linux-kernel - [147/200] cgroups: alloc_css_id() increments hierarchy depth

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Message-Id: <20100701174258.852925976@clark.site>
Date:	Thu, 01 Jul 2010 10:43:57 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Greg Thelen <gthelen@...gle.com>,
	Paul Menage <menage@...gle.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Li Zefan <lizf@...fujitsu.com>
Subject: [147/200] cgroups: alloc_css_id() increments hierarchy depth

2.6.34-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Greg Thelen <gthelen@...gle.com>

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@...ntu:~# ./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@...ntu:~# ./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@...gle.com>
Acked-by: Paul Menage <menage@...gle.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Acked-by: Li Zefan <lizf@...fujitsu.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 kernel/cgroup.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4599,7 +4599,7 @@ static int alloc_css_id(struct cgroup_su
 	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))


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