src/core/path.c - systemd-stable - Rivoreo Source Code Repositories

 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

 /***
   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 <sys/inotify.h>
 #include <sys/epoll.h>
 #include <sys/ioctl.h>
 #include <errno.h>
 #include <unistd.h>

 #include "unit.h"
 #include "unit-name.h"
 #include "path.h"
 #include "mkdir.h"
 #include "dbus-path.h"
 #include "special.h"
 #include "path-util.h"
 #include "macro.h"
 #include "bus-util.h"
 #include "bus-error.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 = -errno;
                 goto fail;
         }

         r = sd_event_add_io(s->unit->manager->event, &s->event_source, s->inotify_fd, EPOLLIN, handler, s);
         if (r < 0)
                 goto fail;

         /* This assumes the path was passed through path_kill_slashes()! */

         for (slash = strchr(s->path, '/'); ; slash = strchr(slash+1, '/')) {
                 char *cut = NULL;
                 int flags;
                 char tmp;

                 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
                         flags = flags_table[s->type];

                 r = inotify_add_watch(s->inotify_fd, s->path, flags);
                 if (r < 0) {
                         if (errno == EACCES || errno == ENOENT) {
                                 if (cut)
                                         *cut = tmp;
                                 break;
                         }

                         log_warning("Failed to add watch on %s: %s", s->path,
                                     errno == ENOSPC ? "too many watches" : strerror(-r));
                         r = -errno;
                         if (cut)
                                 *cut = tmp;
                         goto fail;
                 } else {
                         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';

                                 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 = r;
                         break;
                 }
         }

         if (!exists) {
                 log_error("Failed to add watch on any of the components of %s: %m",
                           s->path);
                 r = -errno; /* 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_unref(s->event_source);
         s->inotify_fd = safe_close(s->inotify_fd);
 }

 int path_spec_fd_event(PathSpec *s, uint32_t revents) {
         _cleanup_free_ uint8_t *buf = NULL;
         struct inotify_event *e;
         ssize_t k;
         int l;
         int r = 0;

         if (revents != EPOLLIN) {
                 log_error("Got invalid poll event on inotify.");
                 return -EINVAL;
         }

         if (ioctl(s->inotify_fd, FIONREAD, &l) < 0) {
                 log_error("FIONREAD failed: %m");
                 return -errno;
         }

         assert(l > 0);

         buf = malloc(l);
         if (!buf)
                 return log_oom();

         k = read(s->inotify_fd, buf, l);
         if (k < 0) {
                 log_error("Failed to read inotify event: %m");
                 return -errno;
         }

         e = (struct inotify_event*) buf;

         while (k > 0) {
                 size_t step;

                 if ((s->type == PATH_CHANGED || s->type == PATH_MODIFIED) &&
                     s->primary_wd == e->wd)
                         r = 1;

                 step = sizeof(struct inotify_event) + e->len;
                 assert(step <= (size_t) k);

                 e = (struct inotify_event*) ((uint8_t*) e + step);
                 k -= step;
         }

         return r;
 }

 static bool path_spec_check_good(PathSpec *s, bool initial) {
         bool good = false;

         switch (s->type) {

         case PATH_EXISTS:
                 good = access(s->path, F_OK) >= 0;
                 break;

         case PATH_EXISTS_GLOB:
                 good = glob_exists(s->path) > 0;
                 break;

         case PATH_DIRECTORY_NOT_EMPTY: {
                 int k;

                 k = dir_is_empty(s->path);
                 good = !(k == -ENOENT || k > 0);
                 break;
         }

         case PATH_CHANGED:
         case PATH_MODIFIED: {
                 bool b;

                 b = access(s->path, F_OK) >= 0;
                 good = !initial && b != s->previous_exists;
                 s->previous_exists = b;
                 break;
         }

         default:
                 ;
         }

         return good;
 }

 static void path_spec_mkdir(PathSpec *s, mode_t mode) {
         int r;

         if (s->type == PATH_EXISTS || s->type == PATH_EXISTS_GLOB)
                 return;

         r = mkdir_p_label(s->path, mode);
         if (r < 0)
                 log_warning("mkdir(%s) failed: %s", s->path, strerror(-r));
 }

 static void path_spec_dump(PathSpec *s, FILE *f, const char *prefix) {
         fprintf(f,
                 "%s%s: %s\n",
                 prefix,
                 path_type_to_string(s->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;
 }

 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);

         path_free_specs(p);
 }

 static int path_add_mount_links(Path *p) {
         PathSpec *s;
         int r;

         assert(p);

         LIST_FOREACH(spec, s, p->specs) {
                 r = unit_require_mounts_for(UNIT(p), s->path);
                 if (r < 0)
                         return r;
         }

         return 0;
 }

 static int path_verify(Path *p) {
         assert(p);

         if (UNIT(p)->load_state != UNIT_LOADED)
                 return 0;

         if (!p->specs) {
                 log_error_unit(UNIT(p)->id,
                                "%s lacks path setting. Refusing.", UNIT(p)->id);
                 return -EINVAL;
         }

         return 0;
 }

 static int path_add_default_dependencies(Path *p) {
         int r;

         assert(p);

         r = unit_add_dependency_by_name(UNIT(p), UNIT_BEFORE,
                                         SPECIAL_PATHS_TARGET, NULL, true);
         if (r < 0)
                 return r;

         if (UNIT(p)->manager->running_as == SYSTEMD_SYSTEM) {
                 r = unit_add_two_dependencies_by_name(UNIT(p), UNIT_AFTER, UNIT_REQUIRES,
                                                       SPECIAL_SYSINIT_TARGET, NULL, true);
                 if (r < 0)
                         return r;
         }

         return unit_add_two_dependencies_by_name(UNIT(p), UNIT_BEFORE, UNIT_CONFLICTS,
                                                  SPECIAL_SHUTDOWN_TARGET, NULL, true);
 }

 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);
         if (r < 0)
                 return r;

         if (u->load_state == UNIT_LOADED) {

                 if (set_isempty(u->dependencies[UNIT_TRIGGERS])) {
                         Unit *x;

                         r = unit_load_related_unit(u, ".service", &x);
                         if (r < 0)
                                 return r;

                         r = unit_add_two_dependencies(u, UNIT_BEFORE, UNIT_TRIGGERS, x, true);
                         if (r < 0)
                                 return r;
                 }

                 r = path_add_mount_links(p);
                 if (r < 0)
                         return r;

                 if (UNIT(p)->default_dependencies) {
                         r = path_add_default_dependencies(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;
         PathSpec *s;

         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",
                 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);

         LIST_FOREACH(spec, s, p->specs)
                 path_spec_dump(s, f, prefix);
 }

 static void path_unwatch(Path *p) {
         PathSpec *s;

         assert(p);

         LIST_FOREACH(spec, s, p->specs)
                 path_spec_unwatch(s);
 }

 static int path_watch(Path *p) {
         int r;
         PathSpec *s;

         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);

         old_state = p->state;
         p->state = state;

         if (state != PATH_WAITING &&
             (state != PATH_RUNNING || p->inotify_triggered))
                 path_unwatch(p);

         if (state != old_state)
                 log_debug("%s changed %s -> %s",
                           UNIT(p)->id,
                           path_state_to_string(old_state),
                           path_state_to_string(state));

         unit_notify(UNIT(p), state_translation_table[old_state], state_translation_table[state], true);
 }

 static void path_enter_waiting(Path *p, bool initial, bool recheck);

 static int path_coldplug(Unit *u) {
         Path *p = PATH(u);

         assert(p);
         assert(p->state == PATH_DEAD);

         if (p->deserialized_state != p->state) {

                 if (p->deserialized_state == PATH_WAITING ||
                     p->deserialized_state == PATH_RUNNING)
                         path_enter_waiting(p, true, true);
                 else
                         path_set_state(p, p->deserialized_state);
         }

         return 0;
 }

 static void path_enter_dead(Path *p, PathResult f) {
         assert(p);

         if (f != PATH_SUCCESS)
                 p->result = f;

         path_set_state(p, p->result != PATH_SUCCESS ? PATH_FAILED : PATH_DEAD);
 }

 static void path_enter_running(Path *p) {
         _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
         int r;

         assert(p);

         /* Don't start job if we are supposed to go down */
         if (unit_stop_pending(UNIT(p)))
                 return;

         r = manager_add_job(UNIT(p)->manager, JOB_START, UNIT_TRIGGER(UNIT(p)),
                             JOB_REPLACE, true, &error, NULL);
         if (r < 0)
                 goto fail;

         p->inotify_triggered = false;

         r = path_watch(p);
         if (r < 0)
                 goto fail;

         path_set_state(p, PATH_RUNNING);
         return;

 fail:
         log_warning("%s failed to queue unit startup job: %s",
                     UNIT(p)->id, bus_error_message(&error, r));
         path_enter_dead(p, PATH_FAILURE_RESOURCES);
 }

 static bool path_check_good(Path *p, bool initial) {
         PathSpec *s;
         bool good = false;

         assert(p);

         LIST_FOREACH(spec, s, p->specs) {
                 good = path_spec_check_good(s, initial);

                 if (good)
                         break;
         }

         return good;
 }

 static void path_enter_waiting(Path *p, bool initial, bool recheck) {
         int r;

         if (recheck)
                 if (path_check_good(p, initial)) {
                         log_debug("%s got triggered.", UNIT(p)->id);
                         path_enter_running(p);
                         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 (recheck)
                 if (path_check_good(p, false)) {
                         log_debug("%s got triggered.", UNIT(p)->id);
                         path_enter_running(p);
                         return;
                 }

         path_set_state(p, PATH_WAITING);
         return;

 fail:
         log_warning("%s failed to enter waiting state: %s",
                     UNIT(p)->id, strerror(-r));
         path_enter_dead(p, PATH_FAILURE_RESOURCES);
 }

 static void path_mkdir(Path *p) {
         PathSpec *s;

         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);

         assert(p);
         assert(p->state == PATH_DEAD || p->state == PATH_FAILED);

         if (UNIT_TRIGGER(u)->load_state != UNIT_LOADED)
                 return -ENOENT;

         path_mkdir(p);

         p->result = PATH_SUCCESS;
         path_enter_waiting(p, true, true);

         return 0;
 }

 static int path_stop(Unit *u) {
         Path *p = PATH(u);

         assert(p);
         assert(p->state == PATH_WAITING || p->state == PATH_RUNNING);

         path_enter_dead(p, PATH_SUCCESS);
         return 0;
 }

 static int path_serialize(Unit *u, FILE *f, FDSet *fds) {
         Path *p = PATH(u);

         assert(u);
         assert(f);
         assert(fds);

         unit_serialize_item(u, f, "state", path_state_to_string(p->state));
         unit_serialize_item(u, f, "result", path_result_to_string(p->result));

         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_debug("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_debug("Failed to parse result value %s", value);
                 else if (f != PATH_SUCCESS)
                         p->result = f;

         } else
                 log_debug("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;
         Path *p;
         int changed;

         assert(s);
         assert(s->unit);
         assert(fd >= 0);

         p = PATH(s->unit);

         if (p->state != PATH_WAITING &&
             p->state != PATH_RUNNING)
                 return 0;

         /* log_debug("inotify wakeup on %s.", u->id); */

         LIST_FOREACH(spec, s, p->specs)
                 if (path_spec_owns_inotify_fd(s, fd))
                         break;

         if (!s) {
                 log_error("Got event on unknown fd.");
                 goto fail;
         }

         changed = path_spec_fd_event(s, revents);
         if (changed < 0)
                 goto fail;

         /* If we are already running, then remember that one event was
          * dispatched so that we restart the service only if something
          * actually changed on disk */
         p->inotify_triggered = true;

         if (changed)
                 path_enter_running(p);
         else
                 path_enter_waiting(p, false, true);

         return 0;

 fail:
         path_enter_dead(p, PATH_FAILURE_RESOURCES);
         return 0;
 }

 static void path_trigger_notify(Unit *u, Unit *other) {
         Path *p = PATH(u);

         assert(u);
         assert(other);

         /* Invoked whenever the unit we trigger changes state or gains
          * or loses a job */

         if (other->load_state != UNIT_LOADED)
                 return;

         if (p->state == PATH_RUNNING &&
             UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(other))) {
                 log_debug_unit(UNIT(p)->id,
                                "%s got notified about unit deactivation.",
                                UNIT(p)->id);

                 /* Hmm, so inotify was triggered since the
                  * last activation, so I guess we need to
                  * recheck what is going on. */
                 path_enter_waiting(p, false, p->inotify_triggered);
         }
 }

 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 const char* const path_state_table[_PATH_STATE_MAX] = {
         [PATH_DEAD] = "dead",
         [PATH_WAITING] = "waiting",
         [PATH_RUNNING] = "running",
         [PATH_FAILED] = "failed"
 };

 DEFINE_STRING_TABLE_LOOKUP(path_state, PathState);

 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",
 };

 DEFINE_STRING_TABLE_LOOKUP(path_result, PathResult);

 const UnitVTable path_vtable = {
         .object_size = sizeof(Path),

         .sections =
                 "Unit\0"
                 "Path\0"
                 "Install\0",

         .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_interface = "org.freedesktop.systemd1.Path",
         .bus_vtable = bus_path_vtable
 };
	/-- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil --/

	/***
	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 <sys/inotify.h>
	#include <sys/epoll.h>
	#include <sys/ioctl.h>
	#include <errno.h>
	#include <unistd.h>

	#include "unit.h"
	#include "unit-name.h"
	#include "path.h"
	#include "mkdir.h"
	#include "dbus-path.h"
	#include "special.h"
	#include "path-util.h"
	#include "macro.h"
	#include "bus-util.h"
	#include "bus-error.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 = -errno;
	goto fail;
	}

	r = sd_event_add_io(s->unit->manager->event, &s->event_source, s->inotify_fd, EPOLLIN, handler, s);
	if (r < 0)
	goto fail;

	/* This assumes the path was passed through path_kill_slashes()! */

	for (slash = strchr(s->path, '/'); ; slash = strchr(slash+1, '/')) {
	char *cut = NULL;
	int flags;
	char tmp;

	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
	flags = flags_table[s->type];

	r = inotify_add_watch(s->inotify_fd, s->path, flags);
	if (r < 0) {
	if (errno == EACCES \|\| errno == ENOENT) {
	if (cut)
	*cut = tmp;
	break;
	}

	log_warning("Failed to add watch on %s: %s", s->path,
	errno == ENOSPC ? "too many watches" : strerror(-r));
	r = -errno;
	if (cut)
	*cut = tmp;
	goto fail;
	} else {
	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';

	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 = r;
	break;
	}
	}

	if (!exists) {
	log_error("Failed to add watch on any of the components of %s: %m",
	s->path);
	r = -errno; /* 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_unref(s->event_source);
	s->inotify_fd = safe_close(s->inotify_fd);
	}

	int path_spec_fd_event(PathSpec *s, uint32_t revents) {
	_cleanup_free_ uint8_t *buf = NULL;
	struct inotify_event *e;
	ssize_t k;
	int l;
	int r = 0;

	if (revents != EPOLLIN) {
	log_error("Got invalid poll event on inotify.");
	return -EINVAL;
	}

	if (ioctl(s->inotify_fd, FIONREAD, &l) < 0) {
	log_error("FIONREAD failed: %m");
	return -errno;
	}

	assert(l > 0);

	buf = malloc(l);
	if (!buf)
	return log_oom();

	k = read(s->inotify_fd, buf, l);
	if (k < 0) {
	log_error("Failed to read inotify event: %m");
	return -errno;
	}

	e = (struct inotify_event*) buf;

	while (k > 0) {
	size_t step;

	if ((s->type == PATH_CHANGED \|\| s->type == PATH_MODIFIED) &&
	s->primary_wd == e->wd)
	r = 1;

	step = sizeof(struct inotify_event) + e->len;
	assert(step <= (size_t) k);

	e = (struct inotify_event) ((uint8_t) e + step);
	k -= step;
	}

	return r;
	}

	static bool path_spec_check_good(PathSpec *s, bool initial) {
	bool good = false;

	switch (s->type) {

	case PATH_EXISTS:
	good = access(s->path, F_OK) >= 0;
	break;

	case PATH_EXISTS_GLOB:
	good = glob_exists(s->path) > 0;
	break;

	case PATH_DIRECTORY_NOT_EMPTY: {
	int k;

	k = dir_is_empty(s->path);
	good = !(k == -ENOENT \|\| k > 0);
	break;
	}

	case PATH_CHANGED:
	case PATH_MODIFIED: {
	bool b;

	b = access(s->path, F_OK) >= 0;
	good = !initial && b != s->previous_exists;
	s->previous_exists = b;
	break;
	}

	default:
	;
	}

	return good;
	}

	static void path_spec_mkdir(PathSpec *s, mode_t mode) {
	int r;

	if (s->type == PATH_EXISTS \|\| s->type == PATH_EXISTS_GLOB)
	return;

	r = mkdir_p_label(s->path, mode);
	if (r < 0)
	log_warning("mkdir(%s) failed: %s", s->path, strerror(-r));
	}

	static void path_spec_dump(PathSpec s, FILE f, const char *prefix) {
	fprintf(f,
	"%s%s: %s\n",
	prefix,
	path_type_to_string(s->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;
	}

	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);

	path_free_specs(p);
	}

	static int path_add_mount_links(Path *p) {
	PathSpec *s;
	int r;

	assert(p);

	LIST_FOREACH(spec, s, p->specs) {
	r = unit_require_mounts_for(UNIT(p), s->path);
	if (r < 0)
	return r;
	}

	return 0;
	}

	static int path_verify(Path *p) {
	assert(p);

	if (UNIT(p)->load_state != UNIT_LOADED)
	return 0;

	if (!p->specs) {
	log_error_unit(UNIT(p)->id,
	"%s lacks path setting. Refusing.", UNIT(p)->id);
	return -EINVAL;
	}

	return 0;
	}

	static int path_add_default_dependencies(Path *p) {
	int r;

	assert(p);

	r = unit_add_dependency_by_name(UNIT(p), UNIT_BEFORE,
	SPECIAL_PATHS_TARGET, NULL, true);
	if (r < 0)
	return r;

	if (UNIT(p)->manager->running_as == SYSTEMD_SYSTEM) {
	r = unit_add_two_dependencies_by_name(UNIT(p), UNIT_AFTER, UNIT_REQUIRES,
	SPECIAL_SYSINIT_TARGET, NULL, true);
	if (r < 0)
	return r;
	}

	return unit_add_two_dependencies_by_name(UNIT(p), UNIT_BEFORE, UNIT_CONFLICTS,
	SPECIAL_SHUTDOWN_TARGET, NULL, true);
	}

	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);
	if (r < 0)
	return r;

	if (u->load_state == UNIT_LOADED) {

	if (set_isempty(u->dependencies[UNIT_TRIGGERS])) {
	Unit *x;

	r = unit_load_related_unit(u, ".service", &x);
	if (r < 0)
	return r;

	r = unit_add_two_dependencies(u, UNIT_BEFORE, UNIT_TRIGGERS, x, true);
	if (r < 0)
	return r;
	}

	r = path_add_mount_links(p);
	if (r < 0)
	return r;

	if (UNIT(p)->default_dependencies) {
	r = path_add_default_dependencies(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;
	PathSpec *s;

	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",
	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);

	LIST_FOREACH(spec, s, p->specs)
	path_spec_dump(s, f, prefix);
	}

	static void path_unwatch(Path *p) {
	PathSpec *s;

	assert(p);

	LIST_FOREACH(spec, s, p->specs)
	path_spec_unwatch(s);
	}

	static int path_watch(Path *p) {
	int r;
	PathSpec *s;

	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);

	old_state = p->state;
	p->state = state;

	if (state != PATH_WAITING &&
	(state != PATH_RUNNING \|\| p->inotify_triggered))
	path_unwatch(p);

	if (state != old_state)
	log_debug("%s changed %s -> %s",
	UNIT(p)->id,
	path_state_to_string(old_state),
	path_state_to_string(state));

	unit_notify(UNIT(p), state_translation_table[old_state], state_translation_table[state], true);
	}

	static void path_enter_waiting(Path *p, bool initial, bool recheck);

	static int path_coldplug(Unit *u) {
	Path *p = PATH(u);

	assert(p);
	assert(p->state == PATH_DEAD);

	if (p->deserialized_state != p->state) {

	if (p->deserialized_state == PATH_WAITING \|\|
	p->deserialized_state == PATH_RUNNING)
	path_enter_waiting(p, true, true);
	else
	path_set_state(p, p->deserialized_state);
	}

	return 0;
	}

	static void path_enter_dead(Path *p, PathResult f) {
	assert(p);

	if (f != PATH_SUCCESS)
	p->result = f;

	path_set_state(p, p->result != PATH_SUCCESS ? PATH_FAILED : PATH_DEAD);
	}

	static void path_enter_running(Path *p) {
	_cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
	int r;

	assert(p);

	/* Don't start job if we are supposed to go down */
	if (unit_stop_pending(UNIT(p)))
	return;

	r = manager_add_job(UNIT(p)->manager, JOB_START, UNIT_TRIGGER(UNIT(p)),
	JOB_REPLACE, true, &error, NULL);
	if (r < 0)
	goto fail;

	p->inotify_triggered = false;

	r = path_watch(p);
	if (r < 0)
	goto fail;

	path_set_state(p, PATH_RUNNING);
	return;

	fail:
	log_warning("%s failed to queue unit startup job: %s",
	UNIT(p)->id, bus_error_message(&error, r));
	path_enter_dead(p, PATH_FAILURE_RESOURCES);
	}

	static bool path_check_good(Path *p, bool initial) {
	PathSpec *s;
	bool good = false;

	assert(p);

	LIST_FOREACH(spec, s, p->specs) {
	good = path_spec_check_good(s, initial);

	if (good)
	break;
	}

	return good;
	}

	static void path_enter_waiting(Path *p, bool initial, bool recheck) {
	int r;

	if (recheck)
	if (path_check_good(p, initial)) {
	log_debug("%s got triggered.", UNIT(p)->id);
	path_enter_running(p);
	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 (recheck)
	if (path_check_good(p, false)) {
	log_debug("%s got triggered.", UNIT(p)->id);
	path_enter_running(p);
	return;
	}

	path_set_state(p, PATH_WAITING);
	return;

	fail:
	log_warning("%s failed to enter waiting state: %s",
	UNIT(p)->id, strerror(-r));
	path_enter_dead(p, PATH_FAILURE_RESOURCES);
	}

	static void path_mkdir(Path *p) {
	PathSpec *s;

	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);

	assert(p);
	assert(p->state == PATH_DEAD \|\| p->state == PATH_FAILED);

	if (UNIT_TRIGGER(u)->load_state != UNIT_LOADED)
	return -ENOENT;

	path_mkdir(p);

	p->result = PATH_SUCCESS;
	path_enter_waiting(p, true, true);

	return 0;
	}

	static int path_stop(Unit *u) {
	Path *p = PATH(u);

	assert(p);
	assert(p->state == PATH_WAITING \|\| p->state == PATH_RUNNING);

	path_enter_dead(p, PATH_SUCCESS);
	return 0;
	}

	static int path_serialize(Unit u, FILE f, FDSet *fds) {
	Path *p = PATH(u);

	assert(u);
	assert(f);
	assert(fds);

	unit_serialize_item(u, f, "state", path_state_to_string(p->state));
	unit_serialize_item(u, f, "result", path_result_to_string(p->result));

	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_debug("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_debug("Failed to parse result value %s", value);
	else if (f != PATH_SUCCESS)
	p->result = f;

	} else
	log_debug("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;
	Path *p;
	int changed;

	assert(s);
	assert(s->unit);
	assert(fd >= 0);

	p = PATH(s->unit);

	if (p->state != PATH_WAITING &&
	p->state != PATH_RUNNING)
	return 0;

	/* log_debug("inotify wakeup on %s.", u->id); */

	LIST_FOREACH(spec, s, p->specs)
	if (path_spec_owns_inotify_fd(s, fd))
	break;

	if (!s) {
	log_error("Got event on unknown fd.");
	goto fail;
	}

	changed = path_spec_fd_event(s, revents);
	if (changed < 0)
	goto fail;

	/* If we are already running, then remember that one event was
	* dispatched so that we restart the service only if something
	* actually changed on disk */
	p->inotify_triggered = true;

	if (changed)
	path_enter_running(p);
	else
	path_enter_waiting(p, false, true);

	return 0;

	fail:
	path_enter_dead(p, PATH_FAILURE_RESOURCES);
	return 0;
	}

	static void path_trigger_notify(Unit u, Unit other) {
	Path *p = PATH(u);

	assert(u);
	assert(other);

	/* Invoked whenever the unit we trigger changes state or gains
	* or loses a job */

	if (other->load_state != UNIT_LOADED)
	return;

	if (p->state == PATH_RUNNING &&
	UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(other))) {
	log_debug_unit(UNIT(p)->id,
	"%s got notified about unit deactivation.",
	UNIT(p)->id);

	/* Hmm, so inotify was triggered since the
	* last activation, so I guess we need to
	* recheck what is going on. */
	path_enter_waiting(p, false, p->inotify_triggered);
	}
	}

	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 const char* const path_state_table[_PATH_STATE_MAX] = {
	[PATH_DEAD] = "dead",
	[PATH_WAITING] = "waiting",
	[PATH_RUNNING] = "running",
	[PATH_FAILED] = "failed"
	};

	DEFINE_STRING_TABLE_LOOKUP(path_state, PathState);

	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",
	};

	DEFINE_STRING_TABLE_LOOKUP(path_result, PathResult);

	const UnitVTable path_vtable = {
	.object_size = sizeof(Path),

	.sections =
	"Unit\0"
	"Path\0"
	"Install\0",

	.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_interface = "org.freedesktop.systemd1.Path",
	.bus_vtable = bus_path_vtable
	};