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cgroup: deprecate remount option changes

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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>
This commit is contained in:
Tejun Heo 2012-04-01 12:09:54 -07:00
parent dd775ae254
commit 8b5a5a9dbc
2 changed files with 14 additions and 0 deletions
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9
Documentation/feature-removal-schedule.txt
View file

@ -539,3 +539,12 @@ Why: There appear to be no production users of the get_robust_list syscall,
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.

5
kernel/cgroup.c
View file

@ -1294,6 +1294,11 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
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))) {