lxc-cgroup: use correct terminology

lxc-cgroup gets or sets the value of a state object (such as
'cpuset.cpus'), not the value of a subsystem (which would be
just 'cpuset').

Signed-off-by: David Ward <david.ward@ll.mit.edu>
Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>

doc/lxc-cgroup.sgml.in

@@ -48,8 +48,8 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 
   <refsynopsisdiv>
     <cmdsynopsis>
-      <command>lxc-start <replaceable>-n name</replaceable>
+      <command>lxc-cgroup -n <replaceable>name</replaceable>
-	<replaceable>subsystem</replaceable> <optional>value</optional>
+	<replaceable>state-object</replaceable> <optional>value</optional>
       </command>
     </cmdsynopsis>
   </refsynopsisdiv>
@@ -58,17 +58,20 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
     <title>Description</title>
 
     <para>
-      <command>lxc-cgroup</command> get or set value from the control
+      <command>lxc-cgroup</command> gets or sets the value of a
-      group associated with the
+      <replaceable>state-object</replaceable> (e.g., 'cpuset.cpus')
-      container <replaceable>name</replaceable>. If
+      in the container's cgroup for the corresponding subsystem (e.g.,
-      no <optional>value</optional> is specified, the value of
+      'cpuset'). If no <optional>value</optional> is specified, the
-      the <replaceable>subsystem</replaceable> is displayed, otherwise
+      current value of the <replaceable>state-object</replaceable> is
-      it is set. The <command>lxc-cgroup</command> does not assume the
+      displayed; otherwise it is set.
-      correctness of the <replaceable>subsystem</replaceable> name, it
-      is up to the user to specify the
-      right <replaceable>subsystem</replaceable> name.
     </para>
 
+    <para>
+      Note that <command>lxc-cgroup</command> does not check that the
+      <replaceable>state-object</replaceable> is valid for the running
+      kernel, or that the corresponding subsystem is contained in any
+      mounted cgroup hierarchy.
+    </para>
   </refsect1>
 
   <refsect1>
@@ -77,11 +80,11 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 
       <varlistentry>
 	<term>
-	  <option><replaceable>subsystem</replaceable></option>
+	  <option><replaceable>state-object</replaceable></option>
 	</term>
 	<listitem>
 	  <para>
-	    Specify the subsystem control group name.
+	    Specify the state object name.
 	  </para>
 	</listitem>
       </varlistentry>
@@ -92,7 +95,7 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 	</term>
 	<listitem>
 	  <para>
-	    Specify the subsystem control group value to be set.
+	    Specify the value to assign to the state object.
 	  </para>
 	</listitem>
       </varlistentry>

src/lxc/cgroup.c

@@ -531,8 +531,8 @@ int lxc_cgroup_path_get(char **path, const char *subsystem, const char *name)
 	static char        buf[MAXPATHLEN];
 	static char        retbuf[MAXPATHLEN];
 
-	/* what lxc_cgroup_set calls subsystem is actually the filename, i.e.
+	/* lxc_cgroup_set passes a state object for the subsystem,
-	   'devices.allow'.  So for our purposee we trim it */
+	 * so trim it to just the subsystem part */
 	if (subsystem) {
 		snprintf(retbuf, MAXPATHLEN, "%s", subsystem);
 		char *s = index(retbuf, '.');

src/lxc/lxc_cgroup.c

@@ -36,7 +36,7 @@ lxc_log_define(lxc_cgroup_ui, lxc_cgroup);
 static int my_checker(const struct lxc_arguments* args)
 {
 	if (!args->argc) {
-		lxc_error(args, "missing cgroup subsystem");
+		lxc_error(args, "missing state object");
 		return -1;
 	}
 	return 0;
@@ -49,13 +49,13 @@ static const struct option my_longopts[] = {
 static struct lxc_arguments my_args = {
 	.progname = "lxc-cgroup",
 	.help     = "\
---name=NAME subsystem [value]\n\
+--name=NAME state-object [value]\n\
 \n\
-lxc-cgroup get or set subsystem value of cgroup\n\
+Get or set the value of a state object (for example, 'cpuset.cpus')\n\
-associated with the NAME container\n\
+in the container's cgroup for the corresponding subsystem.\n\
 \n\
 Options :\n\
-  -n, --name=NAME      NAME for name of the container",
+  -n, --name=NAME      container name",
 	.options  = my_longopts,
 	.parser   = NULL,
 	.checker  = my_checker,
@@ -63,7 +63,7 @@ Options :\n\
 
 int main(int argc, char *argv[])
 {
-	char *subsystem = NULL, *value = NULL;
+	char *state_object = NULL, *value = NULL;
 
 	if (lxc_arguments_parse(&my_args, argc, argv))
 		return -1;
@@ -72,15 +72,15 @@ int main(int argc, char *argv[])
 			 my_args.progname, my_args.quiet))
 		return -1;
 
-	subsystem = my_args.argv[0];
+	state_object = my_args.argv[0];
 
 	if ((argc) > 1)
 		value = my_args.argv[1];
 
 	if (value) {
-		if (lxc_cgroup_set(my_args.name, subsystem, value)) {
+		if (lxc_cgroup_set(my_args.name, state_object, value)) {
 			ERROR("failed to assign '%s' value to '%s' for '%s'",
-				value, subsystem, my_args.name);
+				value, state_object, my_args.name);
 			return -1;
 		}
 	} else {
@@ -88,10 +88,10 @@ int main(int argc, char *argv[])
 		int ret;
 		char buffer[len];
 
-		ret = lxc_cgroup_get(my_args.name, subsystem, buffer, len);
+		ret = lxc_cgroup_get(my_args.name, state_object, buffer, len);
 		if (ret < 0) {
 			ERROR("failed to retrieve value of '%s' for '%s'",
-			      subsystem, my_args.name);
+			      state_object, my_args.name);
 			return -1;
 		}