cgroups: alloc_css_id() increments hierarchy depth

commit 94b3dd0f7bb393d93e84a173b1df9b8b64c83ac4 upstream.

Child groups should have a greater depth than their parents.  Prior to
this change, the parent would incorrectly report zero memory usage for
child cgroups when use_hierarchy is enabled.

test script:
  mount -t cgroup none /cgroups -o memory
  cd /cgroups
  mkdir cg1

  echo 1 > cg1/memory.use_hierarchy
  mkdir cg1/cg11

  echo $$ > cg1/cg11/tasks
  dd if=/dev/zero of=/tmp/foo bs=1M count=1

  echo
  echo CHILD
  grep cache cg1/cg11/memory.stat

  echo
  echo PARENT
  grep cache cg1/memory.stat

  echo $$ > tasks
  rmdir cg1/cg11 cg1
  cd /
  umount /cgroups

Using fae9c79, a recent patch that changed alloc_css_id() depth computation,
the parent incorrectly reports zero usage:
  root@ubuntu:~# ./test
  1+0 records in
  1+0 records out
  1048576 bytes (1.0 MB) copied, 0.0151844 s, 69.1 MB/s

  CHILD
  cache 1048576
  total_cache 1048576

  PARENT
  cache 0
  total_cache 0

With this patch, the parent correctly includes child usage:
  root@ubuntu:~# ./test
  1+0 records in
  1+0 records out
  1048576 bytes (1.0 MB) copied, 0.0136827 s, 76.6 MB/s

  CHILD
  cache 1052672
  total_cache 1052672

  PARENT
  cache 0
  total_cache 1052672

Signed-off-by: Greg Thelen <gthelen@google.com>
Acked-by: Paul Menage <menage@google.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 6d870f2d1228945a94344409012cb3b332a3b0f2..bf4f78f026e8e60fd1d31c601a34b254ba42bbbf 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4599,7 +4599,7 @@ static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
        parent_css = parent->subsys[subsys_id];
        child_css = child->subsys[subsys_id];
        parent_id = parent_css->id;
-       depth = parent_id->depth;
+       depth = parent_id->depth + 1;
 
        child_id = get_new_cssid(ss, depth);
        if (IS_ERR(child_id))