core: make SYSTEMD_CGROUP_CONTROLLER a special string

SYSTEMD_CGROUP_CONTROLLER is currently defined as "name=systemd" which cgroup
utility functions interpret as a named cgroup hierarchy with the specified
named.  With the planned cgroup hybrid mode changes, SYSTEMD_CGROUP_CONTROLLER
would map to different hierarchy names.

This patch makes SYSTEMD_CGROUP_CONTROLLER a special string "_systemd" which is
substituted to "name=systemd" by the cgroup utility functions.  This allows the
callers to address the systemd hierarchy without actually specifying the
hierarchy name allowing the cgroup utility functions to map it to whatever is
appropriate.

Note that SYSTEMD_CGROUP_CONTROLLER was already special on full unified cgroup
hierarchy even before this patch.

diff --git a/src/basic/cgroup-util.c b/src/basic/cgroup-util.c
index 48623fb2350127deff3214d4a907467406aa627f..67c2d3a681e7499bfd0cc86c33b6d8c71f1259fe 100644 (file)
--- a/src/basic/cgroup-util.c
+++ b/src/basic/cgroup-util.c
@@ -542,6 +542,9 @@ static const char *controller_to_dirname(const char *controller) {
          * just cuts off the name= prefixed used for named
          * hierarchies, if it is specified. */
 
+        if (streq(controller, SYSTEMD_CGROUP_CONTROLLER))
+                controller = SYSTEMD_CGROUP_CONTROLLER_LEGACY;
+
         e = startswith(controller, "name=");
         if (e)
                 return e;
@@ -912,7 +915,7 @@ int cg_get_xattr(const char *controller, const char *path, const char *name, voi
 int cg_pid_get_path(const char *controller, pid_t pid, char **path) {
         _cleanup_fclose_ FILE *f = NULL;
         char line[LINE_MAX];
-        const char *fs;
+        const char *fs, *controller_str;
         size_t cs = 0;
         bool unified;
 
@@ -926,8 +929,14 @@ int cg_pid_get_path(const char *controller, pid_t pid, char **path) {
                 controller = SYSTEMD_CGROUP_CONTROLLER;
 
         unified = cg_unified(controller);
-        if (!unified)
-                cs = strlen(controller);
+        if (!unified) {
+                if (streq(controller, SYSTEMD_CGROUP_CONTROLLER))
+                        controller_str = SYSTEMD_CGROUP_CONTROLLER_LEGACY;
+                else
+                        controller_str = controller;
+
+                cs = strlen(controller_str);
+        }
 
         fs = procfs_file_alloca(pid, "cgroup");
         f = fopen(fs, "re");
@@ -964,7 +973,7 @@ int cg_pid_get_path(const char *controller, pid_t pid, char **path) {
 
                         *e = 0;
                         FOREACH_WORD_SEPARATOR(word, k, l, ",", state) {
-                                if (k == cs && memcmp(word, controller, cs) == 0) {
+                                if (k == cs && memcmp(word, controller_str, cs) == 0) {
                                         found = true;
                                         break;
                                 }
@@ -1810,6 +1819,9 @@ bool cg_controller_is_valid(const char *p) {
         if (!p)
                 return false;
 
+        if (streq(p, SYSTEMD_CGROUP_CONTROLLER))
+                return true;
+
         s = startswith(p, "name=");
         if (s)
                 p = s;

diff --git a/src/basic/def.h b/src/basic/def.h
index 2266eff650b60acc598d18c7015c3a5d1f773bcb..3ba275f64be74e2c8c393348417b8ae3601564c7 100644 (file)
--- a/src/basic/def.h
+++ b/src/basic/def.h
@@ -36,7 +36,8 @@
 /* The default value for the net.unix.max_dgram_qlen sysctl */
 #define DEFAULT_UNIX_MAX_DGRAM_QLEN 512UL
 
-#define SYSTEMD_CGROUP_CONTROLLER "name=systemd"
+#define SYSTEMD_CGROUP_CONTROLLER_LEGACY "name=systemd"
+#define SYSTEMD_CGROUP_CONTROLLER "_systemd"
 
 #define SIGNALS_CRASH_HANDLER SIGSEGV,SIGILL,SIGFPE,SIGBUS,SIGQUIT,SIGABRT
 #define SIGNALS_IGNORE SIGPIPE

diff --git a/src/core/cgroup.c b/src/core/cgroup.c
index 17e0857729245d2a4374ffcbb404c4b79213736f..fbb711782ed204014f93abbbe51582fcc885c27d 100644 (file)
--- a/src/core/cgroup.c
+++ b/src/core/cgroup.c
@@ -1799,7 +1799,7 @@ int manager_setup_cgroup(Manager *m) {
         else if (cg_unified(SYSTEMD_CGROUP_CONTROLLER))
                 log_debug("Unified cgroup hierarchy is located at %s. Controllers are on legacy hierarchies.", path);
         else
-                log_debug("Using cgroup controller " SYSTEMD_CGROUP_CONTROLLER ". File system hierarchy is at %s.", path);
+                log_debug("Using cgroup controller " SYSTEMD_CGROUP_CONTROLLER_LEGACY ". File system hierarchy is at %s.", path);
 
         if (!m->test_run) {
                 const char *scope_path;