linux-stable.git/include/linux/cgroup.h, branch v5.1.18

cgroup: Use css_tryget() instead of css_tryget_online() in task_get_css()

2019-06-19T06:00:04+00:00

commit 18fa84a2db0e15b02baa5d94bdb5bd509175d2f6 upstream.

A PF_EXITING task can stay associated with an offline css.  If such
task calls task_get_css(), it can get stuck indefinitely.  This can be
triggered by BSD process accounting which writes to a file with
PF_EXITING set when racing against memcg disable as in the backtrace
at the end.

After this change, task_get_css() may return a css which was already
offline when the function was called.  None of the existing users are
affected by this change.

  INFO: rcu_sched self-detected stall on CPU
  INFO: rcu_sched detected stalls on CPUs/tasks:
  ...
  NMI backtrace for cpu 0
  ...
  Call Trace:
   
   dump_stack+0x46/0x68
   nmi_cpu_backtrace.cold.2+0x13/0x57
   nmi_trigger_cpumask_backtrace+0xba/0xca
   rcu_dump_cpu_stacks+0x9e/0xce
   rcu_check_callbacks.cold.74+0x2af/0x433
   update_process_times+0x28/0x60
   tick_sched_timer+0x34/0x70
   __hrtimer_run_queues+0xee/0x250
   hrtimer_interrupt+0xf4/0x210
   smp_apic_timer_interrupt+0x56/0x110
   apic_timer_interrupt+0xf/0x20
   
  RIP: 0010:balance_dirty_pages_ratelimited+0x28f/0x3d0
  ...
   btrfs_file_write_iter+0x31b/0x563
   __vfs_write+0xfa/0x140
   __kernel_write+0x4f/0x100
   do_acct_process+0x495/0x580
   acct_process+0xb9/0xdb
   do_exit+0x748/0xa00
   do_group_exit+0x3a/0xa0
   get_signal+0x254/0x560
   do_signal+0x23/0x5c0
   exit_to_usermode_loop+0x5d/0xa0
   prepare_exit_to_usermode+0x53/0x80
   retint_user+0x8/0x8

Signed-off-by: Tejun Heo 
Cc: stable@vger.kernel.org # v4.2+
Fixes: ec438699a9ae ("cgroup, block: implement task_get_css() and use it in bio_associate_current()")
Signed-off-by: Greg Kroah-Hartman

cgroup/pids: turn cgroup_subsys->free() into cgroup_subsys->release() to fix the accounting

2019-01-31T14:55:57+00:00

The only user of cgroup_subsys->free() callback is pids_cgrp_subsys which
needs pids_free() to uncharge the pid.

However, ->free() is called from __put_task_struct()->cgroup_free() and this
is too late. Even the trivial program which does

	for (;;) {
		int pid = fork();
		assert(pid >= 0);
		if (pid)
			wait(NULL);
		else
			exit(0);
	}

can run out of limits because release_task()->call_rcu(delayed_put_task_struct)
implies an RCU gp after the task/pid goes away and before the final put().

Test-case:

	mkdir -p /tmp/CG
	mount -t cgroup2 none /tmp/CG
	echo '+pids' > /tmp/CG/cgroup.subtree_control

	mkdir /tmp/CG/PID
	echo 2 > /tmp/CG/PID/pids.max

	perl -e 'while ($p = fork) { wait; } $p // die "fork failed: $!\n"' &
	echo $! > /tmp/CG/PID/cgroup.procs

Without this patch the forking process fails soon after migration.

Rename cgroup_subsys->free() to cgroup_subsys->release() and move the callsite
into the new helper, cgroup_release(), called by release_task() which actually
frees the pid(s).

Reported-by: Herton R. Krzesinski 
Reported-by: Jan Stancek 
Signed-off-by: Oleg Nesterov 
Signed-off-by: Tejun Heo

blkcg: remove additional reference to the css

2018-12-08T05:26:37+00:00

The previous patch in this series removed carrying around a pointer to
the css in blkg. However, the blkg association logic still relied on
taking a reference on the css to ensure we wouldn't fail in getting a
reference for the blkg.

Here the implicit dependency on the css is removed. The association
continues to rely on the tryget logic walking up the blkg tree. This
streamlines the three ways that association can happen: normal, swap,
and writeback.

Signed-off-by: Dennis Zhou 
Acked-by: Tejun Heo 
Reviewed-by: Josef Bacik 
Signed-off-by: Jens Axboe

Merge tag 'for-linus-20181102' of git://git.kernel.dk/linux-block

2018-11-02T18:25:48+00:00

Pull block layer fixes from Jens Axboe:
 "The biggest part of this pull request is the revert of the blkcg
  cleanup series. It had one fix earlier for a stacked device issue, but
  another one was reported. Rather than play whack-a-mole with this,
  revert the entire series and try again for the next kernel release.

  Apart from that, only small fixes/changes.

  Summary:

   - Indentation fixup for mtip32xx (Colin Ian King)

   - The blkcg cleanup series revert (Dennis Zhou)

   - Two NVMe fixes. One fixing a regression in the nvme request
     initialization in this merge window, causing nvme-fc to not work.
     The other is a suspend/resume p2p resource issue (James, Keith)

   - Fix sg discard merge, allowing us to merge in cases where we didn't
     before (Jianchao Wang)

   - Call rq_qos_exit() after the queue is frozen, preventing a hang
     (Ming)

   - Fix brd queue setup, fixing an oops if we fail setting up all
     devices (Ming)"

* tag 'for-linus-20181102' of git://git.kernel.dk/linux-block:
  nvme-pci: fix conflicting p2p resource adds
  nvme-fc: fix request private initialization
  blkcg: revert blkcg cleanups series
  block: brd: associate with queue until adding disk
  block: call rq_qos_exit() after queue is frozen
  mtip32xx: clean an indentation issue, remove extraneous tabs
  block: fix the DISCARD request merge

blkcg: revert blkcg cleanups series

2018-11-02T01:59:53+00:00

This reverts a series committed earlier due to null pointer exception
bug report in [1]. It seems there are edge case interactions that I did
not consider and will need some time to understand what causes the
adverse interactions.

The original series can be found in [2] with a follow up series in [3].

[1] https://www.spinics.net/lists/cgroups/msg20719.html
[2] https://lore.kernel.org/lkml/20180911184137.35897-1-dennisszhou@gmail.com/
[3] https://lore.kernel.org/lkml/20181020185612.51587-1-dennis@kernel.org/

This reverts the following commits:
d459d853c2ed, b2c3fa546705, 101246ec02b5, b3b9f24f5fcc, e2b0989954ae,
f0fcb3ec89f3, c839e7a03f92, bdc2491708c4, 74b7c02a9bc1, 5bf9a1f3b4ef,
a7b39b4e961c, 07b05bcc3213, 49f4c2dc2b50, 27e6fa996c53

Signed-off-by: Dennis Zhou 
Signed-off-by: Jens Axboe

psi: cgroup support

2018-10-26T23:26:32+00:00

On a system that executes multiple cgrouped jobs and independent
workloads, we don't just care about the health of the overall system, but
also that of individual jobs, so that we can ensure individual job health,
fairness between jobs, or prioritize some jobs over others.

This patch implements pressure stall tracking for cgroups.  In kernels
with CONFIG_PSI=y, cgroup2 groups will have cpu.pressure, memory.pressure,
and io.pressure files that track aggregate pressure stall times for only
the tasks inside the cgroup.

Link: http://lkml.kernel.org/r/20180828172258.3185-10-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner 
Acked-by: Tejun Heo 
Acked-by: Peter Zijlstra (Intel) 
Tested-by: Daniel Drake 
Tested-by: Suren Baghdasaryan 
Cc: Christopher Lameter 
Cc: Ingo Molnar 
Cc: Johannes Weiner 
Cc: Mike Galbraith 
Cc: Peter Enderborg 
Cc: Randy Dunlap 
Cc: Shakeel Butt 
Cc: Vinayak Menon 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'for-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

2018-10-26T00:15:46+00:00

Pull cgroup updates from Tejun Heo:
 "All trivial changes - simplification, typo fix and adding
  cond_resched() in a netclassid update loop"

* 'for-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup, netclassid: add a preemption point to write_classid
  rdmacg: fix a typo in rdmacg documentation
  cgroup: Simplify cgroup_ancestor

cgroup: Simplify cgroup_ancestor

2018-09-24T17:38:16+00:00

Simplify cgroup_ancestor function. This is follow-up for
commit 7723628101aa ("bpf: Introduce bpf_skb_ancestor_cgroup_id helper")

Suggested-by: Tejun Heo 
Signed-off-by: Andrey Ignatov 
Signed-off-by: Tejun Heo

blkcg: remove additional reference to the css

2018-09-22T02:29:15+00:00

The previous patch in this series removed carrying around a pointer to
the css in blkg. However, the blkg association logic still relied on
taking a reference on the css to ensure we wouldn't fail in getting a
reference for the blkg.

Here the implicit dependency on the css is removed. The association
continues to rely on the tryget logic walking up the blkg tree. This
streamlines the three ways that association can happen: normal, swap,
and writeback.

Acked-by: Tejun Heo 
Signed-off-by: Dennis Zhou 
Signed-off-by: Jens Axboe

bpf: Introduce bpf_skb_ancestor_cgroup_id helper

2018-08-12T23:02:39+00:00

== Problem description ==

It's useful to be able to identify cgroup associated with skb in TC so
that a policy can be applied to this skb, and existing bpf_skb_cgroup_id
helper can help with this.

Though in real life cgroup hierarchy and hierarchy to apply a policy to
don't map 1:1.

It's often the case that there is a container and corresponding cgroup,
but there are many more sub-cgroups inside container, e.g. because it's
delegated to containerized application to control resources for its
subsystems, or to separate application inside container from infra that
belongs to containerization system (e.g. sshd).

At the same time it may be useful to apply a policy to container as a
whole.

If multiple containers like this are run on a host (what is often the
case) and many of them have sub-cgroups, it may not be possible to apply
per-container policy in TC with existing helpers such as
bpf_skb_under_cgroup or bpf_skb_cgroup_id:

* bpf_skb_cgroup_id will return id of immediate cgroup associated with
  skb, i.e. if it's a sub-cgroup inside container, it can't be used to
  identify container's cgroup;

* bpf_skb_under_cgroup can work only with one cgroup and doesn't scale,
  i.e. if there are N containers on a host and a policy has to be
  applied to M of them (0 <= M <= N), it'd require M calls to
  bpf_skb_under_cgroup, and, if M changes, it'd require to rebuild &
  load new BPF program.

== Solution ==

The patch introduces new helper bpf_skb_ancestor_cgroup_id that can be
used to get id of cgroup v2 that is an ancestor of cgroup associated
with skb at specified level of cgroup hierarchy.

That way admin can place all containers on one level of cgroup hierarchy
(what is a good practice in general and already used in many
configurations) and identify specific cgroup on this level no matter
what sub-cgroup skb is associated with.

E.g. if there is a cgroup hierarchy:
  root/
  root/container1/
  root/container1/app11/
  root/container1/app11/sub-app-a/
  root/container1/app12/
  root/container2/
  root/container2/app21/
  root/container2/app22/
  root/container2/app22/sub-app-b/

, then having skb associated with root/container1/app11/sub-app-a/ it's
possible to get ancestor at level 1, what is container1 and apply policy
for this container, or apply another policy if it's container2.

Policies can be kept e.g. in a hash map where key is a container cgroup
id and value is an action.

Levels where container cgroups are created are usually known in advance
whether cgroup hierarchy inside container may be hard to predict
especially in case when its creation is delegated to containerized
application.

== Implementation details ==

The helper gets ancestor by walking parents up to specified level.

Another option would be to get different kind of "id" from
cgroup->ancestor_ids[level] and use it with idr_find() to get struct
cgroup for ancestor. But that would require radix lookup what doesn't
seem to be better (at least it's not obviously better).

Format of return value of the new helper is same as that of
bpf_skb_cgroup_id.

Signed-off-by: Andrey Ignatov 
Signed-off-by: Daniel Borkmann