path: add .path unit type for monitoring files

1 files changed, 578 insertions, 0 deletions

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
+};