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cgroup: Allow empty assignments of Memory{Low,Min}=

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Currently, an empty assignment of Memory{Low,Min}= directives would be
interpretted as setting it to global default, i.e. zero. However, if we
set a runtime protection value on a unit that inherits parent's
DefaultMemory{Low,Min}=, it is not possible to revert it back to the
state where the DefaultMemory{Low,Min}= is propagated from parent
slice(s).

This patch changes the semantics of the empty assignments to explicitly
nullify any value set by the user previously. Since DBus API uses
uint64_t where 0 is a valid configuration, the patch modifies DBus API
by exploiting the variant type of property value to pass the NULL value.
This commit is contained in:
Michal Koutný
2020-06-02 18:59:47 +02:00
parent db2b8d2e28
commit 53aa85af24
3 changed files with 130 additions and 60 deletions
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src/shared/bus-unit-util.c
+11 -9
View File
@@ -494,16 +494,18 @@ static int bus_append_cgroup_property(sd_bus_message *m, const char *field, cons
if (r < 0)
return bus_log_create_error(r);
return 1;
} else if (isempty(eq) && STR_IN_SET(field, "DefaultMemoryLow",
"DefaultMemoryMin",
"MemoryLow",
"MemoryMin")) {
/* We can't use CGROUP_LIMIT_MIN nor CGROUP_LIMIT_MAX to convey the empty assignment
* so marshall specially as a boolean. */
r = sd_bus_message_append(m, "(sv)", field, "b", 0);
if (r < 0)
return bus_log_create_error(r);
return 1;
} else if (isempty(eq)) {
uint64_t empty_value = STR_IN_SET(field,
"DefaultMemoryLow",
"DefaultMemoryMin",
"MemoryLow",
"MemoryMin") ?
CGROUP_LIMIT_MIN :
CGROUP_LIMIT_MAX;
r = sd_bus_message_append(m, "(sv)", field, "t", empty_value);
r = sd_bus_message_append(m, "(sv)", field, "t", CGROUP_LIMIT_MAX);
if (r < 0)
return bus_log_create_error(r);
return 1;