Task Control Groups: add procfs interface

Add:

/proc/cgroups - general system info

/proc/*/cgroup - per-task cgroup membership info

[a.p.zijlstra@chello.nl: cgroups: bdi init hooks]
Signed-off-by: Paul Menage <menage@google.com>
Cc: Serge E. Hallyn <serue@us.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Kirill Korotaev <dev@openvz.org>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 4fe74d1..0e9a9aa9 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -67,6 +67,7 @@
 #include <linux/mount.h>
 #include <linux/security.h>
 #include <linux/ptrace.h>
+#include <linux/cgroup.h>
 #include <linux/cpuset.h>
 #include <linux/audit.h>
 #include <linux/poll.h>
@@ -2133,6 +2134,9 @@
 #ifdef CONFIG_CPUSETS
 	REG("cpuset",     S_IRUGO, cpuset),
 #endif
+#ifdef CONFIG_CGROUPS
+	REG("cgroup",  S_IRUGO, cgroup),
+#endif
 	INF("oom_score",  S_IRUGO, oom_score),
 	REG("oom_adj",    S_IRUGO|S_IWUSR, oom_adjust),
 #ifdef CONFIG_AUDITSYSCALL
@@ -2419,6 +2423,9 @@
 #ifdef CONFIG_CPUSETS
 	REG("cpuset",    S_IRUGO, cpuset),
 #endif
+#ifdef CONFIG_CGROUPS
+	REG("cgroup",  S_IRUGO, cgroup),
+#endif
 	INF("oom_score", S_IRUGO, oom_score),
 	REG("oom_adj",   S_IRUGO|S_IWUSR, oom_adjust),
 #ifdef CONFIG_AUDITSYSCALL