core: introduce CGroupIOLimitType enums

Currently, there are two cgroup IO limits, bandwidth max for read and write,
and they are hard-coded in various places.  This is fine for two limits but IO
is expected to grow more limits - low, high and max limits for bandwidth and
IOPS - and hard-coding each limit won't make sense.

This patch replaces hard-coded limits with an array indexed by
CGroupIOLimitType and accompanying string and default value tables so that new
limits can be added trivially.

1 files changed, 16 insertions, 34 deletions

diff --git a/src/core/dbus-cgroup.c b/src/core/dbus-cgroup.c
index a2a4a6249c..4372828e30 100644
--- a/src/core/dbus-cgroup.c
+++ b/src/core/dbus-cgroup.c
@@ -80,17 +80,13 @@ static int property_get_io_device_limits(
                 return r;
 
         LIST_FOREACH(device_limits, l, c->io_device_limits) {
-                uint64_t v;
+                CGroupIOLimitType type;
 
-                if (streq(property, "IOReadBandwidthMax"))
-                        v = l->rbps_max;
-                else
-                        v = l->wbps_max;
-
-                if (v == CGROUP_LIMIT_MAX)
+                type = cgroup_io_limit_type_from_string(property);
+                if (type < 0 || l->limits[type] == cgroup_io_limit_defaults[type])
                         continue;
 
-                r = sd_bus_message_append(reply, "(st)", l->path, v);
+                r = sd_bus_message_append(reply, "(st)", l->path, l->limits[type]);
                 if (r < 0)
                         return r;
         }
@@ -273,6 +269,7 @@ int bus_cgroup_set_property(
                 UnitSetPropertiesMode mode,
                 sd_bus_error *error) {
 
+        CGroupIOLimitType iol_type;
         int r;
 
         assert(u);
@@ -416,15 +413,11 @@ int bus_cgroup_set_property(
 
                 return 1;
 
-        } else if (streq(name, "IOReadBandwidthMax") || streq(name, "IOWriteBandwidthMax")) {
+        } else if ((iol_type = cgroup_io_limit_type_from_string(name)) >= 0) {
                 const char *path;
-                bool read = true;
                 unsigned n = 0;
                 uint64_t u64;
 
-                if (streq(name, "IOWriteBandwidthMax"))
-                        read = false;
-
                 r = sd_bus_message_enter_container(message, 'a', "(st)");
                 if (r < 0)
                         return r;
@@ -442,6 +435,8 @@ int bus_cgroup_set_property(
                                 }
 
                                 if (!a) {
+                                        CGroupIOLimitType type;
+
                                         a = new0(CGroupIODeviceLimit, 1);
                                         if (!a)
                                                 return -ENOMEM;
@@ -452,16 +447,13 @@ int bus_cgroup_set_property(
                                                 return -ENOMEM;
                                         }
 
-                                        a->rbps_max = CGROUP_LIMIT_MAX;
-                                        a->wbps_max = CGROUP_LIMIT_MAX;
+                                        for (type = 0; type < _CGROUP_IO_LIMIT_TYPE_MAX; type++)
+                                                a->limits[type] = cgroup_io_limit_defaults[type];
 
                                         LIST_PREPEND(device_limits, c->io_device_limits, a);
                                 }
 
-                                if (read)
-                                        a->rbps_max = u64;
-                                else
-                                        a->wbps_max = u64;
+                                a->limits[iol_type] = u64;
                         }
 
                         n++;
@@ -481,10 +473,7 @@ int bus_cgroup_set_property(
 
                         if (n == 0) {
                                 LIST_FOREACH(device_limits, a, c->io_device_limits)
-                                        if (read)
-                                                a->rbps_max = CGROUP_LIMIT_MAX;
-                                        else
-                                                a->wbps_max = CGROUP_LIMIT_MAX;
+                                        a->limits[iol_type] = cgroup_io_limit_defaults[iol_type];
                         }
 
                         unit_invalidate_cgroup(u, CGROUP_MASK_IO);
@@ -493,17 +482,10 @@ int bus_cgroup_set_property(
                         if (!f)
                                 return -ENOMEM;
 
-                        if (read) {
-                                fputs("IOReadBandwidthMax=\n", f);
-                                LIST_FOREACH(device_limits, a, c->io_device_limits)
-                                        if (a->rbps_max != CGROUP_LIMIT_MAX)
-                                                fprintf(f, "IOReadBandwidthMax=%s %" PRIu64 "\n", a->path, a->rbps_max);
-                        } else {
-                                fputs("IOWriteBandwidthMax=\n", f);
-                                LIST_FOREACH(device_limits, a, c->io_device_limits)
-                                        if (a->wbps_max != CGROUP_LIMIT_MAX)
-                                                fprintf(f, "IOWriteBandwidthMax=%s %" PRIu64 "\n", a->path, a->wbps_max);
-                        }
+                        fprintf(f, "%s=\n", name);
+                        LIST_FOREACH(device_limits, a, c->io_device_limits)
+                                        if (a->limits[iol_type] != cgroup_io_limit_defaults[iol_type])
+                                                fprintf(f, "%s=%s %" PRIu64 "\n", name, a->path, a->limits[iol_type]);
 
                         r = fflush_and_check(f);
                         if (r < 0)