linux-stable.git/kernel/cgroup/cgroup.c, branch v4.14.2

cgroup: Reinit cgroup_taskset structure before cgroup_migrate_execute() returns

2017-09-22T15:14:45+00:00

The cgroup_taskset structure within the larger cgroup_mgctx structure
is supposed to be used once and then discarded. That is not really the
case in the hotplug code path:

cpuset_hotplug_workfn()
 - cgroup_transfer_tasks()
   - cgroup_migrate()
     - cgroup_migrate_add_task()
     - cgroup_migrate_execute()

In this case, the cgroup_migrate() function is called multiple time
with the same cgroup_mgctx structure to transfer the tasks from
one cgroup to another one-by-one. The second time cgroup_migrate()
is called, the cgroup_taskset will be in an incorrect state and so
may cause the system to panic. For example,

  [  150.888410] Faulting instruction address: 0xc0000000001db648
  [  150.888414] Oops: Kernel access of bad area, sig: 11 [#1]
  [  150.888417] SMP NR_CPUS=2048
  [  150.888417] NUMA
  [  150.888419] pSeries
    :
  [  150.888545] NIP [c0000000001db648] cpuset_can_attach+0x58/0x1b0
  [  150.888548] LR [c0000000001db638] cpuset_can_attach+0x48/0x1b0
  [  150.888551] Call Trace:
  [  150.888554] [c0000005f65cb940] [c0000000001db638] cpuset_can_attach+0x48/0x1b 0 (unreliable)
  [  150.888559] [c0000005f65cb9a0] [c0000000001cff04] cgroup_migrate_execute+0xc4/0x4b0
  [  150.888563] [c0000005f65cba20] [c0000000001d7d14] cgroup_transfer_tasks+0x1d4/0x370
  [  150.888568] [c0000005f65cbb70] [c0000000001ddcb0] cpuset_hotplug_workfn+0x710/0x8f0
  [  150.888572] [c0000005f65cbc80] [c00000000012032c] process_one_work+0x1ac/0x4d0
  [  150.888576] [c0000005f65cbd20] [c0000000001206f8] worker_thread+0xa8/0x5b0
  [  150.888580] [c0000005f65cbdc0] [c0000000001293f8] kthread+0x168/0x1b0
  [  150.888584] [c0000005f65cbe30] [c00000000000b368] ret_from_kernel_thread+0x5c/0x74

To allow reuse of the cgroup_mgctx structure, some fields in that
structure are now re-initialized at the end of cgroup_migrate_execute()
function call so that the structure can be reused again in a later
iteration without causing problem.

This bug was introduced in the commit e595cd706982 ("group: track
migration context in cgroup_mgctx") in 4.11. This commit moves the
cgroup_taskset initialization out of cgroup_migrate(). The commit
10467270fb3 ("cgroup: don't call migration methods if there are no
tasks to migrate") helped, but did not completely resolve the problem.

Fixes: e595cd706982bff0211e6fafe5a108421e747fbc ("group: track migration context in cgroup_mgctx")
Signed-off-by: Waiman Long 
Signed-off-by: Tejun Heo 
Cc: stable@vger.kernel.org # v4.11+

Merge branch 'for-4.14/block' of git://git.kernel.dk/linux-block

2017-09-07T18:59:42+00:00

Pull block layer updates from Jens Axboe:
 "This is the first pull request for 4.14, containing most of the code
  changes. It's a quiet series this round, which I think we needed after
  the churn of the last few series. This contains:

   - Fix for a registration race in loop, from Anton Volkov.

   - Overflow complaint fix from Arnd for DAC960.

   - Series of drbd changes from the usual suspects.

   - Conversion of the stec/skd driver to blk-mq. From Bart.

   - A few BFQ improvements/fixes from Paolo.

   - CFQ improvement from Ritesh, allowing idling for group idle.

   - A few fixes found by Dan's smatch, courtesy of Dan.

   - A warning fixup for a race between changing the IO scheduler and
     device remova. From David Jeffery.

   - A few nbd fixes from Josef.

   - Support for cgroup info in blktrace, from Shaohua.

   - Also from Shaohua, new features in the null_blk driver to allow it
     to actually hold data, among other things.

   - Various corner cases and error handling fixes from Weiping Zhang.

   - Improvements to the IO stats tracking for blk-mq from me. Can
     drastically improve performance for fast devices and/or big
     machines.

   - Series from Christoph removing bi_bdev as being needed for IO
     submission, in preparation for nvme multipathing code.

   - Series from Bart, including various cleanups and fixes for switch
     fall through case complaints"

* 'for-4.14/block' of git://git.kernel.dk/linux-block: (162 commits)
  kernfs: checking for IS_ERR() instead of NULL
  drbd: remove BIOSET_NEED_RESCUER flag from drbd_{md_,}io_bio_set
  drbd: Fix allyesconfig build, fix recent commit
  drbd: switch from kmalloc() to kmalloc_array()
  drbd: abort drbd_start_resync if there is no connection
  drbd: move global variables to drbd namespace and make some static
  drbd: rename "usermode_helper" to "drbd_usermode_helper"
  drbd: fix race between handshake and admin disconnect/down
  drbd: fix potential deadlock when trying to detach during handshake
  drbd: A single dot should be put into a sequence.
  drbd: fix rmmod cleanup, remove _all_ debugfs entries
  drbd: Use setup_timer() instead of init_timer() to simplify the code.
  drbd: fix potential get_ldev/put_ldev refcount imbalance during attach
  drbd: new disk-option disable-write-same
  drbd: Fix resource role for newly created resources in events2
  drbd: mark symbols static where possible
  drbd: Send P_NEG_ACK upon write error in protocol != C
  drbd: add explicit plugging when submitting batches
  drbd: change list_for_each_safe to while(list_first_entry_or_null)
  drbd: introduce drbd_recv_header_maybe_unplug
  ...

Merge branch 'for-4.14' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

2017-09-07T05:25:25+00:00

Pull cgroup updates from Tejun Heo:
 "Several notable changes this cycle:

   - Thread mode was merged. This will be used for cgroup2 support for
     CPU and possibly other controllers. Unfortunately, CPU controller
     cgroup2 support didn't make this pull request but most contentions
     have been resolved and the support is likely to be merged before
     the next merge window.

   - cgroup.stat now shows the number of descendant cgroups.

   - cpuset now can enable the easier-to-configure v2 behavior on v1
     hierarchy"

* 'for-4.14' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (21 commits)
  cpuset: Allow v2 behavior in v1 cgroup
  cgroup: Add mount flag to enable cpuset to use v2 behavior in v1 cgroup
  cgroup: remove unneeded checks
  cgroup: misc changes
  cgroup: short-circuit cset_cgroup_from_root() on the default hierarchy
  cgroup: re-use the parent pointer in cgroup_destroy_locked()
  cgroup: add cgroup.stat interface with basic hierarchy stats
  cgroup: implement hierarchy limits
  cgroup: keep track of number of descent cgroups
  cgroup: add comment to cgroup_enable_threaded()
  cgroup: remove unnecessary empty check when enabling threaded mode
  cgroup: update debug controller to print out thread mode information
  cgroup: implement cgroup v2 thread support
  cgroup: implement CSS_TASK_ITER_THREADED
  cgroup: introduce cgroup->dom_cgrp and threaded css_set handling
  cgroup: add @flags to css_task_iter_start() and implement CSS_TASK_ITER_PROCS
  cgroup: reorganize cgroup.procs / task write path
  cgroup: replace css_set walking populated test with testing cgrp->nr_populated_csets
  cgroup: distinguish local and children populated states
  cgroup: remove now unused list_head @pending in cgroup_apply_cftypes()
  ...

cgroup: revert fa06235b8eb0 ("cgroup: reset css on destruction")

2017-09-07T00:27:27+00:00

Commit fa06235b8eb0 ("cgroup: reset css on destruction") caused
css_reset callback to be called from the offlining path.  Although it
solves the problem mentioned in the commit description ("For instance,
memory cgroup needs to reset memory.low, otherwise pages charged to a
dead cgroup might never get reclaimed."), generally speaking, it's not
correct.

An offline cgroup can still be a resource domain, and we shouldn't grant
it more resources than it had before deletion.

For instance, if an offline memory cgroup has dirty pages, we should
still imply i/o limits during writeback.

The css_reset callback is designed to return the cgroup state into the
original state, that means reset all limits and counters.  It's
spomething different from the offlining, and we shouldn't use it from
the offlining path.  Instead, we should adjust necessary settings from
the per-controller css_offline callbacks (e.g.  reset memory.low).

Link: http://lkml.kernel.org/r/20170727130428.28856-2-guro@fb.com
Signed-off-by: Roman Gushchin 
Acked-by: Tejun Heo 
Acked-by: Johannes Weiner 
Cc: Vladimir Davydov 
Cc: Michal Hocko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

cgroup: remove unneeded checks

2017-08-11T17:33:28+00:00

"descendants" and "depth" are declared as int, so they can't be larger
than INT_MAX.  Static checkers complain and it's slightly confusing for
humans as well so let's just remove these conditions.

Signed-off-by: Dan Carpenter 
Signed-off-by: Tejun Heo

cgroup: misc changes

2017-08-11T12:49:01+00:00

Misc trivial changes to prepare for future changes.  No functional
difference.

* Expose cgroup_get(), cgroup_tryget() and cgroup_parent().

* Implement task_dfl_cgroup() which dereferences css_set->dfl_cgrp.

* Rename cgroup_stats_show() to cgroup_stat_show() for consistency
  with the file name.

Signed-off-by: Tejun Heo

cgroup: short-circuit cset_cgroup_from_root() on the default hierarchy

2017-08-02T22:39:38+00:00

Each css_set directly points to the default cgroup it belongs to, so
there's no reason to walk the cgrp_links list on the default
hierarchy.

Signed-off-by: Tejun Heo

cgroup: re-use the parent pointer in cgroup_destroy_locked()

2017-08-02T19:05:20+00:00

As we already have a pointer to the parent cgroup in
cgroup_destroy_locked(), we don't need to calculate it again
to pass as an argument for cgroup1_check_for_release().

Signed-off-by: Roman Gushchin 
Suggested-by: Tejun Heo 
Signed-off-by: Tejun Heo 
Cc: Zefan Li 
Cc: Waiman Long 
Cc: Johannes Weiner 
Cc: kernel-team@fb.com
Cc: linux-kernel@vger.kernel.org

cgroup: add cgroup.stat interface with basic hierarchy stats

2017-08-02T19:05:20+00:00

A cgroup can consume resources even after being deleted by a user.
For example, writing back dirty pages should be accounted and
limited, despite the corresponding cgroup might contain no processes
and being deleted by a user.

In the current implementation a cgroup can remain in such "dying" state
for an undefined amount of time. For instance, if a memory cgroup
contains a pge, mlocked by a process belonging to an other cgroup.

Although the lifecycle of a dying cgroup is out of user's control,
it's important to have some insight of what's going on under the hood.

In particular, it's handy to have a counter which will allow
to detect css leaks.

To solve this problem, add a cgroup.stat interface to
the base cgroup control files with the following metrics:

nr_descendants		total number of visible descendant cgroups
nr_dying_descendants	total number of dying descendant cgroups

Signed-off-by: Roman Gushchin 
Suggested-by: Tejun Heo 
Signed-off-by: Tejun Heo 
Cc: Zefan Li 
Cc: Waiman Long 
Cc: Johannes Weiner 
Cc: kernel-team@fb.com
Cc: cgroups@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

cgroup: implement hierarchy limits

2017-08-02T19:05:20+00:00

Creating cgroup hierearchies of unreasonable size can affect
overall system performance. A user might want to limit the
size of cgroup hierarchy. This is especially important if a user
is delegating some cgroup sub-tree.

To address this issue, introduce an ability to control
the size of cgroup hierarchy.

The cgroup.max.descendants control file allows to set the maximum
allowed number of descendant cgroups.
The cgroup.max.depth file controls the maximum depth of the cgroup
tree. Both are single value r/w files, with "max" default value.

The control files exist on each hierarchy level (including root).
When a new cgroup is created, we check the total descendants
and depth limits on each level, and if none of them are exceeded,
a new cgroup is created.

Only alive cgroups are counted, removed (dying) cgroups are
ignored.

Signed-off-by: Roman Gushchin 
Suggested-by: Tejun Heo 
Signed-off-by: Tejun Heo 
Cc: Zefan Li 
Cc: Waiman Long 
Cc: Johannes Weiner 
Cc: kernel-team@fb.com
Cc: cgroups@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org