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.

v2: Unnecessary explicit cgrp->subsys[] deref in css_online() replaced
    with local variable @css as suggested by Li Zefan.

    Rebased on top of new for-3.12 which includes for-3.11-fixes so
    that ->css_free() invocation added by da0a12ca ("cgroup: fix a
    leak when percpu_ref_init() fails") is converted too.  Suggested
    by Li Zefan.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Acked-by: NAristeu Rozanski <aris@redhat.com>
Acked-by: NDaniel Wagner <daniel.wagner@bmw-carit.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Steven Rostedt <rostedt@goodmis.org>

Currently, controllers have to explicitly follow the cgroup hierarchy
to find the parent of a given css.  cgroup is moving towards using
cgroup_subsys_state as the main controller interface construct, so
let's provide a way to climb the hierarchy using just csses.

This patch implements css_parent() which, given a css, returns its
parent.  The function is guarnateed to valid non-NULL parent css as
long as the target css is not at the top of the hierarchy.

freezer, cpuset, cpu, cpuacct, hugetlb, memory, net_cls and devices
are converted to use css_parent() instead of accessing cgroup->parent
directly.

* __parent_ca() is dropped from cpuacct and its usage is replaced with
  parent_ca().  The only difference between the two was NULL test on
  cgroup->parent which is now embedded in css_parent() making the
  distinction moot.  Note that eventually a css->parent field will be
  added to css and the NULL check in css_parent() will go away.

This patch shouldn't cause any behavior differences.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NLi Zefan <lizefan@huawei.com>

css (cgroup_subsys_state) is usually embedded in a subsys specific
data structure.  Subsystems either use container_of() directly to cast
from css to such data structure or has an accessor function wrapping
such cast.  As cgroup as whole is moving towards using css as the main
interface handle, add and update such accessors to ease dealing with
css's.

All accessors explicitly handle NULL input and return NULL in those
cases.  While this looks like an extra branch in the code, as all
controllers specific data structures have css as the first field, the
casting doesn't involve any offsetting and the compiler can trivially
optimize out the branch.

* blkio, freezer, cpuset, cpu, cpuacct and net_cls didn't have such
  accessor.  Added.

* memory, hugetlb and devices already had one but didn't explicitly
  handle NULL input.  Updated.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NLi Zefan <lizefan@huawei.com>

The names of the two struct cgroup_subsys_state accessors -
cgroup_subsys_state() and task_subsys_state() - are somewhat awkward.
The former clashes with the type name and the latter doesn't even
indicate it's somehow related to cgroup.

We're about to revamp large portion of cgroup API, so, let's rename
them so that they're less awkward.  Most per-controller usages of the
accessors are localized in accessor wrappers and given the amount of
scheduled changes, this isn't gonna add any noticeable headache.

Rename cgroup_subsys_state() to cgroup_css() and task_subsys_state()
to task_css().  This patch is pure rename.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NLi Zefan <lizefan@huawei.com>

Now memcg has the same life cycle with its corresponding cgroup, and a
cgroup is freed via RCU and then mem_cgroup_css_free() will be called in
a work function, so we can simply call __mem_cgroup_free() in
mem_cgroup_css_free().

This actually reverts commit 59927fb9 ("memcg: free mem_cgroup by RCU
to fix oops").
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Cc: Hugh Dickins <hughd@google.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Now memcg has the same life cycle as its corresponding cgroup.  Kill the
useless refcnt.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The cgroup core guarantees it's always safe to access the parent.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Use css_get/put instead of mem_cgroup_get/put.  A simple replacement
will do.

The historical reason that memcg has its own refcnt instead of always
using css_get/put, is that cgroup couldn't be removed if there're still
css refs, so css refs can't be used as long-lived reference.  The
situation has changed so that rmdir a cgroup will succeed regardless css
refs, but won't be freed until css refs goes down to 0.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Use css_get/put instead of mem_cgroup_get/put.

We can't do a simple replacement, because here mem_cgroup_put() is
called during mem_cgroup_css_free(), while mem_cgroup_css_free() won't
be called until css refcnt goes down to 0.

Instead we increment css refcnt in mem_cgroup_css_offline(), and then
check if there's still kmem charges.  If not, css refcnt will be
decremented immediately, otherwise the refcnt will be released after the
last kmem allocation is uncahred.

[akpm@linux-foundation.org: tweak comment]
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: NTejun Heo <tj@kernel.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Use css_get()/css_put() instead of mem_cgroup_get()/mem_cgroup_put().

There are two things being done in the current code:

First, we acquired a css_ref to make sure that the underlying cgroup
would not go away.  That is a short lived reference, and it is put as
soon as the cache is created.

At this point, we acquire a long-lived per-cache memcg reference count
to guarantee that the memcg will still be alive.

so it is:

  enqueue: css_get
  create : memcg_get, css_put
  destroy: memcg_put

So we only need to get rid of the memcg_get, change the memcg_put to
css_put, and get rid of the now extra css_put.

(This changelog is mostly written by Glauber)
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Use css_get/css_put instead of mem_cgroup_get/put.

Note, if at the same time someone is moving @current to a different
cgroup and removing the old cgroup, css_tryget() may return false, and
sock->sk_cgrp won't be initialized, which is fine.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mem_cgroup_css_online calls mem_cgroup_put if memcg_init_kmem fails.
This is not correct because only memcg_propagate_kmem takes an
additional reference while mem_cgroup_sockets_init is allowed to fail as
well (although no current implementation fails) but it doesn't take any
reference.  This all suggests that it should be memcg_propagate_kmem
that should clean up after itself so this patch moves mem_cgroup_put
over there.

Unfortunately this is not that easy (as pointed out by Li Zefan) because
memcg_kmem_mark_dead marks the group dead (KMEM_ACCOUNTED_DEAD) if it is
marked active (KMEM_ACCOUNTED_ACTIVE) which is the case even if
memcg_propagate_kmem fails so the additional reference is dropped in
that case in kmem_cgroup_destroy which means that the reference would be
dropped two times.

The easiest way then would be to simply remove mem_cgrroup_put from
mem_cgroup_css_online and rely on kmem_cgroup_destroy doing the right
thing.
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org>	[3.8]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This reverts commit e4715f01.

mem_cgroup_put is hierarchy aware so mem_cgroup_put(memcg) already drops
an additional reference from all parents so the additional
mem_cgrroup_put(parent) potentially causes use-after-free.
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org>	[3.9+]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The memory we used to hold the memcg arrays is currently accounted to
the current memcg.  But that creates a problem, because that memory can
only be freed after the last user is gone.  Our only way to know which
is the last user, is to hook up to freeing time, but the fact that we
still have some in flight kmallocs will prevent freeing to happen.  I
believe therefore to be just easier to account this memory as global
overhead.
Signed-off-by: NGlauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The memory we used to hold the memcg arrays is currently accounted to
the current memcg.  But that creates a problem, because that memory can
only be freed after the last user is gone.  Our only way to know which
is the last user, is to hook up to freeing time, but the fact that we
still have some in flight kmallocs will prevent freeing to happen.  I
believe therefore to be just easier to account this memory as global
overhead.

This patch (of 2):

Disabling accounting is only relevant for some specific memcg internal
allocations.  Therefore we would initially not have such check at
memcg_kmem_newpage_charge, since direct calls to the page allocator that
are marked with GFP_KMEMCG only happen outside memcg core.  We are
mostly concerned with cache allocations and by having this test at
memcg_kmem_get_cache we are already able to relay the allocation to the
root cache and bypass the memcg caches altogether.

There is one exception, though: the SLUB allocator does not create large
order caches, but rather service large kmallocs directly from the page
allocator.  Therefore, the following sequence, when backed by the SLUB
allocator:

	memcg_stop_kmem_account();
	kmalloc(<large_number>)
	memcg_resume_kmem_account();

would effectively ignore the fact that we should skip accounting, since
it will drive us directly to this function without passing through the
cache selector memcg_kmem_get_cache.  Such large allocations are
extremely rare but can happen, for instance, for the cache arrays.

This was never a problem in practice, because we weren't skipping
accounting for the cache arrays.  All the allocations we were skipping
were fairly small.  However, the fact that we were not skipping those
allocations are a problem and can prevent the memcgs from going away.
As we fix that, we need to make sure that the fix will also work with
the SLUB allocator.
Signed-off-by: NGlauber Costa <glommer@openvz.org>
Reported-by: NMichal Hocko <mhocko@suze.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Remove struct mem_cgroup_lru_info and fold its single member, the
variably sized nodeinfo[0], directly into struct mem_cgroup.  This
should make it more obvious why it has to be the last member there.

Also move the comment that's above that special last member below it, so
it is more visible to somebody that considers appending to the struct
mem_cgroup.
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: David Rientjes <rientjes@google.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@openvz.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mem_cgroup_iter() is too hard to follow.  Factor out the lockless reclaim
iterator loading and updating so it's easier to follow the big picture.

Also document the iterator invalidation mechanism a bit more extensively.
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Reported-by: NTejun Heo <tj@kernel.org>
Reviewed-by: NTejun Heo <tj@kernel.org>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Glauber Costa <glommer@parallels.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

For processes that have detached their mm's, task_in_mem_cgroup()
unnecessarily takes task_lock() when rcu_read_lock() is all that is
necessary to call mem_cgroup_from_task().

While we're here, switch task_in_mem_cgroup() to return bool.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The lockless reclaim hierarchy iterator currently has a misplaced
barrier that can lead to use-after-free crashes.

The reclaim hierarchy iterator consist of a sequence count and a
position pointer that are read and written locklessly, with memory
barriers enforcing ordering.

The write side sets the position pointer first, then updates the
sequence count to "publish" the new position.  Likewise, the read side
must read the sequence count first, then the position.  If the sequence
count is up to date, it's guaranteed that the position is up to date as
well:

  writer:                         reader:
  iter->position = position       if iter->sequence == expected:
  smp_wmb()                           smp_rmb()
  iter->sequence = sequence           position = iter->position

However, the read side barrier is currently misplaced, which can lead to
dereferencing stale position pointers that no longer point to valid
memory.  Fix this.
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Reported-by: NTejun Heo <tj@kernel.org>
Reviewed-by: NTejun Heo <tj@kernel.org>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Glauber Costa <glommer@parallels.com>
Cc: <stable@kernel.org>		[3.10+]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

struct memcg_cache_params has a union.  Different parts of this union
are used for root and non-root caches.  A part with destroying work is
used only for non-root caches.

  BUG: unable to handle kernel paging request at 0000000fffffffe0
  IP: kmem_cache_alloc+0x41/0x1f0
  Modules linked in: netlink_diag af_packet_diag udp_diag tcp_diag inet_diag unix_diag ip6table_filter ip6_tables i2c_piix4 virtio_net virtio_balloon microcode i2c_core pcspkr floppy
  CPU: 0 PID: 1929 Comm: lt-vzctl Tainted: G      D      3.10.0-rc1+ #2
  Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
  RIP: kmem_cache_alloc+0x41/0x1f0
  Call Trace:
   getname_flags.part.34+0x30/0x140
   getname+0x38/0x60
   do_sys_open+0xc5/0x1e0
   SyS_open+0x22/0x30
   system_call_fastpath+0x16/0x1b
  Code: f4 53 48 83 ec 18 8b 05 8e 53 b7 00 4c 8b 4d 08 21 f0 a8 10 74 0d 4c 89 4d c0 e8 1b 76 4a 00 4c 8b 4d c0 e9 92 00 00 00 4d 89 f5 <4d> 8b 45 00 65 4c 03 04 25 48 cd 00 00 49 8b 50 08 4d 8b 38 49
  RIP  [<ffffffff8116b641>] kmem_cache_alloc+0x41/0x1f0
Signed-off-by: NAndrey Vagin <avagin@openvz.org>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Glauber Costa <glommer@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: NMichal Hocko <mhocko@suse.cz>
Cc: Li Zefan <lizefan@huawei.com>
Cc: <stable@vger.kernel.org>	[3.9.x]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Commit 0c59b89c ("mm: memcg: push down PageSwapCache check into
uncharge entry functions") added a VM_BUG_ON() on PageSwapCache in the
uncharge path after checking that page flag once, assuming that the
state is stable in all paths, but this is not the case and the condition
triggers in user environments.  An uncharge after the last page table
reference to the page goes away can race with reclaim adding the page to
swap cache.

Swap cache pages are usually uncharged when they are freed after
swapout, from a path that also handles swap usage accounting and memcg
lifetime management.  However, since the last page table reference is
gone and thus no references to the swap slot left, the swap slot will be
freed shortly when reclaim attempts to write the page to disk.  The
whole swap accounting is not even necessary.

So while the race condition for which this VM_BUG_ON was added is real
and actually existed all along, there are no negative effects.  Remove
the VM_BUG_ON again.
Reported-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Reported-by: NLingzhu Xiang <lxiang@redhat.com>
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Acked-by: NHugh Dickins <hughd@google.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This exports the amount of anonymous transparent hugepages for each
memcg via the new "rss_huge" stat in memory.stat.  The units are in
bytes.

This is helpful to determine the hugepage utilization for individual
jobs on the system in comparison to rss and opportunities where
MADV_HUGEPAGE may be helpful.

The amount of anonymous transparent hugepages is also included in "rss"
for backwards compatibility.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The memcg is not referenced, so it can be destroyed at anytime right
after we exit rcu read section, so it's not safe to access it.

To fix this, we call css_tryget() to get a reference while we're still
in rcu read section.

This also removes a bogus comment above __memcg_create_cache_enqueue().
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NGlauber Costa <glommer@parallels.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

A memcg may livelock when oom if the process that grabs the hierarchy's
oom lock is never the first process with PF_EXITING set in the memcg's
task iteration.

The oom killer, both global and memcg, will defer if it finds an
eligible process that is in the process of exiting and it is not being
ptraced.  The idea is to allow it to exit without using memory reserves
before needlessly killing another process.

This normally works fine except in the memcg case with a large number of
threads attached to the oom memcg.  In this case, the memcg oom killer
only gets called for the process that grabs the hierarchy's oom lock;
all others end up blocked on the memcg's oom waitqueue.  Thus, if the
process that grabs the hierarchy's oom lock is never the first
PF_EXITING process in the memcg's task iteration, the oom killer is
constantly deferred without anything making progress.

The fix is to give PF_EXITING processes access to memory reserves so
that we've marked them as oom killed without any iteration.  This allows
__mem_cgroup_try_charge() to succeed so that the process may exit.  This
makes the memcg oom killer exemption for TIF_MEMDIE tasks, now
immediately granted for processes with pending SIGKILLs and those in the
exit path, to be equivalent to what is done for the global oom killer.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This might cause a use-after-free bug.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Cc: Glauber Costa <glommer@parallels.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

With this patch userland applications that want to maintain the
interactivity/memory allocation cost can use the pressure level
notifications.  The levels are defined like this:

The "low" level means that the system is reclaiming memory for new
allocations.  Monitoring this reclaiming activity might be useful for
maintaining cache level.  Upon notification, the program (typically
"Activity Manager") might analyze vmstat and act in advance (i.e.
prematurely shutdown unimportant services).

The "medium" level means that the system is experiencing medium memory
pressure, the system might be making swap, paging out active file
caches, etc.  Upon this event applications may decide to further analyze
vmstat/zoneinfo/memcg or internal memory usage statistics and free any
resources that can be easily reconstructed or re-read from a disk.

The "critical" level means that the system is actively thrashing, it is
about to out of memory (OOM) or even the in-kernel OOM killer is on its
way to trigger.  Applications should do whatever they can to help the
system.  It might be too late to consult with vmstat or any other
statistics, so it's advisable to take an immediate action.

The events are propagated upward until the event is handled, i.e.  the
events are not pass-through.  Here is what this means: for example you
have three cgroups: A->B->C.  Now you set up an event listener on
cgroups A, B and C, and suppose group C experiences some pressure.  In
this situation, only group C will receive the notification, i.e.  groups
A and B will not receive it.  This is done to avoid excessive
"broadcasting" of messages, which disturbs the system and which is
especially bad if we are low on memory or thrashing.  So, organize the
cgroups wisely, or propagate the events manually (or, ask us to
implement the pass-through events, explaining why would you need them.)

Performance wise, the memory pressure notifications feature itself is
lightweight and does not require much of bookkeeping, in contrast to the
rest of memcg features.  Unfortunately, as of current memcg
implementation, pages accounting is an inseparable part and cannot be
turned off.  The good news is that there are some efforts[1] to improve
the situation; plus, implementing the same, fully API-compatible[2]
interface for CONFIG_MEMCG=n case (e.g.  embedded) is also a viable
option, so it will not require any changes on the userland side.

[1] http://permalink.gmane.org/gmane.linux.kernel.cgroups/6291
[2] http://lkml.org/lkml/2013/2/21/454

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: fix CONFIG_CGROPUPS=n warnings]
Signed-off-by: NAnton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: NKirill A. Shutemov <kirill@shutemov.name>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Glauber Costa <glommer@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Leonid Moiseichuk <leonid.moiseichuk@nokia.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: John Stultz <john.stultz@linaro.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Just a trivial issue I stumbled on while doing something else...
Signed-off-by: NMichel Lespinasse <walken@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Since commit 2d11085e ("memcg: do not create memsw files if swap
accounting is disabled") memsw files are created only if memcg swap
accounting is enabled so it doesn't make any sense to check for it
explicitly in mem_cgroup_read(), mem_cgroup_write() and
mem_cgroup_reset().
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mem_cgroup_iter basically does two things currently.  It takes care of
the house keeping (reference counting, raclaim cookie) and it iterates
through a hierarchy tree (by using cgroup generic tree walk).  The code
would be much more easier to follow if we move the iteration outside of
the function (to __mem_cgrou_iter_next) so the distinction is more
clear.  This patch doesn't introduce any functional changes.
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Ying Han <yinghan@google.com>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Glauber Costa <glommer@parallels.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The current implementation of mem_cgroup_iter has to consider both css
and memcg to find out whether no group has been found (css==NULL - aka
the loop is completed) and that no memcg is associated with the found
node (!memcg - aka css_tryget failed because the group is no longer
alive).  This leads to awkward tweaks like tests for css && !memcg to
skip the current node.

It will be much easier if we got rid off css variable altogether and
only rely on memcg.  In order to do that the iteration part has to skip
dead nodes.  This sounds natural to me and as a nice side effect we will
get a simple invariant that memcg is always alive when non-NULL and all
nodes have been visited otherwise.

We could get rid of the surrounding while loop but keep it in for now to
make review easier.  It will go away in the following patch.
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Ying Han <yinghan@google.com>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Glauber Costa <glommer@parallels.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Now that the per-node-zone-priority iterator caches memory cgroups
rather than their css ids we have to be careful and remove them from the
iterator when they are on the way out otherwise they might live for
unbounded amount of time even though their group is already gone (until
the global/targeted reclaim triggers the zone under priority to find out
the group is dead and let it to find the final rest).

We can fix this issue by relaxing rules for the last_visited memcg.
Instead of taking a reference to the css before it is stored into
iter->last_visited we can just store its pointer and track the number of
removed groups from each memcg's subhierarchy.

This number would be stored into iterator everytime when a memcg is
cached.  If the iter count doesn't match the curent walker root's one we
will start from the root again.  The group counter is incremented
upwards the hierarchy every time a group is removed.

The iter_lock can be dropped because racing iterators cannot leak the
reference anymore as the reference count is not elevated for
last_visited when it is cached.

Locking rules got a bit complicated by this change though.  The iterator
primarily relies on rcu read lock which makes sure that once we see a
valid last_visited pointer then it will be valid for the whole RCU walk.
smp_rmb makes sure that dead_count is read before last_visited and
last_dead_count while smp_wmb makes sure that last_visited is updated
before last_dead_count so the up-to-date last_dead_count cannot point to
an outdated last_visited.  css_tryget then makes sure that the
last_visited is still alive in case the iteration races with the cached
group removal (css is invalidated before mem_cgroup_css_offline
increments dead_count).

In short:
mem_cgroup_iter
 rcu_read_lock()
 dead_count = atomic_read(parent->dead_count)
 smp_rmb()
 if (dead_count != iter->last_dead_count)
 	last_visited POSSIBLY INVALID -> last_visited = NULL
 if (!css_tryget(iter->last_visited))
 	last_visited DEAD -> last_visited = NULL
 next = find_next(last_visited)
 css_tryget(next)
 css_put(last_visited) 	// css would be invalidated and parent->dead_count
 			// incremented if this was the last reference
 iter->last_visited = next
 smp_wmb()
 iter->last_dead_count = dead_count
 rcu_read_unlock()

cgroup_rmdir
 cgroup_destroy_locked
  atomic_add(CSS_DEACT_BIAS, &css->refcnt) // subsequent css_tryget fail
   mem_cgroup_css_offline
    mem_cgroup_invalidate_reclaim_iterators
     while(parent = parent_mem_cgroup)
     	atomic_inc(parent->dead_count)
  css_put(css) // last reference held by cgroup core

Spotted by Ying Han.

Original idea from Johannes Weiner.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Ying Han <yinghan@google.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Glauber Costa <glommer@parallels.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mem_cgroup_iter curently relies on css->id when walking down a group
hierarchy tree.  This is really awkward because the tree walk depends on
the groups creation ordering.  The only guarantee is that a parent node is
visited before its children.

Example:

 1) mkdir -p a a/d a/b/c
 2) mkdir -a a/b/c a/d

Will create the same trees but the tree walks will be different:

 1) a, d, b, c
 2) a, b, c, d

Commit 574bd9f7 ("cgroup: implement generic child / descendant walk
macros") has introduced generic cgroup tree walkers which provide either
pre-order or post-order tree walk.  This patch converts css->id based
iteration to pre-order tree walk to keep the semantic with the original
iterator where parent is always visited before its subtree.

cgroup_for_each_descendant_pre suggests using post_create and
pre_destroy for proper synchronization with groups addidition resp.
removal.  This implementation doesn't use those because a new memory
cgroup is initialized sufficiently for iteration in mem_cgroup_css_alloc
already and css reference counting enforces that the group is alive for
both the last seen cgroup and the found one resp.  it signals that the
group is dead and it should be skipped.

If the reclaim cookie is used we need to store the last visited group
into the iterator so we have to be careful that it doesn't disappear in
the mean time.  Elevated reference count on the css keeps it alive even
though the group have been removed (parked waiting for the last dput so
that it can be freed).

Per node-zone-prio iter_lock has been introduced to ensure that
css_tryget and iter->last_visited is set atomically.  Otherwise two
racing walkers could both take a references and only one release it
leading to a css leak (which pins cgroup dentry).
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Ying Han <yinghan@google.com>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Glauber Costa <glommer@parallels.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The patchset tries to make mem_cgroup_iter saner in the way how it walks
hierarchies.  css->id based traversal is far from being ideal as it is not
deterministic because it depends on the creation ordering.  Additional to
that css_id is considered a burden for cgroup maintainers because it is
quite some code and memcg is the last user of it.  After this series only
the swap accounting uses css_id but that one will follow up later.

Diffstat (if we exclude removed/added comments) looks quite
promising. We got rid of some code:

  $ git diff mmotm... | grep -v "^[+-][[:space:]]*[/ ]\*" | diffstat
   b/include/linux/cgroup.h |    3 ---
   kernel/cgroup.c          |   33 ---------------------------------
   mm/memcontrol.c          |    4 +++-
   3 files changed, 3 insertions(+), 37 deletions(-)

The first patch is just preparatory and it changes when we release css of
the previously returned memcg.  Nothing controlversial.

The second patch is the core of the patchset and it replaces css_get_next
based on css_id by the generic cgroup pre-order.  This brings some
chalanges for the last visited group caching during the reclaim
(mem_cgroup_per_zone::reclaim_iter).  We have to use memcg pointers
directly now which means that we have to keep a reference to those groups'
css to keep them alive.

I also folded iter_lock introduced by https://lkml.org/lkml/2013/1/3/295
in the previous version into this patch.  Johannes felt the race I was
describing should be mostly harmless and I haven't been able to trigger it
so the lock doesn't deserve its own patch.  It is still needed
temporarily, though, because the reference counting on iter->last_visited
depends on it.  It will go away with the next patch.

The next patch fixups an unbounded cgroup removal holdoff caused by the
elevated css refcount.  The issue has been observed by Ying Han.  Johannes
wasn't impressed by the previous version of the fix
(https://lkml.org/lkml/2013/2/8/379) which cleaned up pending references
during mem_cgroup_css_offline when a group is removed.  He has suggested a
different way when the iterator checks whether a cached memcg is still
valid or no.  More on that in the patch but the basic idea is that every
memcg tracks the number removed subgroups and iterator records this number
when a group is cached.  These numbers are checked before
iter->last_visited is about to be used and the iteration is restarted if
it is invalid.

The fourth and fifth patches are an attempt for simplification of the
mem_cgroup_iter.  css juggling is removed and the iteration logic is moved
to a helper so that the reference counting and iteration are separated.

The last patch just removes css_get_next as there is no user for it any
longer.

My testing looked as follows:
        A (use_hierarchy=1, limit_in_bytes=150M)
       /|\
      1 2 3

Children groups were created so that the number is never higher than 3 and
their limits were random between 50-100M.  Each group hosts a kernel build
(starting with tar -xf so the tree is not shared and make -jNUM_CPUs/3)
and terminated after random time - up to 5 minutes) and then it is
removed.

This should exercise both leaf and hierarchical reclaim as well as races
with cgroup removals and debugging messages I added on top proved that.
100 groups were created during the test.

This patch:

css reference counting keeps the cgroup alive even though it has been
already removed.  mem_cgroup_iter relies on this fact and takes a
reference to the returned group.  The reference is then released on the
next iteration or mem_cgroup_iter_break.  mem_cgroup_iter currently
releases the reference right after it gets the last css_id.

This is correct because neither prev's memcg nor cgroup are accessed after
then.  This will change in the next patch so we need to hold the group
alive a bit longer so let's move the css_put at the end of the function.
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Ying Han <yinghan@google.com>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Glauber Costa <glommer@parallels.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Turn on use_hierarchy by default if sane_behavior is specified and
don't create .use_hierarchy file.

It is debatable whether to remove .use_hierarchy file or make it ro as
the former could make transition easier in certain cases; however, the
behavior changes which will be gated by sane_behavior are intensive
including changing basic meaning of certain control knobs in a few
controllers and I don't really think keeping this piece would make
things easier in any noticeable way, so let's remove it.

v2: Explain that mem_cgroup_bind() doesn't have to worry about
    children as suggested by Michal Hocko.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NSerge E. Hallyn <serge.hallyn@ubuntu.com>
Acked-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

As cgroup supports rename, it's unsafe to dereference dentry->d_name
without proper vfs locks. Fix this by using cgroup_name() rather than
dentry directly.

Also open code memcg_cache_name because it is called only from
kmem_cache_dup which frees the returned name right after
kmem_cache_create_memcg makes a copy of it. Such a short-lived
allocation doesn't make too much sense. So replace it by a static
buffer as kmem_cache_dup is called with memcg_cache_mutex.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NGlauber Costa <glommer@parallels.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

Fix a warning from lockdep caused by calling cancel_work_sync() for
uninitialized struct work.  This path has been triggered by destructon
kmem-cache hierarchy via destroying its root kmem-cache.

  cache ffff88003c072d80
  obj ffff88003b410000 cache ffff88003c072d80
  obj ffff88003b924000 cache ffff88003c20bd40
  INFO: trying to register non-static key.
  the code is fine but needs lockdep annotation.
  turning off the locking correctness validator.
  Pid: 2825, comm: insmod Tainted: G           O 3.9.0-rc1-next-20130307+ #611
  Call Trace:
    __lock_acquire+0x16a2/0x1cb0
    lock_acquire+0x8a/0x120
    flush_work+0x38/0x2a0
    __cancel_work_timer+0x89/0xf0
    cancel_work_sync+0xb/0x10
    kmem_cache_destroy_memcg_children+0x81/0xb0
    kmem_cache_destroy+0xf/0xe0
    init_module+0xcb/0x1000 [kmem_test]
    do_one_initcall+0x11a/0x170
    load_module+0x19b0/0x2320
    SyS_init_module+0xc6/0xf0
    system_call_fastpath+0x16/0x1b

Example module to demonstrate:

  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/mm.h>
  #include <linux/workqueue.h>

  int __init mod_init(void)
  {
  	int size = 256;
  	struct kmem_cache *cache;
  	void *obj;
  	struct page *page;

  	cache = kmem_cache_create("kmem_cache_test", size, size, 0, NULL);
  	if (!cache)
  		return -ENOMEM;

  	printk("cache %p\n", cache);

  	obj = kmem_cache_alloc(cache, GFP_KERNEL);
  	if (obj) {
  		page = virt_to_head_page(obj);
  		printk("obj %p cache %p\n", obj, page->slab_cache);
  		kmem_cache_free(cache, obj);
  	}

  	flush_scheduled_work();

  	obj = kmem_cache_alloc(cache, GFP_KERNEL);
  	if (obj) {
  		page = virt_to_head_page(obj);
  		printk("obj %p cache %p\n", obj, page->slab_cache);
  		kmem_cache_free(cache, obj);
  	}

  	kmem_cache_destroy(cache);

  	return -EBUSY;
  }

  module_init(mod_init);
  MODULE_LICENSE("GPL");
Signed-off-by: NKonstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Glauber Costa <glommer@parallels.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Whilst I run the risk of a flogging for disloyalty to the Lord of Sealand,
I do have CONFIG_MEMCG=y CONFIG_MEMCG_KMEM not set, and grow tired of the
"mm/memcontrol.c:4972:12: warning: `memcg_propagate_kmem' defined but not
used [-Wunused-function]" seen in 3.8-rc: move the #ifdef outwards.
Signed-off-by: NHugh Dickins <hughd@google.com>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@parallels.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We should encourage all memcg controller initialization independent on a
specific mem_cgroup to be done here rather than exploit css_alloc
callback and assume that nothing happens before root cgroup is created.
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <htejun@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

memcg_stock are currently initialized during the root cgroup allocation
which is OK but it pointlessly pollutes memcg allocation code with
something that can be called when the memcg subsystem is initialized by
mem_cgroup_init along with other controller specific parts.

This patch wraps the current memcg_stock initialization code into a
helper calls it from the controller subsystem initialization code.
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <htejun@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Per-node-zone soft limit tree is currently initialized when the root
cgroup is created which is OK but it pointlessly pollutes memcg
allocation code with something that can be called when the memcg
subsystem is initialized by mem_cgroup_init along with other controller
specific parts.

While we are at it let's make mem_cgroup_soft_limit_tree_init void
because it doesn't make much sense to report memory failure because if
we fail to allocate memory that early during the boot then we are
screwed anyway (this saves some code).
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <htejun@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>