detect a cgroup named 'lxc'

doc/lxc.sgml.in

@@ -126,27 +126,36 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
       </programlisting>
 
       <para>
-	For the moment the easiest way to have all the features in the
-	kernel is to use the git tree at:
-	<systemitem>
-	  git://git.kernel.org/pub/scm/linux/kernel/git/daveh/linux-2.6-lxc.git
-	</systemitem>
 
-	But the kernel version >= 2.6.27 shipped with the distros, may
+	The kernel version >= 2.6.27 shipped with the distros, will
 	work with <command>lxc</command>, this one will have less
 	functionalities but enough to be interesting.
 
-	The planned kernel version which <command>lxc</command> should
-	be fully functionaly is 2.6.29.
+	With the kernel 2.6.29, <command>lxc</command> is fully
+	functional.
       </para>
 
       <para>
 	Before using the <command>lxc</command>, your system should be
 	configured with the file capabilities, otherwise you will need
-	to run the <command>lxc</command> commands as root. The
-	control group should be mounted anywhere, eg:
-	<command>mount -t cgroup cgroup /cgroup</command>
+	to run the <command>lxc</command> commands as root.
       </para>
+
+      <para>
+	  The control group can be mounted anywhere, eg:
+	  <command>mount -t cgroup cgroup /cgroup</command>.
+
+	  If you want to dedicate a specific cgroup mount point
+	  for <command>lxc</command>, that is to have different cgroups
+	  mounted at different places with different options but
+	  let <command>lxc</command> to use one location, you can bind
+	  the mount point with the <option>lxc</option> name, eg:
+	  <command>mount -t cgroup lxc /cgroup4lxc</command> or
+	  <command>mount -t cgroup -ons,cpuset,freezer,devices
+	  lxc /cgroup4lxc</command>
+
+      </para>
+
   </refsect1>
 
   <refsect1>

src/lxc/cgroup.c

@@ -58,11 +58,20 @@ static int get_cgroup_mount(const char *mtab, char *mnt)
         }
 
         while ((mntent = getmntent(file))) {
-                if (strcmp(mntent->mnt_type, "cgroup"))
-                        continue;
-                strcpy(mnt, mntent->mnt_dir);
-                err = 0;
-                break;
+
+		/* there is a cgroup mounted named "lxc" */
+		if (!strcmp(mntent->mnt_fsname, "lxc") &&
+		    !strcmp(mntent->mnt_type, "cgroup")) {
+			strcpy(mnt, mntent->mnt_dir);
+			err = 0;
+			break;
+		}
+
+		/* fallback to the first non-lxc cgroup found */
+                if (!strcmp(mntent->mnt_type, "cgroup") && err) {
+			strcpy(mnt, mntent->mnt_dir);
+			err = 0;
+		}
         };
 
         fclose(file);
@@ -87,8 +96,7 @@ int lxc_rename_nsgroup(const char *name, pid_t pid)
 
 	ret = rename(oldname, newname);
 	if (ret)
-		SYSERROR("failed to rename cgroup %s->%s",
-				 oldname, newname);
+		SYSERROR("failed to rename cgroup %s->%s", oldname, newname);
 	return ret;
 }
 
@@ -110,8 +118,7 @@ int lxc_link_nsgroup(const char *name)
 	unlink(lxc);
 	ret = symlink(nsgroup, lxc);
 	if (ret)
-		SYSERROR("failed to create symlink %s->%s",
-				 nsgroup, lxc);
+		SYSERROR("failed to create symlink %s->%s", nsgroup, lxc);
       return ret;
 }