On Mon, Nov 3, 2014 at 4:17 PM, Andy Lutomirski <[email protected]> wrote: > On Mon, Nov 3, 2014 at 4:12 PM, Aditya Kali <[email protected]> wrote: >> On Mon, Nov 3, 2014 at 3:48 PM, Andy Lutomirski <[email protected]> wrote: >>> On Mon, Nov 3, 2014 at 3:23 PM, Aditya Kali <[email protected]> wrote: >>>> On Mon, Nov 3, 2014 at 3:15 PM, Andy Lutomirski <[email protected]> >>>> wrote: >>>>> On Mon, Nov 3, 2014 at 3:12 PM, Aditya Kali <[email protected]> wrote: >>>>>> On Fri, Oct 31, 2014 at 5:07 PM, Andy Lutomirski <[email protected]> >>>>>> wrote: >>>>>>> On Fri, Oct 31, 2014 at 12:19 PM, Aditya Kali <[email protected]> >>>>>>> wrote: >>>>>>>> if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) { >>>>>>>> pr_warn("sane_behavior: this is still under >>>>>>>> development and its behaviors will change, proceed at your own >>>>>>>> risk\n"); >>>>>>>> - if (nr_opts != 1) { >>>>>>>> + if (nr_opts > 1) { >>>>>>>> pr_err("sane_behavior: no other mount options >>>>>>>> allowed\n"); >>>>>>>> return -EINVAL; >>>>>>> >>>>>>> This looks wrong. But, if you make the change above, then it'll be >>>>>>> right. >>>>>>> >>>>>> >>>>>> It would have been nice if simple 'mount -t cgroup cgroup <mnt>' from >>>>>> cgroupns does the right thing automatically. >>>>>> >>>>> >>>>> This is a debatable point, but it's not what I meant. Won't your code >>>>> let 'mount -t cgroup -o one_evil_flag cgroup mountpoint' through? >>>>> >>>> >>>> I don't think so. This check "if (nr_opts > 1)" is nested under "if >>>> (opts->flags & CGRP_ROOT_SANE_BEHAVIOR)". So we know that there is >>>> atleast 1 option ('__DEVEL__sane_behavior') present (implicit or not). >>>> Addition of 'one_evil_flag' will make nr_opts = 2 and result in EINVAL >>>> here. >>> >>> But the implicit __DEVEL__sane_behavior doesn't increment nr_opts, right? >>> >> >> Yes. Hence this change makes sure that we don't return EINVAL when >> nr_opts == 0 or nr_opts == 1 :) >> That way, both of the following are equivalent when inside non-init cgroupns: >> >> (1) $ mount -t cgroup -o __DEVEL__sane_behavior cgroup mountpoint >> (2) $ mount -t cgroup cgroup mountpoint >> >> Any other mount option will trigger the error here. > > I still don't get it. Can you walk me through why mount -o > some_other_option -t cgroup cgroup mountpoint causes -EINVAL? >
Argh! You are right. I was totally convinced that this works. But it clearly doesn't if you specify 1 legit mount option. I wanted to make it work for both cases (1) and (2) above. But then this check will have to be changed :( Sorry about the back and forth. I am just going to make it return EINVAL if __DEVEL_sane_behavior is not specified as suggested in the beginning. > --Andy -- Aditya -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
