cgroups: include hierarchy ids in /proc/<pid>/cgroup

Extend the /proc/<pid>/cgroup file to include the appropriate hierarchy ID on
each line.

Currently this ID isn't really needed since a hierarchy can be completely
identified by the set of subsystems bound to it, but this is likely to change
in the near future in order to support stateless subsystems and
merging/rebinding of subsystems.  Getting this change into 2.6.25 reduces the
need for an API change later.

Signed-off-by: Paul Menage <menage@google.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 62f1a5231fe958d2496e99831d015bdf2a8948a5..2727f92383596e4a6f7bec5072b1e804a7801916 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2569,6 +2569,7 @@ static int proc_cgroup_show(struct seq_file *m, void *v)
                /* Skip this hierarchy if it has no active subsystems */
                if (!root->actual_subsys_bits)
                        continue;
+               seq_printf(m, "%lu:", root->subsys_bits);
                for_each_subsys(root, ss)
                        seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
                seq_putc(m, ':');