Adding upstream version 252.22.upstream/252.22

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

1 files changed, 1072 insertions, 0 deletions

diff --git a/src/core/path.c b/src/core/path.c
new file mode 100644
index 0000000..a8144c3
--- /dev/null
+++ b/src/core/path.c
@@ -0,0 +1,1072 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <sys/epoll.h>
+#include <sys/inotify.h>
+#include <unistd.h>
+
+#include "bus-error.h"
+#include "bus-util.h"
+#include "dbus-path.h"
+#include "dbus-unit.h"
+#include "escape.h"
+#include "event-util.h"
+#include "fd-util.h"
+#include "glob-util.h"
+#include "inotify-util.h"
+#include "macro.h"
+#include "mkdir-label.h"
+#include "path.h"
+#include "path-util.h"
+#include "serialize.h"
+#include "special.h"
+#include "stat-util.h"
+#include "string-table.h"
+#include "string-util.h"
+#include "unit-name.h"
+#include "unit.h"
+
+static const UnitActiveState state_translation_table[_PATH_STATE_MAX] = {
+        [PATH_DEAD]    = UNIT_INACTIVE,
+        [PATH_WAITING] = UNIT_ACTIVE,
+        [PATH_RUNNING] = UNIT_ACTIVE,
+        [PATH_FAILED]  = UNIT_FAILED,
+};
+
+static int path_dispatch_io(sd_event_source *source, int fd, uint32_t revents, void *userdata);
+
+int path_spec_watch(PathSpec *s, sd_event_io_handler_t handler) {
+        static const int flags_table[_PATH_TYPE_MAX] = {
+                [PATH_EXISTS]              = IN_DELETE_SELF|IN_MOVE_SELF|IN_ATTRIB,
+                [PATH_EXISTS_GLOB]         = IN_DELETE_SELF|IN_MOVE_SELF|IN_ATTRIB,
+                [PATH_CHANGED]             = IN_DELETE_SELF|IN_MOVE_SELF|IN_ATTRIB|IN_CLOSE_WRITE|IN_CREATE|IN_DELETE|IN_MOVED_FROM|IN_MOVED_TO,
+                [PATH_MODIFIED]            = IN_DELETE_SELF|IN_MOVE_SELF|IN_ATTRIB|IN_CLOSE_WRITE|IN_CREATE|IN_DELETE|IN_MOVED_FROM|IN_MOVED_TO|IN_MODIFY,
+                [PATH_DIRECTORY_NOT_EMPTY] = IN_DELETE_SELF|IN_MOVE_SELF|IN_ATTRIB|IN_CREATE|IN_MOVED_TO,
+        };
+
+        bool exists = false;
+        char *slash, *oldslash = NULL;
+        int r;
+
+        assert(s);
+        assert(s->unit);
+        assert(handler);
+
+        path_spec_unwatch(s);
+
+        s->inotify_fd = inotify_init1(IN_NONBLOCK|IN_CLOEXEC);
+        if (s->inotify_fd < 0) {
+                r = log_error_errno(errno, "Failed to allocate inotify fd: %m");
+                goto fail;
+        }
+
+        r = sd_event_add_io(s->unit->manager->event, &s->event_source, s->inotify_fd, EPOLLIN, handler, s);
+        if (r < 0) {
+                log_error_errno(r, "Failed to add inotify fd to event loop: %m");
+                goto fail;
+        }
+
+        (void) sd_event_source_set_description(s->event_source, "path");
+
+        /* This function assumes the path was passed through path_simplify()! */
+        assert(!strstr(s->path, "//"));
+
+        for (slash = strchr(s->path, '/'); ; slash = strchr(slash+1, '/')) {
+                bool incomplete = false;
+                int flags, wd = -1;
+                char tmp, *cut;
+
+                if (slash) {
+                        cut = slash + (slash == s->path);
+                        tmp = *cut;
+                        *cut = '\0';
+
+                        flags = IN_MOVE_SELF | IN_DELETE_SELF | IN_ATTRIB | IN_CREATE | IN_MOVED_TO;
+                } else {
+                        cut = NULL;
+                        flags = flags_table[s->type];
+                }
+
+                /* If this is a symlink watch both the symlink inode and where it points to. If the inode is
+                 * not a symlink both calls will install the same watch, which is redundant and doesn't
+                 * hurt. */
+                for (int follow_symlink = 0; follow_symlink < 2; follow_symlink ++) {
+                        uint32_t f = flags;
+
+                        SET_FLAG(f, IN_DONT_FOLLOW, !follow_symlink);
+
+                        wd = inotify_add_watch(s->inotify_fd, s->path, f);
+                        if (wd < 0) {
+                                if (IN_SET(errno, EACCES, ENOENT)) {
+                                        incomplete = true; /* This is an expected error, let's accept this
+                                                            * quietly: we have an incomplete watch for
+                                                            * now. */
+                                        break;
+                                }
+
+                                /* This second call to inotify_add_watch() should fail like the previous one
+                                 * and is done for logging the error in a comprehensive way. */
+                                wd = inotify_add_watch_and_warn(s->inotify_fd, s->path, f);
+                                if (wd < 0) {
+                                        if (cut)
+                                                *cut = tmp;
+
+                                        r = wd;
+                                        goto fail;
+                                }
+
+                                /* Hmm, we succeeded in adding the watch this time... let's continue. */
+                        }
+                }
+
+                if (incomplete) {
+                        if (cut)
+                                *cut = tmp;
+
+                        break;
+                }
+
+                exists = true;
+
+                /* Path exists, we don't need to watch parent too closely. */
+                if (oldslash) {
+                        char *cut2 = oldslash + (oldslash == s->path);
+                        char tmp2 = *cut2;
+                        *cut2 = '\0';
+
+                        (void) inotify_add_watch(s->inotify_fd, s->path, IN_MOVE_SELF);
+                        /* Error is ignored, the worst can happen is we get spurious events. */
+
+                        *cut2 = tmp2;
+                }
+
+                if (cut)
+                        *cut = tmp;
+
+                if (slash)
+                        oldslash = slash;
+                else {
+                        /* whole path has been iterated over */
+                        s->primary_wd = wd;
+                        break;
+                }
+        }
+
+        if (!exists) {
+                r = log_error_errno(errno, "Failed to add watch on any of the components of %s: %m", s->path);
+                /* either EACCESS or ENOENT */
+                goto fail;
+        }
+
+        return 0;
+
+fail:
+        path_spec_unwatch(s);
+        return r;
+}
+
+void path_spec_unwatch(PathSpec *s) {
+        assert(s);
+
+        s->event_source = sd_event_source_disable_unref(s->event_source);
+        s->inotify_fd = safe_close(s->inotify_fd);
+}
+
+int path_spec_fd_event(PathSpec *s, uint32_t revents) {
+        union inotify_event_buffer buffer;
+        ssize_t l;
+
+        assert(s);
+
+        if (revents != EPOLLIN)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "Got invalid poll event on inotify.");
+
+        l = read(s->inotify_fd, &buffer, sizeof(buffer));
+        if (l < 0) {
+                if (ERRNO_IS_TRANSIENT(errno))
+                        return 0;
+
+                return log_error_errno(errno, "Failed to read inotify event: %m");
+        }
+
+        if (IN_SET(s->type, PATH_CHANGED, PATH_MODIFIED))
+                FOREACH_INOTIFY_EVENT_WARN(e, buffer, l)
+                        if (s->primary_wd == e->wd)
+                                return 1;
+
+        return 0;
+}
+
+static bool path_spec_check_good(PathSpec *s, bool initial, bool from_trigger_notify, char **ret_trigger_path) {
+        _cleanup_free_ char *trigger = NULL;
+        bool b, good = false;
+
+        assert(s);
+        assert(ret_trigger_path);
+
+        switch (s->type) {
+
+        case PATH_EXISTS:
+                good = access(s->path, F_OK) >= 0;
+                break;
+
+        case PATH_EXISTS_GLOB:
+                good = glob_first(s->path, &trigger) > 0;
+                break;
+
+        case PATH_DIRECTORY_NOT_EMPTY: {
+                int k;
+
+                k = dir_is_empty(s->path, /* ignore_hidden_or_backup= */ true);
+                good = !(IN_SET(k, -ENOENT, -ENOTDIR) || k > 0);
+                break;
+        }
+
+        case PATH_CHANGED:
+        case PATH_MODIFIED:
+                b = access(s->path, F_OK) >= 0;
+                good = !initial && !from_trigger_notify && b != s->previous_exists;
+                s->previous_exists = b;
+                break;
+
+        default:
+                ;
+        }
+
+        if (good) {
+                if (!trigger) {
+                        trigger = strdup(s->path);
+                        if (!trigger)
+                                (void) log_oom_debug();
+                }
+                *ret_trigger_path = TAKE_PTR(trigger);
+        }
+
+        return good;
+}
+
+static void path_spec_mkdir(PathSpec *s, mode_t mode) {
+        int r;
+
+        if (IN_SET(s->type, PATH_EXISTS, PATH_EXISTS_GLOB))
+                return;
+
+        r = mkdir_p_label(s->path, mode);
+        if (r < 0)
+                log_warning_errno(r, "mkdir(%s) failed: %m", s->path);
+}
+
+static void path_spec_dump(PathSpec *s, FILE *f, const char *prefix) {
+        const char *type;
+
+        assert_se(type = path_type_to_string(s->type));
+        fprintf(f, "%s%s: %s\n", prefix, type, s->path);
+}
+
+void path_spec_done(PathSpec *s) {
+        assert(s);
+        assert(s->inotify_fd == -1);
+
+        free(s->path);
+}
+
+static void path_init(Unit *u) {
+        Path *p = PATH(u);
+
+        assert(u);
+        assert(u->load_state == UNIT_STUB);
+
+        p->directory_mode = 0755;
+
+        p->trigger_limit.interval = USEC_INFINITY;
+        p->trigger_limit.burst = UINT_MAX;
+}
+
+void path_free_specs(Path *p) {
+        PathSpec *s;
+
+        assert(p);
+
+        while ((s = p->specs)) {
+                path_spec_unwatch(s);
+                LIST_REMOVE(spec, p->specs, s);
+                path_spec_done(s);
+                free(s);
+        }
+}
+
+static void path_done(Unit *u) {
+        Path *p = PATH(u);
+
+        assert(p);
+
+        p->trigger_notify_event_source = sd_event_source_disable_unref(p->trigger_notify_event_source);
+        path_free_specs(p);
+}
+
+static int path_add_mount_dependencies(Path *p) {
+        int r;
+
+        assert(p);
+
+        LIST_FOREACH(spec, s, p->specs) {
+                r = unit_require_mounts_for(UNIT(p), s->path, UNIT_DEPENDENCY_FILE);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+static int path_verify(Path *p) {
+        assert(p);
+        assert(UNIT(p)->load_state == UNIT_LOADED);
+
+        if (!p->specs)
+                return log_unit_error_errno(UNIT(p), SYNTHETIC_ERRNO(ENOEXEC), "Path unit lacks path setting. Refusing.");
+
+        return 0;
+}
+
+static int path_add_default_dependencies(Path *p) {
+        int r;
+
+        assert(p);
+
+        if (!UNIT(p)->default_dependencies)
+                return 0;
+
+        r = unit_add_dependency_by_name(UNIT(p), UNIT_BEFORE, SPECIAL_PATHS_TARGET, true, UNIT_DEPENDENCY_DEFAULT);
+        if (r < 0)
+                return r;
+
+        if (MANAGER_IS_SYSTEM(UNIT(p)->manager)) {
+                r = unit_add_two_dependencies_by_name(UNIT(p), UNIT_AFTER, UNIT_REQUIRES, SPECIAL_SYSINIT_TARGET, true, UNIT_DEPENDENCY_DEFAULT);
+                if (r < 0)
+                        return r;
+        }
+
+        return unit_add_two_dependencies_by_name(UNIT(p), UNIT_BEFORE, UNIT_CONFLICTS, SPECIAL_SHUTDOWN_TARGET, true, UNIT_DEPENDENCY_DEFAULT);
+}
+
+static int path_add_trigger_dependencies(Path *p) {
+        Unit *x;
+        int r;
+
+        assert(p);
+
+        if (UNIT_TRIGGER(UNIT(p)))
+                return 0;
+
+        r = unit_load_related_unit(UNIT(p), ".service", &x);
+        if (r < 0)
+                return r;
+
+        return unit_add_two_dependencies(UNIT(p), UNIT_BEFORE, UNIT_TRIGGERS, x, true, UNIT_DEPENDENCY_IMPLICIT);
+}
+
+static int path_add_extras(Path *p) {
+        int r;
+
+        assert(p);
+
+        /* To avoid getting pid1 in a busy-loop state (eg: unmet condition on associated service),
+         * set a default trigger limit if the user didn't specify any. */
+        if (p->trigger_limit.interval == USEC_INFINITY)
+                p->trigger_limit.interval = 2 * USEC_PER_SEC;
+
+        if (p->trigger_limit.burst == UINT_MAX)
+                p->trigger_limit.burst = 200;
+
+        r = path_add_trigger_dependencies(p);
+        if (r < 0)
+                return r;
+
+        r = path_add_mount_dependencies(p);
+        if (r < 0)
+                return r;
+
+        return path_add_default_dependencies(p);
+}
+
+static int path_load(Unit *u) {
+        Path *p = PATH(u);
+        int r;
+
+        assert(u);
+        assert(u->load_state == UNIT_STUB);
+
+        r = unit_load_fragment_and_dropin(u, true);
+        if (r < 0)
+                return r;
+
+        if (u->load_state != UNIT_LOADED)
+                return 0;
+
+        r = path_add_extras(p);
+        if (r < 0)
+                return r;
+
+        return path_verify(p);
+}
+
+static void path_dump(Unit *u, FILE *f, const char *prefix) {
+        Path *p = PATH(u);
+        Unit *trigger;
+
+        assert(p);
+        assert(f);
+
+        trigger = UNIT_TRIGGER(u);
+
+        fprintf(f,
+                "%sPath State: %s\n"
+                "%sResult: %s\n"
+                "%sUnit: %s\n"
+                "%sMakeDirectory: %s\n"
+                "%sDirectoryMode: %04o\n"
+                "%sTriggerLimitIntervalSec: %s\n"
+                "%sTriggerLimitBurst: %u\n",
+                prefix, path_state_to_string(p->state),
+                prefix, path_result_to_string(p->result),
+                prefix, trigger ? trigger->id : "n/a",
+                prefix, yes_no(p->make_directory),
+                prefix, p->directory_mode,
+                prefix, FORMAT_TIMESPAN(p->trigger_limit.interval, USEC_PER_SEC),
+                prefix, p->trigger_limit.burst);
+
+        LIST_FOREACH(spec, s, p->specs)
+                path_spec_dump(s, f, prefix);
+}
+
+static void path_unwatch(Path *p) {
+        assert(p);
+
+        LIST_FOREACH(spec, s, p->specs)
+                path_spec_unwatch(s);
+}
+
+static int path_watch(Path *p) {
+        int r;
+
+        assert(p);
+
+        LIST_FOREACH(spec, s, p->specs) {
+                r = path_spec_watch(s, path_dispatch_io);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+static void path_set_state(Path *p, PathState state) {
+        PathState old_state;
+        assert(p);
+
+        if (p->state != state)
+                bus_unit_send_pending_change_signal(UNIT(p), false);
+
+        old_state = p->state;
+        p->state = state;
+
+        if (!IN_SET(state, PATH_WAITING, PATH_RUNNING))
+                path_unwatch(p);
+
+        if (state != old_state)
+                log_unit_debug(UNIT(p), "Changed %s -> %s", path_state_to_string(old_state), path_state_to_string(state));
+
+        unit_notify(UNIT(p), state_translation_table[old_state], state_translation_table[state], 0);
+}
+
+static void path_enter_waiting(Path *p, bool initial, bool from_trigger_notify);
+
+static int path_coldplug(Unit *u) {
+        Path *p = PATH(u);
+
+        assert(p);
+        assert(p->state == PATH_DEAD);
+
+        if (p->deserialized_state != p->state) {
+
+                if (IN_SET(p->deserialized_state, PATH_WAITING, PATH_RUNNING))
+                        path_enter_waiting(p, true, false);
+                else
+                        path_set_state(p, p->deserialized_state);
+        }
+
+        return 0;
+}
+
+static void path_enter_dead(Path *p, PathResult f) {
+        assert(p);
+
+        if (p->result == PATH_SUCCESS)
+                p->result = f;
+
+        unit_log_result(UNIT(p), p->result == PATH_SUCCESS, path_result_to_string(p->result));
+        path_set_state(p, p->result != PATH_SUCCESS ? PATH_FAILED : PATH_DEAD);
+}
+
+static void path_enter_running(Path *p, char *trigger_path) {
+        _cleanup_(activation_details_unrefp) ActivationDetails *details = NULL;
+        _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+        Unit *trigger;
+        Job *job;
+        int r;
+
+        assert(p);
+
+        /* Don't start job if we are supposed to go down */
+        if (unit_stop_pending(UNIT(p)))
+                return;
+
+        if (!ratelimit_below(&p->trigger_limit)) {
+                log_unit_warning(UNIT(p), "Trigger limit hit, refusing further activation.");
+                path_enter_dead(p, PATH_FAILURE_TRIGGER_LIMIT_HIT);
+                return;
+        }
+
+        trigger = UNIT_TRIGGER(UNIT(p));
+        if (!trigger) {
+                log_unit_error(UNIT(p), "Unit to trigger vanished.");
+                path_enter_dead(p, PATH_FAILURE_RESOURCES);
+                return;
+        }
+
+        details = activation_details_new(UNIT(p));
+        if (!details) {
+                r = -ENOMEM;
+                goto fail;
+        }
+
+        r = free_and_strdup(&(ACTIVATION_DETAILS_PATH(details))->trigger_path_filename, trigger_path);
+        if (r < 0)
+                goto fail;
+
+        r = manager_add_job(UNIT(p)->manager, JOB_START, trigger, JOB_REPLACE, NULL, &error, &job);
+        if (r < 0)
+                goto fail;
+
+        job_set_activation_details(job, details);
+
+        path_set_state(p, PATH_RUNNING);
+        path_unwatch(p);
+
+        return;
+
+fail:
+        log_unit_warning(UNIT(p), "Failed to queue unit startup job: %s", bus_error_message(&error, r));
+        path_enter_dead(p, PATH_FAILURE_RESOURCES);
+}
+
+static bool path_check_good(Path *p, bool initial, bool from_trigger_notify, char **ret_trigger_path) {
+        assert(p);
+        assert(ret_trigger_path);
+
+        LIST_FOREACH(spec, s, p->specs)
+                if (path_spec_check_good(s, initial, from_trigger_notify, ret_trigger_path))
+                        return true;
+
+        return false;
+}
+
+static void path_enter_waiting(Path *p, bool initial, bool from_trigger_notify) {
+        _cleanup_free_ char *trigger_path = NULL;
+        Unit *trigger;
+        int r;
+
+        if (p->trigger_notify_event_source)
+                (void) event_source_disable(p->trigger_notify_event_source);
+
+        /* If the triggered unit is already running, so are we */
+        trigger = UNIT_TRIGGER(UNIT(p));
+        if (trigger && !UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(trigger))) {
+                path_set_state(p, PATH_RUNNING);
+                path_unwatch(p);
+                return;
+        }
+
+        if (path_check_good(p, initial, from_trigger_notify, &trigger_path)) {
+                log_unit_debug(UNIT(p), "Got triggered.");
+                path_enter_running(p, trigger_path);
+                return;
+        }
+
+        r = path_watch(p);
+        if (r < 0)
+                goto fail;
+
+        /* Hmm, so now we have created inotify watches, but the file
+         * might have appeared/been removed by now, so we must
+         * recheck */
+
+        if (path_check_good(p, false, from_trigger_notify, &trigger_path)) {
+                log_unit_debug(UNIT(p), "Got triggered.");
+                path_enter_running(p, trigger_path);
+                return;
+        }
+
+        path_set_state(p, PATH_WAITING);
+        return;
+
+fail:
+        log_unit_warning_errno(UNIT(p), r, "Failed to enter waiting state: %m");
+        path_enter_dead(p, PATH_FAILURE_RESOURCES);
+}
+
+static void path_mkdir(Path *p) {
+        assert(p);
+
+        if (!p->make_directory)
+                return;
+
+        LIST_FOREACH(spec, s, p->specs)
+                path_spec_mkdir(s, p->directory_mode);
+}
+
+static int path_start(Unit *u) {
+        Path *p = PATH(u);
+        int r;
+
+        assert(p);
+        assert(IN_SET(p->state, PATH_DEAD, PATH_FAILED));
+
+        r = unit_test_trigger_loaded(u);
+        if (r < 0)
+                return r;
+
+        r = unit_acquire_invocation_id(u);
+        if (r < 0)
+                return r;
+
+        path_mkdir(p);
+
+        p->result = PATH_SUCCESS;
+        path_enter_waiting(p, true, false);
+
+        return 1;
+}
+
+static int path_stop(Unit *u) {
+        Path *p = PATH(u);
+
+        assert(p);
+        assert(IN_SET(p->state, PATH_WAITING, PATH_RUNNING));
+
+        path_enter_dead(p, PATH_SUCCESS);
+        return 1;
+}
+
+static int path_serialize(Unit *u, FILE *f, FDSet *fds) {
+        Path *p = PATH(u);
+
+        assert(u);
+        assert(f);
+        assert(fds);
+
+        (void) serialize_item(f, "state", path_state_to_string(p->state));
+        (void) serialize_item(f, "result", path_result_to_string(p->result));
+
+        LIST_FOREACH(spec, s, p->specs) {
+                const char *type;
+                _cleanup_free_ char *escaped = NULL;
+
+                escaped = cescape(s->path);
+                if (!escaped)
+                        return log_oom();
+
+                assert_se(type = path_type_to_string(s->type));
+                (void) serialize_item_format(f, "path-spec", "%s %i %s",
+                                             type,
+                                             s->previous_exists,
+                                             escaped);
+        }
+
+        return 0;
+}
+
+static int path_deserialize_item(Unit *u, const char *key, const char *value, FDSet *fds) {
+        Path *p = PATH(u);
+
+        assert(u);
+        assert(key);
+        assert(value);
+        assert(fds);
+
+        if (streq(key, "state")) {
+                PathState state;
+
+                state = path_state_from_string(value);
+                if (state < 0)
+                        log_unit_debug(u, "Failed to parse state value: %s", value);
+                else
+                        p->deserialized_state = state;
+
+        } else if (streq(key, "result")) {
+                PathResult f;
+
+                f = path_result_from_string(value);
+                if (f < 0)
+                        log_unit_debug(u, "Failed to parse result value: %s", value);
+                else if (f != PATH_SUCCESS)
+                        p->result = f;
+
+        } else if (streq(key, "path-spec")) {
+                int previous_exists, skip = 0;
+                _cleanup_free_ char *type_str = NULL;
+
+                if (sscanf(value, "%ms %i %n", &type_str, &previous_exists, &skip) < 2)
+                        log_unit_debug(u, "Failed to parse path-spec value: %s", value);
+                else {
+                        _cleanup_free_ char *unescaped = NULL;
+                        ssize_t l;
+                        PathType type;
+
+                        type = path_type_from_string(type_str);
+                        if (type < 0) {
+                                log_unit_warning(u, "Unknown path type \"%s\", ignoring.", type_str);
+                                return 0;
+                        }
+
+                        l = cunescape(value+skip, 0, &unescaped);
+                        if (l < 0) {
+                                log_unit_warning_errno(u, l, "Failed to unescape serialize path: %m");
+                                return 0;
+                        }
+
+                        LIST_FOREACH(spec, s, p->specs)
+                                if (s->type == type &&
+                                    path_equal(s->path, unescaped)) {
+
+                                        s->previous_exists = previous_exists;
+                                        break;
+                                }
+                }
+
+        } else
+                log_unit_debug(u, "Unknown serialization key: %s", key);
+
+        return 0;
+}
+
+_pure_ static UnitActiveState path_active_state(Unit *u) {
+        assert(u);
+
+        return state_translation_table[PATH(u)->state];
+}
+
+_pure_ static const char *path_sub_state_to_string(Unit *u) {
+        assert(u);
+
+        return path_state_to_string(PATH(u)->state);
+}
+
+static int path_dispatch_io(sd_event_source *source, int fd, uint32_t revents, void *userdata) {
+        PathSpec *s = userdata, *found = NULL;
+        Path *p;
+        int changed;
+
+        assert(s);
+        assert(s->unit);
+        assert(fd >= 0);
+
+        p = PATH(s->unit);
+
+        if (!IN_SET(p->state, PATH_WAITING, PATH_RUNNING))
+                return 0;
+
+        LIST_FOREACH(spec, i, p->specs)
+                if (path_spec_owns_inotify_fd(i, fd)) {
+                        found = i;
+                        break;
+                }
+
+        if (!found) {
+                log_error("Got event on unknown fd.");
+                goto fail;
+        }
+
+        changed = path_spec_fd_event(found, revents);
+        if (changed < 0)
+                goto fail;
+
+        if (changed)
+                path_enter_running(p, found->path);
+        else
+                path_enter_waiting(p, false, false);
+
+        return 0;
+
+fail:
+        path_enter_dead(p, PATH_FAILURE_RESOURCES);
+        return 0;
+}
+
+static void path_trigger_notify_impl(Unit *u, Unit *other, bool on_defer);
+
+static int path_trigger_notify_on_defer(sd_event_source *s, void *userdata) {
+        Path *p = ASSERT_PTR(userdata);
+        Unit *trigger;
+
+        assert(s);
+
+        trigger = UNIT_TRIGGER(UNIT(p));
+        if (!trigger) {
+                log_unit_error(UNIT(p), "Unit to trigger vanished.");
+                path_enter_dead(p, PATH_FAILURE_RESOURCES);
+                return 0;
+        }
+
+        path_trigger_notify_impl(UNIT(p), trigger, /* on_defer = */ true);
+        return 0;
+}
+
+static void path_trigger_notify_impl(Unit *u, Unit *other, bool on_defer) {
+        Path *p = PATH(u);
+        int r;
+
+        assert(u);
+        assert(other);
+
+        /* Invoked whenever the unit we trigger changes state or gains or loses a job */
+
+        /* Filter out invocations with bogus state */
+        assert(UNIT_IS_LOAD_COMPLETE(other->load_state));
+
+        /* Don't propagate state changes from the triggered unit if we are already down */
+        if (!IN_SET(p->state, PATH_WAITING, PATH_RUNNING))
+                return;
+
+        /* Propagate start limit hit state */
+        if (other->start_limit_hit) {
+                path_enter_dead(p, PATH_FAILURE_UNIT_START_LIMIT_HIT);
+                return;
+        }
+
+        /* Don't propagate anything if there's still a job queued */
+        if (other->job)
+                return;
+
+        if (p->state == PATH_RUNNING &&
+            UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(other))) {
+                if (!on_defer)
+                        log_unit_debug(u, "Got notified about unit deactivation.");
+        } else if (p->state == PATH_WAITING &&
+                   !UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(other))) {
+                if (!on_defer)
+                        log_unit_debug(u, "Got notified about unit activation.");
+        } else
+                return;
+
+        if (on_defer) {
+                path_enter_waiting(p, /* initial = */ false, /* from_trigger_notify = */ true);
+                return;
+        }
+
+        /* Do not call path_enter_waiting() directly from path_trigger_notify(), as this may be called by
+         * job_install() -> job_finish_and_invalidate() -> unit_trigger_notify(), and path_enter_waiting()
+         * may install another job and will trigger assertion in job_install().
+         * https://github.com/systemd/systemd/issues/24577#issuecomment-1522628906
+         * Hence, first setup defer event source here, and call path_enter_waiting() slightly later. */
+        if (p->trigger_notify_event_source) {
+                r = sd_event_source_set_enabled(p->trigger_notify_event_source, SD_EVENT_ONESHOT);
+                if (r < 0) {
+                        log_unit_warning_errno(u, r, "Failed to enable event source for triggering notify: %m");
+                        path_enter_dead(p, PATH_FAILURE_RESOURCES);
+                        return;
+                }
+        } else {
+                r = sd_event_add_defer(u->manager->event, &p->trigger_notify_event_source, path_trigger_notify_on_defer, p);
+                if (r < 0) {
+                        log_unit_warning_errno(u, r, "Failed to allocate event source for triggering notify: %m");
+                        path_enter_dead(p, PATH_FAILURE_RESOURCES);
+                        return;
+                }
+
+                (void) sd_event_source_set_description(p->trigger_notify_event_source, "path-trigger-notify");
+        }
+}
+
+static void path_trigger_notify(Unit *u, Unit *other) {
+        path_trigger_notify_impl(u, other, /* on_defer = */ false);
+}
+
+static void path_reset_failed(Unit *u) {
+        Path *p = PATH(u);
+
+        assert(p);
+
+        if (p->state == PATH_FAILED)
+                path_set_state(p, PATH_DEAD);
+
+        p->result = PATH_SUCCESS;
+}
+
+static int path_can_start(Unit *u) {
+        Path *p = PATH(u);
+        int r;
+
+        assert(p);
+
+        r = unit_test_start_limit(u);
+        if (r < 0) {
+                path_enter_dead(p, PATH_FAILURE_START_LIMIT_HIT);
+                return r;
+        }
+
+        return 1;
+}
+
+static void activation_details_path_done(ActivationDetails *details) {
+        ActivationDetailsPath *p = ASSERT_PTR(ACTIVATION_DETAILS_PATH(details));
+
+        p->trigger_path_filename = mfree(p->trigger_path_filename);
+}
+
+static void activation_details_path_serialize(ActivationDetails *details, FILE *f) {
+        ActivationDetailsPath *p = ASSERT_PTR(ACTIVATION_DETAILS_PATH(details));
+
+        assert(f);
+
+        if (p->trigger_path_filename)
+                (void) serialize_item(f, "activation-details-path-filename", p->trigger_path_filename);
+}
+
+static int activation_details_path_deserialize(const char *key, const char *value, ActivationDetails **details) {
+        int r;
+
+        assert(key);
+        assert(value);
+
+        if (!details || !*details)
+                return -EINVAL;
+
+        ActivationDetailsPath *p = ACTIVATION_DETAILS_PATH(*details);
+        if (!p)
+                return -EINVAL;
+
+        if (!streq(key, "activation-details-path-filename"))
+                return -EINVAL;
+
+        r = free_and_strdup(&p->trigger_path_filename, value);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+static int activation_details_path_append_env(ActivationDetails *details, char ***strv) {
+        ActivationDetailsPath *p = ACTIVATION_DETAILS_PATH(details);
+        char *s;
+        int r;
+
+        assert(details);
+        assert(strv);
+        assert(p);
+
+        if (isempty(p->trigger_path_filename))
+                return 0;
+
+        s = strjoin("TRIGGER_PATH=", p->trigger_path_filename);
+        if (!s)
+                return -ENOMEM;
+
+        r = strv_consume(strv, TAKE_PTR(s));
+        if (r < 0)
+                return r;
+
+        return 1; /* Return the number of variables added to the env block */
+}
+
+static int activation_details_path_append_pair(ActivationDetails *details, char ***strv) {
+        ActivationDetailsPath *p = ACTIVATION_DETAILS_PATH(details);
+        int r;
+
+        assert(details);
+        assert(strv);
+        assert(p);
+
+        if (isempty(p->trigger_path_filename))
+                return 0;
+
+        r = strv_extend(strv, "trigger_path");
+        if (r < 0)
+                return r;
+
+        r = strv_extend(strv, p->trigger_path_filename);
+        if (r < 0)
+                return r;
+
+        return 1; /* Return the number of pairs added to the env block */
+}
+
+static const char* const path_type_table[_PATH_TYPE_MAX] = {
+        [PATH_EXISTS]              = "PathExists",
+        [PATH_EXISTS_GLOB]         = "PathExistsGlob",
+        [PATH_DIRECTORY_NOT_EMPTY] = "DirectoryNotEmpty",
+        [PATH_CHANGED]             = "PathChanged",
+        [PATH_MODIFIED]            = "PathModified",
+};
+
+DEFINE_STRING_TABLE_LOOKUP(path_type, PathType);
+
+static const char* const path_result_table[_PATH_RESULT_MAX] = {
+        [PATH_SUCCESS]                      = "success",
+        [PATH_FAILURE_RESOURCES]            = "resources",
+        [PATH_FAILURE_START_LIMIT_HIT]      = "start-limit-hit",
+        [PATH_FAILURE_UNIT_START_LIMIT_HIT] = "unit-start-limit-hit",
+        [PATH_FAILURE_TRIGGER_LIMIT_HIT]    = "trigger-limit-hit",
+};
+
+DEFINE_STRING_TABLE_LOOKUP(path_result, PathResult);
+
+const UnitVTable path_vtable = {
+        .object_size = sizeof(Path),
+
+        .sections =
+                "Unit\0"
+                "Path\0"
+                "Install\0",
+        .private_section = "Path",
+
+        .can_transient = true,
+        .can_fail = true,
+        .can_trigger = true,
+
+        .init = path_init,
+        .done = path_done,
+        .load = path_load,
+
+        .coldplug = path_coldplug,
+
+        .dump = path_dump,
+
+        .start = path_start,
+        .stop = path_stop,
+
+        .serialize = path_serialize,
+        .deserialize_item = path_deserialize_item,
+
+        .active_state = path_active_state,
+        .sub_state_to_string = path_sub_state_to_string,
+
+        .trigger_notify = path_trigger_notify,
+
+        .reset_failed = path_reset_failed,
+
+        .bus_set_property = bus_path_set_property,
+
+        .can_start = path_can_start,
+};
+
+const ActivationDetailsVTable activation_details_path_vtable = {
+        .object_size = sizeof(ActivationDetailsPath),
+
+        .done = activation_details_path_done,
+        .serialize = activation_details_path_serialize,
+        .deserialize = activation_details_path_deserialize,
+        .append_env = activation_details_path_append_env,
+        .append_pair = activation_details_path_append_pair,
+};