core: add support for IOReadIOPSMax and IOWriteIOPSMax

cgroup IO controller supports maximum limits for both bandwidth and IOPS but
systemd resource control currently only supports bandwidth limits.  This patch
adds support for IOReadIOPSMax and IOWriteIOPSMax when unified cgroup hierarchy
is in use.

It isn't difficult to also add BlockIOReadIOPS and BlockIOWriteIOPS for legacy
hierarchies but IO control on legacy hierarchies is half-broken anyway, so
let's leave it alone for now.

src/basic/cgroup-util.c

@@ -2272,11 +2272,15 @@ int cg_weight_parse(const char *s, uint64_t *ret) {
 const uint64_t cgroup_io_limit_defaults[_CGROUP_IO_LIMIT_TYPE_MAX] = {
         [CGROUP_IO_RBPS_MAX]    = CGROUP_LIMIT_MAX,
         [CGROUP_IO_WBPS_MAX]    = CGROUP_LIMIT_MAX,
+        [CGROUP_IO_RIOPS_MAX]   = CGROUP_LIMIT_MAX,
+        [CGROUP_IO_WIOPS_MAX]   = CGROUP_LIMIT_MAX,
 };
 
 static const char* const cgroup_io_limit_type_table[_CGROUP_IO_LIMIT_TYPE_MAX] = {
         [CGROUP_IO_RBPS_MAX]    = "IOReadBandwidthMax",
         [CGROUP_IO_WBPS_MAX]    = "IOWriteBandwidthMax",
+        [CGROUP_IO_RIOPS_MAX]   = "IOReadIOPSMax",
+        [CGROUP_IO_WIOPS_MAX]   = "IOWriteIOPSMax",
 };
 
 DEFINE_STRING_TABLE_LOOKUP(cgroup_io_limit_type, CGroupIOLimitType);

src/basic/cgroup-util.h

@@ -76,6 +76,8 @@ static inline bool CGROUP_WEIGHT_IS_OK(uint64_t x) {
 typedef enum CGroupIOLimitType {
         CGROUP_IO_RBPS_MAX,
         CGROUP_IO_WBPS_MAX,
+        CGROUP_IO_RIOPS_MAX,
+        CGROUP_IO_WIOPS_MAX,
 
         _CGROUP_IO_LIMIT_TYPE_MAX,
         _CGROUP_IO_LIMIT_TYPE_INVALID = -1