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core: add FileDescriptorStorePreserve=on-success option

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Currently with FileDescriptorStorePreserve=yes the FD store is kept around
regardless of what happens to a unit, which is useful in many cases. But in
some cases, for example when complex services crash horribly, it's hard to
reason about what was in the intermediate state, and it's better to start
fresh.

Add a new 'on-success' option for the FileDescriptorStorePreserve= setting
that keeps it around only for as long as the unit doesn't go to a persistently
failed state.

This is especially useful in combination with LUO, where we don't want to
keep around LUO sessions created by units that then proceeded to crash and
burn, and might be in a bad state afterwards.
This commit is contained in:
Luca Boccassi
2026-05-21 10:14:08 +01:00
parent 00276b963c
commit 67dea1409b
9 changed files with 130 additions and 29 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/core/execute.c
+4 -3
View File
@@ -3182,9 +3182,10 @@ static const char* const exec_utmp_mode_table[_EXEC_UTMP_MODE_MAX] = {
DEFINE_STRING_TABLE_LOOKUP(exec_utmp_mode, ExecUtmpMode);
static const char* const exec_preserve_mode_table[_EXEC_PRESERVE_MODE_MAX] = {
[EXEC_PRESERVE_NO] = "no",
[EXEC_PRESERVE_YES] = "yes",
[EXEC_PRESERVE_RESTART] = "restart",
[EXEC_PRESERVE_NO] = "no",
[EXEC_PRESERVE_YES] = "yes",
[EXEC_PRESERVE_RESTART] = "restart",
[EXEC_PRESERVE_ON_SUCCESS] = "on-success",
};
DEFINE_STRING_TABLE_LOOKUP_WITH_BOOLEAN(exec_preserve_mode, ExecPreserveMode, EXEC_PRESERVE_YES);
src/core/execute.h
+1
View File
@@ -61,6 +61,7 @@ typedef enum ExecPreserveMode {
EXEC_PRESERVE_NO,
EXEC_PRESERVE_YES,
EXEC_PRESERVE_RESTART,
EXEC_PRESERVE_ON_SUCCESS,
_EXEC_PRESERVE_MODE_MAX,
_EXEC_PRESERVE_MODE_INVALID = -EINVAL,
} ExecPreserveMode;
src/core/luo.c
+1 -1
View File
@@ -204,7 +204,7 @@ int manager_luo_serialize_fd_stores(Manager *m, FILE **ret_f, FDSet **ret_fds) {
s = SERVICE(u);
if (s->fd_store_preserve_mode != EXEC_PRESERVE_YES)
if (!IN_SET(s->fd_store_preserve_mode, EXEC_PRESERVE_YES, EXEC_PRESERVE_ON_SUCCESS))
continue;
if (!s->fd_store)
src/core/service.c
+8 -6
View File
@@ -699,7 +699,7 @@ int service_add_fd_store(Service *s, int fd_in, const char *name, bool do_poll,
* unit and the original fdname. This way fdstore persistence chains all the way up to whichever
* entity is ultimately responsible for surviving across kexec/restart, regardless of fdname
* length or charset constraints. */
if (propagate_upstream && s->fd_store_preserve_mode == EXEC_PRESERVE_YES) {
if (propagate_upstream && IN_SET(s->fd_store_preserve_mode, EXEC_PRESERVE_YES, EXEC_PRESERVE_ON_SUCCESS)) {
Manager *m = ASSERT_PTR(UNIT(s)->manager);
char idx_str[STRLEN(SERVICE_FDSTORE_SUB_FDNAME_PREFIX) + DECIMAL_STR_MAX(uint64_t)];
@@ -721,7 +721,7 @@ int service_add_fd_store(Service *s, int fd_in, const char *name, bool do_poll,
LIST_PREPEND(fd_store, s->fd_store, TAKE_PTR(fs));
s->n_fd_store++;
if (propagate_upstream && s->fd_store_preserve_mode == EXEC_PRESERVE_YES)
if (propagate_upstream && IN_SET(s->fd_store_preserve_mode, EXEC_PRESERVE_YES, EXEC_PRESERVE_ON_SUCCESS))
/* Refresh the JSON mapping memfd so the supervisor can resolve the new index. Do this
* after LIST_PREPEND so the new entry is visible to the helper. */
(void) service_propagate_fd_store_mapping_upstream(UNIT(s)->manager);
@@ -876,7 +876,7 @@ static int service_attach_external_fd_to_fdstore(Unit *u, int fd, const char *fd
if (r > 0 &&
s->state == SERVICE_DEAD &&
s->deserialized_state == SERVICE_DEAD &&
s->fd_store_preserve_mode == EXEC_PRESERVE_YES) {
IN_SET(s->fd_store_preserve_mode, EXEC_PRESERVE_YES, EXEC_PRESERVE_ON_SUCCESS)) {
service_set_state(s, SERVICE_DEAD_RESOURCES_PINNED);
s->deserialized_state = SERVICE_DEAD_RESOURCES_PINNED;
}
@@ -2350,7 +2350,7 @@ static bool service_will_restart(Unit *u) {
static ServiceState service_determine_dead_state(Service *s) {
assert(s);
return SERVICE_FD_STORE_POPULATED(s) && s->fd_store_preserve_mode == EXEC_PRESERVE_YES ? SERVICE_DEAD_RESOURCES_PINNED : SERVICE_DEAD;
return SERVICE_FD_STORE_POPULATED(s) && IN_SET(s->fd_store_preserve_mode, EXEC_PRESERVE_YES, EXEC_PRESERVE_ON_SUCCESS) ? SERVICE_DEAD_RESOURCES_PINNED : SERVICE_DEAD;
}
static void service_enter_dead(Service *s, ServiceResult f, bool allow_restart) {
@@ -2454,7 +2454,8 @@ static void service_enter_dead(Service *s, ServiceResult f, bool allow_restart)
unit_destroy_runtime_data(UNIT(s), &s->exec_context, /* destroy_runtime_dir= */ true);
/* Also get rid of the fd store, if that's configured. */
if (s->fd_store_preserve_mode == EXEC_PRESERVE_NO)
if (s->fd_store_preserve_mode == EXEC_PRESERVE_NO ||
(s->fd_store_preserve_mode == EXEC_PRESERVE_ON_SUCCESS && s->state == SERVICE_FAILED))
service_release_fd_store(s);
/* Get rid of the IPC bits of the user */
@@ -6119,7 +6120,8 @@ static void service_release_resources(Unit *u) {
service_release_extra_fds(s);
s->root_directory_fd = asynchronous_close(s->root_directory_fd);
if (s->fd_store_preserve_mode != EXEC_PRESERVE_YES)
if (IN_SET(s->fd_store_preserve_mode, EXEC_PRESERVE_NO, EXEC_PRESERVE_RESTART) ||
(s->fd_store_preserve_mode == EXEC_PRESERVE_ON_SUCCESS && s->state == SERVICE_FAILED))
service_release_fd_store(s);
if (s->state == SERVICE_DEAD_RESOURCES_PINNED && !SERVICE_FD_STORE_POPULATED(s))
src/shared/varlink-io.systemd.Unit.c
+2 -1
View File
@@ -25,7 +25,8 @@ SD_VARLINK_DEFINE_ENUM_TYPE(
ExecPreserveMode,
SD_VARLINK_DEFINE_ENUM_VALUE(no),
SD_VARLINK_DEFINE_ENUM_VALUE(yes),
SD_VARLINK_DEFINE_ENUM_VALUE(restart));
SD_VARLINK_DEFINE_ENUM_VALUE(restart),
SD_VARLINK_DEFINE_ENUM_VALUE(on_success));
SD_VARLINK_DEFINE_ENUM_TYPE(
ExecKeyringMode,