) {
+        assert(d);
+
+        /* Didn't exist before, but does now? if so, generate a new invocation ID for it */
+        if (previous == DEVICE_NOT_FOUND && now != DEVICE_NOT_FOUND)
+                (void) unit_acquire_invocation_id(UNIT(d));
+
+        if (FLAGS_SET(now, DEVICE_FOUND_UDEV))
+                /* When the device is known to udev we consider it plugged. */
+                device_set_state(d, DEVICE_PLUGGED);
+        else if (now != DEVICE_NOT_FOUND && !FLAGS_SET(previous, DEVICE_FOUND_UDEV))
+                /* 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 void device_update_found_one(Device *d, DeviceFound found, DeviceFound mask) {
+        Manager *m;
+
+        assert(d);
+
+        m = UNIT(d)->manager;
+
+        if (MANAGER_IS_RUNNING(m) && (m->honor_device_enumeration || MANAGER_IS_USER(m))) {
+                DeviceFound n, previous;
+
+                /* When we are already running, then apply the new mask right-away, and trigger state changes
+                 * right-away */
+
+                n = (d->found & ~mask) | (found & mask);
+                if (n == d->found)
+                        return;
+
+                previous = d->found;
+                d->found = n;
+
+                device_found_changed(d, previous, n);
+        } else
+                /* We aren't running yet, let's apply the new mask to the shadow variable instead, which we'll apply as
+                 * soon as we catch-up with the state. */
+                d->enumerated_found = (d->enumerated_found & ~mask) | (found & mask);
+}
+
+static void device_update_found_by_sysfs(Manager *m, const char *sysfs, DeviceFound found, DeviceFound mask) {
+        Device *d, *l, *n;
+
+        assert(m);
+        assert(sysfs);
+
+        if (mask == 0)
+                return;
+
+        l = hashmap_get(m->devices_by_sysfs, sysfs);
+        LIST_FOREACH_SAFE(same_sysfs, d, n, l)
+                device_update_found_one(d, found, mask);
+}
+
+static int device_update_found_by_name(Manager *m, const char *path, DeviceFound found, DeviceFound mask) {
+        _cleanup_free_ char *e = NULL;
+        Unit *u;
+        int r;
+
+        assert(m);
+        assert(path);
+
+        if (mask == 0)
+                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), found, mask);
+        return 0;
+}
+
+static bool device_is_ready(sd_device *dev) {
+        const char *ready;
+
+        assert(dev);
+
+        if (device_is_renaming(dev) > 0)
+                return false;
+
+        /* Is it really tagged as 'systemd' right now? */
+        if (sd_device_has_current_tag(dev, "systemd") <= 0)
+                return false;
+
+        if (sd_device_get_property_value(dev, "SYSTEMD_READY", &ready) < 0)
+                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 */
+        LIST_FOREACH_AFTER(same_sysfs, other, d)
+                if (startswith(UNIT(other)->id, "sys-"))
+                        return UNIT(other);
+
+        LIST_FOREACH_BEFORE(same_sysfs, other, d) {
+                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;
+        _cleanup_set_free_ Set *set = NULL;
+        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)
+                        return r;
+        }
+
+        LIST_FOREACH_BEFORE(same_sysfs, other, d) {
+                r = set_put(set, other);
+                if (r < 0)
+                        return r;
+        }
+
+        *_set = TAKE_PTR(set);
+        return 1;
+}
+
+static void device_shutdown(Manager *m) {
+        assert(m);
+
+        m->device_monitor = sd_device_monitor_unref(m->device_monitor);
+        m->devices_by_sysfs = hashmap_free(m->devices_by_sysfs);
+}
+
+static void device_enumerate(Manager *m) {
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+        sd_device *dev;
+        int r;
+
+        assert(m);
+
+        if (!m->device_monitor) {
+                r = sd_device_monitor_new(&m->device_monitor);
+                if (r < 0) {
+                        log_error_errno(r, "Failed to allocate device monitor: %m");
+                        goto fail;
+                }
+
+                /* This will fail if we are unprivileged, but that
+                 * should not matter much, as user instances won't run
+                 * during boot. */
+                (void) sd_device_monitor_set_receive_buffer_size(m->device_monitor, 128*1024*1024);
+
+                r = sd_device_monitor_filter_add_match_tag(m->device_monitor, "systemd");
+                if (r < 0) {
+                        log_error_errno(r, "Failed to add udev tag match: %m");
+                        goto fail;
+                }
+
+                r = sd_device_monitor_attach_event(m->device_monitor, m->event);
+                if (r < 0) {
+                        log_error_errno(r, "Failed to attach event to device monitor: %m");
+                        goto fail;
+                }
+
+                r = sd_device_monitor_start(m->device_monitor, device_dispatch_io, m);
+                if (r < 0) {
+                        log_error_errno(r, "Failed to start device monitor: %m");
+                        goto fail;
+                }
+        }
+
+        r = sd_device_enumerator_new(&e);
+        if (r < 0) {
+                log_error_errno(r, "Failed to allocate device enumerator: %m");
+                goto fail;
+        }
+
+        r = sd_device_enumerator_add_match_tag(e, "systemd");
+        if (r < 0) {
+                log_error_errno(r, "Failed to set tag for device enumeration: %m");
+                goto fail;
+        }
+
+        FOREACH_DEVICE(e, dev) {
+                const char *sysfs;
+
+                if (!device_is_ready(dev))
+                        continue;
+
+                (void) device_process_new(m, dev);
+
+                if (sd_device_get_syspath(dev, &sysfs) < 0)
+                        continue;
+
+                device_update_found_by_sysfs(m, sysfs, DEVICE_FOUND_UDEV, DEVICE_FOUND_UDEV);
+        }
+
+        return;
+
+fail:
+        device_shutdown(m);
+}
+
+static void device_propagate_reload_by_sysfs(Manager *m, const char *sysfs) {
+        Device *d, *l, *n;
+        int r;
+
+        assert(m);
+        assert(sysfs);
+
+        l = hashmap_get(m->devices_by_sysfs, sysfs);
+        LIST_FOREACH_SAFE(same_sysfs, d, n, l) {
+                if (d->state == DEVICE_DEAD)
+                        continue;
+
+                r = manager_propagate_reload(m, UNIT(d), JOB_REPLACE, NULL);
+                if (r < 0)
+                        log_warning_errno(r, "Failed to propagate reload, ignoring: %m");
+        }
+}
+
+static int device_remove_old(Manager *m, sd_device *dev) {
+        _cleanup_free_ char *syspath_old = NULL, *e = NULL;
+        const char *devpath_old;
+        int r;
+
+        r = sd_device_get_property_value(dev, "DEVPATH_OLD", &devpath_old);
+        if (r < 0) {
+                log_device_debug_errno(dev, r, "Failed to get DEVPATH_OLD= property on 'move' uevent, ignoring: %m");
+                return 0;
+        }
+
+        syspath_old = path_join("/sys", devpath_old);
+        if (!syspath_old)
+                return log_oom();
+
+        r = unit_name_from_path(syspath_old, ".device", &e);
+        if (r < 0)
+                return log_device_error_errno(dev, r, "Failed to generate unit name from old device path: %m");
+
+        device_update_found_by_sysfs(m, syspath_old, 0, DEVICE_FOUND_UDEV|DEVICE_FOUND_MOUNT|DEVICE_FOUND_SWAP);
+        return 0;
+}
+
+static int device_dispatch_io(sd_device_monitor *monitor, sd_device *dev, void *userdata) {
+        Manager *m = userdata;
+        DeviceAction action;
+        const char *sysfs;
+        int r;
+
+        assert(m);
+        assert(dev);
+
+        r = sd_device_get_syspath(dev, &sysfs);
+        if (r < 0) {
+                log_device_error_errno(dev, r, "Failed to get device sys path: %m");
+                return 0;
+        }
+
+        r = device_get_action(dev, &action);
+        if (r < 0) {
+                log_device_error_errno(dev, r, "Failed to get udev action: %m");
+                return 0;
+        }
+
+        if (!IN_SET(action, DEVICE_ACTION_ADD, DEVICE_ACTION_REMOVE, DEVICE_ACTION_MOVE))
+                device_propagate_reload_by_sysfs(m, sysfs);
+
+        if (action == DEVICE_ACTION_MOVE)
+                (void) device_remove_old(m, dev);
+
+        /* A change event can signal that a device is becoming ready, in particular if the device is using
+         * the SYSTEMD_READY logic in udev so we need to reach the else block of the following if, even for
+         * change events */
+        if (action == DEVICE_ACTION_REMOVE) {
+                r = swap_process_device_remove(m, dev);
+                if (r < 0)
+                        log_device_warning_errno(dev, r, "Failed to process swap device remove event, ignoring: %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, 0, DEVICE_FOUND_UDEV|DEVICE_FOUND_MOUNT|DEVICE_FOUND_SWAP);
+
+        } else if (device_is_ready(dev)) {
+
+                (void) device_process_new(m, dev);
+
+                r = swap_process_device_new(m, dev);
+                if (r < 0)
+                        log_device_warning_errno(dev, r, "Failed to process swap device new event, ignoring: %m");
+
+                manager_dispatch_load_queue(m);
+
+                /* The device is found now, set the udev found bit */
+                device_update_found_by_sysfs(m, sysfs, DEVICE_FOUND_UDEV, DEVICE_FOUND_UDEV);
+
+        } 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, 0, DEVICE_FOUND_UDEV);
+
+        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;
+}
+
+static int validate_node(Manager *m, const char *node, sd_device **ret) {
+        struct stat st;
+        int r;
+
+        assert(m);
+        assert(node);
+        assert(ret);
+
+        /* Validates a device node that showed up in /proc/swaps or /proc/self/mountinfo if it makes sense for us to
+         * track. Note that this validator is fine within missing device nodes, but not with badly set up ones! */
+
+        if (!path_startswith(node, "/dev")) {
+                *ret = NULL;
+                return 0; /* bad! */
+        }
+
+        if (stat(node, &st) < 0) {
+                if (errno != ENOENT)
+                        return log_error_errno(errno, "Failed to stat() device node file %s: %m", node);
+
+                *ret = NULL;
+                return 1; /* good! (though missing) */
+
+        } else {
+                _cleanup_(sd_device_unrefp) sd_device *dev = NULL;
+
+                r = device_new_from_stat_rdev(&dev, &st);
+                if (r == -ENOENT) {
+                        *ret = NULL;
+                        return 1; /* good! (though missing) */
+                } else if (r == -ENOTTY) {
+                        *ret = NULL;
+                        return 0; /* bad! (not a device node but some other kind of file system node) */
+                } else if (r < 0)
+                        return log_error_errno(r, "Failed to get udev device from devnum %u:%u: %m", major(st.st_rdev), minor(st.st_rdev));
+
+                *ret = TAKE_PTR(dev);
+                return 1; /* good! */
+        }
+}
+
+void device_found_node(Manager *m, const char *node, DeviceFound found, DeviceFound mask) {
+        int r;
+
+        assert(m);
+        assert(node);
+
+        if (!device_supported())
+                return;
+
+        if (mask == 0)
+                return;
+
+        /* 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.
+         *
+         * This takes a pair of DeviceFound flags parameters. The 'mask' parameter is a bit mask that indicates which
+         * bits of 'found' to copy into the per-device DeviceFound flags field. Thus, this function may be used to set
+         * and unset individual bits in a single call, while merging partially with previous state. */
+
+        if ((found & mask) != 0) {
+                _cleanup_(sd_device_unrefp) sd_device *dev = NULL;
+
+                /* 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. But first, let's validate if
+                 * everything is alright with the device node. */
+
+                r = validate_node(m, node, &dev);
+                if (r <= 0)
+                        return; /* Don't create a device unit for this if the device node is borked. */
+
+                (void) device_setup_unit(m, dev, node, false);
+        }
+
+        /* Update the device unit's state, should it exist */
+        (void) device_update_found_by_name(m, node, found, mask);
+}
+
+bool device_shall_be_bound_by(Unit *device, Unit *u) {
+        assert(device);
+        assert(u);
+
+        if (u->type != UNIT_MOUNT)
+                return false;
+
+        return DEVICE(device)->bind_mounts;
+}
+
+const UnitVTable device_vtable = {
+        .object_size = sizeof(Device),
+        .sections =
+                "Unit\0"
+                "Device\0"
+                "Install\0",
+
+        .gc_jobs = true,
+
+        .init = device_init,
+        .done = device_done,
+        .load = device_load,
+
+        .coldplug = device_coldplug,
+        .catchup = device_catchup,
+
+        .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,
+
+        .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.",
+                },
+        },
+};