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Systemd/src/core/path.c
Lennart Poettering 6fcbec6f9b core: whenever we change state of a unit, force out PropertiesChanged bus signal 
This allows clients to follow our internal state changes safely.

Previously, quick state changes (for example, when we restart a unit due
to Restart= after it quickly transitioned through DEAD/FAILED states)
would be coalesced into one bus signal event, with this change there's
the guarantee that all state changes after the unit was announced ones
are reflected on th bus.

Note we only do this kind of guaranteed flushing only for unit state
changes, not for other unit property changes, where clients still have
to expect coalescing. This is because the unit state is a very
important, high-level concept.

Fixes: #10185
2018-12-01 12:53:26 +01:00

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/* SPDX-License-Identifier: LGPL-2.1+ */
#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 "fd-util.h"
#include "fs-util.h"
#include "glob-util.h"
#include "macro.h"
#include "mkdir.h"
#include "path.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 = -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;
(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, '/')) {
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 (IN_SET(errno, EACCES, ENOENT)) {
if (cut)
*cut = tmp;
break;
}
r = log_warning_errno(errno, "Failed to add watch on %s: %s", s->path, errno == ENOSPC ? "too many watches" : strerror(-r));
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';
(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 = r;
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_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;
struct inotify_event *e;
ssize_t l;
int r = 0;
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 (IN_SET(errno, EAGAIN, EINTR))
return 0;
return log_error_errno(errno, "Failed to read inotify event: %m");
}
FOREACH_INOTIFY_EVENT(e, buffer, l) {
if (IN_SET(s->type, PATH_CHANGED, PATH_MODIFIED) &&
s->primary_wd == e->wd)
r = 1;
}
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 (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) {
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_dependencies(Path *p) {
PathSpec *s;
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);
if (UNIT(p)->load_state != UNIT_LOADED)
return 0;
if (!p->specs) {
log_unit_error(UNIT(p), "Path unit lacks path setting. Refusing.");
return -ENOEXEC;
}
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 (!hashmap_isempty(UNIT(p)->dependencies[UNIT_TRIGGERS]))
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_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) {
r = path_add_trigger_dependencies(p);
if (r < 0)
return r;
r = path_add_mount_dependencies(p);
if (r < 0)
return r;
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);
if (p->state != state)
bus_unit_send_pending_change_signal(UNIT(p), false);
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_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 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 (IN_SET(p->deserialized_state, PATH_WAITING, 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 (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) {
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
Unit *trigger;
int r;
assert(p);
/* Don't start job if we are supposed to go down */
if (unit_stop_pending(UNIT(p)))
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;
}
r = manager_add_job(UNIT(p)->manager, JOB_START, trigger, JOB_REPLACE, &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_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) {
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_unit_debug(UNIT(p), "Got triggered.");
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_unit_debug(UNIT(p), "Got triggered.");
path_enter_running(p);
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) {
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);
Unit *trigger;
int r;
assert(p);
assert(IN_SET(p->state, PATH_DEAD, PATH_FAILED));
trigger = UNIT_TRIGGER(u);
if (!trigger || trigger->load_state != UNIT_LOADED) {
log_unit_error(u, "Refusing to start, unit to trigger not loaded.");
return -ENOENT;
}
r = unit_start_limit_test(u);
if (r < 0) {
path_enter_dead(p, PATH_FAILURE_START_LIMIT_HIT);
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, true);
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));
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
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;
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;
/* 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_unit_debug(UNIT(p), "Got notified about unit deactivation.");
/* 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_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",
};
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,
.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_vtable = bus_path_vtable,
.bus_set_property = bus_path_set_property,
};
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