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Add /sys/kernel/mm/lru_gen/enabled as a kill switch. Components that
can be disabled include:
0x0001: the multi-gen LRU core
0x0002: walking page table, when arch_has_hw_pte_young() returns
true
0x0004: clearing the accessed bit in non-leaf PMD entries, when
CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG=y
[yYnN]: apply to all the components above
E.g.,
echo y >/sys/kernel/mm/lru_gen/enabled
cat /sys/kernel/mm/lru_gen/enabled
0x0007
echo 5 >/sys/kernel/mm/lru_gen/enabled
cat /sys/kernel/mm/lru_gen/enabled
0x0005
NB: the page table walks happen on the scale of seconds under heavy memory
pressure, in which case the mmap_lock contention is a lesser concern,
compared with the LRU lock contention and the I/O congestion. So far the
only well-known case of the mmap_lock contention happens on Android, due
to Scudo [1] which allocates several thousand VMAs for merely a few
hundred MBs. The SPF and the Maple Tree also have provided their own
assessments [2][3]. However, if walking page tables does worsen the
mmap_lock contention, the kill switch can be used to disable it. In this
case the multi-gen LRU will suffer a minor performance degradation, as
shown previously.
Clearing the accessed bit in non-leaf PMD entries can also be disabled,
since this behavior was not tested on x86 varieties other than Intel and
AMD.
[1] https://source.android.com/devices/tech/debug/scudo
[2] https://lore.kernel.org/r/20220128131006.67712-1-michel@lespinasse.org/
[3] https://lore.kernel.org/r/20220426150616.3937571-1-Liam.Howlett@oracle.com/
Link: https://lkml.kernel.org/r/20220918080010.2920238-11-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@google.com>
Acked-by: Brian Geffon <bgeffon@google.com>
Acked-by: Jan Alexander Steffens (heftig) <heftig@archlinux.org>
Acked-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Acked-by: Steven Barrett <steven@liquorix.net>
Acked-by: Suleiman Souhlal <suleiman@google.com>
Tested-by: Daniel Byrne <djbyrne@mtu.edu>
Tested-by: Donald Carr <d@chaos-reins.com>
Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Tested-by: Konstantin Kharlamov <Hi-Angel@yandex.ru>
Tested-by: Shuang Zhai <szhai2@cs.rochester.edu>
Tested-by: Sofia Trinh <sofia.trinh@edi.works>
Tested-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michael Larabel <Michael@MichaelLarabel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The implementation of strscpy() is more robust and safer.
That's now the recommended way to copy NUL terminated strings.
Signed-off-by: ye xingchen <ye.xingchen@zte.com.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>
It could directly return 'cgroup_update_dfl_csses' to simplify code.
Signed-off-by: William Dean <williamsukatube@163.com>
Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
After merging 836ac87d ("cgroup: fix cgroup_get_from_id") into for-6.1, its
combination with two commits in for-6.1 - 4534dee9 ("cgroup: cgroup: Honor
caller's cgroup NS when resolving cgroup id") and fa7e439c ("cgroup:
Homogenize cgroup_get_from_id() return value") - makes the gotos in the
error handling path too ugly while not adding anything of value.
All that the gotos are saving is one extra kernfs_put() call. Let's remove
the gotos and perform error returns directly.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Michal Koutný <mkoutny@suse.com>
for-6.0 has the following fix for cgroup_get_from_id().
836ac87d ("cgroup: fix cgroup_get_from_id")
which conflicts with the following two commits in for-6.1.
4534dee9 ("cgroup: cgroup: Honor caller's cgroup NS when resolving cgroup id")
fa7e439c ("cgroup: Homogenize cgroup_get_from_id() return value")
While the resolution is straightforward, the code ends up pretty ugly
afterwards. Let's pull for-6.0-fixes into for-6.1 so that the code can be
fixed up there.
Signed-off-by: Tejun Heo <tj@kernel.org>
cgroup has to be one kernfs dir, otherwise kernel panic is caused,
especially cgroup id is provide from userspace.
Reported-by: Marco Patalano <mpatalan@redhat.com>
Fixes: 6b658c4863c1 ("scsi: cgroup: Add cgroup_get_from_id()")
Cc: Muneendra <muneendra.kumar@broadcom.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Acked-by: Mukesh Ojha <quic_mojha@quicinc.com>
Cc: stable@vger.kernel.org # v5.14+
Signed-off-by: Tejun Heo <tj@kernel.org>
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Merge 6.0-rc5 into driver-core-next
We need the driver core and debugfs changes in this branch.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
PSI accounts stalls for each cgroup separately and aggregates it
at each level of the hierarchy. This may cause non-negligible overhead
for some workloads when under deep level of the hierarchy.
commit 3958e2d0c34e ("cgroup: make per-cgroup pressure stall tracking configurable")
make PSI to skip per-cgroup stall accounting, only account system-wide
to avoid this each level overhead.
But for our use case, we also want leaf cgroup PSI stats accounted for
userspace adjustment on that cgroup, apart from only system-wide adjustment.
So this patch introduce a per-cgroup PSI accounting disable/re-enable
interface "cgroup.pressure", which is a read-write single value file that
allowed values are "0" and "1", the defaults is "1" so per-cgroup
PSI stats is enabled by default.
Implementation details:
It should be relatively straight-forward to disable and re-enable
state aggregation, time tracking, averaging on a per-cgroup level,
if we can live with losing history from while it was disabled.
I.e. the avgs will restart from 0, total= will have gaps.
But it's hard or complex to stop/restart groupc->tasks[] updates,
which is not implemented in this patch. So we always update
groupc->tasks[] and PSI_ONCPU bit in psi_group_change() even when
the cgroup PSI stats is disabled.
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lkml.kernel.org/r/20220907090332.2078-1-zhouchengming@bytedance.com
cgroup_psi() can't return psi_group for root cgroup, so we have many
open code "psi = cgroup_ino(cgrp) == 1 ? &psi_system : cgrp->psi".
This patch move cgroup_psi() definition to <linux/psi.h>, in which
we can return psi_system for root cgroup, so can handle all cgroups.
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/20220825164111.29534-9-zhouchengming@bytedance.com
Now PSI already tracked workload pressure stall information for
CPU, memory and IO. Apart from these, IRQ/SOFTIRQ could have
obvious impact on some workload productivity, such as web service
workload.
When CONFIG_IRQ_TIME_ACCOUNTING, we can get IRQ/SOFTIRQ delta time
from update_rq_clock_task(), in which we can record that delta
to CPU curr task's cgroups as PSI_IRQ_FULL status.
Note we don't use PSI_IRQ_SOME since IRQ/SOFTIRQ always happen in
the current task on the CPU, make nothing productive could run
even if it were runnable, so we only use PSI_IRQ_FULL.
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/20220825164111.29534-8-zhouchengming@bytedance.com
commit 3958e2d0c34e ("cgroup: make per-cgroup pressure stall tracking configurable")
make PSI can be configured to skip per-cgroup stall accounting. And
doesn't expose PSI files in cgroup hierarchy.
This patch do the same thing when psi_disabled.
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/20220825164111.29534-3-zhouchengming@bytedance.com
Rewrite the core freezer to behave better wrt thawing and be simpler
in general.
By replacing PF_FROZEN with TASK_FROZEN, a special block state, it is
ensured frozen tasks stay frozen until thawed and don't randomly wake
up early, as is currently possible.
As such, it does away with PF_FROZEN and PF_FREEZER_SKIP, freeing up
two PF_flags (yay!).
Specifically; the current scheme works a little like:
freezer_do_not_count();
schedule();
freezer_count();
And either the task is blocked, or it lands in try_to_freezer()
through freezer_count(). Now, when it is blocked, the freezer
considers it frozen and continues.
However, on thawing, once pm_freezing is cleared, freezer_count()
stops working, and any random/spurious wakeup will let a task run
before its time.
That is, thawing tries to thaw things in explicit order; kernel
threads and workqueues before doing bringing SMP back before userspace
etc.. However due to the above mentioned races it is entirely possible
for userspace tasks to thaw (by accident) before SMP is back.
This can be a fatal problem in asymmetric ISA architectures (eg ARMv9)
where the userspace task requires a special CPU to run.
As said; replace this with a special task state TASK_FROZEN and add
the following state transitions:
TASK_FREEZABLE -> TASK_FROZEN
__TASK_STOPPED -> TASK_FROZEN
__TASK_TRACED -> TASK_FROZEN
The new TASK_FREEZABLE can be set on any state part of TASK_NORMAL
(IOW. TASK_INTERRUPTIBLE and TASK_UNINTERRUPTIBLE) -- any such state
is already required to deal with spurious wakeups and the freezer
causes one such when thawing the task (since the original state is
lost).
The special __TASK_{STOPPED,TRACED} states *can* be restored since
their canonical state is in ->jobctl.
With this, frozen tasks need an explicit TASK_FROZEN wakeup and are
free of undue (early / spurious) wakeups.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20220822114649.055452969@infradead.org
Daniel Borkmann says:
====================
pull-request: bpf-next 2022-09-05
The following pull-request contains BPF updates for your *net-next* tree.
We've added 106 non-merge commits during the last 18 day(s) which contain
a total of 159 files changed, 5225 insertions(+), 1358 deletions(-).
There are two small merge conflicts, resolve them as follows:
1) tools/testing/selftests/bpf/DENYLIST.s390x
Commit 27e23836ce22 ("selftests/bpf: Add lru_bug to s390x deny list") in
bpf tree was needed to get BPF CI green on s390x, but it conflicted with
newly added tests on bpf-next. Resolve by adding both hunks, result:
[...]
lru_bug # prog 'printk': failed to auto-attach: -524
setget_sockopt # attach unexpected error: -524 (trampoline)
cb_refs # expected error message unexpected error: -524 (trampoline)
cgroup_hierarchical_stats # JIT does not support calling kernel function (kfunc)
htab_update # failed to attach: ERROR: strerror_r(-524)=22 (trampoline)
[...]
2) net/core/filter.c
Commit 1227c1771dd2 ("net: Fix data-races around sysctl_[rw]mem_(max|default).")
from net tree conflicts with commit 29003875bd5b ("bpf: Change bpf_setsockopt(SOL_SOCKET)
to reuse sk_setsockopt()") from bpf-next tree. Take the code as it is from
bpf-next tree, result:
[...]
if (getopt) {
if (optname == SO_BINDTODEVICE)
return -EINVAL;
return sk_getsockopt(sk, SOL_SOCKET, optname,
KERNEL_SOCKPTR(optval),
KERNEL_SOCKPTR(optlen));
}
return sk_setsockopt(sk, SOL_SOCKET, optname,
KERNEL_SOCKPTR(optval), *optlen);
[...]
The main changes are:
1) Add any-context BPF specific memory allocator which is useful in particular for BPF
tracing with bonus of performance equal to full prealloc, from Alexei Starovoitov.
2) Big batch to remove duplicated code from bpf_{get,set}sockopt() helpers as an effort
to reuse the existing core socket code as much as possible, from Martin KaFai Lau.
3) Extend BPF flow dissector for BPF programs to just augment the in-kernel dissector
with custom logic. In other words, allow for partial replacement, from Shmulik Ladkani.
4) Add a new cgroup iterator to BPF with different traversal options, from Hao Luo.
5) Support for BPF to collect hierarchical cgroup statistics efficiently through BPF
integration with the rstat framework, from Yosry Ahmed.
6) Support bpf_{g,s}et_retval() under more BPF cgroup hooks, from Stanislav Fomichev.
7) BPF hash table and local storages fixes under fully preemptible kernel, from Hou Tao.
8) Add various improvements to BPF selftests and libbpf for compilation with gcc BPF
backend, from James Hilliard.
9) Fix verifier helper permissions and reference state management for synchronous
callbacks, from Kumar Kartikeya Dwivedi.
10) Add support for BPF selftest's xskxceiver to also be used against real devices that
support MAC loopback, from Maciej Fijalkowski.
11) Various fixes to the bpf-helpers(7) man page generation script, from Quentin Monnet.
12) Document BPF verifier's tnum_in(tnum_range(), ...) gotchas, from Shung-Hsi Yu.
13) Various minor misc improvements all over the place.
* https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (106 commits)
bpf: Optimize rcu_barrier usage between hash map and bpf_mem_alloc.
bpf: Remove usage of kmem_cache from bpf_mem_cache.
bpf: Remove prealloc-only restriction for sleepable bpf programs.
bpf: Prepare bpf_mem_alloc to be used by sleepable bpf programs.
bpf: Remove tracing program restriction on map types
bpf: Convert percpu hash map to per-cpu bpf_mem_alloc.
bpf: Add percpu allocation support to bpf_mem_alloc.
bpf: Batch call_rcu callbacks instead of SLAB_TYPESAFE_BY_RCU.
bpf: Adjust low/high watermarks in bpf_mem_cache
bpf: Optimize call_rcu in non-preallocated hash map.
bpf: Optimize element count in non-preallocated hash map.
bpf: Relax the requirement to use preallocated hash maps in tracing progs.
samples/bpf: Reduce syscall overhead in map_perf_test.
selftests/bpf: Improve test coverage of test_maps
bpf: Convert hash map to bpf_mem_alloc.
bpf: Introduce any context BPF specific memory allocator.
selftest/bpf: Add test for bpf_getsockopt()
bpf: Change bpf_getsockopt(SOL_IPV6) to reuse do_ipv6_getsockopt()
bpf: Change bpf_getsockopt(SOL_IP) to reuse do_ip_getsockopt()
bpf: Change bpf_getsockopt(SOL_TCP) to reuse do_tcp_getsockopt()
...
====================
Link: https://lore.kernel.org/r/20220905161136.9150-1-daniel@iogearbox.net
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
CFTYPE_PRESSURE is used to flag PSI related files so that they are not
created if PSI is disabled during boot. It's a bit weird to use a generic
flag to mark a specific file type. Let's instead move the PSI files into its
own cftypes array and add/rm them conditionally. This is a bit more code but
cleaner.
No userland visible changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Let's track whether a cftype is currently added or not using a new flag
__CFTYPE_ADDED so that duplicate operations can be failed safely and
consistently allow using empty cftypes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Currently, changes in "cpust.cpus" of a partition root is not allowed if
it violates the sibling cpu exclusivity rule when the check is done
in the validate_change() function. That is inconsistent with the
other cpuset changes that are always allowed but may make a partition
invalid.
Update the cpuset code to allow cpumask change even if it violates the
sibling cpu exclusivity rule, but invalidate the partition instead
just like the other changes. However, other sibling partitions with
conflicting cpumask will also be invalidated in order to not violating
the exclusivity rule. This behavior is specific to this partition
rule violation.
Note that a previous commit has made sibling cpu exclusivity rule check
the last check of validate_change(). So if -EINVAL is returned, we can
be sure that sibling cpu exclusivity rule violation is the only rule
that is broken.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This patch moves down the exclusive cpu and memory check in
validate_change(). There is no functional change.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
There are a number of different reasons which can cause a partition to
become invalid. A user seeing an invalid partition may not know exactly
why. To help user to get a better understanding of the underlying reason,
The cpuset.cpus.partition control file, when read, will now report the
reason why a partition become invalid. When a partition does become
invalid, reading the control file will show "root invalid (<reason>)"
where <reason> is a string that describes why the partition is invalid.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cpuset v1 uses the sched_load_balance control file to determine if load
balancing should be enabled. Cpuset v2 gets rid of sched_load_balance
as its use may require disabling load balancing at cgroup root.
For workloads that require very low latency like DPDK, the latency
jitters caused by periodic load balancing may exceed the desired
latency limit.
When cpuset v2 is in use, the only way to avoid this latency cost is to
use the "isolcpus=" kernel boot option to isolate a set of CPUs. After
the kernel boot, however, there is no way to add or remove CPUs from
this isolated set. For workloads that are more dynamic in nature, that
means users have to provision enough CPUs for the worst case situation
resulting in excess idle CPUs.
To address this issue for cpuset v2, a new cpuset.cpus.partition type
"isolated" is added which allows the creation of a cpuset partition
without load balancing. This will allow system administrators to
dynamically adjust the size of isolated partition to the current need
of the workload without rebooting the system.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Currently, enabling a partition root is only allowed if all the
constraints of a valid partition are satisfied. Even changes to
"cpuset.cpus" may not be allowed in some cases. Moreover, there are
limits to changes made to a parent cpuset if it is a valid partition
root. This is contrary to the general cgroup v2 philosophy.
This patch relaxes the constraints of changing the state of "cpuset.cpus"
and "cpuset.cpus.partition". Now all valid changes ("member" or "root")
to "cpuset.cpus.partition" are allowed even if there are child cpusets
underneath it.
Trying to make a cpuset a partition root, however, will cause its state
to become invalid if the following constraints of a valid partition
root are not satisfied.
1) The "cpuset.cpus" is non-empty and exclusive.
2) The parent cpuset is a valid partition root.
3) The "cpuset.cpus" overlaps parent's "cpuset.cpus".
Similarly, almost all changes to "cpuset.cpus" are allowed with the
exception that if the underlying CS_CPU_EXCLUSIVE flag is set, the
exclusivity rule will still apply.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Currently, a partition root cannot have empty "cpuset.cpus.effective".
As a result, a parent partition root cannot distribute out all its
CPUs to child partitions with no CPUs left. However in most cases,
there shouldn't be any tasks associated with intermediate nodes of the
default hierarchy. So the current rule is too restrictive and can waste
valuable CPU resource.
To address this issue, we are now allowing a partition to have empty
"cpuset.cpus.effective" as long as it has no task. Since cpuset is
threaded, no-internal-process rule does not apply. So it is possible
to have tasks in a partition root with child sub-partitions even though
that should be uncommon.
A parent partition with no task can now have all its CPUs distributed out
to its child partitions. The top cpuset always have some house-keeping
tasks running and so its list of effective cpu can't be empty.
Once a partition with empty "cpuset.cpus.effective" is formed, no
new task can be moved into it until "cpuset.cpus.effective" becomes
non-empty.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The partition root state (PRS) macro names do not currently match the
external names. Change them to match the external names and add helper
functions to read or change the state.
Shorten the cpuset argument of update_parent_subparts_cpumask() to cs
to match other cpuset functions.
Remove the new_prs argument from notify_partition_change() as the
cs->partition_root_state has already been set to new_prs before it
is called.
There is no functional change.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Previously, update_tasks_cpumask() is not supposed to be called with
top cpuset. With cpuset partition that takes CPUs away from the top
cpuset, adjusting the cpus_mask of the tasks in the top cpuset is
necessary. Percpu kthreads, however, are ignored.
Fixes: ee8dde0cd2ce ("cpuset: Add new v2 cpuset.sched.partition flag")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
pids.peak tracks the high watermark of usage for number of pids. This
helps give a better baseline on which to set pids.max. Polling
pids.current isn't really feasible, since it would potentially miss
short-lived spikes.
This interface is analogous to memory.peak.
Signed-off-by: Josh Don <joshdon@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
There's a seemingly harmless data-race around cgrp_dfl_visible detected by
kernel concurrency sanitizer. Let's remove it by throwing WRITE/READ_ONCE at
it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Abhishek Shah <abhishek.shah@columbia.edu>
Cc: Gabriel Ryan <gabe@cs.columbia.edu>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Link: https://lore.kernel.org/netdev/20220819072256.fn7ctciefy4fc4cu@wittgenstein/
Add cgroup_file_show() which allows toggling visibility of a cgroup file
using the new kernfs_show(). This will be used to hide psi interface files
on cgroups where it's disabled.
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Tested-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220828050440.734579-10-tj@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cgroup id is user provided datum hence extend its return domain to
include possible error reason (similar to cgroup_get_from_fd()).
This change also fixes commit d4ccaf58a847 ("bpf: Introduce cgroup
iter") that would use NULL instead of proper error handling in
d4ccaf58a847 ("bpf: Introduce cgroup iter").
Additionally, neither of: fc_appid_store, bpf_iter_attach_cgroup,
mem_cgroup_get_from_ino (callers of cgroup_get_from_fd) is built without
CONFIG_CGROUPS (depends via CONFIG_BLK_CGROUP, direct, transitive
CONFIG_MEMCG respectively) transitive, so drop the singular definition
not needed with !CONFIG_CGROUPS.
Fixes: d4ccaf58a847 ("bpf: Introduce cgroup iter")
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cgroup ids are resolved in the global scope. That may be needed sometime
(in future) but currently it violates virtual view provided through
cgroup namespaces.
There are currently following users of the resolution:
- fc_appid_store
- bpf_iter_attach_cgroup
- mem_cgroup_get_from_ino
None of the is a called on behalf of kernel but the resolution is made
with proper userspace context, hence the default to current->nsproxy
makes sens. (This doesn't rule out cgroup_get_from_id with cgroup NS
parameter in the future.)
Since cgroup ids are defined on v2 hierarchy only, we simply check
existence in the cgroup namespace by looking at ancestry on the default
hierarchy.
Fixes: 6b658c4863c1 ("scsi: cgroup: Add cgroup_get_from_id()")
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
cgroup_get_from_path() is not widely used function. Its callers presume
the path is resolved under cgroup namespace. (There is one caller
currently and resolving in init NS won't make harm (netfilter). However,
future users may be subject to different effects when resolving
globally.)
Since, there's currently no use for the global resolution, modify the
existing function to take cgroup NS into account.
Fixes: a79a908fd2b0 ("cgroup: introduce cgroup namespaces")
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Enable bpf programs to make use of rstat to collect cgroup hierarchical
stats efficiently:
- Add cgroup_rstat_updated() kfunc, for bpf progs that collect stats.
- Add cgroup_rstat_flush() sleepable kfunc, for bpf progs that read stats.
- Add an empty bpf_rstat_flush() hook that is called during rstat
flushing, for bpf progs that flush stats to attach to. Attaching a bpf
prog to this hook effectively registers it as a flush callback.
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Hao Luo <haoluo@google.com>
Link: https://lore.kernel.org/r/20220824233117.1312810-4-haoluo@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Root cause:
The rebind_subsystems() is no lock held when move css object from A
list to B list,then let B's head be treated as css node at
list_for_each_entry_rcu().
Solution:
Add grace period before invalidating the removed rstat_css_node.
Reported-by: Jing-Ting Wu <jing-ting.wu@mediatek.com>
Suggested-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Jing-Ting Wu <jing-ting.wu@mediatek.com>
Tested-by: Jing-Ting Wu <jing-ting.wu@mediatek.com>
Link: https://lore.kernel.org/linux-arm-kernel/d8f0bc5e2fb6ed259f9334c83279b4c011283c41.camel@mediatek.com/T/
Acked-by: Mukesh Ojha <quic_mojha@quicinc.com>
Fixes: a7df69b81aac ("cgroup: rstat: support cgroup1")
Cc: stable@vger.kernel.org # v5.13+
Signed-off-by: Tejun Heo <tj@kernel.org>
Andrii Nakryiko says:
====================
bpf-next 2022-08-17
We've added 45 non-merge commits during the last 14 day(s) which contain
a total of 61 files changed, 986 insertions(+), 372 deletions(-).
The main changes are:
1) New bpf_ktime_get_tai_ns() BPF helper to access CLOCK_TAI, from Kurt
Kanzenbach and Jesper Dangaard Brouer.
2) Few clean ups and improvements for libbpf 1.0, from Andrii Nakryiko.
3) Expose crash_kexec() as kfunc for BPF programs, from Artem Savkov.
4) Add ability to define sleepable-only kfuncs, from Benjamin Tissoires.
5) Teach libbpf's bpf_prog_load() and bpf_map_create() to gracefully handle
unsupported names on old kernels, from Hangbin Liu.
6) Allow opting out from auto-attaching BPF programs by libbpf's BPF skeleton,
from Hao Luo.
7) Relax libbpf's requirement for shared libs to be marked executable, from
Henqgi Chen.
8) Improve bpf_iter internals handling of error returns, from Hao Luo.
9) Few accommodations in libbpf to support GCC-BPF quirks, from James Hilliard.
10) Fix BPF verifier logic around tracking dynptr ref_obj_id, from Joanne Koong.
11) bpftool improvements to handle full BPF program names better, from Manu
Bretelle.
12) bpftool fixes around libcap use, from Quentin Monnet.
13) BPF map internals clean ups and improvements around memory allocations,
from Yafang Shao.
14) Allow to use cgroup_get_from_file() on cgroupv1, allowing BPF cgroup
iterator to work on cgroupv1, from Yosry Ahmed.
15) BPF verifier internal clean ups, from Dave Marchevsky and Joanne Koong.
16) Various fixes and clean ups for selftests/bpf and vmtest.sh, from Daniel
Xu, Artem Savkov, Joanne Koong, Andrii Nakryiko, Shibin Koikkara Reeny.
* https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (45 commits)
selftests/bpf: Few fixes for selftests/bpf built in release mode
libbpf: Clean up deprecated and legacy aliases
libbpf: Streamline bpf_attr and perf_event_attr initialization
libbpf: Fix potential NULL dereference when parsing ELF
selftests/bpf: Tests libbpf autoattach APIs
libbpf: Allows disabling auto attach
selftests/bpf: Fix attach point for non-x86 arches in test_progs/lsm
libbpf: Making bpf_prog_load() ignore name if kernel doesn't support
selftests/bpf: Update CI kconfig
selftests/bpf: Add connmark read test
selftests/bpf: Add existing connection bpf_*_ct_lookup() test
bpftool: Clear errno after libcap's checks
bpf: Clear up confusion in bpf_skb_adjust_room()'s documentation
bpftool: Fix a typo in a comment
libbpf: Add names for auxiliary maps
bpf: Use bpf_map_area_alloc consistently on bpf map creation
bpf: Make __GFP_NOWARN consistent in bpf map creation
bpf: Use bpf_map_area_free instread of kvfree
bpf: Remove unneeded memset in queue_stack_map creation
libbpf: preserve errno across pr_warn/pr_info/pr_debug
...
====================
Link: https://lore.kernel.org/r/20220817215656.1180215-1-andrii@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Bringing up a CPU may involve creating and destroying tasks which requires
read-locking threadgroup_rwsem, so threadgroup_rwsem nests inside
cpus_read_lock(). However, cpuset's ->attach(), which may be called with
thredagroup_rwsem write-locked, also wants to disable CPU hotplug and
acquires cpus_read_lock(), leading to a deadlock.
Fix it by guaranteeing that ->attach() is always called with CPU hotplug
disabled and removing cpus_read_lock() call from cpuset_attach().
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-and-tested-by: Imran Khan <imran.f.khan@oracle.com>
Reported-and-tested-by: Xuewen Yan <xuewen.yan@unisoc.com>
Fixes: 05c7b7a92cc8 ("cgroup/cpuset: Fix a race between cpuset_attach() and cpu hotplug")
Cc: stable@vger.kernel.org # v5.17+
psi_trigger_create()'s 'nbytes' parameter is not used, so we can remove it.
Signed-off-by: Hao Jia <jiahao.os@bytedance.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Every cgroup knows all its ancestors through its ->ancestor_ids[]. There's
no advantage to remembering the IDs instead of the pointers directly and
this makes the array useless for finding an actual ancestor cgroup forcing
cgroup_ancestor() to iteratively walk up the hierarchy instead. Let's
replace cgroup->ancestor_ids[] with ->ancestors[] and remove the walking-up
from cgroup_ancestor().
While at it, improve comments around cgroup_root->cgrp_ancestor_storage.
This patch shouldn't cause user-visible behavior differences.
v2: Update cgroup_ancestor() to use ->ancestors[].
v3: cgroup_root->cgrp_ancestor_storage's type is updated to match
cgroup->ancestors[]. Better comments.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
cgroup_get_from_file() currently fails with -EBADF if called on cgroup
v1. However, the current implementation works on cgroup v1 as well, so
the restriction is unnecessary.
This enabled cgroup_get_from_fd() to work on cgroup v1, which would be
the only thing stopping bpf cgroup_iter from supporting cgroup v1.
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Hao Luo <haoluo@google.com>
Link: https://lore.kernel.org/r/20220805214821.1058337-3-haoluo@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-urgent-2022-08-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Ingo Molnar:
"Various fixes: a deadline scheduler fix, a migration fix, a Sparse fix
and a comment fix"
* tag 'sched-urgent-2022-08-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/core: Do not requeue task on CPU excluded from cpus_mask
sched/rt: Fix Sparse warnings due to undefined rt.c declarations
exit: Fix typo in comment: s/sub-theads/sub-threads
sched, cpuset: Fix dl_cpu_busy() panic due to empty cs->cpus_allowed
* threadgroup_rwsem write locking is skipped when configuring controllers in
empty subtrees. Combined with CLONE_INTO_CGROUP, this allows the common
static usage pattern to not grab threadgroup_rwsem at all (glibc still
doesn't seem ready for CLONE_INTO_CGROUP unfortunately).
* threadgroup_rwsem used to be put into non-percpu mode by default due to
latency concerns in specific use cases. There's no reason for everyone
else to pay for it. Make the behavior optional.
* psi no longer allocates memory when disabled.
along with some code cleanups.
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Merge tag 'cgroup-for-5.20' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup updates from Tejun Heo:
"Several core optimizations:
- threadgroup_rwsem write locking is skipped when configuring
controllers in empty subtrees.
Combined with CLONE_INTO_CGROUP, this allows the common static
usage pattern to not grab threadgroup_rwsem at all (glibc still
doesn't seem ready for CLONE_INTO_CGROUP unfortunately).
- threadgroup_rwsem used to be put into non-percpu mode by default
due to latency concerns in specific use cases. There's no reason
for everyone else to pay for it. Make the behavior optional.
- psi no longer allocates memory when disabled.
... along with some code cleanups"
* tag 'cgroup-for-5.20' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: Skip subtree root in cgroup_update_dfl_csses()
cgroup: remove "no" prefixed mount options
cgroup: Make !percpu threadgroup_rwsem operations optional
cgroup: Add "no" prefixed mount options
cgroup: Elide write-locking threadgroup_rwsem when updating csses on an empty subtree
cgroup.c: remove redundant check for mixable cgroup in cgroup_migrate_vet_dst
cgroup.c: add helper __cset_cgroup_from_root to cleanup duplicated codes
psi: dont alloc memory for psi by default
With cgroup v2, the cpuset's cpus_allowed mask can be empty indicating
that the cpuset will just use the effective CPUs of its parent. So
cpuset_can_attach() can call task_can_attach() with an empty mask.
This can lead to cpumask_any_and() returns nr_cpu_ids causing the call
to dl_bw_of() to crash due to percpu value access of an out of bound
CPU value. For example:
[80468.182258] BUG: unable to handle page fault for address: ffffffff8b6648b0
:
[80468.191019] RIP: 0010:dl_cpu_busy+0x30/0x2b0
:
[80468.207946] Call Trace:
[80468.208947] cpuset_can_attach+0xa0/0x140
[80468.209953] cgroup_migrate_execute+0x8c/0x490
[80468.210931] cgroup_update_dfl_csses+0x254/0x270
[80468.211898] cgroup_subtree_control_write+0x322/0x400
[80468.212854] kernfs_fop_write_iter+0x11c/0x1b0
[80468.213777] new_sync_write+0x11f/0x1b0
[80468.214689] vfs_write+0x1eb/0x280
[80468.215592] ksys_write+0x5f/0xe0
[80468.216463] do_syscall_64+0x5c/0x80
[80468.224287] entry_SYSCALL_64_after_hwframe+0x44/0xae
Fix that by using effective_cpus instead. For cgroup v1, effective_cpus
is the same as cpus_allowed. For v2, effective_cpus is the real cpumask
to be used by tasks within the cpuset anyway.
Also update task_can_attach()'s 2nd argument name to cs_effective_cpus to
reflect the change. In addition, a check is added to task_can_attach()
to guard against the possibility that cpumask_any_and() may return a
value >= nr_cpu_ids.
Fixes: 7f51412a415d ("sched/deadline: Fix bandwidth check/update when migrating tasks between exclusive cpusets")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/20220803015451.2219567-1-longman@redhat.com
Load-balancing improvements:
============================
- Improve NUMA balancing on AMD Zen systems for affine workloads.
- Improve the handling of reduced-capacity CPUs in load-balancing.
- Energy Model improvements: fix & refine all the energy fairness metrics (PELT),
and remove the conservative threshold requiring 6% energy savings to
migrate a task. Doing this improves power efficiency for most workloads,
and also increases the reliability of energy-efficiency scheduling.
- Optimize/tweak select_idle_cpu() to spend (much) less time searching
for an idle CPU on overloaded systems. There's reports of several
milliseconds spent there on large systems with large workloads ...
[ Since the search logic changed, there might be behavioral side effects. ]
- Improve NUMA imbalance behavior. On certain systems
with spare capacity, initial placement of tasks is non-deterministic,
and such an artificial placement imbalance can persist for a long time,
hurting (and sometimes helping) performance.
The fix is to make fork-time task placement consistent with runtime
NUMA balancing placement.
Note that some performance regressions were reported against this,
caused by workloads that are not memory bandwith limited, which benefit
from the artificial locality of the placement bug(s). Mel Gorman's
conclusion, with which we concur, was that consistency is better than
random workload benefits from non-deterministic bugs:
"Given there is no crystal ball and it's a tradeoff, I think it's
better to be consistent and use similar logic at both fork time
and runtime even if it doesn't have universal benefit."
- Improve core scheduling by fixing a bug in sched_core_update_cookie() that
caused unnecessary forced idling.
- Improve wakeup-balancing by allowing same-LLC wakeup of idle CPUs for newly
woken tasks.
- Fix a newidle balancing bug that introduced unnecessary wakeup latencies.
ABI improvements/fixes:
=======================
- Do not check capabilities and do not issue capability check denial messages
when a scheduler syscall doesn't require privileges. (Such as increasing niceness.)
- Add forced-idle accounting to cgroups too.
- Fix/improve the RSEQ ABI to not just silently accept unknown flags.
(No existing tooling is known to have learned to rely on the previous behavior.)
- Depreciate the (unused) RSEQ_CS_FLAG_NO_RESTART_ON_* flags.
Optimizations:
==============
- Optimize & simplify leaf_cfs_rq_list()
- Micro-optimize set_nr_{and_not,if}_polling() via try_cmpxchg().
Misc fixes & cleanups:
======================
- Fix the RSEQ self-tests on RISC-V and Glibc 2.35 systems.
- Fix a full-NOHZ bug that can in some cases result in the tick not being
re-enabled when the last SCHED_RT task is gone from a runqueue but there's
still SCHED_OTHER tasks around.
- Various PREEMPT_RT related fixes.
- Misc cleanups & smaller fixes.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2022-08-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
"Load-balancing improvements:
- Improve NUMA balancing on AMD Zen systems for affine workloads.
- Improve the handling of reduced-capacity CPUs in load-balancing.
- Energy Model improvements: fix & refine all the energy fairness
metrics (PELT), and remove the conservative threshold requiring 6%
energy savings to migrate a task. Doing this improves power
efficiency for most workloads, and also increases the reliability
of energy-efficiency scheduling.
- Optimize/tweak select_idle_cpu() to spend (much) less time
searching for an idle CPU on overloaded systems. There's reports of
several milliseconds spent there on large systems with large
workloads ...
[ Since the search logic changed, there might be behavioral side
effects. ]
- Improve NUMA imbalance behavior. On certain systems with spare
capacity, initial placement of tasks is non-deterministic, and such
an artificial placement imbalance can persist for a long time,
hurting (and sometimes helping) performance.
The fix is to make fork-time task placement consistent with runtime
NUMA balancing placement.
Note that some performance regressions were reported against this,
caused by workloads that are not memory bandwith limited, which
benefit from the artificial locality of the placement bug(s). Mel
Gorman's conclusion, with which we concur, was that consistency is
better than random workload benefits from non-deterministic bugs:
"Given there is no crystal ball and it's a tradeoff, I think
it's better to be consistent and use similar logic at both fork
time and runtime even if it doesn't have universal benefit."
- Improve core scheduling by fixing a bug in
sched_core_update_cookie() that caused unnecessary forced idling.
- Improve wakeup-balancing by allowing same-LLC wakeup of idle CPUs
for newly woken tasks.
- Fix a newidle balancing bug that introduced unnecessary wakeup
latencies.
ABI improvements/fixes:
- Do not check capabilities and do not issue capability check denial
messages when a scheduler syscall doesn't require privileges. (Such
as increasing niceness.)
- Add forced-idle accounting to cgroups too.
- Fix/improve the RSEQ ABI to not just silently accept unknown flags.
(No existing tooling is known to have learned to rely on the
previous behavior.)
- Depreciate the (unused) RSEQ_CS_FLAG_NO_RESTART_ON_* flags.
Optimizations:
- Optimize & simplify leaf_cfs_rq_list()
- Micro-optimize set_nr_{and_not,if}_polling() via try_cmpxchg().
Misc fixes & cleanups:
- Fix the RSEQ self-tests on RISC-V and Glibc 2.35 systems.
- Fix a full-NOHZ bug that can in some cases result in the tick not
being re-enabled when the last SCHED_RT task is gone from a
runqueue but there's still SCHED_OTHER tasks around.
- Various PREEMPT_RT related fixes.
- Misc cleanups & smaller fixes"
* tag 'sched-core-2022-08-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (32 commits)
rseq: Kill process when unknown flags are encountered in ABI structures
rseq: Deprecate RSEQ_CS_FLAG_NO_RESTART_ON_* flags
sched/core: Fix the bug that task won't enqueue into core tree when update cookie
nohz/full, sched/rt: Fix missed tick-reenabling bug in dequeue_task_rt()
sched/core: Always flush pending blk_plug
sched/fair: fix case with reduced capacity CPU
sched/core: Use try_cmpxchg in set_nr_{and_not,if}_polling
sched/core: add forced idle accounting for cgroups
sched/fair: Remove the energy margin in feec()
sched/fair: Remove task_util from effective utilization in feec()
sched/fair: Use the same cpumask per-PD throughout find_energy_efficient_cpu()
sched/fair: Rename select_idle_mask to select_rq_mask
sched, drivers: Remove max param from effective_cpu_util()/sched_cpu_util()
sched/fair: Decay task PELT values during wakeup migration
sched/fair: Provide u64 read for 32-bits arch helper
sched/fair: Introduce SIS_UTIL to search idle CPU based on sum of util_avg
sched: only perform capability check on privileged operation
sched: Remove unused function group_first_cpu()
sched/fair: Remove redundant word " *"
selftests/rseq: check if libc rseq support is registered
...
The cgroup_update_dfl_csses() function updates css associations when a
cgroup's subtree_control file is modified. Any changes made to a cgroup's
subtree_control file, however, will only affect its descendants but not
the cgroup itself. So there is no point in migrating csses associated
with that cgroup. We can skip them instead.
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
30312730bd02 ("cgroup: Add "no" prefixed mount options") added "no" prefixed
mount options to allow turning them off and 6a010a49b63a ("cgroup: Make
!percpu threadgroup_rwsem operations optional") added one more "no" prefixed
mount option. However, Michal pointed out that the "no" prefixed options
aren't necessary in allowing mount options to be turned off:
# grep group /proc/mounts
cgroup2 /sys/fs/cgroup cgroup2 rw,nosuid,nodev,relatime,nsdelegate,memory_recursiveprot 0 0
# mount -o remount,nsdelegate,memory_recursiveprot none /sys/fs/cgroup
# grep cgroup /proc/mounts
cgroup2 /sys/fs/cgroup cgroup2 rw,relatime,nsdelegate,memory_recursiveprot 0 0
Note that this is different from the remount behavior when the mount(1) is
invoked without the device argument - "none":
# grep cgroup /proc/mounts
cgroup2 /sys/fs/cgroup cgroup2 rw,nosuid,nodev,noexec,relatime,nsdelegate,memory_recursiveprot 0 0
# mount -o remount,nsdelegate,memory_recursiveprot /sys/fs/cgroup
# grep cgroup /proc/mounts
cgroup2 /sys/fs/cgroup cgroup2 rw,nosuid,nodev,noexec,relatime,nsdelegate,memory_recursiveprot 0 0
While a bit confusing, given that there is a way to turn off the options,
there's no reason to have the explicit "no" prefixed options. Let's remove
them.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
3942a9bd7b58 ("locking, rcu, cgroup: Avoid synchronize_sched() in
__cgroup_procs_write()") disabled percpu operations on threadgroup_rwsem
because the impiled synchronize_rcu() on write locking was pushing up the
latencies too much for android which constantly moves processes between
cgroups.
This makes the hotter paths - fork and exit - slower as they're always
forced into the slow path. There is no reason to force this on everyone
especially given that more common static usage pattern can now completely
avoid write-locking the rwsem. Write-locking is elided when turning on and
off controllers on empty sub-trees and CLONE_INTO_CGROUP enables seeding a
cgroup without grabbing the rwsem.
Restore the default percpu operations and introduce the mount option
"favordynmods" and config option CGROUP_FAVOR_DYNMODS for users who need
lower latencies for the dynamic operations.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Michal Koutn� <mkoutny@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Dmitry Shmidt <dimitrysh@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
We allow modifying these mount options via remount. Let's add "no" prefixed
variants so that they can be turned off too.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
