Messages in this thread | | | Date | Wed, 14 Dec 2011 11:09:14 +0400 | From | Glauber Costa <> | Subject | Re: [PATCH 2/3] make clone_children a flag |
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On 12/14/2011 06:29 AM, Li Zefan wrote: > Tejun Heo wrote: >> On Sun, Dec 11, 2011 at 03:45:37PM +0100, Glauber Costa wrote: >>> There is no reason to have a flags field, and then a separate >>> bool field just to indicate if the clone_children flag is set. >>> Make it a flag >>> >>> Signed-off-by: Glauber Costa<glommer@parallels.com> >> >> Doesn't this change how remount conditions are checked? >>
Well, I was thinking it wouldn't, because I patched all callers. But I forget life is not always that simple: After you mentioned, I checked and we do test for changes in the flag field explicitly on remount. So I missed that, indeed.
> Right. Currently we can do this: > > # mount -t cgroup xxx /mnt > # mount -o remount,clone_children /mnt > > with this patch, the above remount will fail. > > But..the current bevaiour of remount is a bit confusing in that remount > with/without "clone_children" has no effect on anything: > > # mount -t cgroup -o clone_children xxx /mnt > # cat /mnt/cgroup.clone_children > 1 > # mount -o remount xxx /mnt > # mount | grep cgroup > xxx on /mnt type cgroup (rw,clone_children) > # cat /mnt/cgroup.clone_children > 1
That's indeed confusing, and it comes from the fact that we always inherit clone_children from the parent - which is sane, IMHO. So this flag only has any value in establishing the initial behaviour of the top root cgroup. I wonder then if it wouldn't better to just be explicit and fail in this case ?
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