On Sat, Feb 09, 2013 at 04:04:02AM +0000, Serge E. Hallyn wrote: > Quoting Aristeu Rozanski (aris@xxxxxxxxxx): > > devcg: propagate local changes down the hierarchy > > > > This patch makes all changes propagate down in hierarchy respecting when > > possible local configurations. > > > > Behavior changes will clean up exceptions in all the children except when the > > parent changes the behavior from allow to deny and the child's behavior was > > already deny, in which case the local exceptions will be reused. The inverse > > is not possible: you can't have a parent with behavior deny and a child with > > behavior accept. > > > > New exceptions allowing additional access to devices won't be propagated, but > > it'll be possible to add an exception to access all of part of the newly > > allowed device(s). > > > > New exceptions disallowing access to devices will be propagated down and the > > local group's exceptions will be revalidated for the new situation. > > Example: > > A > > / \ > > B > > > > group behavior exceptions > > A allow "b 8:* rwm", "c 116:1 rw" > > B deny "c 1:3 rwm", "c 116:2 rwm", "b 3:* rwm" > > > > If a new exception is added to group A: > > # echo "c 116:* r" > A/devices.deny > > it'll propagate down and after revalidating B's local exceptions, the exception > > "c 116:2 rwm" will be removed. > > > > In case parent behavior or exceptions change and local settings are not > > allowed anymore, they'll be deleted. > > Do you have a use case which would be broken if we simply refuse to > allow behavior changes for any cgroup with children? > > It seems like that would drastically simplify much of this. We would > no longer need local.exceptions at all, right? Your comment says > > * local set rules, saved so when a parent propagates new rules, the > * local preferences can be preserved > > but if there were no parent behavior changes, then any exception change > in a parent could be enforced by simply removing violating exceptions > in the child, and subsequently refusing the addition of new rules in the > child which are not allowed in the parent. Both of which you already do. > > Or am I thinking wrongly? That would be an option even simpler than not keeping local settings. In production I doubt the sysadmin will keep playing with permissions, although until one gets right, it'll be annoying as hell to have to remove the whole hierarchy because you forgot to add a certain device to the list. -- Aristeu -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
