linux-stable.git/mm/memcontrol.c, branch linux-3.16.y

mm: memcg: switch to css_tryget() in get_mem_cgroup_from_mm()

2019-12-19T15:59:01+00:00

commit 00d484f354d85845991b40141d40ba9e5eb60faf upstream.

We've encountered a rcu stall in get_mem_cgroup_from_mm():

  rcu: INFO: rcu_sched self-detected stall on CPU
  rcu: 33-....: (21000 ticks this GP) idle=6c6/1/0x4000000000000002 softirq=35441/35441 fqs=5017
  (t=21031 jiffies g=324821 q=95837) NMI backtrace for cpu 33
  <...>
  RIP: 0010:get_mem_cgroup_from_mm+0x2f/0x90
  <...>
   __memcg_kmem_charge+0x55/0x140
   __alloc_pages_nodemask+0x267/0x320
   pipe_write+0x1ad/0x400
   new_sync_write+0x127/0x1c0
   __kernel_write+0x4f/0xf0
   dump_emit+0x91/0xc0
   writenote+0xa0/0xc0
   elf_core_dump+0x11af/0x1430
   do_coredump+0xc65/0xee0
   get_signal+0x132/0x7c0
   do_signal+0x36/0x640
   exit_to_usermode_loop+0x61/0xd0
   do_syscall_64+0xd4/0x100
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

The problem is caused by an exiting task which is associated with an
offline memcg.  We're iterating over and over in the do {} while
(!css_tryget_online()) loop, but obviously the memcg won't become online
and the exiting task won't be migrated to a live memcg.

Let's fix it by switching from css_tryget_online() to css_tryget().

As css_tryget_online() cannot guarantee that the memcg won't go offline,
the check is usually useless, except some rare cases when for example it
determines if something should be presented to a user.

A similar problem is described by commit 18fa84a2db0e ("cgroup: Use
css_tryget() instead of css_tryget_online() in task_get_css()").

Johannes:

: The bug aside, it doesn't matter whether the cgroup is online for the
: callers.  It used to matter when offlining needed to evacuate all charges
: from the memcg, and so needed to prevent new ones from showing up, but we
: don't care now.

Link: http://lkml.kernel.org/r/20191106225131.3543616-1-guro@fb.com
Signed-off-by: Roman Gushchin 
Acked-by: Johannes Weiner 
Acked-by: Tejun Heo 
Reviewed-by: Shakeel Butt 
Cc: Michal Hocko 
Cc: Michal Koutn 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings

mm: remove rest usage of VM_NONLINEAR and pte_file()

2018-10-03T03:09:52+00:00

commit 0661a33611fca12570cba48d9344ce68834ee86c upstream.

One bit in ->vm_flags is unused now!

Signed-off-by: Kirill A. Shutemov 
Cc: Dan Carpenter 
Cc: Michal Hocko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
[bwh: Backported to 3.16: Drop changes in mm/debug.c]
Signed-off-by: Ben Hutchings

memcg: only free spare array when readers are done

2016-02-02T19:09:49+00:00

commit 6611d8d76132f86faa501de9451a89bf23fb2371 upstream.

A spare array holding mem cgroup threshold events is kept around to make
sure we can always safely deregister an event and have an array to store
the new set of events in.

In the scenario where we're going from 1 to 0 registered events, the
pointer to the primary array containing 1 event is copied to the spare
slot, and then the spare slot is freed because no events are left.
However, it is freed before calling synchronize_rcu(), which means
readers may still be accessing threshold->primary after it is freed.

Fixed by only freeing after synchronize_rcu().

Signed-off-by: Martijn Coenen 
Cc: Johannes Weiner 
Acked-by: Michal Hocko 
Cc: Vladimir Davydov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Luis Henriques

memcg: remove extra newlines from memcg oom kill log

2015-02-04T10:58:34+00:00

commit 0346dadbf041a2606bcb5bd27828b0d105897f4a upstream.

Commit e61734c55c24 ("cgroup: remove cgroup->name") added two extra
newlines to memcg oom kill log messages.  This makes dmesg hard to read
and parse.  The issue affects 3.15+.

Example:

  Task in /t                          <<< extra #1
   killed as a result of limit of /t
                                      <<< extra #2
  memory: usage 102400kB, limit 102400kB, failcnt 274712

Remove the extra newlines from memcg oom kill messages, so the messages
look like:

  Task in /t killed as a result of limit of /t
  memory: usage 102400kB, limit 102400kB, failcnt 240649

Fixes: e61734c55c24 ("cgroup: remove cgroup->name")
Signed-off-by: Greg Thelen 
Acked-by: Michal Hocko 
Acked-by: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Luis Henriques

mm: memcontrol: do not iterate uninitialized memcgs

2014-10-09T19:23:47+00:00

commit 2f7dd7a4100ad4affcb141605bef178ab98ccb18 upstream.

The cgroup iterators yield css objects that have not yet gone through
css_online(), but they are not complete memcgs at this point and so the
memcg iterators should not return them.  Commit d8ad30559715 ("mm/memcg:
iteration skip memcgs not yet fully initialized") set out to implement
exactly this, but it uses CSS_ONLINE, a cgroup-internal flag that does
not meet the ordering requirements for memcg, and so the iterator may
skip over initialized groups, or return partially initialized memcgs.

The cgroup core can not reasonably provide a clear answer on whether the
object around the css has been fully initialized, as that depends on
controller-specific locking and lifetime rules.  Thus, introduce a
memcg-specific flag that is set after the memcg has been initialized in
css_online(), and read before mem_cgroup_iter() callers access the memcg
members.

Signed-off-by: Johannes Weiner 
Cc: Tejun Heo 
Acked-by: Michal Hocko 
Cc: Hugh Dickins 
Cc: Peter Zijlstra 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

memcg: oom_notify use-after-free fix

2014-07-31T00:16:13+00:00

Paul Furtado has reported the following GPF:

  general protection fault: 0000 [#1] SMP
  Modules linked in: ipv6 dm_mod xen_netfront coretemp hwmon x86_pkg_temp_thermal crc32_pclmul crc32c_intel ghash_clmulni_intel aesni_intel ablk_helper cryptd lrw gf128mul glue_helper aes_x86_64 microcode pcspkr ext4 jbd2 mbcache raid0 xen_blkfront
  CPU: 3 PID: 3062 Comm: java Not tainted 3.16.0-rc5 #1
  task: ffff8801cfe8f170 ti: ffff8801d2ec4000 task.ti: ffff8801d2ec4000
  RIP: e030:mem_cgroup_oom_synchronize+0x140/0x240
  RSP: e02b:ffff8801d2ec7d48  EFLAGS: 00010283
  RAX: 0000000000000001 RBX: ffff88009d633800 RCX: 000000000000000e
  RDX: fffffffffffffffe RSI: ffff88009d630200 RDI: ffff88009d630200
  RBP: ffff8801d2ec7da8 R08: 0000000000000012 R09: 00000000fffffffe
  R10: 0000000000000000 R11: 0000000000000000 R12: ffff88009d633800
  R13: ffff8801d2ec7d48 R14: dead000000100100 R15: ffff88009d633a30
  FS:  00007f1748bb4700(0000) GS:ffff8801def80000(0000) knlGS:0000000000000000
  CS:  e033 DS: 0000 ES: 0000 CR0: 000000008005003b
  CR2: 00007f4110300308 CR3: 00000000c05f7000 CR4: 0000000000002660
  Call Trace:
    pagefault_out_of_memory+0x18/0x90
    mm_fault_error+0xa9/0x1a0
    __do_page_fault+0x478/0x4c0
    do_page_fault+0x2c/0x40
    page_fault+0x28/0x30
  Code: 44 00 00 48 89 df e8 40 ca ff ff 48 85 c0 49 89 c4 74 35 4c 8b b0 30 02 00 00 4c 8d b8 30 02 00 00 4d 39 fe 74 1b 0f 1f 44 00 00 <49> 8b 7e 10 be 01 00 00 00 e8 42 d2 04 00 4d 8b 36 4d 39 fe 75
  RIP  mem_cgroup_oom_synchronize+0x140/0x240

Commit fb2a6fc56be6 ("mm: memcg: rework and document OOM waiting and
wakeup") has moved mem_cgroup_oom_notify outside of memcg_oom_lock
assuming it is protected by the hierarchical OOM-lock.

Although this is true for the notification part the protection doesn't
cover unregistration of event which can happen in parallel now so
mem_cgroup_oom_notify can see already unlinked and/or freed
mem_cgroup_eventfd_list.

Fix this by using memcg_oom_lock also in mem_cgroup_oom_notify.

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=80881

Fixes: fb2a6fc56be6 (mm: memcg: rework and document OOM waiting and wakeup)
Signed-off-by: Michal Hocko 
Reported-by: Paul Furtado 
Tested-by: Paul Furtado 
Acked-by: Johannes Weiner 
Cc: 	[3.12+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

2014-06-09T22:03:33+00:00

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
  ...

mm: memcontrol: remove unnecessary memcg argument from soft limit functions

2014-06-06T23:08:17+00:00

Signed-off-by: Johannes Weiner 
Acked-by: Michal Hocko 
Cc: Jianyu Zhan 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: memcontrol: clean up memcg zoneinfo lookup

2014-06-06T23:08:17+00:00

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 
Signed-off-by: Johannes Weiner 
Acked-by: Michal Hocko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

vmscan: memcg: always use swappiness of the reclaimed memcg

2014-06-06T23:08:17+00:00

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 
Acked-by: Johannes Weiner 
Cc: Tejun Heo 
Signed-off-by: Hugh Dickins 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds