On Thu, Aug 01, 2013 at 05:49:46PM -0400, Tejun Heo wrote: > cgroup is currently in the process of transitioning to using struct > cgroup_subsys_state * as the primary handle instead of struct cgroup * > in subsystem implementations for the following reasons. > > * With unified hierarchy, subsystems will be dynamically bound and > unbound from cgroups and thus css's (cgroup_subsys_state) may be > created and destroyed dynamically over the lifetime of a cgroup, > which is different from the current state where all css's are > allocated and destroyed together with the associated cgroup. This > in turn means that cgroup_css() should be synchronized and may > return NULL, making it more cumbersome to use. > > * Differing levels of per-subsystem granularity in the unified > hierarchy means that the task and descendant iterators should behave > differently depending on the specific subsystem the iteration is > being performed for. > > * In majority of the cases, subsystems only care about its part in the > cgroup hierarchy - ie. the hierarchy of css's. Subsystem methods > often obtain the matching css pointer from the cgroup and don't > bother with the cgroup pointer itself. Passing around css fits > much better. > > This patch converts all cgroup_subsys methods to take @css instead of > @cgroup. The conversions are mostly straight-forward. A few > noteworthy changes are > > * ->css_alloc() now takes css of the parent cgroup rather than the > pointer to the new cgroup as the css for the new cgroup doesn't > exist yet. Knowing the parent css is enough for all the existing > subsystems. > > * In kernel/cgroup.c::offline_css(), unnecessary open coded css > dereference is replaced with local variable access. > > This patch shouldn't cause any behavior differences. > > Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> > Cc: Li Zefan <lizefan@xxxxxxxxxx> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxx> > Cc: Balbir Singh <bsingharora@xxxxxxxxx> > Cc: Aristeu Rozanski <aris@xxxxxxxxxx> > Cc: Matt Helsley <matthltc@xxxxxxxxxx> > Cc: Daniel Wagner <daniel.wagner@xxxxxxxxxxxx> > Cc: Vivek Goyal <vgoyal@xxxxxxxxxx> > Cc: Jens Axboe <axboe@xxxxxxxxx> > Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> > --- > block/blk-cgroup.c | 25 +++++++++++----------- blk-cgroup changes look good to me. Acked-by: Vivek Goyal <vgoyal@xxxxxxxxxx> Vivek _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
