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condition: add new ConditionKernelModuleLoaded=

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This introduces a new unit condition check: that matches if a specific
kmod module is allowed. This should be generally useful, but there's one
usecase in particular: we can optimize modprobe@.service with this and
avoid forking out a bunch of modprobe requests during boot for the same
kmods.

Checking if a kernel module is loaded is more complicated than just
checking if /sys/module/$MODULE/ exists, since kernel modules typically
take a while to initialize and we must check that this is complete (by
checking if the sysfs attr "initstate" is "live").
This commit is contained in:
Lennart Poettering
2024-11-28 13:00:34 +01:00
committed by Yu Watanabe
parent c9011f170b
commit 3c702e8210
6 changed files with 104 additions and 0 deletions
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11
man/systemd.unit.xml
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@@ -1989,6 +1989,16 @@
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ConditionKernelModuleLoaded=</varname></term>
<listitem><para>Test whether the specified kernel module has been loaded and is already fully
initialized.</para>
<xi:include href="version-info.xml" xpointer="v258"/>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>AssertArchitecture=</varname></term>
<term><varname>AssertVirtualization=</varname></term>
@@ -2022,6 +2032,7 @@
<term><varname>AssertMemoryPressure=</varname></term>
<term><varname>AssertCPUPressure=</varname></term>
<term><varname>AssertIOPressure=</varname></term>
<term><varname>AssertKernelModuleLoaded=</varname></term>
<listitem><para>Similar to the <varname>ConditionArchitecture=</varname>,
<varname>ConditionVirtualization=</varname>, …, condition settings described above, these settings

2
src/core/load-fragment-gperf.gperf.in
View File

@@ -374,6 +374,7 @@ Unit.ConditionOSRelease, config_parse_unit_condition_string
Unit.ConditionMemoryPressure, config_parse_unit_condition_string, CONDITION_MEMORY_PRESSURE, offsetof(Unit, conditions)
Unit.ConditionCPUPressure, config_parse_unit_condition_string, CONDITION_CPU_PRESSURE, offsetof(Unit, conditions)
Unit.ConditionIOPressure, config_parse_unit_condition_string, CONDITION_IO_PRESSURE, offsetof(Unit, conditions)
Unit.ConditionKernelModuleLoaded, config_parse_unit_condition_string, CONDITION_KERNEL_MODULE_LOADED, offsetof(Unit, conditions)
Unit.AssertPathExists, config_parse_unit_condition_path, CONDITION_PATH_EXISTS, offsetof(Unit, asserts)
Unit.AssertPathExistsGlob, config_parse_unit_condition_path, CONDITION_PATH_EXISTS_GLOB, offsetof(Unit, asserts)
Unit.AssertPathIsDirectory, config_parse_unit_condition_path, CONDITION_PATH_IS_DIRECTORY, offsetof(Unit, asserts)
@@ -406,6 +407,7 @@ Unit.AssertOSRelease, config_parse_unit_condition_string
Unit.AssertMemoryPressure, config_parse_unit_condition_string, CONDITION_MEMORY_PRESSURE, offsetof(Unit, asserts)
Unit.AssertCPUPressure, config_parse_unit_condition_string, CONDITION_CPU_PRESSURE, offsetof(Unit, asserts)
Unit.AssertIOPressure, config_parse_unit_condition_string, CONDITION_IO_PRESSURE, offsetof(Unit, asserts)
Unit.AssertKernelModuleLoaded, config_parse_unit_condition_string, CONDITION_KERNEL_MODULE_LOADED, offsetof(Unit, asserts)
Unit.CollectMode, config_parse_collect_mode, 0, offsetof(Unit, collect_mode)
Service.PIDFile, config_parse_pid_file, 0, offsetof(Service, pid_file)
Service.ExecCondition, config_parse_exec, SERVICE_EXEC_CONDITION, offsetof(Service, exec_command)

56
src/shared/condition.c
View File

@@ -1155,6 +1155,59 @@ static int condition_test_psi(Condition *c, char **env) {
return *current <= limit;
}
static int condition_test_kernel_module_loaded(Condition *c, char **env) {
int r;
assert(c);
assert(c->parameter);
assert(c->type == CONDITION_KERNEL_MODULE_LOADED);
/* Checks whether a specific kernel module is fully loaded (i.e. with the full initialization routine
* complete). */
_cleanup_free_ char *normalized = strreplace(c->parameter, "-", "_");
if (!normalized)
return log_oom_debug();
if (!filename_is_valid(normalized)) {
log_debug("Kernel module name '%s' is not valid, hence reporting it to not be loaded.", normalized);
return false;
}
_cleanup_free_ char *p = path_join("/sys/module/", normalized);
if (!p)
return log_oom_debug();
_cleanup_close_ int dir_fd = open(p, O_PATH|O_DIRECTORY|O_CLOEXEC);
if (dir_fd < 0) {
if (errno == ENOENT) {
log_debug_errno(errno, "'%s/' does not exist, kernel module '%s' not loaded.", p, normalized);
return false;
}
return log_debug_errno(errno, "Failed to open directory '%s/': %m", p);
}
_cleanup_free_ char *initstate = NULL;
r = read_virtual_file_at(dir_fd, "initstate", SIZE_MAX, &initstate, NULL);
if (r == -ENOENT) {
log_debug_errno(r, "'%s/' exists but '%s/initstate' does not, kernel module '%s' is built-in, hence loaded.", p, p, normalized);
return true;
}
if (r < 0)
return log_debug_errno(r, "Failed to open '%s/initstate': %m", p);
delete_trailing_chars(initstate, WHITESPACE);
if (!streq(initstate, "live")) {
log_debug("Kernel module '%s' is reported as '%s', hence not loaded.", normalized, initstate);
return false;
}
log_debug("Kernel module '%s' detected as loaded.", normalized);
return true;
}
int condition_test(Condition *c, char **env) {
static int (*const condition_tests[_CONDITION_TYPE_MAX])(Condition *c, char **env) = {
@@ -1191,6 +1244,7 @@ int condition_test(Condition *c, char **env) {
[CONDITION_MEMORY_PRESSURE] = condition_test_psi,
[CONDITION_CPU_PRESSURE] = condition_test_psi,
[CONDITION_IO_PRESSURE] = condition_test_psi,
[CONDITION_KERNEL_MODULE_LOADED] = condition_test_kernel_module_loaded,
};
int r, b;
@@ -1315,6 +1369,7 @@ static const char* const condition_type_table[_CONDITION_TYPE_MAX] = {
[CONDITION_MEMORY_PRESSURE] = "ConditionMemoryPressure",
[CONDITION_CPU_PRESSURE] = "ConditionCPUPressure",
[CONDITION_IO_PRESSURE] = "ConditionIOPressure",
[CONDITION_KERNEL_MODULE_LOADED] = "ConditionKernelModuleLoaded",
};
DEFINE_STRING_TABLE_LOOKUP(condition_type, ConditionType);
@@ -1353,6 +1408,7 @@ static const char* const assert_type_table[_CONDITION_TYPE_MAX] = {
[CONDITION_MEMORY_PRESSURE] = "AssertMemoryPressure",
[CONDITION_CPU_PRESSURE] = "AssertCPUPressure",
[CONDITION_IO_PRESSURE] = "AssertIOPressure",
[CONDITION_KERNEL_MODULE_LOADED] = "AssertKernelModuleLoaded",
};
DEFINE_STRING_TABLE_LOOKUP(assert_type, ConditionType);

1
src/shared/condition.h
View File

@@ -45,6 +45,7 @@ typedef enum ConditionType {
CONDITION_GROUP,
CONDITION_CONTROL_GROUP_CONTROLLER,
CONDITION_KERNEL_MODULE_LOADED,
_CONDITION_TYPE_MAX,
_CONDITION_TYPE_INVALID = -EINVAL,

33
src/test/test-condition.c
View File

@@ -1308,4 +1308,37 @@ TEST(condition_test_psi) {
condition_free(condition);
}
TEST(condition_test_kernel_module_loaded) {
Condition *condition;
int r;
condition = condition_new(CONDITION_KERNEL_MODULE_LOADED, "", /* trigger= */ false, /* negate= */ false);
assert_se(condition);
ASSERT_OK_ZERO(condition_test(condition, environ));
condition_free(condition);
condition = condition_new(CONDITION_KERNEL_MODULE_LOADED, "..", /* trigger= */ false, /* negate= */ false);
assert_se(condition);
ASSERT_OK_ZERO(condition_test(condition, environ));
condition_free(condition);
if (access("/sys/module/", F_OK) < 0)
return (void) log_tests_skipped("/sys/module not available, skipping.");
FOREACH_STRING(m, "random", "vfat", "fat", "cec", "binfmt_misc", "binfmt-misc") {
condition = condition_new(CONDITION_KERNEL_MODULE_LOADED, m, /* trigger= */ false, /* negate= */ false);
assert_se(condition);
r = condition_test(condition, environ);
ASSERT_OK(r);
condition_free(condition);
log_notice("kmod %s is loaded: %s", m, yes_no(r));
}
condition = condition_new(CONDITION_KERNEL_MODULE_LOADED, "idefinitelydontexist", /* trigger= */ false, /* negate= */ false);
assert_se(condition);
ASSERT_OK_ZERO(condition_test(condition, environ));
condition_free(condition);
}
DEFINE_TEST_MAIN(LOG_DEBUG);

1
units/modprobe@.service
View File

@@ -13,6 +13,7 @@ DefaultDependencies=no
Before=sysinit.target
Documentation=man:modprobe(8)
ConditionCapability=CAP_SYS_MODULE
ConditionKernelModuleLoaded=!%i
StartLimitIntervalSec=0
[Service]