path: add .path unit type for monitoring files

19 files changed, 919 insertions, 25 deletions

diff --git a/Makefile.am b/Makefile.am
index b404bbedff..9b0e04f905 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -77,7 +77,8 @@ interface_DATA = \
 	org.freedesktop.systemd1.Mount.xml \
 	org.freedesktop.systemd1.Automount.xml \
 	org.freedesktop.systemd1.Snapshot.xml \
-	org.freedesktop.systemd1.Swap.xml
+	org.freedesktop.systemd1.Swap.xml \
+	org.freedesktop.systemd1.Path.xml
 
 dist_systemunit_DATA = \
 	units/emergency.service \
@@ -189,6 +190,7 @@ COMMON_SOURCES = \
         src/snapshot.c \
         src/socket.c \
         src/timer.c \
+	src/path.c \
         src/load-dropin.c \
         src/execute.c \
         src/dbus.c \
@@ -205,6 +207,7 @@ COMMON_SOURCES = \
 	src/dbus-snapshot.c \
 	src/dbus-device.c \
 	src/dbus-execute.c \
+	src/dbus-path.c \
 	src/cgroup.c \
 	src/mount-setup.c \
 	src/hostname-setup.c \
diff --git a/src/automount.c b/src/automount.c
index 32680461c2..d83f3ed053 100644
--- a/src/automount.c
+++ b/src/automount.c
@@ -562,12 +562,15 @@ static int automount_start(Unit *u) {
 
         assert(a);
 
+        assert(a->state == AUTOMOUNT_DEAD || a->state == AUTOMOUNT_MAINTAINANCE);
+
         if (path_is_mount_point(a->where)) {
                 log_error("Path %s is already a mount point, refusing start for %s", a->where, u->meta.id);
                 return -EEXIST;
         }
 
-        assert(a->state == AUTOMOUNT_DEAD || a->state == AUTOMOUNT_MAINTAINANCE);
+        if (a->mount->meta.load_state != UNIT_LOADED)
+                return -ENOENT;
 
         a->failure = false;
         automount_enter_waiting(a);
diff --git a/src/conf-parser.c b/src/conf-parser.c
index 6994211b10..20f7641b13 100644
--- a/src/conf-parser.c
+++ b/src/conf-parser.c
@@ -337,6 +337,8 @@ int config_parse_path(
         if (!(n = strdup(rvalue)))
                 return -ENOMEM;
 
+        path_kill_slashes(n);
+
         free(*s);
         *s = n;
 
@@ -441,6 +443,8 @@ int config_parse_path_strv(
                         goto fail;
                 }
 
+                path_kill_slashes(n[k]);
+
                 k++;
         }
 
diff --git a/src/dbus-path.c b/src/dbus-path.c
new file mode 100644
index 0000000000..ed1dc265fc
--- /dev/null
+++ b/src/dbus-path.c
@@ -0,0 +1,52 @@
+/*-*- Mode: C; c-basic-offset: 8 -*-*/
+
+/***
+  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 General Public License as published by
+  the Free Software Foundation; either version 2 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
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <errno.h>
+
+#include "dbus-unit.h"
+#include "dbus-path.h"
+#include "dbus-execute.h"
+
+#define BUS_PATH_INTERFACE                                             \
+        " <interface name=\"org.freedesktop.systemd1.Path\">\n"        \
+        "  <property name=\"Unit\" type=\"s\"  access=\"read\"/>\n"     \
+        " </interface>\n"                                               \
+
+#define INTROSPECTION                                                   \
+        DBUS_INTROSPECT_1_0_XML_DOCTYPE_DECL_NODE                       \
+        "<node>\n"                                                      \
+        BUS_UNIT_INTERFACE                                              \
+        BUS_PATH_INTERFACE                                             \
+        BUS_PROPERTIES_INTERFACE                                        \
+        BUS_INTROSPECTABLE_INTERFACE                                    \
+        "</node>\n"
+
+const char bus_path_interface[] = BUS_PATH_INTERFACE;
+
+DBusHandlerResult bus_path_message_handler(Unit *u, DBusMessage *message) {
+        const BusProperty properties[] = {
+                BUS_UNIT_PROPERTIES,
+                { "org.freedesktop.systemd1.Path", "Unit", bus_property_append_string, "s", &u->path.unit->meta.id },
+                { NULL, NULL, NULL, NULL, NULL }
+        };
+
+        return bus_default_message_handler(u->meta.manager, message, INTROSPECTION, properties);
+}
diff --git a/src/dbus-path.h b/src/dbus-path.h
new file mode 100644
index 0000000000..15f5869894
--- /dev/null
+++ b/src/dbus-path.h
@@ -0,0 +1,33 @@
+/*-*- Mode: C; c-basic-offset: 8 -*-*/
+
+#ifndef foodbuspathhfoo
+#define foodbuspathhfoo
+
+/***
+  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 General Public License as published by
+  the Free Software Foundation; either version 2 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
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <dbus/dbus.h>
+
+#include "unit.h"
+
+DBusHandlerResult bus_path_message_handler(Unit *u, DBusMessage *message);
+
+extern const char bus_path_interface[];
+
+#endif
diff --git a/src/dbus.c b/src/dbus.c
index 6dd495d4df..f5bbc5815a 100644
--- a/src/dbus.c
+++ b/src/dbus.c
@@ -41,6 +41,7 @@
 #include "dbus-snapshot.h"
 #include "dbus-swap.h"
 #include "dbus-timer.h"
+#include "dbus-path.h"
 
 static const char bus_properties_interface[] = BUS_PROPERTIES_INTERFACE;
 static const char bus_introspectable_interface[] = BUS_INTROSPECTABLE_INTERFACE;
@@ -60,6 +61,7 @@ const char *const bus_interface_table[] = {
         "org.freedesktop.systemd1.Snapshot",   bus_snapshot_interface,
         "org.freedesktop.systemd1.Swap",       bus_swap_interface,
         "org.freedesktop.systemd1.Timer",      bus_timer_interface,
+        "org.freedesktop.systemd1.Path",       bus_path_interface,
         NULL
 };
 
diff --git a/src/load-fragment.c b/src/load-fragment.c
index 889e621100..a706880b9a 100644
--- a/src/load-fragment.c
+++ b/src/load-fragment.c
@@ -213,6 +213,8 @@ static int config_parse_listen(
                         free(p);
                         return -ENOMEM;
                 }
+
+                path_kill_slashes(p->path);
         } else {
                 p->type = SOCKET_SOCKET;
 
@@ -450,6 +452,8 @@ static int config_parse_exec(
         nce->argv = n;
         nce->path = path;
 
+        path_kill_slashes(nce->path);
+
         exec_command_append_list(e, nce);
 
         return 0;
@@ -1068,6 +1072,77 @@ static int config_parse_timer_unit(
         return 0;
 }
 
+static int config_parse_path_spec(
+                const char *filename,
+                unsigned line,
+                const char *section,
+                const char *lvalue,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        Path *p = data;
+        PathSpec *s;
+        PathType b;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+        assert(data);
+
+        if ((b = path_type_from_string(lvalue)) < 0) {
+                log_error("[%s:%u] Failed to parse path type: %s", filename, line, lvalue);
+                return -EINVAL;
+        }
+
+        if (!path_is_absolute(rvalue)) {
+                log_error("[%s:%u] Path is not absolute: %s", filename, line, rvalue);
+                return -EINVAL;
+        }
+
+        if (!(s = new0(PathSpec, 1)))
+                return -ENOMEM;
+
+        if (!(s->path = strdup(rvalue))) {
+                free(s);
+                return -ENOMEM;
+        }
+
+        path_kill_slashes(s->path);
+
+        s->type = b;
+        s->inotify_fd = -1;
+
+        LIST_PREPEND(PathSpec, spec, p->specs, s);
+
+        return 0;
+}
+
+static int config_parse_path_unit(
+                const char *filename,
+                unsigned line,
+                const char *section,
+                const char *lvalue,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        Path *t = data;
+        int r;
+
+        if (endswith(rvalue, ".path")) {
+                log_error("[%s:%u] Unit cannot be of type path: %s", filename, line, rvalue);
+                return -EINVAL;
+        }
+
+        if ((r = manager_load_unit(t->meta.manager, rvalue, NULL, &t->unit)) < 0) {
+                log_error("[%s:%u] Failed to load unit: %s", filename, line, rvalue);
+                return r;
+        }
+
+        return 0;
+}
+
 #define FOLLOW_MAX 8
 
 static int open_follow(char **filename, FILE **_f, Set *names, char **_final) {
@@ -1269,7 +1344,8 @@ static int load_from_path(Unit *u, const char *path) {
                 [UNIT_MOUNT]     = "Mount",
                 [UNIT_AUTOMOUNT] = "Automount",
                 [UNIT_SNAPSHOT]  = "Snapshot",
-                [UNIT_SWAP]      = "Swap"
+                [UNIT_SWAP]      = "Swap",
+                [UNIT_PATH]      = "Path"
         };
 
 #define EXEC_CONTEXT_CONFIG_ITEMS(context, section) \
@@ -1386,15 +1462,20 @@ static int load_from_path(Unit *u, const char *path) {
 
                 { "Where",                  config_parse_path,            &u->automount.where,                             "Automount" },
 
-                { "What",                   config_parse_path,            &u->swap.parameters_fragment.what,               "Swap" },
-                { "Priority",               config_parse_int,             &u->swap.parameters_fragment.priority,           "Swap" },
+                { "What",                   config_parse_path,            &u->swap.parameters_fragment.what,               "Swap"    },
+                { "Priority",               config_parse_int,             &u->swap.parameters_fragment.priority,           "Swap"    },
+
+                { "OnActive",               config_parse_timer,           &u->timer,                                       "Timer"   },
+                { "OnBoot",                 config_parse_timer,           &u->timer,                                       "Timer"   },
+                { "OnStartup",              config_parse_timer,           &u->timer,                                       "Timer"   },
+                { "OnUnitActive",           config_parse_timer,           &u->timer,                                       "Timer"   },
+                { "OnUnitInactive",         config_parse_timer,           &u->timer,                                       "Timer"   },
+                { "Unit",                   config_parse_timer_unit,      &u->timer,                                       "Timer"   },
 
-                { "OnActive",               config_parse_timer,           &u->timer,                                       "Timer" },
-                { "OnBoot",                 config_parse_timer,           &u->timer,                                       "Timer" },
-                { "OnStartup",              config_parse_timer,           &u->timer,                                       "Timer" },
-                { "OnUnitActive",           config_parse_timer,           &u->timer,                                       "Timer" },
-                { "OnUnitInactive",         config_parse_timer,           &u->timer,                                       "Timer" },
-                { "Unit",                   config_parse_timer_unit,      &u->timer,                                       "Timer" },
+                { "PathExists",             config_parse_path_spec,       &u->path,                                        "Path"    },
+                { "PathChanged",            config_parse_path_spec,       &u->path,                                        "Path"    },
+                { "DirectoryNotEmpty",      config_parse_path_spec,       &u->path,                                        "Path"    },
+                { "Unit",                   config_parse_path_unit,       &u->path,                                        "Path"    },
 
                 { NULL, NULL, NULL, NULL }
         };
diff --git a/src/mount.c b/src/mount.c
index 01fc2dffbb..dfe4f875e1 100644
--- a/src/mount.c
+++ b/src/mount.c
@@ -167,6 +167,19 @@ static int mount_add_swap_links(Mount *m) {
         return 0;
 }
 
+static int mount_add_path_links(Mount *m) {
+        Meta *other;
+        int r;
+
+        assert(m);
+
+        LIST_FOREACH(units_per_type, other, m->meta.manager->units_per_type[UNIT_PATH])
+                if ((r = path_add_one_mount_link((Path*) other, m)) < 0)
+                        return r;
+
+        return 0;
+}
+
 static int mount_add_automount_links(Mount *m) {
         Meta *other;
         int r;
@@ -341,6 +354,9 @@ static int mount_load(Unit *u) {
                 if ((r = mount_add_swap_links(m)) < 0)
                         return r;
 
+                if ((r = mount_add_path_links(m)) < 0)
+                        return r;
+
                 if ((r = mount_add_automount_links(m)) < 0)
                         return r;
 
diff --git a/src/path.c b/src/path.c
new file mode 100644
index 0000000000..b40a8297ff
--- /dev/null
+++ b/src/path.c
@@ -0,0 +1,578 @@
+/*-*- Mode: C; c-basic-offset: 8 -*-*/
+
+/***
+  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 General Public License as published by
+  the Free Software Foundation; either version 2 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
+  General Public License for more details.
+
+  You should have received a copy of the GNU 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 "dbus-path.h"
+
+static const UnitActiveState state_translation_table[_PATH_STATE_MAX] = {
+        [PATH_DEAD] = UNIT_INACTIVE,
+        [PATH_WAITING] = UNIT_ACTIVE,
+        [PATH_RUNNING] = UNIT_ACTIVE,
+        [PATH_MAINTAINANCE] = UNIT_INACTIVE
+};
+
+static void path_done(Unit *u) {
+        Path *p = PATH(u);
+        PathSpec *s;
+
+        assert(p);
+
+        while ((s = p->specs)) {
+                LIST_REMOVE(PathSpec, spec, p->specs, s);
+                free(s);
+        }
+}
+
+int path_add_one_mount_link(Path *p, Mount *m) {
+        PathSpec *s;
+        int r;
+
+        assert(p);
+        assert(m);
+
+        if (p->meta.load_state != UNIT_LOADED ||
+            m->meta.load_state != UNIT_LOADED)
+                return 0;
+
+        LIST_FOREACH(spec, s, p->specs) {
+
+                if (!path_startswith(s->path, m->where))
+                        continue;
+
+                if ((r = unit_add_dependency(UNIT(m), UNIT_BEFORE, UNIT(p), true)) < 0)
+                        return r;
+
+                if ((r = unit_add_dependency(UNIT(p), UNIT_REQUIRES, UNIT(m), true)) < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+static int path_add_mount_links(Path *p) {
+        Meta *other;
+        int r;
+
+        assert(p);
+
+        LIST_FOREACH(units_per_type, other, p->meta.manager->units_per_type[UNIT_MOUNT])
+                if ((r = path_add_one_mount_link(p, (Mount*) other)) < 0)
+                        return r;
+
+        return 0;
+}
+
+static int path_verify(Path *p) {
+        assert(p);
+
+        if (UNIT(p)->meta.load_state != UNIT_LOADED)
+                return 0;
+
+        if (!p->specs) {
+                log_error("%s lacks path setting. Refusing.", p->meta.id);
+                return -EINVAL;
+        }
+
+        return 0;
+}
+
+static int path_load(Unit *u) {
+        Path *p = PATH(u);
+        int r;
+
+        assert(u);
+        assert(u->meta.load_state == UNIT_STUB);
+
+        if ((r = unit_load_fragment_and_dropin(u)) < 0)
+                return r;
+
+        if (u->meta.load_state == UNIT_LOADED) {
+
+                if (!p->unit)
+                        if ((r = unit_load_related_unit(u, ".service", &p->unit)))
+                                return r;
+
+                if ((r = unit_add_dependency(u, UNIT_BEFORE, p->unit, true)) < 0)
+                        return r;
+
+                if ((r = path_add_mount_links(p)) < 0)
+                        return r;
+        }
+
+        return path_verify(p);
+}
+
+static void path_dump(Unit *u, FILE *f, const char *prefix) {
+        Path *p = PATH(u);
+        const char *prefix2;
+        char *p2;
+        PathSpec *s;
+
+        p2 = strappend(prefix, "\t");
+        prefix2 = p2 ? p2 : prefix;
+
+        fprintf(f,
+                "%sPath State: %s\n"
+                "%sUnit: %s\n",
+                prefix, path_state_to_string(p->state),
+                prefix, p->unit->meta.id);
+
+        LIST_FOREACH(spec, s, p->specs)
+                fprintf(f,
+                        "%s%s: %s\n",
+                        prefix,
+                        path_type_to_string(s->type),
+                        s->path);
+
+        free(p2);
+}
+
+static void path_unwatch_one(Path *p, PathSpec *s) {
+
+        if (s->inotify_fd < 0)
+                return;
+
+        unit_unwatch_fd(UNIT(p), &s->watch);
+
+        close_nointr_nofail(s->inotify_fd);
+        s->inotify_fd = -1;
+}
+
+static int path_watch_one(Path *p, PathSpec *s) {
+        static const int flags_table[_PATH_TYPE_MAX] = {
+                [PATH_EXISTS] = IN_DELETE_SELF|IN_MOVE_SELF,
+                [PATH_CHANGED] = IN_DELETE_SELF|IN_MOVE_SELF|IN_ATTRIB|IN_CLOSE_WRITE|IN_CREATE|IN_DELETE|IN_MOVED_FROM|IN_MOVED_TO,
+                [PATH_DIRECTORY_NOT_EMPTY] = IN_DELETE_SELF|IN_MOVE_SELF|IN_CREATE|IN_MOVED_TO
+        };
+
+        bool exists = false;
+        char *k;
+        int r;
+
+        assert(p);
+        assert(s);
+
+        path_unwatch_one(p, s);
+
+        if (!(k = strdup(s->path)))
+                return -ENOMEM;
+
+        if ((s->inotify_fd = inotify_init1(IN_NONBLOCK|IN_CLOEXEC)) < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        if (unit_watch_fd(UNIT(p), s->inotify_fd, EPOLLIN, &s->watch) < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        if ((s->primary_wd = inotify_add_watch(s->inotify_fd, k, flags_table[s->type])) >= 0)
+                exists = true;
+
+        for (;;) {
+                int flags;
+                char *slash;
+
+                /* This assumes the path was passed through path_kill_slashes()! */
+                if (!(slash = strrchr(k, '/')))
+                        break;
+
+                *slash = 0;
+
+                flags = IN_DELETE_SELF|IN_MOVE_SELF;
+                if (!exists)
+                        flags |= IN_CREATE | IN_MOVED_TO | IN_ATTRIB;
+
+                if (inotify_add_watch(s->inotify_fd, k, flags) >= 0)
+                        exists = true;
+        }
+
+        return 0;
+
+fail:
+        free(k);
+
+        path_unwatch_one(p, s);
+        return r;
+}
+
+static void path_unwatch(Path *p) {
+        PathSpec *s;
+
+        assert(p);
+
+        LIST_FOREACH(spec, s, p->specs)
+                path_unwatch_one(p, s);
+}
+
+static int path_watch(Path *p) {
+        int r;
+        PathSpec *s;
+
+        assert(p);
+
+        LIST_FOREACH(spec, s, p->specs)
+                if ((r = path_watch_one(p, s)) < 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)
+                path_unwatch(p);
+
+        if (state != old_state)
+                log_debug("%s changed %s -> %s",
+                          p->meta.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]);
+}
+
+static void path_enter_waiting(Path *p, bool initial);
+
+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);
+                else
+                        path_set_state(p, p->deserialized_state);
+        }
+
+        return 0;
+}
+
+static void path_enter_dead(Path *p, bool success) {
+        assert(p);
+
+        if (!success)
+                p->failure = true;
+
+        path_set_state(p, p->failure ? PATH_MAINTAINANCE : PATH_DEAD);
+}
+
+static void path_enter_running(Path *p) {
+        int r;
+        assert(p);
+
+        if ((r = manager_add_job(UNIT(p)->meta.manager, JOB_START, p->unit, JOB_REPLACE, true, NULL)) < 0)
+                goto fail;
+
+        path_set_state(p, PATH_RUNNING);
+        return;
+
+fail:
+        log_warning("%s failed to queue unit startup job: %s", p->meta.id, strerror(-r));
+        path_enter_dead(p, false);
+}
+
+
+static void path_enter_waiting(Path *p, bool initial) {
+        PathSpec *s;
+        int r;
+        bool good = false;
+
+        LIST_FOREACH(spec, s, p->specs) {
+
+                switch (s->type) {
+
+                case PATH_EXISTS:
+                        good = access(s->path, F_OK) >= 0;
+                        break;
+
+                case PATH_DIRECTORY_NOT_EMPTY:
+                        good = dir_is_empty(s->path) == 0;
+                        break;
+
+                case PATH_CHANGED: {
+                        bool b;
+
+                        b = access(s->path, F_OK) >= 0;
+                        good = !initial && b != s->previous_exists;
+                        s->previous_exists = b;
+                        break;
+                }
+
+                default:
+                        ;
+                }
+
+                if (good)
+                        break;
+        }
+
+        if (good) {
+                path_enter_running(p);
+                return;
+        }
+
+        if ((r = path_watch(p)) < 0)
+                goto fail;
+
+        path_set_state(p, PATH_WAITING);
+        return;
+
+fail:
+        log_warning("%s failed to enter waiting state: %s", p->meta.id, strerror(-r));
+        path_enter_dead(p, false);
+}
+
+static int path_start(Unit *u) {
+        Path *p = PATH(u);
+
+        assert(p);
+        assert(p->state == PATH_DEAD || p->state == PATH_MAINTAINANCE);
+
+        if (p->unit->meta.load_state != UNIT_LOADED)
+                return -ENOENT;
+
+        p->failure = false;
+path_enter_waiting(p, 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, true);
+        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));
+
+        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;
+
+                if ((state = path_state_from_string(value)) < 0)
+                        log_debug("Failed to parse state value %s", value);
+                else
+                        p->deserialized_state = state;
+        } else
+                log_debug("Unknown serialization key '%s'", key);
+
+        return 0;
+}
+
+static UnitActiveState path_active_state(Unit *u) {
+        assert(u);
+
+        return state_translation_table[PATH(u)->state];
+}
+
+static const char *path_sub_state_to_string(Unit *u) {
+        assert(u);
+
+        return path_state_to_string(PATH(u)->state);
+}
+
+static void path_fd_event(Unit *u, int fd, uint32_t events, Watch *w) {
+        Path *p = PATH(u);
+        int l;
+        ssize_t k;
+        struct inotify_event *buf = NULL;
+        PathSpec *s;
+
+        assert(p);
+        assert(fd >= 0);
+
+        if (p->state != PATH_WAITING)
+                return;
+
+        log_debug("inotify wakeup on %s.", u->meta.id);
+
+        if (events != EPOLLIN) {
+                log_error("Got Invalid poll event on inotify.");
+                goto fail;
+        }
+
+        LIST_FOREACH(spec, s, p->specs)
+                if (s->inotify_fd == fd)
+                        break;
+
+        if (!s) {
+                log_error("Got event on unknown fd.");
+                goto fail;
+        }
+
+        if (ioctl(fd, FIONREAD, &l) < 0) {
+                log_error("FIONREAD failed: %s", strerror(errno));
+                goto fail;
+        }
+
+        if (!(buf = malloc(l))) {
+                log_error("Failed to allocate buffer: %s", strerror(-ENOMEM));
+                goto fail;
+        }
+
+        if ((k = read(fd, buf, l)) < 0) {
+                log_error("Failed to read inotify event: %s", strerror(-errno));
+                goto fail;
+        }
+
+        if ((size_t) k < sizeof(struct inotify_event) ||
+            (size_t) k < sizeof(struct inotify_event) + buf->len) {
+                log_error("inotify event too small.");
+                goto fail;
+        }
+
+        if (s->type == PATH_CHANGED && s->primary_wd == buf->wd)
+                path_enter_running(p);
+        else
+                path_enter_waiting(p, false);
+
+        free(buf);
+
+        return;
+
+fail:
+        free(buf);
+        path_enter_dead(p, false);
+}
+
+void path_unit_notify(Unit *u, UnitActiveState new_state) {
+        char *n;
+        int r;
+        Iterator i;
+
+        if (u->meta.type == UNIT_PATH)
+                return;
+
+        SET_FOREACH(n, u->meta.names, i) {
+                char *k;
+                Unit *t;
+                Path *p;
+
+                if (!(k = unit_name_change_suffix(n, ".path"))) {
+                        r = -ENOMEM;
+                        goto fail;
+                }
+
+                t = manager_get_unit(u->meta.manager, k);
+                free(k);
+
+                if (!t)
+                        continue;
+
+                if (t->meta.load_state != UNIT_LOADED)
+                        continue;
+
+                p = PATH(t);
+
+                if (p->unit != u)
+                        continue;
+
+                if (p->state == PATH_RUNNING && new_state == UNIT_INACTIVE) {
+                        log_debug("%s got notified about unit deactivation.", p->meta.id);
+                        path_enter_waiting(p, false);
+                }
+        }
+
+        return;
+
+fail:
+        log_error("Failed find path unit: %s", strerror(-r));
+}
+
+static const char* const path_state_table[_PATH_STATE_MAX] = {
+        [PATH_DEAD] = "dead",
+        [PATH_WAITING] = "waiting",
+        [PATH_RUNNING] = "running",
+        [PATH_MAINTAINANCE] = "maintainance"
+};
+
+DEFINE_STRING_TABLE_LOOKUP(path_state, PathState);
+
+static const char* const path_type_table[_PATH_TYPE_MAX] = {
+        [PATH_EXISTS] = "PathExists",
+        [PATH_CHANGED] = "PathChanged",
+        [PATH_DIRECTORY_NOT_EMPTY] = "DirectoryNotEmpty"
+};
+
+DEFINE_STRING_TABLE_LOOKUP(path_type, PathType);
+
+const UnitVTable path_vtable = {
+        .suffix = ".path",
+
+        .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,
+
+        .fd_event = path_fd_event,
+
+        .bus_message_handler = bus_path_message_handler
+};
diff --git a/src/path.h b/src/path.h
new file mode 100644
index 0000000000..21a7dc4934
--- /dev/null
+++ b/src/path.h
@@ -0,0 +1,85 @@
+/*-*- Mode: C; c-basic-offset: 8 -*-*/
+
+#ifndef foopathhfoo
+#define foopathhfoo
+
+/***
+  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 General Public License as published by
+  the Free Software Foundation; either version 2 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
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+typedef struct Path Path;
+
+#include "unit.h"
+#include "mount.h"
+
+typedef enum PathState {
+        PATH_DEAD,
+        PATH_WAITING,
+        PATH_RUNNING,
+        PATH_MAINTAINANCE,
+        _PATH_STATE_MAX,
+        _PATH_STATE_INVALID = -1
+} PathState;
+
+typedef enum PathType {
+        PATH_EXISTS,
+        PATH_DIRECTORY_NOT_EMPTY,
+        PATH_CHANGED,
+        _PATH_TYPE_MAX,
+        _PATH_TYPE_INVALID = -1
+} PathType;
+
+typedef struct PathSpec {
+        PathType type;
+        char *path;
+
+        int inotify_fd;
+        int primary_wd;
+        bool previous_exists;
+
+        Watch watch;
+
+        LIST_FIELDS(struct PathSpec, spec);
+} PathSpec;
+
+struct Path {
+        Meta meta;
+
+        LIST_HEAD(PathSpec, specs);
+
+        PathState state, deserialized_state;
+        Unit *unit;
+
+        bool failure;
+};
+
+void path_unit_notify(Unit *u, UnitActiveState new_state);
+
+/* Called from the mount code figure out if a mount is a dependency of
+ * any of the paths of this path object */
+int path_add_one_mount_link(Path *p, Mount *m);
+
+extern const UnitVTable path_vtable;
+
+const char* path_state_to_string(PathState i);
+PathState path_state_from_string(const char *s);
+
+const char* path_type_to_string(PathType i);
+PathType path_type_from_string(const char *s);
+
+#endif
diff --git a/src/service.c b/src/service.c
index 07b6e4e05a..2f699cd1e6 100644
--- a/src/service.c
+++ b/src/service.c
@@ -1708,7 +1708,6 @@ static int service_start(Unit *u) {
         /* Make sure we don't enter a busy loop of some kind. */
         if (!ratelimit_test(&s->ratelimit)) {
                 log_warning("%s start request repeated too quickly, refusing to start.", u->meta.id);
-                service_enter_dead(s, false, true);
                 return -ECANCELED;
         }
 
diff --git a/src/socket.c b/src/socket.c
index ef7674f463..909151752c 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -58,7 +58,6 @@ static void socket_init(Unit *u) {
         assert(u);
         assert(u->meta.load_state == UNIT_STUB);
 
-        s->timer_watch.type = WATCH_INVALID;
         s->backlog = SOMAXCONN;
         s->timeout_usec = DEFAULT_TIMEOUT_USEC;
         s->directory_mode = 0755;
diff --git a/src/socket.h b/src/socket.h
index 5aa5f2783c..2067eb4254 100644
--- a/src/socket.h
+++ b/src/socket.h
@@ -62,9 +62,7 @@ typedef enum SocketType {
         _SOCKET_FIFO_INVALID = -1
 } SocketType;
 
-typedef struct SocketPort SocketPort;
-
-struct SocketPort {
+typedef struct SocketPort {
         SocketType type;
         int fd;
 
@@ -72,8 +70,8 @@ struct SocketPort {
         char *path;
         Watch fd_watch;
 
-        LIST_FIELDS(SocketPort, port);
-};
+        LIST_FIELDS(struct SocketPort, port);
+} SocketPort;
 
 struct Socket {
         Meta meta;
diff --git a/src/timer.c b/src/timer.c
index e95b4d66e1..b025051f2b 100644
--- a/src/timer.c
+++ b/src/timer.c
@@ -41,7 +41,6 @@ static void timer_init(Unit *u) {
         assert(u->meta.load_state == UNIT_STUB);
 
         t->next_elapse = (usec_t) -1;
-        t->timer_watch.type = WATCH_INVALID;
 }
 
 static void timer_done(Unit *u) {
@@ -274,8 +273,12 @@ static int timer_start(Unit *u) {
         Timer *t = TIMER(u);
 
         assert(t);
-        assert(t->state == TIMER_DEAD);
+        assert(t->state == TIMER_DEAD || t->state == TIMER_MAINTAINANCE);
+
+        if (t->unit->meta.load_state != UNIT_LOADED)
+                return -ENOENT;
 
+        t->failure = false;
         timer_enter_waiting(t, true);
         return 0;
 }
@@ -373,9 +376,12 @@ void timer_unit_notify(Unit *u, UnitActiveState new_state) {
                 if (!p)
                         continue;
 
+                if (p->meta.load_state != UNIT_LOADED)
+                        continue;
+
                 t = TIMER(p);
 
-                if (t->meta.load_state != UNIT_LOADED)
+                if (t->unit != u)
                         continue;
 
                 /* Reenable all timers that depend on unit state */
diff --git a/src/timer.h b/src/timer.h
index 69c5609a9c..eb22688a3b 100644
--- a/src/timer.h
+++ b/src/timer.h
@@ -61,11 +61,9 @@ struct Timer {
         Meta meta;
 
         LIST_HEAD(TimerValue, values);
-
-        TimerState state, deserialized_state;
-
         usec_t next_elapse;
 
+        TimerState state, deserialized_state;
         Unit *unit;
 
         Watch timer_watch;
diff --git a/src/unit.c b/src/unit.c
index 2af2685e0d..57b3b77954 100644
--- a/src/unit.c
+++ b/src/unit.c
@@ -48,7 +48,8 @@ const UnitVTable * const unit_vtable[_UNIT_TYPE_MAX] = {
         [UNIT_MOUNT] = &mount_vtable,
         [UNIT_AUTOMOUNT] = &automount_vtable,
         [UNIT_SNAPSHOT] = &snapshot_vtable,
-        [UNIT_SWAP] = &swap_vtable
+        [UNIT_SWAP] = &swap_vtable,
+        [UNIT_PATH] = &path_vtable
 };
 
 Unit *unit_new(Manager *m) {
@@ -956,6 +957,7 @@ void unit_notify(Unit *u, UnitActiveState os, UnitActiveState ns) {
                 u->meta.active_exit_timestamp = ts;
 
         timer_unit_notify(u, ns);
+        path_unit_notify(u, ns);
 
         if (u->meta.job) {
 
diff --git a/src/unit.h b/src/unit.h
index fd0defe2d1..f585fa6238 100644
--- a/src/unit.h
+++ b/src/unit.h
@@ -62,6 +62,7 @@ enum UnitType {
         UNIT_SNAPSHOT,
         UNIT_TIMER,
         UNIT_SWAP,
+        UNIT_PATH,
         _UNIT_TYPE_MAX,
         _UNIT_TYPE_INVALID = -1
 };
@@ -201,6 +202,7 @@ struct Meta {
 #include "automount.h"
 #include "snapshot.h"
 #include "swap.h"
+#include "path.h"
 
 union Unit {
         Meta meta;
@@ -213,6 +215,7 @@ union Unit {
         Automount automount;
         Snapshot snapshot;
         Swap swap;
+        Path path;
 };
 
 struct UnitVTable {
@@ -344,6 +347,7 @@ DEFINE_CAST(MOUNT, Mount);
 DEFINE_CAST(AUTOMOUNT, Automount);
 DEFINE_CAST(SNAPSHOT, Snapshot);
 DEFINE_CAST(SWAP, Swap);
+DEFINE_CAST(PATH, Path);
 
 Unit *unit_new(Manager *m);
 void unit_free(Unit *u);
diff --git a/src/util.c b/src/util.c
index a8ea4a97ab..7664df59d0 100644
--- a/src/util.c
+++ b/src/util.c
@@ -2092,6 +2092,35 @@ bool is_device_path(const char *path) {
                 path_startswith(path, "/sys/");
 }
 
+int dir_is_empty(const char *path) {
+        DIR *d;
+        int r;
+        struct dirent buf, *de;
+
+        if (!(d = opendir(path)))
+                return -errno;
+
+        for (;;) {
+                if ((r = readdir_r(d, &buf, &de)) > 0) {
+                        r = -r;
+                        break;
+                }
+
+                if (!de) {
+                        r = 1;
+                        break;
+                }
+
+                if (!ignore_file(de->d_name)) {
+                        r = 0;
+                        break;
+                }
+        }
+
+        closedir(d);
+        return r;
+}
+
 static const char *const ioprio_class_table[] = {
         [IOPRIO_CLASS_NONE] = "none",
         [IOPRIO_CLASS_RT] = "realtime",
diff --git a/src/util.h b/src/util.h
index b411df0cf2..efc993c370 100644
--- a/src/util.h
+++ b/src/util.h
@@ -247,6 +247,8 @@ int path_is_mount_point(const char *path);
 
 bool is_device_path(const char *path);
 
+int dir_is_empty(const char *path);
+
 extern char * __progname;
 
 const char *ioprio_class_to_string(int i);