From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: Re: [PATCH 2/3] make clone_children a flag Date: Wed, 14 Dec 2011 11:09:14 +0400 Message-ID: <4EE84B9A.90901@parallels.com> References: <1323614738-7405-1-git-send-email-glommer@parallels.com> <1323614738-7405-4-git-send-email-glommer@parallels.com> <20111213153921.GE25802@google.com> <4EE80A0D.7090808@cn.fujitsu.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4EE80A0D.7090808-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Li Zefan Cc: Tejun Heo , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, jbottomley-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, bsingharora-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, devel-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org, kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org 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 >> >> 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 ? -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html