Re: [PATCH] cgroups: handle failure of cgroup_populate_dir() at mount/remount
From: Li Zefan
Date: Tue May 26 2009 - 23:23:22 EST
KAMEZAWA Hiroyuki wrote:
> On Wed, 27 May 2009 09:07:31 +0800
> Li Zefan <lizf@xxxxxxxxxxxxxx> wrote:
>> Paul Menage wrote:
>>> On Fri, May 22, 2009 at 1:25 AM, KAMEZAWA Hiroyuki
>>> <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
>>>> Hm, shouldn't we allow "noprefix" to be effective only agaisnt cpuset ?
>>>> I think it's just for backward-compatibility of cpuset.
>>>> (I don't like the option at all.)
>>> Yes, exposing the "noprefix" option externally was one of the mistakes
>>> I made when developing cgroups.
>>> It seems to me really unlikely that anyone is using "noprefix" for
>> And "noprefix" is not documented in cgroups.txt, so I guess not
>> many people know this option. Even libcgroup doesn't handle it.
>>> anything other than implicitly when mounting the "cpuset" filesystem.
>>> So I'd be inclined to just forbid it if we're mounting more than just
>>> the cpuset subsystem. A bit of a nasty abstraction violation, but it
>>> makes more sense overall. The only problem is that someone *might* be
>>> using it - do we have any way to determine how, and how big do they
>>> have to be before we care?
>> I think we can never know..
> How about this method ?
> - add "noprefix" to "to-be-removed" list.
> - add "WARNING: noprefix option will be removed in 2.6.32 (or 2.6.31)" now
> - remove "noprefix" in 2.6.31-rc or later
I don't see how we can remove noprefix while reserve the compatibility of
As Paul Menage said, we can allow noprefix to be used only if we mount just
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
@@ -886,6 +886,11 @@ static int parse_cgroupfs_options(char *data,
+ if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
+ (opts->subsys_bits & ~cpuset_subsys_id) != 0)
+ return -EINVAL;
/* We can't have an empty hierarchy */
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