Merge branch 'for-3.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:
 "A lot of activities on the cgroup front.  Most changes aren't visible
  to userland at all at this point and are laying foundation for the
  planned unified hierarchy.

   - The biggest change is decoupling the lifetime management of css
     (cgroup_subsys_state) from that of cgroup's.  Because controllers
     (cpu, memory, block and so on) will need to be dynamically enabled
     and disabled, css which is the association point between a cgroup
     and a controller may come and go dynamically across the lifetime of
     a cgroup.  Till now, css's were created when the associated cgroup
     was created and stayed till the cgroup got destroyed.

     Assumptions around this tight coupling permeated through cgroup
     core and controllers.  These assumptions are gradually removed,
     which consists bulk of patches, and css destruction path is
     completely decoupled from cgroup destruction path.  Note that
     decoupling of creation path is relatively easy on top of these
     changes and the patchset is pending for the next window.

   - cgroup has its own event mechanism cgroup.event_control, which is
     only used by memcg.  It is overly complex trying to achieve high
     flexibility whose benefits seem dubious at best.  Going forward,
     new events will simply generate file modified event and the
     existing mechanism is being made specific to memcg.  This pull
     request contains prepatory patches for such change.

   - Various fixes and cleanups"

Fixed up conflict in kernel/cgroup.c as per Tejun.

* 'for-3.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (69 commits)
  cgroup: fix cgroup_css() invocation in css_from_id()
  cgroup: make cgroup_write_event_control() use css_from_dir() instead of __d_cgrp()
  cgroup: make cgroup_event hold onto cgroup_subsys_state instead of cgroup
  cgroup: implement CFTYPE_NO_PREFIX
  cgroup: make cgroup_css() take cgroup_subsys * instead and allow NULL subsys
  cgroup: rename cgroup_css_from_dir() to css_from_dir() and update its syntax
  cgroup: fix cgroup_write_event_control()
  cgroup: fix subsystem file accesses on the root cgroup
  cgroup: change cgroup_from_id() to css_from_id()
  cgroup: use css_get() in cgroup_create() to check CSS_ROOT
  cpuset: remove an unncessary forward declaration
  cgroup: RCU protect each cgroup_subsys_state release
  cgroup: move subsys file removal to kill_css()
  cgroup: factor out kill_css()
  cgroup: decouple cgroup_subsys_state destruction from cgroup destruction
  cgroup: replace cgroup->css_kill_cnt with ->nr_css
  cgroup: bounce cgroup_subsys_state ref kill confirmation to a work item
  cgroup: move cgroup->subsys[] assignment to online_css()
  cgroup: reorganize css init / exit paths
  cgroup: add __rcu modifier to cgroup->subsys[]
  ...

diff --cc fs/bio.c
Simple merge

diff --cc include/linux/vmpressure.h
Simple merge

diff --cc kernel/cgroup.c
index e919633,b5f4989..e0aeb32
--- 1/kernel/cgroup.c
--- 2/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@@ -802,9 -830,9 +830,8 @@@ static struct cgroup *task_cgroup_from_
   */
  
  static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
 -static struct dentry *cgroup_lookup(struct inode *, struct dentry *, unsigned int);
  static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
- static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
-                              unsigned long subsys_mask);
+ static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask);
  static const struct inode_operations cgroup_dir_inode_operations;
  static const struct file_operations proc_cgroupstats_operations;
  
@@@ -4497,50 -4694,12 +4686,28 @@@ static int cgroup_destroy_locked(struc
                return -EBUSY;
  
        /*
-        * Block new css_tryget() by killing css refcnts.  cgroup core
-        * guarantees that, by the time ->css_offline() is invoked, no new
-        * css reference will be given out via css_tryget().  We can't
-        * simply call percpu_ref_kill() and proceed to offlining css's
-        * because percpu_ref_kill() doesn't guarantee that the ref is seen
-        * as killed on all CPUs on return.
-        *
-        * Use percpu_ref_kill_and_confirm() to get notifications as each
-        * css is confirmed to be seen as killed on all CPUs.  The
-        * notification callback keeps track of the number of css's to be
-        * killed and schedules cgroup_offline_fn() to perform the rest of
-        * destruction once the percpu refs of all css's are confirmed to
-        * be killed.
 +       * Make sure there's no live children.  We can't test ->children
 +       * emptiness as dead children linger on it while being destroyed;
 +       * otherwise, "rmdir parent/child parent" may fail with -EBUSY.
 +       */
 +      empty = true;
 +      rcu_read_lock();
 +      list_for_each_entry_rcu(child, &cgrp->children, sibling) {
 +              empty = cgroup_is_dead(child);
 +              if (!empty)
 +                      break;
 +      }
 +      rcu_read_unlock();
 +      if (!empty)
 +              return -EBUSY;
 +
 +      /*
+        * Initiate massacre of all css's.  cgroup_destroy_css_killed()
+        * will be invoked to perform the rest of destruction once the
+        * percpu refs of all css's are confirmed to be killed.
         */
-       atomic_set(&cgrp->css_kill_cnt, 1);
-       for_each_root_subsys(cgrp->root, ss) {
-               struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
- 
-               /*
-                * Killing would put the base ref, but we need to keep it
-                * alive until after ->css_offline.
-                */
-               percpu_ref_get(&css->refcnt);
- 
-               atomic_inc(&cgrp->css_kill_cnt);
-               percpu_ref_kill_and_confirm(&css->refcnt, css_ref_killed_fn);
-       }
-       cgroup_css_killed(cgrp);
+       for_each_root_subsys(cgrp->root, ss)
+               kill_css(cgroup_css(cgrp, ss));
  
        /*
         * Mark @cgrp dead.  This prevents further task migration and child

diff --cc kernel/cpuset.c
index ea1966d,95f4b25..6bf981e
--- 1/kernel/cpuset.c
--- 2/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@@ -1608,17 -1591,16 +1595,18 @@@ typedef enum 
        FILE_SPREAD_SLAB,
  } cpuset_filetype_t;
  
- static int cpuset_write_u64(struct cgroup *cgrp, struct cftype *cft, u64 val)
+ static int cpuset_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
+                           u64 val)
  {
-       struct cpuset *cs = cgroup_cs(cgrp);
+       struct cpuset *cs = css_cs(css);
        cpuset_filetype_t type = cft->private;
 -      int retval = -ENODEV;
 +      int retval = 0;
  
        mutex_lock(&cpuset_mutex);
 -      if (!is_cpuset_online(cs))
 +      if (!is_cpuset_online(cs)) {
 +              retval = -ENODEV;
                goto out_unlock;
 +      }
  
        switch (type) {
        case FILE_CPU_EXCLUSIVE:

diff --cc kernel/events/core.c
Simple merge

diff --cc kernel/sched/core.c
Simple merge

diff --cc mm/memcontrol.c
index 0878ff7,b89d4cb..3b83957
--- 1/mm/memcontrol.c
--- 2/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@@ -6335,12 -6304,11 +6304,12 @@@ static void mem_cgroup_css_offline(stru
        mem_cgroup_invalidate_reclaim_iterators(memcg);
        mem_cgroup_reparent_charges(memcg);
        mem_cgroup_destroy_all_caches(memcg);
 +      vmpressure_cleanup(&memcg->vmpressure);
  }
  
- static void mem_cgroup_css_free(struct cgroup *cont)
+ static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
  {
-       struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
+       struct mem_cgroup *memcg = mem_cgroup_from_css(css);
  
        memcg_destroy_kmem(memcg);
        __mem_cgroup_free(memcg);

diff --cc mm/vmpressure.c
Simple merge