cgroup: deprecate remount option changes
This patch marks the following features for deprecation.
* Rebinding subsys by remount: Never reached useful state - only works
on empty hierarchies.
* release_agent update by remount: release_agent itself will be
replaced with conventional fsnotify notification.
v2: Lennart pointed out that "name=" is necessary for mounts w/o any
controller attached. Drop "name=" deprecation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Lennart Poettering <mzxreary@0pointer.de>
diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index c1be806..5298e12 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -539,3 +539,12 @@
of ASLR. It was only ever intended for debugging, so it should be
removed.
Who: Kees Cook <keescook@chromium.org>
+
+----------------------------
+
+What: cgroup option updates via remount
+When: March 2013
+Why: Remount currently allows changing bound subsystems and
+ release_agent. Rebinding is hardly useful as it only works
+ when the hierarchy is empty and release_agent itself should be
+ replaced with conventional fsnotify.
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index ed64cca..741c120 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1294,6 +1294,11 @@
if (ret)
goto out_unlock;
+ /* See feature-removal-schedule.txt */
+ if (opts.subsys_bits != root->actual_subsys_bits || opts.release_agent)
+ pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
+ task_tgid_nr(current), current->comm);
+
/* Don't allow flags or name to change at remount */
if (opts.flags != root->flags ||
(opts.name && strcmp(opts.name, root->name))) {
