Pull cgroup updates from Tejun Heo:
"A lot of activities on cgroup side. Heavy restructuring including
locking simplification took place to improve the code base and enable
implementation of the unified hierarchy, which currently exists behind
a __DEVEL__ mount option. The core support is mostly complete but
individual controllers need further work. To explain the design and
rationales of the the unified hierarchy
Documentation/cgroups/unified-hierarchy.txt
is added.
Another notable change is css (cgroup_subsys_state - what each
controller uses to identify and interact with a cgroup) iteration
update. This is part of continuing updates on css object lifetime and
visibility. cgroup started with reference count draining on removal
way back and is now reaching a point where csses behave and are
iterated like normal refcnted objects albeit with some complexities to
allow distinguishing the state where they're being deleted. The css
iteration update isn't taken advantage of yet but is planned to be
used to simplify memcg significantly"
* 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (77 commits)
cgroup: disallow disabled controllers on the default hierarchy
cgroup: don't destroy the default root
cgroup: disallow debug controller on the default hierarchy
cgroup: clean up MAINTAINERS entries
cgroup: implement css_tryget()
device_cgroup: use css_has_online_children() instead of has_children()
cgroup: convert cgroup_has_live_children() into css_has_online_children()
cgroup: use CSS_ONLINE instead of CGRP_DEAD
cgroup: iterate cgroup_subsys_states directly
cgroup: introduce CSS_RELEASED and reduce css iteration fallback window
cgroup: move cgroup->serial_nr into cgroup_subsys_state
cgroup: link all cgroup_subsys_states in their sibling lists
cgroup: move cgroup->sibling and ->children into cgroup_subsys_state
cgroup: remove cgroup->parent
device_cgroup: remove direct access to cgroup->children
memcg: update memcg_has_children() to use css_next_child()
memcg: remove tasks/children test from mem_cgroup_force_empty()
cgroup: remove css_parent()
cgroup: skip refcnting on normal root csses and cgrp_dfl_root self css
cgroup: use cgroup->self.refcnt for cgroup refcnting
...
Memcg zoneinfo lookup sites have either the page, the zone, or the node
id and zone index, but sites that only have the zone have to look up the
node id and zone index themselves, whereas sites that already have those
two integers use a function for a simple pointer chase.
Provide mem_cgroup_zone_zoneinfo() that takes a zone pointer and let
sites that already have node id and zone index - all for each node, for
each zone iterators - use &memcg->nodeinfo[nid]->zoneinfo[zid].
Rename page_cgroup_zoneinfo() to mem_cgroup_page_zoneinfo() to match.
Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Memory reclaim always uses swappiness of the reclaim target memcg
(origin of the memory pressure) or vm_swappiness for global memory
reclaim. This behavior was consistent (except for difference between
global and hard limit reclaim) because swappiness was enforced to be
consistent within each memcg hierarchy.
After "mm: memcontrol: remove hierarchy restrictions for swappiness and
oom_control" each memcg can have its own swappiness independent of
hierarchical parents, though, so the consistency guarantee is gone.
This can lead to an unexpected behavior. Say that a group is explicitly
configured to not swapout by memory.swappiness=0 but its memory gets
swapped out anyway when the memory pressure comes from its parent with a
It is also unexpected that the knob is meaningless without setting the
hard limit which would trigger the reclaim and enforce the swappiness.
There are setups where the hard limit is configured higher in the
hierarchy by an administrator and children groups are under control of
somebody else who is interested in the swapout behavior but not
necessarily about the memory limit.
From a semantic point of view swappiness is an attribute defining anon
vs.
file proportional scanning of LRU which is memcg specific (unlike
charges which are propagated up the hierarchy) so it should be applied
to the particular memcg's LRU regardless where the memory pressure comes
from.
This patch removes vmscan_swappiness() and stores the swappiness into
the scan_control structure. mem_cgroup_swappiness is then used to
provide the correct value before shrink_lruvec is called. The global
vm_swappiness is used for the root memcg.
[hughd@google.com: oopses immediately when booted with cgroup_disable=memory]
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mem_cgroup_force_empty_list() can iterate a large number of pages on an
lru and mem_cgroup_move_parent() doesn't return an errno unless certain
criteria, none of which indicate that the iteration may be taking too
long, is met.
We have encountered the following stack trace many times indicating
"need_resched set for > 51000020 ns (51 ticks) without schedule", for
example:
scheduler_tick()
<timer irq>
mem_cgroup_move_account+0x4d/0x1d5
mem_cgroup_move_parent+0x8d/0x109
mem_cgroup_reparent_charges+0x149/0x2ba
mem_cgroup_css_offline+0xeb/0x11b
cgroup_offline_fn+0x68/0x16b
process_one_work+0x129/0x350
If this iteration is taking too long, we still need to do cond_resched()
even when an individual page is not busy.
[rientjes@google.com: changelog]
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Current names are rather inconsistent. Let's try to improve them.
Brief change log:
** old name ** ** new name **
kmem_cache_create_memcg memcg_create_kmem_cache
memcg_kmem_create_cache memcg_regsiter_cache
memcg_kmem_destroy_cache memcg_unregister_cache
kmem_cache_destroy_memcg_children memcg_cleanup_cache_params
mem_cgroup_destroy_all_caches memcg_unregister_all_caches
create_work memcg_register_cache_work
memcg_create_cache_work_func memcg_register_cache_func
memcg_create_cache_enqueue memcg_schedule_register_cache
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It isn't worth complicating the code by allocating it on the first access,
because it only takes 256 bytes.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Instead of calling back to memcontrol.c from kmem_cache_create_memcg in
order to just create the name of a per memcg cache, let's allocate it in
place. We only need to pass the memcg name to kmem_cache_create_memcg for
that - everything else can be done in slab_common.c.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It is only used in __mem_cgroup_begin_update_page_stat(), the name is
confusing and 2 routines for one thing also confuse people, so fold this
function seems more clear.
[akpm@linux-foundation.org: fix typo, per Michal]
Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
static values are automatically initialized to NULL
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Replace places where __get_cpu_var() is used for an address calculation
with this_cpu_ptr().
Signed-off-by: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
At present, we have the following mutexes protecting data related to per
memcg kmem caches:
- slab_mutex. This one is held during the whole kmem cache creation
and destruction paths. We also take it when updating per root cache
memcg_caches arrays (see memcg_update_all_caches). As a result, taking
it guarantees there will be no changes to any kmem cache (including per
memcg). Why do we need something else then? The point is it is
private to slab implementation and has some internal dependencies with
other mutexes (get_online_cpus). So we just don't want to rely upon it
and prefer to introduce additional mutexes instead.
- activate_kmem_mutex. Initially it was added to synchronize
initializing kmem limit (memcg_activate_kmem). However, since we can
grow per root cache memcg_caches arrays only on kmem limit
initialization (see memcg_update_all_caches), we also employ it to
protect against memcg_caches arrays relocation (e.g. see
__kmem_cache_destroy_memcg_children).
- We have a convention not to take slab_mutex in memcontrol.c, but we
want to walk over per memcg memcg_slab_caches lists there (e.g. for
destroying all memcg caches on offline). So we have per memcg
slab_caches_mutex's protecting those lists.
The mutexes are taken in the following order:
activate_kmem_mutex -> slab_mutex -> memcg::slab_caches_mutex
Such a syncrhonization scheme has a number of flaws, for instance:
- We can't call kmem_cache_{destroy,shrink} while walking over a
memcg::memcg_slab_caches list due to locking order. As a result, in
mem_cgroup_destroy_all_caches we schedule the
memcg_cache_params::destroy work shrinking and destroying the cache.
- We don't have a mutex to synchronize per memcg caches destruction
between memcg offline (mem_cgroup_destroy_all_caches) and root cache
destruction (__kmem_cache_destroy_memcg_children). Currently we just
don't bother about it.
This patch simplifies it by substituting per memcg slab_caches_mutex's
with the global memcg_slab_mutex. It will be held whenever a new per
memcg cache is created or destroyed, so it protects per root cache
memcg_caches arrays and per memcg memcg_slab_caches lists. The locking
order is following:
activate_kmem_mutex -> memcg_slab_mutex -> slab_mutex
This allows us to call kmem_cache_{create,shrink,destroy} under the
memcg_slab_mutex. As a result, we don't need memcg_cache_params::destroy
work any more - we can simply destroy caches while iterating over a per
memcg slab caches list.
Also using the global mutex simplifies synchronization between concurrent
per memcg caches creation/destruction, e.g. mem_cgroup_destroy_all_caches
vs __kmem_cache_destroy_memcg_children.
The downside of this is that we substitute per-memcg slab_caches_mutex's
with a hummer-like global mutex, but since we already take either the
slab_mutex or the cgroup_mutex along with a memcg::slab_caches_mutex, it
shouldn't hurt concurrency a lot.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently we have two pairs of kmemcg-related functions that are called on
slab alloc/free. The first is memcg_{bind,release}_pages that count the
total number of pages allocated on a kmem cache. The second is
memcg_{un}charge_slab that {un}charge slab pages to kmemcg resource
counter. Let's just merge them to keep the code clean.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patchset is a part of preparations for kmemcg re-parenting. It
targets at simplifying kmemcg work-flows and synchronization.
First, it removes async per memcg cache destruction (see patches 1, 2).
Now caches are only destroyed on memcg offline. That means the caches
that are not empty on memcg offline will be leaked. However, they are
already leaked, because memcg_cache_params::nr_pages normally never drops
to 0 so the destruction work is never scheduled except kmem_cache_shrink
is called explicitly. In the future I'm planning reaping such dead caches
on vmpressure or periodically.
Second, it substitutes per memcg slab_caches_mutex's with the global
memcg_slab_mutex, which should be taken during the whole per memcg cache
creation/destruction path before the slab_mutex (see patch 3). This
greatly simplifies synchronization among various per memcg cache
creation/destruction paths.
I'm still not quite sure about the end picture, in particular I don't know
whether we should reap dead memcgs' kmem caches periodically or try to
merge them with their parents (see https://lkml.org/lkml/2014/4/20/38 for
more details), but whichever way we choose, this set looks like a
reasonable change to me, because it greatly simplifies kmemcg work-flows
and eases further development.
This patch (of 3):
After a memcg is offlined, we mark its kmem caches that cannot be deleted
right now due to pending objects as dead by setting the
memcg_cache_params::dead flag, so that memcg_release_pages will schedule
cache destruction (memcg_cache_params::destroy) as soon as the last slab
of the cache is freed (memcg_cache_params::nr_pages drops to zero).
I guess the idea was to destroy the caches as soon as possible, i.e.
immediately after freeing the last object. However, it just doesn't work
that way, because kmem caches always preserve some pages for the sake of
performance, so that nr_pages never gets to zero unless the cache is
shrunk explicitly using kmem_cache_shrink. Of course, we could account
the total number of objects on the cache or check if all the slabs
allocated for the cache are empty on kmem_cache_free and schedule
destruction if so, but that would be too costly.
Thus we have a piece of code that works only when we explicitly call
kmem_cache_shrink, but complicates the whole picture a lot. Moreover,
it's racy in fact. For instance, kmem_cache_shrink may free the last slab
and thus schedule cache destruction before it finishes checking that the
cache is empty, which can lead to use-after-free.
So I propose to remove this async cache destruction from
memcg_release_pages, and check if the cache is empty explicitly after
calling kmem_cache_shrink instead. This will simplify things a lot w/o
introducing any functional changes.
And regarding dead memcg caches (i.e. those that are left hanging around
after memcg offline for they have objects), I suppose we should reap them
either periodically or on vmpressure as Glauber suggested initially. I'm
going to implement this later.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Eric has reported that he can see task(s) stuck in memcg OOM handler
regularly. The only way out is to
echo 0 > $GROUP/memory.oom_control
His usecase is:
- Setup a hierarchy with memory and the freezer (disable kernel oom and
have a process watch for oom).
- In that memory cgroup add a process with one thread per cpu.
- In one thread slowly allocate once per second I think it is 16M of ram
and mlock and dirty it (just to force the pages into ram and stay
there).
- When oom is achieved loop:
* attempt to freeze all of the tasks.
* if frozen send every task SIGKILL, unfreeze, remove the directory in
cgroupfs.
Eric has then pinpointed the issue to be memcg specific.
All tasks are sitting on the memcg_oom_waitq when memcg oom is disabled.
Those that have received fatal signal will bypass the charge and should
continue on their way out. The tricky part is that the exit path might
trigger a page fault (e.g. exit_robust_list), thus the memcg charge,
while its memcg is still under OOM because nobody has released any charges
yet.
Unlike with the in-kernel OOM handler the exiting task doesn't get
TIF_MEMDIE set so it doesn't shortcut further charges of the killed task
and falls to the memcg OOM again without any way out of it as there are no
fatal signals pending anymore.
This patch fixes the issue by checking PF_EXITING early in
mem_cgroup_try_charge and bypass the charge same as if it had fatal
signal pending or TIF_MEMDIE set.
Normally exiting tasks (aka not killed) will bypass the charge now but
this should be OK as the task is leaving and will release memory and
increasing the memory pressure just to release it in a moment seems
dubious wasting of cycles. Besides that charges after exit_signals should
be rare.
I am bringing this patch again (rebased on the current mmotm tree). I
hope we can move forward finally. If there is still an opposition then
I would really appreciate a concurrent approach so that we can discuss
alternatives.
http://comments.gmane.org/gmane.linux.kernel.stable/77650 is a reference
to the followup discussion when the patch has been dropped from the mmotm
last time.
Reported-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It is only used in slab and should not be used anywhere else so there is
no need in exporting it.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Per-memcg swappiness and oom killing can currently not be tweaked on a
memcg that is part of a hierarchy, but not the root of that hierarchy.
Users have complained that they can't configure this when they turned on
hierarchy mode. In fact, with hierarchy mode becoming the default, this
restriction disables the tunables entirely.
But there is no good reason for this restriction. The settings for
swappiness and OOM killing are taken from whatever memcg whose limit
triggered reclaim and OOM invocation, regardless of its position in the
hierarchy tree.
Allow setting swappiness on any group. The knob on the root memcg
already reads the global VM swappiness, make it writable as well.
Allow disabling the OOM killer on any non-root memcg.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently to allocate a page that should be charged to kmemcg (e.g.
threadinfo), we pass __GFP_KMEMCG flag to the page allocator. The page
allocated is then to be freed by free_memcg_kmem_pages. Apart from
looking asymmetrical, this also requires intrusion to the general
allocation path. So let's introduce separate functions that will
alloc/free pages charged to kmemcg.
The new functions are called alloc_kmem_pages and free_kmem_pages. They
should be used when the caller actually would like to use kmalloc, but
has to fall back to the page allocator for the allocation is large.
They only differ from alloc_pages and free_pages in that besides
allocating or freeing pages they also charge them to the kmem resource
counter of the current memory cgroup.
[sfr@canb.auug.org.au: export kmalloc_order() to modules]
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Greg Thelen <gthelen@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We have only a few places where we actually want to charge kmem so
instead of intruding into the general page allocation path with
__GFP_KMEMCG it's better to explictly charge kmem there. All kmem
charges will be easier to follow that way.
This is a step towards removing __GFP_KMEMCG. It removes __GFP_KMEMCG
from memcg caches' allocflags. Instead it makes slab allocation path
call memcg_charge_kmem directly getting memcg to charge from the cache's
memcg params.
This also eliminates any possibility of misaccounting an allocation
going from one memcg's cache to another memcg, because now we always
charge slabs against the memcg the cache belongs to. That's why this
patch removes the big comment to memcg_kmem_get_cache.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Greg Thelen <gthelen@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 284f39afea ("mm: memcg: push !mm handling out to page cache
charge function") explicitly checks for page cache charges without any
mm context (from kernel thread context[1]).
This seemed to be the only possible case where memory could be charged
without mm context so commit 03583f1a63 ("memcg: remove unnecessary
!mm check from try_get_mem_cgroup_from_mm()") removed the mm check from
get_mem_cgroup_from_mm(). This however caused another NULL ptr
dereference during early boot when loopback kernel thread splices to
tmpfs as reported by Stephan Kulow:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000360
IP: get_mem_cgroup_from_mm.isra.42+0x2b/0x60
Oops: 0000 [#1] SMP
Modules linked in: btrfs dm_multipath dm_mod scsi_dh multipath raid10 raid456 async_raid6_recov async_memcpy async_pq raid6_pq async_xor xor async_tx raid1 raid0 md_mod parport_pc parport nls_utf8 isofs usb_storage iscsi_ibft iscsi_boot_sysfs arc4 ecb fan thermal nfs lockd fscache nls_iso8859_1 nls_cp437 sg st hid_generic usbhid af_packet sunrpc sr_mod cdrom ata_generic uhci_hcd virtio_net virtio_blk ehci_hcd usbcore ata_piix floppy processor button usb_common virtio_pci virtio_ring virtio edd squashfs loop ppa]
CPU: 0 PID: 97 Comm: loop1 Not tainted 3.15.0-rc5-5-default #1
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
Call Trace:
__mem_cgroup_try_charge_swapin+0x40/0xe0
mem_cgroup_charge_file+0x8b/0xd0
shmem_getpage_gfp+0x66b/0x7b0
shmem_file_splice_read+0x18f/0x430
splice_direct_to_actor+0xa2/0x1c0
do_lo_receive+0x5a/0x60 [loop]
loop_thread+0x298/0x720 [loop]
kthread+0xc6/0xe0
ret_from_fork+0x7c/0xb0
Also Branimir Maksimovic reported the following oops which is tiggered
for the swapcache charge path from the accounting code for kernel threads:
CPU: 1 PID: 160 Comm: kworker/u8:5 Tainted: P OE 3.15.0-rc5-core2-custom #159
Hardware name: System manufacturer System Product Name/MAXIMUSV GENE, BIOS 1903 08/19/2013
task: ffff880404e349b0 ti: ffff88040486a000 task.ti: ffff88040486a000
RIP: get_mem_cgroup_from_mm.isra.42+0x2b/0x60
Call Trace:
__mem_cgroup_try_charge_swapin+0x45/0xf0
mem_cgroup_charge_file+0x9c/0xe0
shmem_getpage_gfp+0x62c/0x770
shmem_write_begin+0x38/0x40
generic_perform_write+0xc5/0x1c0
__generic_file_aio_write+0x1d1/0x3f0
generic_file_aio_write+0x4f/0xc0
do_sync_write+0x5a/0x90
do_acct_process+0x4b1/0x550
acct_process+0x6d/0xa0
do_exit+0x827/0xa70
kthread+0xc3/0xf0
This patch fixes the issue by reintroducing mm check into
get_mem_cgroup_from_mm. We could do the same trick in
__mem_cgroup_try_charge_swapin as we do for the regular page cache path
but it is not worth troubles. The check is not that expensive and it is
better to have get_mem_cgroup_from_mm more robust.
[1] - http://marc.info/?l=linux-mm&m=139463617808941&w=2
Fixes: 03583f1a63 ("memcg: remove unnecessary !mm check from try_get_mem_cgroup_from_mm()")
Reported-and-tested-by: Stephan Kulow <coolo@suse.com>
Reported-by: Branimir Maksimovic <branimir.maksimovic@gmail.com>
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently, memcg_has_children() and mem_cgroup_hierarchy_write()
directly test cgroup->children for list emptiness. It's semantically
correct in traditional hierarchies as it actually wants to test for
any children dead or alive; however, cgroup->children is not a
published field and scheduled to go away.
This patch moves out .use_hierarchy test out of memcg_has_children()
and updates it to use css_next_child() to test whether there exists
any children. With .use_hierarchy test moved out, it can also be used
by mem_cgroup_hierarchy_write().
A side note: As .use_hierarchy is going away, it doesn't really matter
but I'm not sure about how it's used in __memcg_activate_kmem(). The
condition tested by memcg_has_children() is mushy when seen from
userland as its result is affected by dead csses which aren't visible
from userland. I think the rule would be a lot clearer if we have a
dedicated "freshly minted" flag which gets cleared when the first task
is migrated into it or the first child is created and then gate
activation with that.
v2: Added comment noting that testing use_hierarchy is the
responsibility of the callers of memcg_has_children() as suggested
by Michal Hocko.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Tejun has correctly pointed out that tasks/children test in
mem_cgroup_force_empty is not correct because there is no other locking
which preserves this state throughout the rest of the function so both
new tasks can join the group or new children groups can be added while
somebody is writing to memory.force_empty. A new task would break
mem_cgroup_reparent_charges expectation that all failures as described
by mem_cgroup_force_empty_list are temporal and there is no way out.
The main use case for the knob as described by
Documentation/cgroups/memory.txt is to:
"
The typical use case for this interface is before calling rmdir().
Because rmdir() moves all pages to parent, some out-of-use page caches can be
moved to the parent. If you want to avoid that, force_empty will be useful.
"
This means that reparenting is not really required as rmdir will
reparent pages implicitly from the safe context. If we remove it from
mem_cgroup_force_empty then we are safe even with existing tasks because
the number of reclaim attempts is bounded. Moreover the knob still does
what the documentation claims (modulo reparenting which doesn't make any
difference) and users might expect. Longterm we want to deprecate the
whole knob and put the reparented pages to the tail of parent LRU during
cgroup removal.
tj: Removed unused variable @cgrp from mem_cgroup_force_empty()
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
cgroup in general is moving towards using cgroup_subsys_state as the
fundamental structural component and css_parent() was introduced to
convert from using cgroup->parent to css->parent. It was quite some
time ago and we're moving forward with making css more prominent.
This patch drops the trivial wrapper css_parent() and let the users
dereference css->parent. While at it, explicitly mark fields of css
which are public and immutable.
v2: New usage from device_cgroup.c converted.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: "David S. Miller" <davem@davemloft.net>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Johannes Weiner <hannes@cmpxchg.org>
cftype->trigger() is pointless. It's trivial to ignore the input
buffer from a regular ->write() operation. Convert all ->trigger()
users to ->write() and remove ->trigger().
This patch doesn't introduce any visible behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Convert all cftype->write_string() users to the new cftype->write()
which maps directly to kernfs write operation and has full access to
kernfs and cgroup contexts. The conversions are mostly mechanical.
* @css and @cft are accessed using of_css() and of_cft() accessors
respectively instead of being specified as arguments.
* Should return @nbytes on success instead of 0.
* @buf is not trimmed automatically. Trim if necessary. Note that
blkcg and netprio don't need this as the parsers already handle
whitespaces.
cftype->write_string() has no user left after the conversions and
removed.
While at it, remove unnecessary local variable @p in
cgroup_subtree_control_write() and stale comment about
CGROUP_LOCAL_BUFFER_SIZE in cgroup_freezer.c.
This patch doesn't introduce any visible behavior changes.
v2: netprio was missing from conversion. Converted.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Aristeu Rozanski <arozansk@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: "David S. Miller" <davem@davemloft.net>
Unlike the more usual refcnting, what css_tryget() provides is the
distinction between online and offline csses instead of protection
against upping a refcnt which already reached zero. cgroup is
planning to provide actual tryget which fails if the refcnt already
reached zero. Let's rename the existing trygets so that they clearly
indicate that they're onliness.
I thought about keeping the existing names as-are and introducing new
names for the planned actual tryget; however, given that each
controller participates in the synchronization of the online state, it
seems worthwhile to make it explicit that these functions are about
on/offline state.
Rename css_tryget() to css_tryget_online() and css_tryget_from_dir()
to css_tryget_online_from_dir(). This is pure rename.
v2: cgroup_freezer grew new usages of css_tryget(). Update
accordingly.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Dave Jones reports the following crash when find_get_pages_tag() runs
into an exceptional entry:
kernel BUG at mm/filemap.c:1347!
RIP: find_get_pages_tag+0x1cb/0x220
Call Trace:
find_get_pages_tag+0x36/0x220
pagevec_lookup_tag+0x21/0x30
filemap_fdatawait_range+0xbe/0x1e0
filemap_fdatawait+0x27/0x30
sync_inodes_sb+0x204/0x2a0
sync_inodes_one_sb+0x19/0x20
iterate_supers+0xb2/0x110
sys_sync+0x44/0xb0
ia32_do_call+0x13/0x13
1343 /*
1344 * This function is never used on a shmem/tmpfs
1345 * mapping, so a swap entry won't be found here.
1346 */
1347 BUG();
After commit 0cd6144aad ("mm + fs: prepare for non-page entries in
page cache radix trees") this comment and BUG() are out of date because
exceptional entries can now appear in all mappings - as shadows of
recently evicted pages.
However, as Hugh Dickins notes,
"it is truly surprising for a PAGECACHE_TAG_WRITEBACK (and probably
any other PAGECACHE_TAG_*) to appear on an exceptional entry.
I expect it comes down to an occasional race in RCU lookup of the
radix_tree: lacking absolute synchronization, we might sometimes
catch an exceptional entry, with the tag which really belongs with
the unexceptional entry which was there an instant before."
And indeed, not only is the tree walk lockless, the tags are also read
in chunks, one radix tree node at a time. There is plenty of time for
page reclaim to swoop in and replace a page that was already looked up
as tagged with a shadow entry.
Remove the BUG() and update the comment. While reviewing all other
lookup sites for whether they properly deal with shadow entries of
evicted pages, update all the comments and fix memcg file charge moving
to not miss shmem/tmpfs swapcache pages.
Fixes: 0cd6144aad ("mm + fs: prepare for non-page entries in page cache radix trees")
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Dave Jones <davej@redhat.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Until now, cgroup->id has been used to identify all the associated
csses and css_from_id() takes cgroup ID and returns the matching css
by looking up the cgroup and then dereferencing the css associated
with it; however, now that the lifetimes of cgroup and css are
separate, this is incorrect and breaks on the unified hierarchy when a
controller is disabled and enabled back again before the previous
instance is released.
This patch adds css->id which is a subsystem-unique ID and converts
css_from_id() to look up by the new css->id instead. memcg is the
only user of css_from_id() and also converted to use css->id instead.
For traditional hierarchies, this shouldn't make any functional
difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jianyu Zhan <nasa4836@gmail.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, cgroup->id is allocated from 0, which is always assigned to
the root cgroup; unfortunately, memcg wants to use ID 0 to indicate
invalid IDs and ends up incrementing all IDs by one.
It's reasonable to reserve 0 for special purposes. This patch updates
cgroup core so that ID 0 is not used and the root cgroups get ID 1.
The ID incrementing is removed form memcg.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently we destroy children caches at the very beginning of
kmem_cache_destroy(). This is wrong, because the root cache will not
necessarily be destroyed in the end - if it has aliases (refcount > 0),
kmem_cache_destroy() will simply decrement its refcount and return. In
this case, at best we will get a bunch of warnings in dmesg, like this
one:
kmem_cache_destroy kmalloc-32:0: Slab cache still has objects
CPU: 1 PID: 7139 Comm: modprobe Tainted: G B W 3.13.0+ #117
Call Trace:
dump_stack+0x49/0x5b
kmem_cache_destroy+0xdf/0xf0
kmem_cache_destroy_memcg_children+0x97/0xc0
kmem_cache_destroy+0xf/0xf0
xfs_mru_cache_uninit+0x21/0x30 [xfs]
exit_xfs_fs+0x2e/0xc44 [xfs]
SyS_delete_module+0x198/0x1f0
system_call_fastpath+0x16/0x1b
At worst - if kmem_cache_destroy() will race with an allocation from a
memcg cache - the kernel will panic.
This patch fixes this by moving children caches destruction after the
check if the cache has aliases. Plus, it forbids destroying a root
cache if it still has children caches, because each children cache keeps
a reference to its parent.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Glauber Costa <glommer@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently, memcg_unregister_cache(), which deletes the cache being
destroyed from the memcg_slab_caches list, is called after
__kmem_cache_shutdown() (see kmem_cache_destroy()), which starts to
destroy the cache.
As a result, one can access a partially destroyed cache while traversing
a memcg_slab_caches list, which can have deadly consequences (for
instance, cache_show() called for each cache on a memcg_slab_caches list
from mem_cgroup_slabinfo_read() will dereference pointers to already
freed data).
To fix this, let's move memcg_unregister_cache() before the cache
destruction process beginning, issuing memcg_register_cache() on failure.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Glauber Costa <glommer@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Memcg-awareness turned kmem_cache_create() into a dirty interweaving of
memcg-only and except-for-memcg calls. To clean this up, let's move the
code responsible for memcg cache creation to a separate function.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Glauber Costa <glommer@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch cleans up the memcg cache creation path as follows:
- Move memcg cache name creation to a separate function to be called
from kmem_cache_create_memcg(). This allows us to get rid of the mutex
protecting the temporary buffer used for the name formatting, because
the whole cache creation path is protected by the slab_mutex.
- Get rid of memcg_create_kmem_cache(). This function serves as a proxy
to kmem_cache_create_memcg(). After separating the cache name creation
path, it would be reduced to a function call, so let's inline it.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Glauber Costa <glommer@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mem_cgroup_newpage_charge is used only for charging anonymous memory so
it is better to rename it to mem_cgroup_charge_anon.
mem_cgroup_cache_charge is used for file backed memory so rename it to
mem_cgroup_charge_file.
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Some callsites pass a memcg directly, some callsites pass an mm that
then has to be translated to a memcg. This makes for a terrible
function interface.
Just push the mm-to-memcg translation into the respective callsites and
always pass a memcg to mem_cgroup_try_charge().
[mhocko@suse.cz: add charge mm helper]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
__mem_cgroup_try_charge duplicates get_mem_cgroup_from_mm for charges
which came without a memcg. The only reason seems to be a tiny
optimization when css_tryget is not called if the charge can be consumed
from the stock. Nevertheless css_tryget is very cheap since it has been
reworked to use per-cpu counting so this optimization doesn't give us
anything these days.
So let's drop the code duplication so that the code is more readable.
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Instead of returning NULL from try_get_mem_cgroup_from_mm() when the mm
owner is exiting, just return root_mem_cgroup. This makes sense for all
callsites and gets rid of some of them having to fallback manually.
[fengguang.wu@intel.com: fix warnings]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Users pass either a mm that has been established under task lock, or use
a verified current->mm, which means the task can't be exiting.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Only page cache charges can happen without an mm context, so push this
special case out of the inner core and into the cache charge function.
An ancient comment explains that the mm can also be NULL in case the
task is currently being migrated, but that is not actually true with the
current case, so just remove it.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mem_cgroup_charge_common() is used by both cache and anon pages, but
most of its body only applies to anon pages and the remainder is not
worth having in a separate function.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It used to disable preemption and run sanity checks but now it's only
taking a number out of one percpu counter and putting it into another.
Do this directly in the callsite and save the indirection.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull cgroup updates from Tejun Heo:
"A lot updates for cgroup:
- The biggest one is cgroup's conversion to kernfs. cgroup took
after the long abandoned vfs-entangled sysfs implementation and
made it even more convoluted over time. cgroup's internal objects
were fused with vfs objects which also brought in vfs locking and
object lifetime rules. Naturally, there are places where vfs rules
don't fit and nasty hacks, such as credential switching or lock
dance interleaving inode mutex and cgroup_mutex with object serial
number comparison thrown in to decide whether the operation is
actually necessary, needed to be employed.
After conversion to kernfs, internal object lifetime and locking
rules are mostly isolated from vfs interactions allowing shedding
of several nasty hacks and overall simplification. This will also
allow implmentation of operations which may affect multiple cgroups
which weren't possible before as it would have required nesting
i_mutexes.
- Various simplifications including dropping of module support,
easier cgroup name/path handling, simplified cgroup file type
handling and task_cg_lists optimization.
- Prepatory changes for the planned unified hierarchy, which is still
a patchset away from being actually operational. The dummy
hierarchy is updated to serve as the default unified hierarchy.
Controllers which aren't claimed by other hierarchies are
associated with it, which BTW was what the dummy hierarchy was for
anyway.
- Various fixes from Li and others. This pull request includes some
patches to add missing slab.h to various subsystems. This was
triggered xattr.h include removal from cgroup.h. cgroup.h
indirectly got included a lot of files which brought in xattr.h
which brought in slab.h.
There are several merge commits - one to pull in kernfs updates
necessary for converting cgroup (already in upstream through
driver-core), others for interfering changes in the fixes branch"
* 'for-3.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (74 commits)
cgroup: remove useless argument from cgroup_exit()
cgroup: fix spurious lockdep warning in cgroup_exit()
cgroup: Use RCU_INIT_POINTER(x, NULL) in cgroup.c
cgroup: break kernfs active_ref protection in cgroup directory operations
cgroup: fix cgroup_taskset walking order
cgroup: implement CFTYPE_ONLY_ON_DFL
cgroup: make cgrp_dfl_root mountable
cgroup: drop const from @buffer of cftype->write_string()
cgroup: rename cgroup_dummy_root and related names
cgroup: move ->subsys_mask from cgroupfs_root to cgroup
cgroup: treat cgroup_dummy_root as an equivalent hierarchy during rebinding
cgroup: remove NULL checks from [pr_cont_]cgroup_{name|path}()
cgroup: use cgroup_setup_root() to initialize cgroup_dummy_root
cgroup: reorganize cgroup bootstrapping
cgroup: relocate setting of CGRP_DEAD
cpuset: use rcu_read_lock() to protect task_cs()
cgroup_freezer: document freezer_fork() subtleties
cgroup: update cgroup_transfer_tasks() to either succeed or fail
cgroup: drop task_lock() protection around task->cgroups
cgroup: update how a newly forked task gets associated with css_set
...
cftype->write_string() just passes on the writeable buffer from kernfs
and there's no reason to add const restriction on the buffer. The
only thing const achieves is unnecessarily complicating parsing of the
buffer. Drop const from @buffer.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Sometimes the cleanup after memcg hierarchy testing gets stuck in
mem_cgroup_reparent_charges(), unable to bring non-kmem usage down to 0.
There may turn out to be several causes, but a major cause is this: the
workitem to offline parent can get run before workitem to offline child;
parent's mem_cgroup_reparent_charges() circles around waiting for the
child's pages to be reparented to its lrus, but it's holding
cgroup_mutex which prevents the child from reaching its
mem_cgroup_reparent_charges().
Further testing showed that an ordered workqueue for cgroup_destroy_wq
is not always good enough: percpu_ref_kill_and_confirm's call_rcu_sched
stage on the way can mess up the order before reaching the workqueue.
Instead, when offlining a memcg, call mem_cgroup_reparent_charges() on
all its children (and grandchildren, in the correct order) to have their
charges reparented first.
Fixes: e5fca243ab ("cgroup: use a dedicated workqueue for cgroup destruction")
Signed-off-by: Filipe Brandenburger <filbranden@google.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org> [v3.10+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 0eef615665 ("memcg: fix css reference leak and endless loop in
mem_cgroup_iter") got the interaction with the commit a few before it
d8ad305597 ("mm/memcg: iteration skip memcgs not yet fully
initialized") slightly wrong, and we didn't notice at the time.
It's elusive, and harder to get than the original, but for a couple of
days before rc1, I several times saw a endless loop similar to that
supposedly being fixed.
This time it was a tighter loop in __mem_cgroup_iter_next(): because we
can get here when our root has already been offlined, and the ordering
of conditions was such that we then just cycled around forever.
Fixes: 0eef615665 ("memcg: fix css reference leak and endless loop in mem_cgroup_iter").
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Greg Thelen <gthelen@google.com>
Cc: <stable@vger.kernel.org> [3.12+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Kirill has reported the following:
Task in /test killed as a result of limit of /test
memory: usage 10240kB, limit 10240kB, failcnt 51
memory+swap: usage 10240kB, limit 10240kB, failcnt 0
kmem: usage 0kB, limit 18014398509481983kB, failcnt 0
Memory cgroup stats for /test:
BUG: sleeping function called from invalid context at kernel/cpu.c:68
in_atomic(): 1, irqs_disabled(): 0, pid: 66, name: memcg_test
2 locks held by memcg_test/66:
#0: (memcg_oom_lock#2){+.+...}, at: [<ffffffff81131014>] pagefault_out_of_memory+0x14/0x90
#1: (oom_info_lock){+.+...}, at: [<ffffffff81197b2a>] mem_cgroup_print_oom_info+0x2a/0x390
CPU: 2 PID: 66 Comm: memcg_test Not tainted 3.14.0-rc1-dirty #745
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS Bochs 01/01/2011
Call Trace:
__might_sleep+0x16a/0x210
get_online_cpus+0x1c/0x60
mem_cgroup_read_stat+0x27/0xb0
mem_cgroup_print_oom_info+0x260/0x390
dump_header+0x88/0x251
? trace_hardirqs_on+0xd/0x10
oom_kill_process+0x258/0x3d0
mem_cgroup_oom_synchronize+0x656/0x6c0
? mem_cgroup_charge_common+0xd0/0xd0
pagefault_out_of_memory+0x14/0x90
mm_fault_error+0x91/0x189
__do_page_fault+0x48e/0x580
do_page_fault+0xe/0x10
page_fault+0x22/0x30
which complains that mem_cgroup_read_stat cannot be called from an atomic
context but mem_cgroup_print_oom_info takes a spinlock. Change
oom_info_lock to a mutex.
This was introduced by 947b3dd1a8 ("memcg, oom: lock
mem_cgroup_print_oom_info").
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Reported-by: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
cgroup_task_count() read-locks css_set_lock and walks all tasks to
count them and then returns the result. The only thing all the users
want is determining whether the cgroup is empty or not. This patch
implements cgroup_has_tasks() which tests whether cgroup->cset_links
is empty, replaces all cgroup_task_count() usages and unexports it.
Note that the test isn't synchronized. This is the same as before.
The test has always been racy.
This will help planned css_set locking update.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
cgroup->name handling became quite complicated over time involving
dedicated struct cgroup_name for RCU protection. Now that cgroup is
on kernfs, we can drop all of it and simply use kernfs_name/path() and
friends. Replace cgroup->name and all related code with kernfs
name/path constructs.
* Reimplement cgroup_name() and cgroup_path() as thin wrappers on top
of kernfs counterparts, which involves semantic changes.
pr_cont_cgroup_name() and pr_cont_cgroup_path() added.
* cgroup->name handling dropped from cgroup_rename().
* All users of cgroup_name/path() updated to the new semantics. Users
which were formatting the string just to printk them are converted
to use pr_cont_cgroup_name/path() instead, which simplifies things
quite a bit. As cgroup_name() no longer requires RCU read lock
around it, RCU lockings which were protecting only cgroup_name() are
removed.
v2: Comment above oom_info_lock updated as suggested by Michal.
v3: dummy_top doesn't have a kn associated and
pr_cont_cgroup_name/path() ended up calling the matching kernfs
functions with NULL kn leading to oops. Test for NULL kn and
print "/" if so. This issue was reported by Fengguang Wu.
v4: Rebased on top of 0ab02ca8f8 ("cgroup: protect modifications to
cgroup_idr with cgroup_mutex").
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
