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:
<IRQ>
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
</IRQ>
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 <tj@kernel.org>
Cc: stable@vger.kernel.org # v4.2+
Fixes: ec438699a9 ("cgroup, block: implement task_get_css() and use it in bio_associate_current()")
Currently the lifetime of bpf programs attached to a cgroup is bound
to the lifetime of the cgroup itself. It means that if a user
forgets (or intentionally avoids) to detach a bpf program before
removing the cgroup, it will stay attached up to the release of the
cgroup. Since the cgroup can stay in the dying state (the state
between being rmdir()'ed and being released) for a very long time, it
leads to a waste of memory. Also, it blocks a possibility to implement
the memcg-based memory accounting for bpf objects, because a circular
reference dependency will occur. Charged memory pages are pinning the
corresponding memory cgroup, and if the memory cgroup is pinning
the attached bpf program, nothing will be ever released.
A dying cgroup can not contain any processes, so the only chance for
an attached bpf program to be executed is a live socket associated
with the cgroup. So in order to release all bpf data early, let's
count associated sockets using a new percpu refcounter. On cgroup
removal the counter is transitioned to the atomic mode, and as soon
as it reaches 0, all bpf programs are detached.
Because cgroup_bpf_release() can block, it can't be called from
the percpu ref counter callback directly, so instead an asynchronous
work is scheduled.
The reference counter is not socket specific, and can be used for any
other types of programs, which can be executed from a cgroup-bpf hook
outside of the process context, had such a need arise in the future.
Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: jolsa@redhat.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
A task should never enter the exit path with the task->frozen bit set.
Any frozen task must enter the signal handling loop and the only
way to escape is through cgroup_leave_frozen(true), which
unconditionally drops the task->frozen bit. So it means that
cgroyp_freezer_frozen_exit() has zero chances to be called and
has to be removed.
Let's put a WARN_ON_ONCE() instead of the cgroup_freezer_frozen_exit()
call to catch any potential leak of the task's frozen bit.
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cgroup v1 implements the freezer controller, which provides an ability
to stop the workload in a cgroup and temporarily free up some
resources (cpu, io, network bandwidth and, potentially, memory)
for some other tasks. Cgroup v2 lacks this functionality.
This patch implements freezer for cgroup v2.
Cgroup v2 freezer tries to put tasks into a state similar to jobctl
stop. This means that tasks can be killed, ptraced (using
PTRACE_SEIZE*), and interrupted. It is possible to attach to
a frozen task, get some information (e.g. read registers) and detach.
It's also possible to migrate a frozen tasks to another cgroup.
This differs cgroup v2 freezer from cgroup v1 freezer, which mostly
tried to imitate the system-wide freezer. However uninterruptible
sleep is fine when all tasks are going to be frozen (hibernation case),
it's not the acceptable state for some subset of the system.
Cgroup v2 freezer is not supporting freezing kthreads.
If a non-root cgroup contains kthread, the cgroup still can be frozen,
but the kthread will remain running, the cgroup will be shown
as non-frozen, and the notification will not be delivered.
* PTRACE_ATTACH is not working because non-fatal signal delivery
is blocked in frozen state.
There are some interface differences between cgroup v1 and cgroup v2
freezer too, which are required to conform the cgroup v2 interface
design principles:
1) There is no separate controller, which has to be turned on:
the functionality is always available and is represented by
cgroup.freeze and cgroup.events cgroup control files.
2) The desired state is defined by the cgroup.freeze control file.
Any hierarchical configuration is allowed.
3) The interface is asynchronous. The actual state is available
using cgroup.events control file ("frozen" field). There are no
dedicated transitional states.
4) It's allowed to make any changes with the cgroup hierarchy
(create new cgroups, remove old cgroups, move tasks between cgroups)
no matter if some cgroups are frozen.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
No-objection-from-me-by: Oleg Nesterov <oleg@redhat.com>
Cc: kernel-team@fb.com
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 <hkrzesin@redhat.com>
Reported-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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 <dennis@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Merge tag 'for-linus-20181102' of git://git.kernel.dk/linux-block
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
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 <hannes@cmpxchg.org>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Daniel Drake <drake@endlessm.com>
Tested-by: Suren Baghdasaryan <surenb@google.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <jweiner@fb.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Enderborg <peter.enderborg@sony.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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
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 <tj@kernel.org>
Signed-off-by: Dennis Zhou <dennisszhou@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
== 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 <rdna@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Currently, rstat flush path is protected with a mutex which is fine as
all the existing users are from interface file show path. However,
rstat is being generalized for use by controllers and flushing from
atomic contexts will be necessary.
This patch replaces cgroup_rstat_mutex with a spinlock and adds a
irq-safe flush function - cgroup_rstat_flush_irqsafe(). Explicit
yield handling is added to the flush path so that other flush
functions can yield to other threads and flushers.
Signed-off-by: Tejun Heo <tj@kernel.org>
cgroup_rstat is being generalized so that controllers can use it too.
This patch factors out and exposes the following interface functions.
* cgroup_rstat_updated(): Renamed from cgroup_rstat_cpu_updated() for
consistency.
* cgroup_rstat_flush_hold/release(): Factored out from base stat
implementation.
* cgroup_rstat_flush(): Verbatim expose.
While at it, drop assert on cgroup_rstat_mutex in
cgroup_base_stat_flush() as it crosses layers and make a minor comment
update.
v2: Added EXPORT_SYMBOL_GPL(cgroup_rstat_updated) to fix a build bug.
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull cgroup updates from Tejun Heo:
"Cgroup2 cpu controller support is finally merged.
- Basic cpu statistics support to allow monitoring by default without
the CPU controller enabled.
- cgroup2 cpu controller support.
- /sys/kernel/cgroup files to help dealing with new / optional
features"
* 'for-4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: export list of cgroups v2 features using sysfs
cgroup: export list of delegatable control files using sysfs
cgroup: mark @cgrp __maybe_unused in cpu_stat_show()
MAINTAINERS: relocate cpuset.c
cgroup, sched: Move basic cpu stats from cgroup.stat to cpu.stat
sched: Implement interface for cgroup unified hierarchy
sched: Misc preps for cgroup unified hierarchy interface
sched/cputime: Add dummy cputime_adjust() implementation for CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
cgroup: statically initialize init_css_set->dfl_cgrp
cgroup: Implement cgroup2 basic CPU usage accounting
cpuacct: Introduce cgroup_account_cputime[_field]()
sched/cputime: Expose cputime_adjust()
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The basic cpu stat is currently shown with "cpu." prefix in
cgroup.stat, and the same information is duplicated in cpu.stat when
cpu controller is enabled. This is ugly and not very scalable as we
want to expand the coverage of stat information which is always
available.
This patch makes cgroup core always create "cpu.stat" file and show
the basic cpu stat there and calls the cpu controller to show the
extra stats when enabled. This ensures that the same information
isn't presented in multiple places and makes future expansion of basic
stats easier.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
In cgroup1, while cpuacct isn't actually controlling any resources, it
is a separate controller due to combination of two factors -
1. enabling cpu controller has significant side effects, and 2. we
have to pick one of the hierarchies to account CPU usages on. cpuacct
controller is effectively used to designate a hierarchy to track CPU
usages on.
cgroup2's unified hierarchy removes the second reason and we can
account basic CPU usages by default. While we can use cpuacct for
this purpose, both its interface and implementation leave a lot to be
desired - it collects and exposes two sources of truth which don't
agree with each other and some of the exposed statistics don't make
much sense. Also, it propagates all the way up the hierarchy on each
accounting event which is unnecessary.
This patch adds basic resource accounting mechanism to cgroup2's
unified hierarchy and accounts CPU usages using it.
* All accountings are done per-cpu and don't propagate immediately.
It just bumps the per-cgroup per-cpu counters and links to the
parent's updated list if not already on it.
* On a read, the per-cpu counters are collected into the global ones
and then propagated upwards. Only the per-cpu counters which have
changed since the last read are propagated.
* CPU usage stats are collected and shown in "cgroup.stat" with "cpu."
prefix. Total usage is collected from scheduling events. User/sys
breakdown is sourced from tick sampling and adjusted to the usage
using cputime_adjust().
This keeps the accounting side hot path O(1) and per-cpu and the read
side O(nr_updated_since_last_read).
v2: Minor changes and documentation updates as suggested by Waiman and
Roman.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Roman Gushchin <guro@fb.com>
Introduce cgroup_account_cputime[_field]() which wrap cpuacct_charge()
and cgroup_account_field(). This doesn't introduce any functional
changes and will be used to add cgroup basic resource accounting.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
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
...
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 <tj@kernel.org>
By default we output cgroup id in blktrace. This adds an option to
display cgroup path. Since get cgroup path is a relativly heavy
operation, we don't enable it by default.
with the option enabled, blktrace will output something like this:
dd-1353 [007] d..2 293.015252: 8,0 /test/level D R 24 + 8 [dd]
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Add an API to export cgroup fhandle info. We don't export a full 'struct
file_handle', there are unrequired info. Sepcifically, cgroup is always
a directory, so we don't need a 'FILEID_INO32_GEN_PARENT' type fhandle,
we only need export the inode number and generation number just like
what generic_fh_to_dentry does. And we can avoid the overhead of getting
an inode too, since kernfs_node_id (ino and generation) has all the info
required.
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
inode number and generation can identify a kernfs node. We are going to
export the identification by exportfs operations, so put ino and
generation into a separate structure. It's convenient when later patches
use the identification.
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
cgroup v2 is in the process of growing thread granularity support.
Once thread mode is enabled, the root cgroup of the subtree serves as
the dom_cgrp to which the processes of the subtree conceptually belong
and domain-level resource consumptions not tied to any specific task
are charged. In the subtree, threads won't be subject to process
granularity or no-internal-task constraint and can be distributed
arbitrarily across the subtree.
This patch implements a new task iterator flag CSS_TASK_ITER_THREADED,
which, when used on a dom_cgrp, makes the iteration include the tasks
on all the associated threaded css_sets. "cgroup.procs" read path is
updated to use it so that reading the file on a proc_cgrp lists all
processes. This will also be used by controller implementations which
need to walk processes or tasks at the resource domain level.
Task iteration is implemented nested in css_set iteration. If
CSS_TASK_ITER_THREADED is specified, after walking tasks of each
!threaded css_set, all the associated threaded css_sets are visited
before moving onto the next !threaded css_set.
v2: ->cur_pcset renamed to ->cur_dcset. Updated for the new
enable-threaded-per-cgroup behavior.
Signed-off-by: Tejun Heo <tj@kernel.org>
cgroup v2 is in the process of growing thread granularity support. A
threaded subtree is composed of a thread root and threaded cgroups
which are proper members of the subtree.
The root cgroup of the subtree serves as the domain cgroup to which
the processes (as opposed to threads / tasks) of the subtree
conceptually belong and domain-level resource consumptions not tied to
any specific task are charged. Inside the subtree, threads won't be
subject to process granularity or no-internal-task constraint and can
be distributed arbitrarily across the subtree.
This patch introduces cgroup->dom_cgrp along with threaded css_set
handling.
* cgroup->dom_cgrp points to self for normal and thread roots. For
proper thread subtree members, points to the dom_cgrp (the thread
root).
* css_set->dom_cset points to self if for normal and thread roots. If
threaded, points to the css_set which belongs to the cgrp->dom_cgrp.
The dom_cgrp serves as the resource domain and keeps the matching
csses available. The dom_cset holds those csses and makes them
easily accessible.
* All threaded csets are linked on their dom_csets to enable iteration
of all threaded tasks.
* cgroup->nr_threaded_children keeps track of the number of threaded
children.
This patch adds the above but doesn't actually use them yet. The
following patches will build on top.
v4: ->nr_threaded_children added.
v3: ->proc_cgrp/cset renamed to ->dom_cgrp/cset. Updated for the new
enable-threaded-per-cgroup behavior.
v2: Added cgroup_is_threaded() helper.
Signed-off-by: Tejun Heo <tj@kernel.org>
css_task_iter currently always walks all tasks. With the scheduled
cgroup v2 thread support, the iterator would need to handle multiple
types of iteration. As a preparation, add @flags to
css_task_iter_start() and implement CSS_TASK_ITER_PROCS. If the flag
is not specified, it walks all tasks as before. When asserted, the
iterator only walks the group leaders.
For now, the only user of the flag is cgroup v2 "cgroup.procs" file
which no longer needs to skip non-leader tasks in cgroup_procs_next().
Note that cgroup v1 "cgroup.procs" can't use the group leader walk as
v1 "cgroup.procs" doesn't mean "list all thread group leaders in the
cgroup" but "list all thread group id's with any threads in the
cgroup".
While at it, update cgroup_procs_show() to use task_pid_vnr() instead
of task_tgid_vnr(). As the iteration guarantees that the function
only sees group leaders, this doesn't change the output and will allow
sharing the function for thread iteration.
Signed-off-by: Tejun Heo <tj@kernel.org>
cgrp->populated_cnt counts both local (the cgroup's populated
css_sets) and subtree proper (populated children) so that it's only
zero when the whole subtree, including self, is empty.
This patch splits the counter into two so that local and children
populated states are tracked separately. It allows finer-grained
tests on the state of the hierarchy which will be used to replace
css_set walking local populated test.
Signed-off-by: Tejun Heo <tj@kernel.org>
In most cases, a cgroup controller don't care about the liftimes of
cgroups. For the controller, a css becomes online when ->css_online()
is called on it and offline when ->css_offline() is called.
However, cpuset is special in that the user interface it exposes cares
whether certain cgroups exist or not. Combined with the RCU delay
between cgroup removal and css offlining, this can lead to user
visible behavior oddities where operations which should succeed after
cgroup removals fail for some time period. The effects of cgroup
removals are delayed when seen from userland.
This patch adds css_is_dying() which tests whether offline is pending
and updates is_cpuset_online() so that the function returns false also
while offline is pending. This gets rid of the userland visible
delays.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Link: http://lkml.kernel.org/r/327ca1f5-7957-fbb9-9e5f-9ba149d40ba2@oracle.com
Cc: stable@vger.kernel.org
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull cgroup updates from Tejun Heo:
"Nothing major. Two notable fixes are Li's second stab at fixing the
long-standing race condition in the mount path and suppression of
spurious warning from cgroup_get(). All other changes are trivial"
* 'for-4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: mark cgroup_get() with __maybe_unused
cgroup: avoid attaching a cgroup root to two different superblocks, take 2
cgroup: fix spurious warnings on cgroup_is_dead() from cgroup_sk_alloc()
cgroup: move cgroup_subsys_state parent field for cache locality
cpuset: Remove cpuset_update_active_cpus()'s parameter.
cgroup: switch to BUG_ON()
cgroup: drop duplicate header nsproxy.h
kernel: convert css_set.refcount from atomic_t to refcount_t
kernel: convert cgroup_namespace.count from atomic_t to refcount_t
Creation of a kthread goes through a couple interlocked stages between
the kthread itself and its creator. Once the new kthread starts
running, it initializes itself and wakes up the creator. The creator
then can further configure the kthread and then let it start doing its
job by waking it up.
In this configuration-by-creator stage, the creator is the only one
that can wake it up but the kthread is visible to userland. When
altering the kthread's attributes from userland is allowed, this is
fine; however, for cases where CPU affinity is critical,
kthread_bind() is used to first disable affinity changes from userland
and then set the affinity. This also prevents the kthread from being
migrated into non-root cgroups as that can affect the CPU affinity and
many other things.
Unfortunately, the cgroup side of protection is racy. While the
PF_NO_SETAFFINITY flag prevents further migrations, userland can win
the race before the creator sets the flag with kthread_bind() and put
the kthread in a non-root cgroup, which can lead to all sorts of
problems including incorrect CPU affinity and starvation.
This bug got triggered by userland which periodically tries to migrate
all processes in the root cpuset cgroup to a non-root one. Per-cpu
workqueue workers got caught while being created and ended up with
incorrected CPU affinity breaking concurrency management and sometimes
stalling workqueue execution.
This patch adds task->no_cgroup_migration which disallows the task to
be migrated by userland. kthreadd starts with the flag set making
every child kthread start in the root cgroup with migration
disallowed. The flag is cleared after the kthread finishes
initialization by which time PF_NO_SETAFFINITY is set if the kthread
should stay in the root cgroup.
It'd be better to wait for the initialization instead of failing but I
couldn't think of a way of implementing that without adding either a
new PF flag, or sleeping and retrying from waiting side. Even if
userland depends on changing cgroup membership of a kthread, it either
has to be synchronized with kthread_create() or periodically repeat,
so it's unlikely that this would break anything.
v2: Switch to a simpler implementation using a new task_struct bit
field suggested by Oleg.
Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Reported-and-debugged-by: Chris Mason <clm@fb.com>
Cc: stable@vger.kernel.org # v4.3+ (we can't close the race on < v4.3)
Signed-off-by: Tejun Heo <tj@kernel.org>
refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull cgroup updates from Tejun Heo:
- tracepoints for basic cgroup management operations added
- kernfs and cgroup path formatting functions updated to behave in the
style of strlcpy()
- non-critical bug fixes
* 'for-4.9' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
blkcg: Unlock blkcg_pol_mutex only once when cpd == NULL
cgroup: fix error handling regressions in proc_cgroup_show() and cgroup_release_agent()
cpuset: fix error handling regression in proc_cpuset_show()
cgroup: add tracepoints for basic operations
cgroup: make cgroup_path() and friends behave in the style of strlcpy()
kernfs: remove kernfs_path_len()
kernfs: make kernfs_path*() behave in the style of strlcpy()
kernfs: add dummy implementation of kernfs_path_from_node()
Pull namespace updates from Eric Biederman:
"This set of changes is a number of smaller things that have been
overlooked in other development cycles focused on more fundamental
change. The devpts changes are small things that were a distraction
until we managed to kill off DEVPTS_MULTPLE_INSTANCES. There is an
trivial regression fix to autofs for the unprivileged mount changes
that went in last cycle. A pair of ioctls has been added by Andrey
Vagin making it is possible to discover the relationships between
namespaces when referring to them through file descriptors.
The big user visible change is starting to add simple resource limits
to catch programs that misbehave. With namespaces in general and user
namespaces in particular allowing users to use more kinds of
resources, it has become important to have something to limit errant
programs. Because the purpose of these limits is to catch errant
programs the code needs to be inexpensive to use as it always on, and
the default limits need to be high enough that well behaved programs
on well behaved systems don't encounter them.
To this end, after some review I have implemented per user per user
namespace limits, and use them to limit the number of namespaces. The
limits being per user mean that one user can not exhause the limits of
another user. The limits being per user namespace allow contexts where
the limit is 0 and security conscious folks can remove from their
threat anlysis the code used to manage namespaces (as they have
historically done as it root only). At the same time the limits being
per user namespace allow other parts of the system to use namespaces.
Namespaces are increasingly being used in application sand boxing
scenarios so an all or nothing disable for the entire system for the
security conscious folks makes increasing use of these sandboxes
impossible.
There is also added a limit on the maximum number of mounts present in
a single mount namespace. It is nontrivial to guess what a reasonable
system wide limit on the number of mount structure in the kernel would
be, especially as it various based on how a system is using
containers. A limit on the number of mounts in a mount namespace
however is much easier to understand and set. In most cases in
practice only about 1000 mounts are used. Given that some autofs
scenarious have the potential to be 30,000 to 50,000 mounts I have set
the default limit for the number of mounts at 100,000 which is well
above every known set of users but low enough that the mount hash
tables don't degrade unreaonsably.
These limits are a start. I expect this estabilishes a pattern that
other limits for resources that namespaces use will follow. There has
been interest in making inotify event limits per user per user
namespace as well as interest expressed in making details about what
is going on in the kernel more visible"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (28 commits)
autofs: Fix automounts by using current_real_cred()->uid
mnt: Add a per mount namespace limit on the number of mounts
netns: move {inc,dec}_net_namespaces into #ifdef
nsfs: Simplify __ns_get_path
tools/testing: add a test to check nsfs ioctl-s
nsfs: add ioctl to get a parent namespace
nsfs: add ioctl to get an owning user namespace for ns file descriptor
kernel: add a helper to get an owning user namespace for a namespace
devpts: Change the owner of /dev/pts/ptmx to the mounter of /dev/pts
devpts: Remove sync_filesystems
devpts: Make devpts_kill_sb safe if fsi is NULL
devpts: Simplify devpts_mount by using mount_nodev
devpts: Move the creation of /dev/pts/ptmx into fill_super
devpts: Move parse_mount_options into fill_super
userns: When the per user per user namespace limit is reached return ENOSPC
userns; Document per user per user namespace limits.
mntns: Add a limit on the number of mount namespaces.
netns: Add a limit on the number of net namespaces
cgroupns: Add a limit on the number of cgroup namespaces
ipcns: Add a limit on the number of ipc namespaces
...
This commit adds an inline function to cgroup.h to check whether a given
task is under a given cgroup hierarchy. This is to avoid having to put
ifdefs in .c files to gate access to cgroups. When cgroups are disabled
this always returns true.
Signed-off-by: Sargun Dhillon <sargun@sargun.me>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
cgroup_path() and friends used to format the path from the end and
thus the resulting path usually didn't start at the start of the
passed in buffer. Also, when the buffer was too small, the partial
result was truncated from the head rather than tail and there was no
way to tell how long the full path would be. These make the functions
less robust and more awkward to use.
With recent updates to kernfs_path(), cgroup_path() and friends can be
made to behave in strlcpy() style.
* cgroup_path(), cgroup_path_ns[_locked]() and task_cgroup_path() now
always return the length of the full path. If buffer is too small,
it contains nul terminated truncated output.
* All users updated accordingly.
v2: cgroup_path() usage in kernel/sched/debug.c converted.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Serge Hallyn <serge.hallyn@ubuntu.com>
Cc: Peter Zijlstra <peterz@infradead.org>
kernfs_path*() functions always return the length of the full path but
the path content is undefined if the length is larger than the
provided buffer. This makes its behavior different from strlcpy() and
requires error handling in all its users even when they don't care
about truncation. In addition, the implementation can actully be
simplified by making it behave properly in strlcpy() style.
* Update kernfs_path_from_node_locked() to always fill up the buffer
with path. If the buffer is not large enough, the output is
truncated and terminated.
* kernfs_path() no longer needs error handling. Make it a simple
inline wrapper around kernfs_path_from_node().
* sysfs_warn_dup()'s use of kernfs_path() doesn't need error handling.
Updated accordingly.
* cgroup_path()'s use of kernfs_path() updated to retain the old
behavior.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Add a helper function to get a cgroup2 from a fd. It will be
stored in a bpf array (BPF_MAP_TYPE_CGROUP_ARRAY) which will
be introduced in the later patch.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Introduce the ability to create new cgroup namespace. The newly created
cgroup namespace remembers the cgroup of the process at the point
of creation of the cgroup namespace (referred as cgroupns-root).
The main purpose of cgroup namespace is to virtualize the contents
of /proc/self/cgroup file. Processes inside a cgroup namespace
are only able to see paths relative to their namespace root
(unless they are moved outside of their cgroupns-root, at which point
they will see a relative path from their cgroupns-root).
For a correctly setup container this enables container-tools
(like libcontainer, lxc, lmctfy, etc.) to create completely virtualized
containers without leaking system level cgroup hierarchy to the task.
This patch only implements the 'unshare' part of the cgroupns.
Signed-off-by: Aditya Kali <adityakali@google.com>
Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull cgroup updates from Tejun Heo:
- cgroup v2 interface is now official. It's no longer hidden behind a
devel flag and can be mounted using the new cgroup2 fs type.
Unfortunately, cpu v2 interface hasn't made it yet due to the
discussion around in-process hierarchical resource distribution and
only memory and io controllers can be used on the v2 interface at the
moment.
- The existing documentation which has always been a bit of mess is
relocated under Documentation/cgroup-v1/. Documentation/cgroup-v2.txt
is added as the authoritative documentation for the v2 interface.
- Some features are added through for-4.5-ancestor-test branch to
enable netfilter xt_cgroup match to use cgroup v2 paths. The actual
netfilter changes will be merged through the net tree which pulled in
the said branch.
- Various cleanups
* 'for-4.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: rename cgroup documentations
cgroup: fix a typo.
cgroup: Remove resource_counter.txt in Documentation/cgroup-legacy/00-INDEX.
cgroup: demote subsystem init messages to KERN_DEBUG
cgroup: Fix uninitialized variable warning
cgroup: put controller Kconfig options in meaningful order
cgroup: clean up the kernel configuration menu nomenclature
cgroup_pids: fix a typo.
Subject: cgroup: Fix incomplete dd command in blkio documentation
cgroup: kill cgrp_ss_priv[CGROUP_CANFORK_COUNT] and friends
cpuset: Replace all instances of time_t with time64_t
cgroup: replace unified-hierarchy.txt with a proper cgroup v2 documentation
cgroup: rename Documentation/cgroups/ to Documentation/cgroup-legacy/
cgroup: replace __DEVEL__sane_behavior with cgroup2 fs type
Conflicts:
drivers/net/geneve.c
Here we had an overlapping change, where in 'net' the extraneous stats
bump was being removed whilst in 'net-next' the final argument to
udp_tunnel6_xmit_skb() was being changed.
Signed-off-by: David S. Miller <davem@davemloft.net>
In cgroup v1, dealing with cgroup membership was difficult because the
number of membership associations was unbound. As a result, cgroup v1
grew several controllers whose primary purpose is either tagging
membership or pull in configuration knobs from other subsystems so
that cgroup membership test can be avoided.
net_cls and net_prio controllers are examples of the latter. They
allow configuring network-specific attributes from cgroup side so that
network subsystem can avoid testing cgroup membership; unfortunately,
these are not only cumbersome but also problematic.
Both net_cls and net_prio aren't properly hierarchical. Both inherit
configuration from the parent on creation but there's no interaction
afterwards. An ancestor doesn't restrict the behavior in its subtree
in anyway and configuration changes aren't propagated downwards.
Especially when combined with cgroup delegation, this is problematic
because delegatees can mess up whatever network configuration
implemented at the system level. net_prio would allow the delegatees
to set whatever priority value regardless of CAP_NET_ADMIN and net_cls
the same for classid.
While it is possible to solve these issues from controller side by
implementing hierarchical allowable ranges in both controllers, it
would involve quite a bit of complexity in the controllers and further
obfuscate network configuration as it becomes even more difficult to
tell what's actually being configured looking from the network side.
While not much can be done for v1 at this point, as membership
handling is sane on cgroup v2, it'd be better to make cgroup matching
behave like other network matches and classifiers than introducing
further complications.
In preparation, this patch updates sock->sk_cgrp_data handling so that
it points to the v2 cgroup that sock was created in until either
net_prio or net_cls is used. Once either of the two is used,
sock->sk_cgrp_data reverts to its previous role of carrying prioidx
and classid. This is to avoid adding yet another cgroup related field
to struct sock.
As the mode switching can happen at most once per boot, the switching
mechanism is aimed at lowering hot path overhead. It may leak a
finite, likely small, number of cgroup refs and report spurious
prioidx or classid on switching; however, dynamic updates of prioidx
and classid have always been racy and lossy - socks between creation
and fd installation are never updated, config changes don't update
existing sockets at all, and prioidx may index with dead and recycled
cgroup IDs. Non-critical inaccuracies from small race windows won't
make any noticeable difference.
This patch doesn't make use of the pointer yet. The following patch
will implement netfilter match for cgroup2 membership.
v2: Use sock_cgroup_data to avoid inflating struct sock w/ another
cgroup specific field.
v3: Add comments explaining why sock_data_prioidx() and
sock_data_classid() use different fallback values.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Daniel Wagner <daniel.wagner@bmw-carit.de>
CC: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Now that nobody use the "priv" arg passed to can_fork/cancel_fork/fork we can
kill CGROUP_CANFORK_COUNT/SUBSYS_TAG/etc and cgrp_ss_priv[] in copy_process().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Consider the following v2 hierarchy.
P0 (+memory) --- P1 (-memory) --- A
\- B
P0 has memory enabled in its subtree_control while P1 doesn't. If
both A and B contain processes, they would belong to the memory css of
P1. Now if memory is enabled on P1's subtree_control, memory csses
should be created on both A and B and A's processes should be moved to
the former and B's processes the latter. IOW, enabling controllers
can cause atomic migrations into different csses.
The core cgroup migration logic has been updated accordingly but the
controller migration methods haven't and still assume that all tasks
migrate to a single target css; furthermore, the methods were fed the
css in which subtree_control was updated which is the parent of the
target csses. pids controller depends on the migration methods to
move charges and this made the controller attribute charges to the
wrong csses often triggering the following warning by driving a
counter negative.
WARNING: CPU: 1 PID: 1 at kernel/cgroup_pids.c:97 pids_cancel.constprop.6+0x31/0x40()
Modules linked in:
CPU: 1 PID: 1 Comm: systemd Not tainted 4.4.0-rc1+ #29
...
ffffffff81f65382 ffff88007c043b90 ffffffff81551ffc 0000000000000000
ffff88007c043bc8 ffffffff810de202 ffff88007a752000 ffff88007a29ab00
ffff88007c043c80 ffff88007a1d8400 0000000000000001 ffff88007c043bd8
Call Trace:
[<ffffffff81551ffc>] dump_stack+0x4e/0x82
[<ffffffff810de202>] warn_slowpath_common+0x82/0xc0
[<ffffffff810de2fa>] warn_slowpath_null+0x1a/0x20
[<ffffffff8118e031>] pids_cancel.constprop.6+0x31/0x40
[<ffffffff8118e0fd>] pids_can_attach+0x6d/0xf0
[<ffffffff81188a4c>] cgroup_taskset_migrate+0x6c/0x330
[<ffffffff81188e05>] cgroup_migrate+0xf5/0x190
[<ffffffff81189016>] cgroup_attach_task+0x176/0x200
[<ffffffff8118949d>] __cgroup_procs_write+0x2ad/0x460
[<ffffffff81189684>] cgroup_procs_write+0x14/0x20
[<ffffffff811854e5>] cgroup_file_write+0x35/0x1c0
[<ffffffff812e26f1>] kernfs_fop_write+0x141/0x190
[<ffffffff81265f88>] __vfs_write+0x28/0xe0
[<ffffffff812666fc>] vfs_write+0xac/0x1a0
[<ffffffff81267019>] SyS_write+0x49/0xb0
[<ffffffff81bcef32>] entry_SYSCALL_64_fastpath+0x12/0x76
This patch fixes the bug by removing @css parameter from the three
migration methods, ->can_attach, ->cancel_attach() and ->attach() and
updating cgroup_taskset iteration helpers also return the destination
css in addition to the task being migrated. All controllers are
updated accordingly.
* Controllers which don't care whether there are one or multiple
target csses can be converted trivially. cpu, io, freezer, perf,
netclassid and netprio fall in this category.
* cpuset's current implementation assumes that there's single source
and destination and thus doesn't support v2 hierarchy already. The
only change made by this patchset is how that single destination css
is obtained.
* memory migration path already doesn't do anything on v2. How the
single destination css is obtained is updated and the prep stage of
mem_cgroup_can_attach() is reordered to accomodate the change.
* pids is the only controller which was affected by this bug. It now
correctly handles multi-destination migrations and no longer causes
counter underflow from incorrect accounting.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-tested-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Implement cgroup_get_from_path() using kernfs_walk_and_get() which
obtains a default hierarchy cgroup from its path. This will be used
to allow cgroup path based matching from outside cgroup proper -
e.g. networking and perf.
v2: Add EXPORT_SYMBOL_GPL(cgroup_get_from_path).
Signed-off-by: Tejun Heo <tj@kernel.org>
cgroup_is_descendant() currently walks up the hierarchy and compares
each ancestor to the cgroup in question. While enough for cgroup core
usages, this can't be used in hot paths to test cgroup membership.
This patch adds cgroup->ancestor_ids[] which records the IDs of all
ancestors including self and cgroup->level for the nesting level.
This allows testing whether a given cgroup is a descendant of another
in three finite steps - testing whether the two belong to the same
hierarchy, whether the descendant candidate is at the same or a higher
level than the ancestor and comparing the recorded ancestor_id at the
matching level. cgroup_is_descendant() is accordingly reimplmented
and made inline.
Signed-off-by: Tejun Heo <tj@kernel.org>
6f60eade24 ("cgroup: generalize obtaining the handles of and
notifying cgroup files") introduced cftype->file_offset so that the
handles for per-css file instances can be recorded. These handles
then can be used, for example, to generate file modified
notifications.
Unfortunately, it made the wrong assumption that files are created
once for a given css and removed on its destruction. Due to the
dependencies among subsystems, a css may be hidden from userland and
then later shown again. This is implemented by removing and
re-creating the affected files, so the associated kernfs_node for a
given cgroup file may change over time. This incorrect assumption led
to the corruption of css->files lists.
Reimplement cftype->file_offset handling so that cgroup_file->kn is
protected by a lock and updated as files are created and destroyed.
This also makes keeping them on per-cgroup list unnecessary.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: James Sedgwick <jsedgwick@fb.com>
Fixes: 6f60eade24 ("cgroup: generalize obtaining the handles of and notifying cgroup files")
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Zefan Li <lizefan@huawei.com>
cgroup_exit() is called when a task exits and disassociates the
exiting task from its cgroups and half-attach it to the root cgroup.
This is unnecessary and undesirable.
No controller actually needs an exiting task to be disassociated with
non-root cgroups. Both cpu and perf_event controllers update the
association to the root cgroup from their exit callbacks just to keep
consistent with the cgroup core behavior.
Also, this disassociation makes it difficult to track resources held
by zombies or determine where the zombies came from. Currently, pids
controller is completely broken as it uncharges on exit and zombies
always escape the resource restriction. With cgroup association being
reset on exit, fixing it is pretty painful.
There's no reason to reset cgroup membership on exit. The zombie can
be removed from its css_set so that it doesn't show up on
"cgroup.procs" and thus can't be migrated or interfere with cgroup
removal. It can still pin and point to the css_set so that its cgroup
membership is maintained. This patch makes cgroup core keep zombies
associated with their cgroups at the time of exit.
* Previous patches decoupled populated_cnt tracking from css_set
lifetime, so a dying task can be simply unlinked from its css_set
while pinning and pointing to the css_set. This keeps css_set
association from task side alive while hiding it from "cgroup.procs"
and populated_cnt tracking. The css_set reference is dropped when
the task_struct is freed.
* ->exit() callback no longer needs the css arguments as the
associated css never changes once PF_EXITING is set. Removed.
* cpu and perf_events controllers no longer need ->exit() callbacks.
There's no reason to explicitly switch away on exit. The final
schedule out is enough. The callbacks are removed.
* On traditional hierarchies, nothing changes. "/proc/PID/cgroup"
still reports "/" for all zombies. On the default hierarchy,
"/proc/PID/cgroup" keeps reporting the cgroup that the task belonged
to at the time of exit. If the cgroup gets removed before the task
is reaped, " (deleted)" is appended.
v2: Build brekage due to missing dummy cgroup_free() when
!CONFIG_CGROUP fixed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
css_set_rwsem is the inner lock protecting css_sets and is accessed
from hot paths such as fork and exit. Internally, it has no reason to
be a rwsem or even mutex. There are no internal blocking operations
while holding it. This was rwsem because css task iteration used to
expose it to external iterator users. As the previous patch updated
css task iteration such that the locking is not leaked to its users,
there's no reason to keep it a rwsem.
This patch converts css_set_rwsem to a spinlock and rename it to
css_set_lock. It uses bh-safe operations as a planned usage needs to
access it from RCU callback context.
Signed-off-by: Tejun Heo <tj@kernel.org>
css_sets are synchronized through css_set_rwsem but the locking scheme
is kinda bizarre. The hot paths - fork and exit - have to write lock
the rwsem making the rw part pointless; furthermore, many readers
already hold cgroup_mutex.
One of the readers is css task iteration. It read locks the rwsem
over the entire duration of iteration. This leads to silly locking
behavior. When cpuset tries to migrate processes of a cgroup to a
different NUMA node, css_set_rwsem is held across the entire migration
attempt which can take a long time locking out forking, exiting and
other cgroup operations.
This patch updates css task iteration so that it locks css_set_rwsem
only while the iterator is being advanced. css task iteration
involves two levels - css_set and task iteration. As css_sets in use
are practically immutable, simply pinning the current one is enough
for resuming iteration afterwards. Task iteration is tricky as tasks
may leave their css_set while iteration is in progress. This is
solved by keeping track of active iterators and advancing them if
their next task leaves its css_set.
v2: put_task_struct() in css_task_iter_next() moved outside
css_set_rwsem. A later patch will add cgroup operations to
task_struct free path which may grab the same lock and this avoids
deadlock possibilities.
css_set_move_task() updated to use list_for_each_entry_safe() when
walking task_iters and advancing them. This is necessary as
advancing an iter may remove it from the list.
Signed-off-by: Tejun Heo <tj@kernel.org>
Currently, cgroup_has_tasks() tests whether the target cgroup has any
css_set linked to it. This works because a css_set's refcnt converges
with the number of tasks linked to it and thus there's no css_set
linked to a cgroup if it doesn't have any live tasks.
To help tracking resource usage of zombie tasks, putting the ref of
css_set will be separated from disassociating the task from the
css_set which means that a cgroup may have css_sets linked to it even
when it doesn't have any live tasks.
This patch replaces cgroup_has_tasks() with cgroup_is_populated()
which tests cgroup->nr_populated instead which locally counts the
number of populated css_sets. Unlike cgroup_has_tasks(),
cgroup_is_populated() is recursive - if any of the descendants is
populated, the cgroup is populated too. While this changes the
meaning of the test, all the existing users are okay with the change.
While at it, replace the open-coded ->populated_cnt test in
cgroup_events_show() with cgroup_is_populated().
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
It wasn't explicitly documented but, when a process is being migrated,
cpuset and memcg depend on cgroup_taskset_first() returning the
threadgroup leader; however, this approach is somewhat ghetto and
would no longer work for the planned multi-process migration.
This patch introduces explicit cgroup_taskset_for_each_leader() which
iterates over only the threadgroup leaders and replaces
cgroup_taskset_first() usages for accessing the leader with it.
This prepares both memcg and cpuset for multi-process migration. This
patch also updates the documentation for cgroup_taskset_for_each() to
clarify the iteration rules and removes comments mentioning task
ordering in tasksets.
v2: A previous patch which added threadgroup leader test was dropped.
Patch updated accordingly.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Zefan Li <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
cgroup core handles creations and removals of cgroup interface files
as described by cftypes. There are cases where the handle for a given
file instance is necessary, for example, to generate a file modified
event. Currently, this is handled by explicitly matching the callback
method pointer and storing the file handle manually in
cgroup_add_file(). While this simple approach works for cgroup core
files, it can't for controller interface files.
This patch generalizes cgroup interface file handle handling. struct
cgroup_file is defined and each cftype can optionally tell cgroup core
to store the file handle by setting ->file_offset. A file handle
remains accessible as long as the containing css is accessible.
Both "cgroup.procs" and "cgroup.events" are converted to use the new
generic mechanism instead of hooking directly into cgroup_add_file().
Also, cgroup_file_notify() which takes a struct cgroup_file and
generates a file modified event on it is added and replaces explicit
kernfs_notify() invocations.
This generalizes cgroup file handle handling and allows controllers to
generate file modified notifications.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
cgroup_on_dfl() tests whether the cgroup's root is the default
hierarchy; however, an individual controller is only interested in
whether the controller is attached to the default hierarchy and never
tests a cgroup which doesn't belong to the hierarchy that the
controller is attached to.
This patch replaces cgroup_on_dfl() tests in controllers with faster
static_key based cgroup_subsys_on_dfl(). This leaves cgroup core as
the only user of cgroup_on_dfl() and the function is moved from the
header file to cgroup.c.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Zefan Li <lizefan@huawei.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Whether a subsys is enabled and attached to the default hierarchy
seldom changes and may be tested in the hot paths. This patch
implements static_key based cgroup_subsys_enabled() and
cgroup_subsys_on_dfl() tests.
The following patches will update the users and remove duplicate
mechanisms.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Zefan Li <lizefan@huawei.com>
Traditionally, each cgroup controller implemented whatever interface
it wanted leading to interfaces which are widely inconsistent.
Examining the requirements of the controllers readily yield that there
are only a few control schemes shared among all.
Two major controllers already had to implement new interface for the
unified hierarchy due to significant structural changes. Let's take
the chance to establish common conventions throughout all controllers.
This patch defines CGROUP_WEIGHT_MIN/DFL/MAX to be used on all weight
based control knobs and documents the conventions that controllers
should follow on the unified hierarchy. Except for io.weight knob,
all existing unified hierarchy knobs are already compliant. A
follow-up patch will update io.weight.
v2: Added descriptions of min, low and high knobs.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Add a new cgroup subsystem callback can_fork that conditionally
states whether or not the fork is accepted or rejected by a cgroup
policy. In addition, add a cancel_fork callback so that if an error
occurs later in the forking process, any state modified by can_fork can
be reverted.
Allow for a private opaque pointer to be passed from cgroup_can_fork to
cgroup_post_fork, allowing for the fork state to be stored by each
subsystem separately.
Also add a tagging system for cgroup_subsys.h to allow for CGROUP_<TAG>
enumerations to be be defined and used. In addition, explicitly add a
CGROUP_CANFORK_COUNT macro to make arrays easier to define.
This is in preparation for implementing the pids cgroup subsystem.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull cgroup updates from Tejun Heo:
- threadgroup_lock got reorganized so that its users can pick the
actual locking mechanism to use. Its only user - cgroups - is
updated to use a percpu_rwsem instead of per-process rwsem.
This makes things a bit lighter on hot paths and allows cgroups to
perform and fail multi-task (a process) migrations atomically.
Multi-task migrations are used in several places including the
unified hierarchy.
- Delegation rule and documentation added to unified hierarchy. This
will likely be the last interface update from the cgroup core side
for unified hierarchy before lifting the devel mask.
- Some groundwork for the pids controller which is scheduled to be
merged in the coming devel cycle.
* 'for-4.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: add delegation section to unified hierarchy documentation
cgroup: require write perm on common ancestor when moving processes on the default hierarchy
cgroup: separate out cgroup_procs_write_permission() from __cgroup_procs_write()
kernfs: make kernfs_get_inode() public
MAINTAINERS: add a cgroup core co-maintainer
cgroup: fix uninitialised iterator in for_each_subsys_which
cgroup: replace explicit ss_mask checking with for_each_subsys_which
cgroup: use bitmask to filter for_each_subsys
cgroup: add seq_file forward declaration for struct cftype
cgroup: simplify threadgroup locking
sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem
sched, cgroup: reorganize threadgroup locking
cgroup: switch to unsigned long for bitmasks
cgroup: reorganize include/linux/cgroup.h
cgroup: separate out include/linux/cgroup-defs.h
cgroup: fix some comment typos
bio_associate_current() currently open codes task_css() and
css_tryget_online() to find and pin $current's blkcg css. Abstract it
into task_get_css() which is implemented from cgroup side. As a task
is always associated with an online css for every subsystem except
while the css_set update is propagating, task_get_css() retries till
css_tryget_online() succeeds.
This is a cleanup and shouldn't lead to noticeable behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
From c4d440938b5e2015c70594fe6666a099c844f929 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Wed, 13 May 2015 16:21:40 -0400
Over time, cgroup.h grew organically and doesn't have much logical
structure at this point. Separation of cgroup-defs.h in the previous
patch gives us a good chance for reorganizing cgroup.h as changes to
the header are likely to cause conflicts anyway.
This patch reorganizes cgroup.h so that it has consistent logical
grouping.
This is pure reorganization.
v2: Relocating #ifdef CONFIG_CGROUPS caused build failure when cgroup
is disabled. Dropped.
Signed-off-by: Tejun Heo <tj@kernel.org>
From 2d728f74bfc071df06773e2fd7577dd5dab6425d Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Wed, 13 May 2015 15:37:01 -0400
This patch separates out cgroup-defs.h from cgroup.h which has grown a
lot of dependencies. cgroup-defs.h currently only contains constant
and type definitions and can be used to break circular include
dependency. While moving, definitions are reordered so that
cgroup-defs.h has consistent logical structure.
This patch is pure reorganization.
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull cgroup update from Tejun Heo:
"cpuset got simplified a bit. cgroup core got a fix on unified
hierarchy and grew some effective css related interfaces which will be
used for blkio support for writeback IO traffic which is currently
being worked on"
* 'for-3.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: implement cgroup_get_e_css()
cgroup: add cgroup_subsys->css_e_css_changed()
cgroup: add cgroup_subsys->css_released()
cgroup: fix the async css offline wait logic in cgroup_subtree_control_write()
cgroup: restructure child_subsys_mask handling in cgroup_subtree_control_write()
cgroup: separate out cgroup_calc_child_subsys_mask() from cgroup_refresh_child_subsys_mask()
cpuset: lock vs unlock typo
cpuset: simplify cpuset_node_allowed API
cpuset: convert callback_mutex to a spinlock
Merge first patchbomb from Andrew Morton:
- a few minor cifs fixes
- dma-debug upadtes
- ocfs2
- slab
- about half of MM
- procfs
- kernel/exit.c
- panic.c tweaks
- printk upates
- lib/ updates
- checkpatch updates
- fs/binfmt updates
- the drivers/rtc tree
- nilfs
- kmod fixes
- more kernel/exit.c
- various other misc tweaks and fixes
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (190 commits)
exit: pidns: fix/update the comments in zap_pid_ns_processes()
exit: pidns: alloc_pid() leaks pid_namespace if child_reaper is exiting
exit: exit_notify: re-use "dead" list to autoreap current
exit: reparent: call forget_original_parent() under tasklist_lock
exit: reparent: avoid find_new_reaper() if no children
exit: reparent: introduce find_alive_thread()
exit: reparent: introduce find_child_reaper()
exit: reparent: document the ->has_child_subreaper checks
exit: reparent: s/while_each_thread/for_each_thread/ in find_new_reaper()
exit: reparent: fix the cross-namespace PR_SET_CHILD_SUBREAPER reparenting
exit: reparent: fix the dead-parent PR_SET_CHILD_SUBREAPER reparenting
exit: proc: don't try to flush /proc/tgid/task/tgid
exit: release_task: fix the comment about group leader accounting
exit: wait: drop tasklist_lock before psig->c* accounting
exit: wait: don't use zombie->real_parent
exit: wait: cleanup the ptrace_reparented() checks
usermodehelper: kill the kmod_thread_locker logic
usermodehelper: don't use CLONE_VFORK for ____call_usermodehelper()
fs/hfs/catalog.c: fix comparison bug in hfs_cat_keycmp
nilfs2: fix the nilfs_iget() vs. nilfs_new_inode() races
...
Charges currently pin the css indirectly by playing tricks during
css_offline(): user pages stall the offlining process until all of them
have been reparented, whereas kmemcg acquires a keep-alive reference if
outstanding kernel pages are detected at that point.
In preparation for removing all this complexity, make the pinning explicit
and acquire a css references for every charged page.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Implement cgroup_get_e_css() which finds and gets the effective css
for the specified cgroup and subsystem combination. This function
always returns a valid pinned css. This will be used by cgroup
writeback support.
While at it, add comment to cgroup_e_css() to explain why that
function is different from cgroup_get_e_css() and has to test
cgrp->child_subsys_mask instead of cgroup_css(cgrp, ss).
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Zefan Li <lizefan@huawei.com>
Add a new cgroup_subsys operatoin ->css_e_css_changed(). This is
invoked if any of the effective csses seen from the css's cgroup may
have changed. This will be used to implement cgroup writeback
support.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Zefan Li <lizefan@huawei.com>
Add a new cgroup subsys callback css_released(). This is called when
the reference count of the css (cgroup_subsys_state) reaches zero
before RCU scheduling free.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Zefan Li <lizefan@huawei.com>
We call put_css_set() after setting CGRP_RELEASABLE flag in
cgroup_task_migrate(), but in other places we call it without setting
the flag. I don't see the necessity of this flag.
Moreover once the flag is set, it will never be cleared, unless writing
to the notify_on_release control file, so it can be quite confusing
if we look at the output of debug.releasable.
# mount -t cgroup -o debug xxx /cgroup
# mkdir /cgroup/child
# cat /cgroup/child/debug.releasable
0 <-- shows 0 though the cgroup is empty
# echo $$ > /cgroup/child/tasks
# cat /cgroup/child/debug.releasable
0
# echo $$ > /cgroup/tasks && echo $$ > /cgroup/child/tasks
# cat /proc/child/debug.releasable
1 <-- shows 1 though the cgroup is not empty
This patch removes the flag, and now debug.releasable shows if the
cgroup is empty or not.
Signed-off-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
After we implemented default unified hierarchy, cgrp->kn can never
be NULL.
Signed-off-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Use the ONE macro instead of REG, and we can simplify proc_cgroup_show().
Signed-off-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Instead of using a global work to schedule release agent on removable
cgroups, we change to use a per-cgroup work to do this, which makes
the code much simpler.
v2: use a dedicated work instead of reusing css->destroy_work. (Tejun)
Signed-off-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
cgroup now distinguishes cftypes for the default and legacy
hierarchies more explicitly by using separate arrays and
CFTYPE_ONLY_ON_DFL and CFTYPE_INSANE should be and are used only
inside cgroup core proper. Let's make it clear that the flags are
internal by prefixing them with double underscores.
CFTYPE_INSANE is renamed to __CFTYPE_NOT_ON_DFL for consistency. The
two flags are also collected and assigned bits >= 16 so that they
aren't mixed with the published flags.
v2: Convert the extra ones in cgroup_exit_cftypes() which are added by
revision to the previous patch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Until now, cftype arrays carried files for both the default and legacy
hierarchies and the files which needed to be used on only one of them
were flagged with either CFTYPE_ONLY_ON_DFL or CFTYPE_INSANE. This
gets confusing very quickly and we may end up exposing interface files
to the default hierarchy without thinking it through.
This patch makes cgroup core provide separate sets of interfaces for
cftype handling so that the cftypes for the default and legacy
hierarchies are clearly distinguished. The previous two patches
renamed the existing ones so that they clearly indicate that they're
for the legacy hierarchies. This patch adds the interface for the
default hierarchy and apply them selectively depending on the
hierarchy type.
* cftypes added through cgroup_subsys->dfl_cftypes and
cgroup_add_dfl_cftypes() only show up on the default hierarchy.
* cftypes added through cgroup_subsys->legacy_cftypes and
cgroup_add_legacy_cftypes() only show up on the legacy hierarchies.
* cgroup_subsys->dfl_cftypes and ->legacy_cftypes can point to the
same array for the cases where the interface files are identical on
both types of hierarchies.
* This makes all the existing subsystem interface files legacy-only by
default and all subsystems will have no interface file created when
enabled on the default hierarchy. Each subsystem should explicitly
review and compose the interface for the default hierarchy.
* A boot param "cgroup__DEVEL__legacy_files_on_dfl" is added which
makes subsystems which haven't decided the interface files for the
default hierarchy to present the legacy files on the default
hierarchy so that its behavior on the default hierarchy can be
tested. As the awkward name suggests, this is for development only.
* memcg's CFTYPE_INSANE on "use_hierarchy" is noop now as the whole
array isn't used on the default hierarchy. The flag is removed.
v2: Updated documentation for cgroup__DEVEL__legacy_files_on_dfl.
v3: Clear CFTYPE_ONLY_ON_DFL and CFTYPE_INSANE when cfts are removed
as suggested by Li.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vivek Goyal <vgoyal@redhat.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@kernel.org>
Cc: Aristeu Rozanski <aris@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Currently, cftypes added by cgroup_add_cftypes() are used for both the
unified default hierarchy and legacy ones and subsystems can mark each
file with either CFTYPE_ONLY_ON_DFL or CFTYPE_INSANE if it has to
appear only on one of them. This is quite hairy and error-prone.
Also, we may end up exposing interface files to the default hierarchy
without thinking it through.
cgroup_subsys will grow two separate cftype addition functions and
apply each only on the hierarchies of the matching type. This will
allow organizing cftypes in a lot clearer way and encourage subsystems
to scrutinize the interface which is being exposed in the new default
hierarchy.
In preparation, this patch adds cgroup_add_legacy_cftypes() which
currently is a simple wrapper around cgroup_add_cftypes() and replaces
all cgroup_add_cftypes() usages with it.
While at it, this patch drops a completely spurious return from
__hugetlb_cgroup_file_init().
This patch doesn't introduce any functional differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Currently, cgroup_subsys->base_cftypes is used for both the unified
default hierarchy and legacy ones and subsystems can mark each file
with either CFTYPE_ONLY_ON_DFL or CFTYPE_INSANE if it has to appear
only on one of them. This is quite hairy and error-prone. Also, we
may end up exposing interface files to the default hierarchy without
thinking it through.
cgroup_subsys will grow two separate cftype arrays and apply each only
on the hierarchies of the matching type. This will allow organizing
cftypes in a lot clearer way and encourage subsystems to scrutinize
the interface which is being exposed in the new default hierarchy.
In preparation, this patch renames cgroup_subsys->base_cftypes to
cgroup_subsys->legacy_cftypes. This patch is pure rename.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vivek Goyal <vgoyal@redhat.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@kernel.org>
Cc: Aristeu Rozanski <aris@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
sane_behavior has been used as a development vehicle for the default
unified hierarchy. Now that the default hierarchy is in place, the
flag became redundant and confusing as its usage is allowed on all
hierarchies. There are gonna be either the default hierarchy or
legacy ones. Let's make that clear by removing sane_behavior support
on non-default hierarchies.
This patch replaces cgroup_sane_behavior() with cgroup_on_dfl(). The
comment on top of CGRP_ROOT_SANE_BEHAVIOR is moved to on top of
cgroup_on_dfl() with sane_behavior specific part dropped.
On the default and legacy hierarchies w/o sane_behavior, this
shouldn't cause any behavior differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
cgroup_root->flags only contains CGRP_ROOT_* flags and there's no
reason to mask the flags. Remove CGRP_ROOT_OPTION_MASK.
This doesn't cause any behavior differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, the blkio subsystem attributes all of writeback IOs to the
root. One of the issues is that there's no way to tell who originated
a writeback IO from block layer. Those IOs are usually issued
asynchronously from a task which didn't have anything to do with
actually generating the dirty pages. The memory subsystem, when
enabled, already keeps track of the ownership of each dirty page and
it's desirable for blkio to piggyback instead of adding its own
per-page tag.
blkio piggybacking on memory is an implementation detail which
preferably should be handled automatically without requiring explicit
userland action. To achieve that, this patch implements
cgroup_subsys->depends_on which contains the mask of subsystems which
should be enabled together when the subsystem is enabled.
The previous patches already implemented the support for enabled but
invisible subsystems and cgroup_subsys->depends_on can be easily
implemented by updating cgroup_refresh_child_subsys_mask() so that it
calculates cgroup->child_subsys_mask considering
cgroup_subsys->depends_on of the explicitly enabled subsystems.
Documentation/cgroups/unified-hierarchy.txt is updated to explain that
subsystems may not become immediately available after being unused
from userland and that dependency could be a factor in it. As
subsystems may already keep residual references, this doesn't
significantly change how subsystem rebinding can be used.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
cgroup is implementing support for subsystem dependency which would
require a way to enable a subsystem even when it's not directly
configured through "cgroup.subtree_control".
The previous patches added support for explicitly and implicitly
enabled subsystems and showing/hiding their interface files. An
explicitly enabled subsystem may become implicitly enabled if it's
turned off through "cgroup.subtree_control" but there are subsystems
depending on it. In such cases, the subsystem, as it's turned off
when seen from userland, shouldn't enforce any resource control.
Also, the subsystem may be explicitly turned on later again and its
interface files should be as close to the intial state as possible.
This patch adds cgroup_subsys->css_reset() which is invoked when a css
is hidden. The callback should disable resource control and reset the
state to the vanilla state.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
cgroup is implementing support for subsystem dependency which would
require a way to enable a subsystem even when it's not directly
configured through "cgroup.subtree_control".
The preceding patch distinguished cgroup->subtree_control and
->child_subsys_mask where the former is the subsystems explicitly
configured by the userland and the latter is all enabled subsystems
currently is equal to the former but will include subsystems
implicitly enabled through dependency.
Subsystems which are enabled due to dependency shouldn't be visible to
userland. This patch updates cgroup_subtree_control_write() and
create_css() such that interface files are not created for implicitly
enabled subsytems.
* @visible paramter is added to create_css(). Interface files are
created only when true.
* If an already implicitly enabled subsystem is turned on through
"cgroup.subtree_control", the existing css should be used. css
draining is skipped.
* cgroup_subtree_control_write() computes the new target
cgroup->child_subsys_mask and create/kill or show/hide csses
accordingly.
As the two subsystem masks are still kept identical, this patch
doesn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
cgroup is implementing support for subsystem dependency which would
require a way to enable a subsystem even when it's not directly
configured through "cgroup.subtree_control".
Previously, cgroup->child_subsys_mask directly reflected
"cgroup.subtree_control" and the enabled subsystems in the child
cgroups. This patch adds cgroup->subtree_control which
"cgroup.subtree_control" operates on. cgroup->child_subsys_mask is
now calculated from cgroup->subtree_control by
cgroup_refresh_child_subsys_mask(), which sets it identical to
cgroup->subtree_control for now.
This will allow using cgroup->child_subsys_mask for all the enabled
subsystems including the implicit ones and ->subtree_control for
tracking the explicitly requested ones. This patch keeps the two
masks identical and doesn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
The debug controller, as its name suggests, exposes cgroup core
internals to userland to aid debugging. Unfortunately, except for the
name, there's no provision to prevent its usage in production
configurations and the controller is widely enabled and mounted
leaking internal details to userland. Like most other debug
information, the information exposed by debug isn't interesting even
for debugging itself once the related parts are working reliably.
This controller has no reason for existing. This patch implements
cgrp_dfl_root_inhibit_ss_mask which can suppress specific subsystems
on the default hierarchy and adds the debug subsystem to it so that it
can be gradually deprecated as usages move towards the unified
hierarchy.
Signed-off-by: Tejun Heo <tj@kernel.org>
Implement css_tryget() which tries to grab a cgroup_subsys_state's
reference as long as it already hasn't reached zero. Combined with
the recent css iterator changes to include offline && !released csses
during traversal, this can be used to access csses regardless of its
online state.
v2: Take the new flag CSS_NO_REF into account.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Now that cgroup liveliness and css onliness are the same state,
convert cgroup_has_live_children() into css_has_online_children() so
that it can be used for actual csses too. The function now uses
css_for_each_child() for iteration and is published.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Use CSS_ONLINE on the self css to indicate whether a cgroup has been
killed instead of CGRP_DEAD. This will allow re-using css online test
for cgroup liveliness test. This doesn't introduce any functional
change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, css_next_child() is implemented as finding the next child
cgroup which has the css enabled, which used to be the only way to do
it as only cgroups participated in sibling lists and thus could be
iteratd. This works as long as what's required during iteration is
not missing online csses; however, it turns out that there are use
cases where offlined but not yet released csses need to be iterated.
This is difficult to implement through cgroup iteration the unified
hierarchy as there may be multiple dying csses for the same subsystem
associated with single cgroup.
After the recent changes, the cgroup self and regular csses behave
identically in how they're linked and unlinked from the sibling lists
including assertion of CSS_RELEASED and css_next_child() can simply
switch to iterating csses directly. This both simplifies the logic
and ensures that all visible non-released csses are included in the
iteration whether there are multiple dying csses for a subsystem or
not.
As all other iterators depend on css_next_child() for sibling
iteration, this changes behaviors of all css iterators. Add and
update explanations on the css states which are included in traversal
to all iterators.
As css iteration could always contain offlined csses, this shouldn't
break any of the current users and new usages which need iteration of
all on and offline csses can make use of the new semantics.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
css iterations allow the caller to drop RCU read lock. As long as the
caller keeps the current position accessible, it can simply re-grab
RCU read lock later and continue iteration. This is achieved by using
CGRP_DEAD to detect whether the current positions next pointer is safe
to dereference and if not re-iterate from the beginning to the next
position using ->serial_nr.
CGRP_DEAD is used as the marker to invalidate the next pointer and the
only requirement is that the marker is set before the next sibling
starts its RCU grace period. Because CGRP_DEAD is set at the end of
cgroup_destroy_locked() but the cgroup is unlinked when the reference
count reaches zero, we currently have a rather large window where this
fallback re-iteration logic can be triggered.
This patch introduces CSS_RELEASED which is set when a css is unlinked
from its sibling list. This still keeps the re-iteration logic
working while drastically reducing the window of its activation.
While at it, rewrite the comment in css_next_child() to reflect the
new flag and better explain the synchronization.
This will also enable iterating csses directly instead of through
cgroups.
v2: CSS_RELEASED now assigned to 1 << 2 as 1 << 0 is used by
CSS_NO_REF.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
We're moving towards using cgroup_subsys_states as the fundamental
structural blocks. All csses including the cgroup->self and actual
ones now form trees through css->children and ->sibling which follow
the same rules as what cgroup->children and ->sibling followed. This
patch moves cgroup->serial_nr which is used to implement css iteration
into css.
Note that all csses, regardless of their types, allocate their serial
numbers from the same monotonically increasing counter. This doesn't
affect the ordering needed by css iteration or cause any other
material behavior changes. This will be used to update css iteration.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
We're moving towards using cgroup_subsys_states as the fundamental
structural blocks. Let's move cgroup->sibling and ->children into
cgroup_subsys_state. This is pure move without functional change and
only cgroup->self's fields are actually used. Other csses will make
use of the fields later.
While at it, update init_and_link_css() so that it zeroes the whole
css before initializing it and remove explicit zeroing of ->flags.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup->parent is redundant as cgroup->self.parent can also be used to
determine the parent cgroup and we're moving towards using
cgroup_subsys_states as the fundamental structural blocks. This patch
introduces cgroup_parent() which follows cgroup->self.parent and
removes cgroup->parent.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
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>
