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When a task exits, css_set_move_task(tsk, cset, NULL, false) unlinks the task
from its cgroup. From the cgroup's perspective, the task is now gone. If this
makes the cgroup empty, it can be removed, triggering ->css_offline() callbacks
that notify controllers the cgroup is going offline resource-wise.
However, the exiting task can still run, perform memory operations, and schedule
until the final context switch in finish_task_switch(). This creates a confusing
situation where controllers are told a cgroup is offline while resource
activities are still happening in it. While this hasn't broken existing
controllers, it has caused direct confusion for sched_ext schedulers.
Split cgroup_task_exit() into two functions. cgroup_task_exit() now only calls
the subsystem exit callbacks and continues to be called from do_exit(). The
css_set cleanup is moved to the new cgroup_task_dead() which is called from
finish_task_switch() after the final context switch, so that the cgroup only
appears empty after the task is truly done running.
This also reorders operations so that subsys->exit() is now called before
unlinking from the cgroup, which shouldn't break anything.
Cc: Dan Schatzberg <dschatzberg@meta.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The current names cgroup_exit(), cgroup_release(), and cgroup_free() are
confusing because they look like they're operating on cgroups themselves when
they're actually task lifecycle hooks. For example, cgroup_init() initializes
the cgroup subsystem while cgroup_exit() is a task exit notification to
cgroup. Rename them to cgroup_task_exit(), cgroup_task_release(), and
cgroup_task_free() to make it clear that these operate on tasks.
Cc: Dan Schatzberg <dschatzberg@meta.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next
Pull bpf updates from Alexei Starovoitov:
- Support pulling non-linear xdp data with bpf_xdp_pull_data() kfunc
(Amery Hung)
Applied as a stable branch in bpf-next and net-next trees.
- Support reading skb metadata via bpf_dynptr (Jakub Sitnicki)
Also a stable branch in bpf-next and net-next trees.
- Enforce expected_attach_type for tailcall compatibility (Daniel
Borkmann)
- Replace path-sensitive with path-insensitive live stack analysis in
the verifier (Eduard Zingerman)
This is a significant change in the verification logic. More details,
motivation, long term plans are in the cover letter/merge commit.
- Support signed BPF programs (KP Singh)
This is another major feature that took years to materialize.
Algorithm details are in the cover letter/marge commit
- Add support for may_goto instruction to s390 JIT (Ilya Leoshkevich)
- Add support for may_goto instruction to arm64 JIT (Puranjay Mohan)
- Fix USDT SIB argument handling in libbpf (Jiawei Zhao)
- Allow uprobe-bpf program to change context registers (Jiri Olsa)
- Support signed loads from BPF arena (Kumar Kartikeya Dwivedi and
Puranjay Mohan)
- Allow access to union arguments in tracing programs (Leon Hwang)
- Optimize rcu_read_lock() + migrate_disable() combination where it's
used in BPF subsystem (Menglong Dong)
- Introduce bpf_task_work_schedule*() kfuncs to schedule deferred
execution of BPF callback in the context of a specific task using the
kernel’s task_work infrastructure (Mykyta Yatsenko)
- Enforce RCU protection for KF_RCU_PROTECTED kfuncs (Kumar Kartikeya
Dwivedi)
- Add stress test for rqspinlock in NMI (Kumar Kartikeya Dwivedi)
- Improve the precision of tnum multiplier verifier operation
(Nandakumar Edamana)
- Use tnums to improve is_branch_taken() logic (Paul Chaignon)
- Add support for atomic operations in arena in riscv JIT (Pu Lehui)
- Report arena faults to BPF error stream (Puranjay Mohan)
- Search for tracefs at /sys/kernel/tracing first in bpftool (Quentin
Monnet)
- Add bpf_strcasecmp() kfunc (Rong Tao)
- Support lookup_and_delete_elem command in BPF_MAP_STACK_TRACE (Tao
Chen)
* tag 'bpf-next-6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (197 commits)
libbpf: Replace AF_ALG with open coded SHA-256
selftests/bpf: Add stress test for rqspinlock in NMI
selftests/bpf: Add test case for different expected_attach_type
bpf: Enforce expected_attach_type for tailcall compatibility
bpftool: Remove duplicate string.h header
bpf: Remove duplicate crypto/sha2.h header
libbpf: Fix error when st-prefix_ops and ops from differ btf
selftests/bpf: Test changing packet data from kfunc
selftests/bpf: Add stacktrace map lookup_and_delete_elem test case
selftests/bpf: Refactor stacktrace_map case with skeleton
bpf: Add lookup_and_delete_elem for BPF_MAP_STACK_TRACE
selftests/bpf: Fix flaky bpf_cookie selftest
selftests/bpf: Test changing packet data from global functions with a kfunc
bpf: Emit struct bpf_xdp_sock type in vmlinux BTF
selftests/bpf: Task_work selftest cleanup fixes
MAINTAINERS: Delete inactive maintainers from AF_XDP
bpf: Mark kfuncs as __noclone
selftests/bpf: Add kprobe multi write ctx attach test
selftests/bpf: Add kprobe write ctx attach test
selftests/bpf: Add uprobe context ip register change test
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup updates from Tejun Heo:
- Extensive cpuset code cleanup and refactoring work with no functional
changes: CPU mask computation logic refactoring, introducing new
helpers, removing redundant code paths, and improving error handling
for better maintainability.
- A few bug fixes to cpuset including fixes for partition creation
failures when isolcpus is in use, missing error returns, and null
pointer access prevention in free_tmpmasks().
- Core cgroup changes include replacing the global percpu_rwsem with
per-threadgroup rwsem when writing to cgroup.procs for better
scalability, workqueue conversions to use WQ_PERCPU and
system_percpu_wq to prepare for workqueue default switching from
percpu to unbound, and removal of unused code including the
post_attach callback.
- New cgroup.stat.local time accounting feature that tracks frozen time
duration.
- Misc changes including selftests updates (new freezer time tests and
backward compatibility fixes), documentation sync, string function
safety improvements, and 64-bit division fixes.
* tag 'cgroup-for-6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (39 commits)
cpuset: remove is_prs_invalid helper
cpuset: remove impossible warning in update_parent_effective_cpumask
cpuset: remove redundant special case for null input in node mask update
cpuset: fix missing error return in update_cpumask
cpuset: Use new excpus for nocpu error check when enabling root partition
cpuset: fix failure to enable isolated partition when containing isolcpus
Documentation: cgroup-v2: Sync manual toctree
cpuset: use partition_cpus_change for setting exclusive cpus
cpuset: use parse_cpulist for setting cpus.exclusive
cpuset: introduce partition_cpus_change
cpuset: refactor cpus_allowed_validate_change
cpuset: refactor out validate_partition
cpuset: introduce cpus_excl_conflict and mems_excl_conflict helpers
cpuset: refactor CPU mask buffer parsing logic
cpuset: Refactor exclusive CPU mask computation logic
cpuset: change return type of is_partition_[in]valid to bool
cpuset: remove unused assignment to trialcs->partition_root_state
cpuset: move the root cpuset write check earlier
cgroup/cpuset: Remove redundant rcu_read_lock/unlock() in spin_lock
cgroup: Remove redundant rcu_read_lock/unlock() in spin_lock
...
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull namespace updates from Christian Brauner:
"This contains a larger set of changes around the generic namespace
infrastructure of the kernel.
Each specific namespace type (net, cgroup, mnt, ...) embedds a struct
ns_common which carries the reference count of the namespace and so
on.
We open-coded and cargo-culted so many quirks for each namespace type
that it just wasn't scalable anymore. So given there's a bunch of new
changes coming in that area I've started cleaning all of this up.
The core change is to make it possible to correctly initialize every
namespace uniformly and derive the correct initialization settings
from the type of the namespace such as namespace operations, namespace
type and so on. This leaves the new ns_common_init() function with a
single parameter which is the specific namespace type which derives
the correct parameters statically. This also means the compiler will
yell as soon as someone does something remotely fishy.
The ns_common_init() addition also allows us to remove ns_alloc_inum()
and drops any special-casing of the initial network namespace in the
network namespace initialization code that Linus complained about.
Another part is reworking the reference counting. The reference
counting was open-coded and copy-pasted for each namespace type even
though they all followed the same rules. This also removes all open
accesses to the reference count and makes it private and only uses a
very small set of dedicated helpers to manipulate them just like we do
for e.g., files.
In addition this generalizes the mount namespace iteration
infrastructure introduced a few cycles ago. As reminder, the vfs makes
it possible to iterate sequentially and bidirectionally through all
mount namespaces on the system or all mount namespaces that the caller
holds privilege over. This allow userspace to iterate over all mounts
in all mount namespaces using the listmount() and statmount() system
call.
Each mount namespace has a unique identifier for the lifetime of the
systems that is exposed to userspace. The network namespace also has a
unique identifier working exactly the same way. This extends the
concept to all other namespace types.
The new nstree type makes it possible to lookup namespaces purely by
their identifier and to walk the namespace list sequentially and
bidirectionally for all namespace types, allowing userspace to iterate
through all namespaces. Looking up namespaces in the namespace tree
works completely locklessly.
This also means we can move the mount namespace onto the generic
infrastructure and remove a bunch of code and members from struct
mnt_namespace itself.
There's a bunch of stuff coming on top of this in the future but for
now this uses the generic namespace tree to extend a concept
introduced first for pidfs a few cycles ago. For a while now we have
supported pidfs file handles for pidfds. This has proven to be very
useful.
This extends the concept to cover namespaces as well. It is possible
to encode and decode namespace file handles using the common
name_to_handle_at() and open_by_handle_at() apis.
As with pidfs file handles, namespace file handles are exhaustive,
meaning it is not required to actually hold a reference to nsfs in
able to decode aka open_by_handle_at() a namespace file handle.
Instead the FD_NSFS_ROOT constant can be passed which will let the
kernel grab a reference to the root of nsfs internally and thus decode
the file handle.
Namespaces file descriptors can already be derived from pidfds which
means they aren't subject to overmount protection bugs. IOW, it's
irrelevant if the caller would not have access to an appropriate
/proc/<pid>/ns/ directory as they could always just derive the
namespace based on a pidfd already.
It has the same advantage as pidfds. It's possible to reliably and for
the lifetime of the system refer to a namespace without pinning any
resources and to compare them trivially.
Permission checking is kept simple. If the caller is located in the
namespace the file handle refers to they are able to open it otherwise
they must hold privilege over the owning namespace of the relevant
namespace.
The namespace file handle layout is exposed as uapi and has a stable
and extensible format. For now it simply contains the namespace
identifier, the namespace type, and the inode number. The stable
format means that userspace may construct its own namespace file
handles without going through name_to_handle_at() as they are already
allowed for pidfs and cgroup file handles"
* tag 'namespace-6.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (65 commits)
ns: drop assert
ns: move ns type into struct ns_common
nstree: make struct ns_tree private
ns: add ns_debug()
ns: simplify ns_common_init() further
cgroup: add missing ns_common include
ns: use inode initializer for initial namespaces
selftests/namespaces: verify initial namespace inode numbers
ns: rename to __ns_ref
nsfs: port to ns_ref_*() helpers
net: port to ns_ref_*() helpers
uts: port to ns_ref_*() helpers
ipv4: use check_net()
net: use check_net()
net-sysfs: use check_net()
user: port to ns_ref_*() helpers
time: port to ns_ref_*() helpers
pid: port to ns_ref_*() helpers
ipc: port to ns_ref_*() helpers
cgroup: port to ns_ref_*() helpers
...
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We have dedicated headers for all namespace types. Add one for the
cgroup namespace as well. Now it's consistent for all namespace types
and easy to figure out what to include.
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Every namespace type has a container_of(ns, <ns_type>, ns) static inline
function that is currently not exposed in the header. So we have a bunch
of places that open-code it via container_of(). Move it to the headers
so we can use it directly.
Reviewed-by: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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The bpf_cgroup_from_id kfunc relies on cgroup_get_from_id to obtain the
cgroup corresponding to a given cgroup ID. This helper can be called in
a lot of contexts where the current thread can be random. A recent
example was its use in sched_ext's ops.tick(), to obtain the root cgroup
pointer. Since the current task can be whatever random user space task
preempted by the timer tick, this makes the behavior of the helper
unreliable.
Refactor out __cgroup_get_from_id as the non-namespace aware version of
cgroup_get_from_id, and change bpf_cgroup_from_id to make use of it.
There is no compatibility breakage here, since changing the namespace
against which the lookup is being done to the root cgroup namespace only
permits a wider set of lookups to succeed now. The cgroup IDs across
namespaces are globally unique, and thus don't need to be retranslated.
Reported-by: Dan Schatzberg <dschatzberg@meta.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20250915032618.1551762-2-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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With the introduction of clone3 in commit 7f192e3cd316 ("fork: add
clone3") the effective bit width of clone_flags on all architectures was
increased from 32-bit to 64-bit, with a new type of u64 for the flags.
However, for most consumers of clone_flags the interface was not
changed from the previous type of unsigned long.
While this works fine as long as none of the new 64-bit flag bits
(CLONE_CLEAR_SIGHAND and CLONE_INTO_CGROUP) are evaluated, this is still
undesirable in terms of the principle of least surprise.
Thus, this commit fixes all relevant interfaces of callees to
sys_clone3/copy_process (excluding the architecture-specific
copy_thread) to consistently pass clone_flags as u64, so that
no truncation to 32-bit integers occurs on 32-bit architectures.
Signed-off-by: Simon Schuster <schuster.simon@siemens-energy.com>
Link: https://lore.kernel.org/20250901-nios2-implement-clone3-v2-2-53fcf5577d57@siemens-energy.com
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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The CS_ONLINE flag was introduced prior to the CSS_ONLINE flag in the
cpuset subsystem. Currently, the flag setting sequence is as follows:
1. cpuset_css_online() sets CS_ONLINE
2. css->flags gets CSS_ONLINE set
...
3. cgroup->kill_css sets CSS_DYING
4. cpuset_css_offline() clears CS_ONLINE
5. css->flags clears CSS_ONLINE
The is_cpuset_online() check currently occurs between steps 1 and 3.
However, it would be equally safe to perform this check between steps 2
and 3, as CSS_ONLINE provides the same synchronization guarantee as
CS_ONLINE.
Since CS_ONLINE is redundant with CSS_ONLINE and provides no additional
synchronization benefits, we can safely remove it to simplify the code.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup updates from Tejun Heo:
- cgroup rstat shared the tracking tree across all controllers with the
rationale being that a cgroup which is using one resource is likely
to be using other resources at the same time (ie. if something is
allocating memory, it's probably consuming CPU cycles).
However, this turned out to not scale very well especially with memcg
using rstat for internal operations which made memcg stat read and
flush patterns substantially different from other controllers. JP
Kobryn split the rstat tree per controller.
- cgroup BPF support was hooking into cgroup init/exit paths directly.
Convert them to use a notifier chain instead so that other usages can
be added easily. The two of the patches which implement this are
mislabeled as belonging to sched_ext instead of cgroup. Sorry.
- Relatively minor cpuset updates
- Documentation updates
* tag 'cgroup-for-6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (23 commits)
sched_ext: Convert cgroup BPF support to use cgroup_lifetime_notifier
sched_ext: Introduce cgroup_lifetime_notifier
cgroup: Minor reorganization of cgroup_create()
cgroup, docs: cpu controller's interaction with various scheduling policies
cgroup, docs: convert space indentation to tab indentation
cgroup: avoid per-cpu allocation of size zero rstat cpu locks
cgroup, docs: be specific about bandwidth control of rt processes
cgroup: document the rstat per-cpu initialization
cgroup: helper for checking rstat participation of css
cgroup: use subsystem-specific rstat locks to avoid contention
cgroup: use separate rstat trees for each subsystem
cgroup: compare css to cgroup::self in helper for distingushing css
cgroup: warn on rstat usage by early init subsystems
cgroup/cpuset: drop useless cpumask_empty() in compute_effective_exclusive_cpumask()
cgroup/rstat: Improve cgroup_rstat_push_children() documentation
cgroup: fix goto ordering in cgroup_init()
cgroup: fix pointer check in css_rstat_init()
cgroup/cpuset: Add warnings to catch inconsistency in exclusive CPUs
cgroup/cpuset: Fix obsolete comment in cpuset_css_offline()
cgroup/cpuset: Always use cpu_active_mask
...
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull misc vfs updates from Christian Brauner:
"This contains the usual selections of misc updates for this cycle.
Features:
- Use folios for symlinks in the page cache
FUSE already uses folios for its symlinks. Mirror that conversion
in the generic code and the NFS code. That lets us get rid of a few
folio->page->folio conversions in this path, and some of the few
remaining users of read_cache_page() / read_mapping_page()
- Try and make a few filesystem operations killable on the VFS
inode->i_mutex level
- Add sysctl vfs_cache_pressure_denom for bulk file operations
Some workloads need to preserve more dentries than we currently
allow through out sysctl interface
A HDFS servers with 12 HDDs per server, on a HDFS datanode startup
involves scanning all files and caching their metadata (including
dentries and inodes) in memory. Each HDD contains approximately 2
million files, resulting in a total of ~20 million cached dentries
after initialization
To minimize dentry reclamation, they set vfs_cache_pressure to 1.
Despite this configuration, memory pressure conditions can still
trigger reclamation of up to 50% of cached dentries, reducing the
cache from 20 million to approximately 10 million entries. During
the subsequent cache rebuild period, any HDFS datanode restart
operation incurs substantial latency penalties until full cache
recovery completes
To maintain service stability, more dentries need to be preserved
during memory reclamation. The current minimum reclaim ratio (1/100
of total dentries) remains too aggressive for such workload. This
patch introduces vfs_cache_pressure_denom for more granular cache
pressure control
The configuration [vfs_cache_pressure=1,
vfs_cache_pressure_denom=10000] effectively maintains the full 20
million dentry cache under memory pressure, preventing datanode
restart performance degradation
- Avoid some jumps in inode_permission() using likely()/unlikely()
- Avid a memory access which is most likely a cache miss when
descending into devcgroup_inode_permission()
- Add fastpath predicts for stat() and fdput()
- Anonymous inodes currently don't come with a proper mode causing
issues in the kernel when we want to add useful VFS debug assert.
Fix that by giving them a proper mode and masking it off when we
report it to userspace which relies on them not having any mode
- Anonymous inodes currently allow to change inode attributes because
the VFS falls back to simple_setattr() if i_op->setattr isn't
implemented. This means the ownership and mode for every single
user of anon_inode_inode can be changed. Block that as it's either
useless or actively harmful. If specific ownership is needed the
respective subsystem should allocate anonymous inodes from their
own private superblock
- Raise SB_I_NODEV and SB_I_NOEXEC on the anonymous inode superblock
- Add proper tests for anonymous inode behavior
- Make it easy to detect proper anonymous inodes and to ensure that
we can detect them in codepaths such as readahead()
Cleanups:
- Port pidfs to the new anon_inode_{g,s}etattr() helpers
- Try to remove the uselib() system call
- Add unlikely branch hint return path for poll
- Add unlikely branch hint on return path for core_sys_select
- Don't allow signals to interrupt getdents copying for fuse
- Provide a size hint to dir_context for during readdir()
- Use writeback_iter directly in mpage_writepages
- Update compression and mtime descriptions in initramfs
documentation
- Update main netfs API document
- Remove useless plus one in super_cache_scan()
- Remove unnecessary NULL-check guards during setns()
- Add separate separate {get,put}_cgroup_ns no-op cases
Fixes:
- Fix typo in root= kernel parameter description
- Use KERN_INFO for infof()|info_plog()|infofc()
- Correct comments of fs_validate_description()
- Mark an unlikely if condition with unlikely() in
vfs_parse_monolithic_sep()
- Delete macro fsparam_u32hex()
- Remove unused and problematic validate_constant_table()
- Fix potential unsigned integer underflow in fs_name()
- Make file-nr output the total allocated file handles"
* tag 'vfs-6.16-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (43 commits)
fs: Pass a folio to page_put_link()
nfs: Use a folio in nfs_get_link()
fs: Convert __page_get_link() to use a folio
fs/read_write: make default_llseek() killable
fs/open: make do_truncate() killable
fs/open: make chmod_common() and chown_common() killable
include/linux/fs.h: add inode_lock_killable()
readdir: supply dir_context.count as readdir buffer size hint
vfs: Add sysctl vfs_cache_pressure_denom for bulk file operations
fuse: don't allow signals to interrupt getdents copying
Documentation: fix typo in root= kernel parameter description
include/cgroup: separate {get,put}_cgroup_ns no-op case
kernel/nsproxy: remove unnecessary guards
fs: use writeback_iter directly in mpage_writepages
fs: remove useless plus one in super_cache_scan()
fs: add S_ANON_INODE
fs: remove uselib() system call
device_cgroup: avoid access to ->i_rdev in the common case in devcgroup_inode_permission()
fs/fs_parse: Remove unused and problematic validate_constant_table()
fs: touch up predicts in inode_permission()
...
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Other subsystems may make use of the cgroup hierarchy with the cgroup_bpf
support being one such example. For such a feature, it's useful to be able
to hook into cgroup creation and destruction paths to perform
feature-specific initializations and cleanups.
Add cgroup_lifetime_notifier which generates CGROUP_LIFETIME_ONLINE and
CGROUP_LIFETIME_OFFLINE events whenever cgroups are created and destroyed,
respectively.
The next patch will convert cgroup_bpf to use the new notifier and other
uses are planned.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Adjust the implementation of css_is_cgroup() so that it compares the given
css to cgroup::self. Rename the function to css_is_self() in order to
reflect that. Change the existing css->ss NULL check to a warning in the
true branch. Finally, adjust call sites to use the new function name.
Signed-off-by: JP Kobryn <inwardvessel@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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When CONFIG_CGROUPS is not selected, {get,put}_cgroup_ns become no-ops
and therefore it is not necessary to compile in the code for changing
the reference count.
When CONFIG_CGROUP is selected, there is no valid case where
either of {get,put}_cgroup_ns() will be called with a NULL argument.
Signed-off-by: Joel Savitz <jsavitz@redhat.com>
Link: https://lore.kernel.org/20250508184930.183040-3-jsavitz@redhat.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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This non-functional change serves as preparation for moving to
subsystem-based rstat trees. To simplify future commits, change the
signatures of existing cgroup-based rstat functions to become css-based and
rename them to reflect that.
Though the signatures have changed, the implementations have not. Within
these functions use the css->cgroup pointer to obtain the associated cgroup
and allow code to function the same just as it did before this patch. At
applicable call sites, pass the subsystem-specific css pointer as an
argument or pass a pointer to cgroup::self if not in subsystem context.
Note that cgroup_rstat_updated_list() and cgroup_rstat_push_children()
are not altered yet since there would be a larger amount of css to
cgroup conversions which may overcomplicate the code at this
intermediate phase.
Signed-off-by: JP Kobryn <inwardvessel@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The cgroup struct has a css field called "self". The main difference
between this css and the others found in the cgroup::subsys array is that
cgroup::self has a NULL subsystem pointer. There are several places where
checks are performed to determine whether the css in question is
cgroup::self or not. Instead of accessing css->ss directly, introduce a
helper function that shows the intent and use where applicable.
Signed-off-by: JP Kobryn <inwardvessel@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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There is a possible race between removing a cgroup diectory that is
a partition root and the creation of a new partition. The partition
to be removed can be dying but still online, it doesn't not currently
participate in checking for exclusive CPUs conflict, but the exclusive
CPUs are still there in subpartitions_cpus and isolated_cpus. These
two cpumasks are global states that affect the operation of cpuset
partitions. The exclusive CPUs in dying cpusets will only be removed
when cpuset_css_offline() function is called after an RCU delay.
As a result, it is possible that a new partition can be created with
exclusive CPUs that overlap with those of a dying one. When that dying
partition is finally offlined, it removes those overlapping exclusive
CPUs from subpartitions_cpus and maybe isolated_cpus resulting in an
incorrect CPU configuration.
This bug was found when a warning was triggered in
remote_partition_disable() during testing because the subpartitions_cpus
mask was empty.
One possible way to fix this is to iterate the dying cpusets as well and
avoid using the exclusive CPUs in those dying cpusets. However, this
can still cause random partition creation failures or other anomalies
due to racing. A better way to fix this race is to reset the partition
state at the moment when a cpuset is being killed.
Introduce a new css_killed() CSS function pointer and call it, if
defined, before setting CSS_DYING flag in kill_css(). Also update the
css_is_dying() helper to use the CSS_DYING flag introduced by commit
33c35aa48178 ("cgroup: Prevent kill_css() from being called more than
once") for proper synchronization.
Add a new cpuset_css_killed() function to reset the partition state of
a valid partition root if it is being killed.
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>
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Now that the rstat lock is being re-acquired on every CPU iteration in
cgroup_rstat_flush_locked(), having the initially acquire the lock is
unnecessary and unclear.
Inline cgroup_rstat_flush_locked() into cgroup_rstat_flush() and move
the lock/unlock calls to the beginning and ending of the loop body to
make the critical section obvious.
cgroup_rstat_flush_hold/release() do not make much sense with the lock
being dropped and reacquired internally. Since it has no external
callers, remove it and explicitly acquire the lock in
cgroup_base_stat_cputime_show() instead.
This leaves the code with a single flushing function,
cgroup_rstat_flush().
Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Use one set of files when there is no difference between default and
legacy files, similar to regular subsys files registration. No
functional change.
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Acked-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Tejun Heo <tj@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext
Pull sched_ext support from Tejun Heo:
"This implements a new scheduler class called ‘ext_sched_class’, or
sched_ext, which allows scheduling policies to be implemented as BPF
programs.
The goals of this are:
- Ease of experimentation and exploration: Enabling rapid iteration
of new scheduling policies.
- Customization: Building application-specific schedulers which
implement policies that are not applicable to general-purpose
schedulers.
- Rapid scheduler deployments: Non-disruptive swap outs of scheduling
policies in production environments"
See individual commits for more documentation, but also the cover letter
for the latest series:
Link: https://lore.kernel.org/all/20240618212056.2833381-1-tj@kernel.org/
* tag 'sched_ext-for-6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: (110 commits)
sched: Move update_other_load_avgs() to kernel/sched/pelt.c
sched_ext: Don't trigger ops.quiescent/runnable() on migrations
sched_ext: Synchronize bypass state changes with rq lock
scx_qmap: Implement highpri boosting
sched_ext: Implement scx_bpf_dispatch[_vtime]_from_dsq()
sched_ext: Compact struct bpf_iter_scx_dsq_kern
sched_ext: Replace consume_local_task() with move_local_task_to_local_dsq()
sched_ext: Move consume_local_task() upward
sched_ext: Move sanity check and dsq_mod_nr() into task_unlink_from_dsq()
sched_ext: Reorder args for consume_local/remote_task()
sched_ext: Restructure dispatch_to_local_dsq()
sched_ext: Fix processs_ddsp_deferred_locals() by unifying DTL_INVALID handling
sched_ext: Make find_dsq_for_dispatch() handle SCX_DSQ_LOCAL_ON
sched_ext: Refactor consume_remote_task()
sched_ext: Rename scx_kfunc_set_sleepable to unlocked and relocate
sched_ext: Add missing static to scx_dump_data
sched_ext: Add missing static to scx_has_op[]
sched_ext: Temporarily work around pick_task_scx() being called without balance_scx()
sched_ext: Add a cgroup scheduler which uses flattened hierarchy
sched_ext: Add cgroup support
...
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Patch series "mm, memcg: cg2 memory{.swap,}.peak write handlers", v7.
This patch (of 2):
Other mechanisms for querying the peak memory usage of either a process or
v1 memory cgroup allow for resetting the high watermark. Restore parity
with those mechanisms, but with a less racy API.
For example:
- Any write to memory.max_usage_in_bytes in a cgroup v1 mount resets
the high watermark.
- writing "5" to the clear_refs pseudo-file in a processes's proc
directory resets the peak RSS.
This change is an evolution of a previous patch, which mostly copied the
cgroup v1 behavior, however, there were concerns about races/ownership
issues with a global reset, so instead this change makes the reset
filedescriptor-local.
Writing any non-empty string to the memory.peak and memory.swap.peak
pseudo-files reset the high watermark to the current usage for subsequent
reads through that same FD.
Notably, following Johannes's suggestion, this implementation moves the
O(FDs that have written) behavior onto the FD write(2) path. Instead, on
the page-allocation path, we simply add one additional watermark to
conditionally bump per-hierarchy level in the page-counter.
Additionally, this takes Longman's suggestion of nesting the
page-charging-path checks for the two watermarks to reduce the number of
common-case comparisons.
This behavior is particularly useful for work scheduling systems that need
to track memory usage of worker processes/cgroups per-work-item. Since
memory can't be squeezed like CPU can (the OOM-killer has opinions), these
systems need to track the peak memory usage to compute system/container
fullness when binpacking workitems.
Most notably, Vimeo's use-case involves a system that's doing global
binpacking across many Kubernetes pods/containers, and while we can use
PSI for some local decisions about overload, we strive to avoid packing
workloads too tightly in the first place. To facilitate this, we track
the peak memory usage. However, since we run with long-lived workers (to
amortize startup costs) we need a way to track the high watermark while a
work-item is executing. Polling runs the risk of missing short spikes
that last for timescales below the polling interval, and peak memory
tracking at the cgroup level is otherwise perfect for this use-case.
As this data is used to ensure that binpacked work ends up with sufficient
headroom, this use-case mostly avoids the inaccuracies surrounding
reclaimable memory.
Link: https://lkml.kernel.org/r/20240730231304.761942-1-davidf@vimeo.com
Link: https://lkml.kernel.org/r/20240729143743.34236-1-davidf@vimeo.com
Link: https://lkml.kernel.org/r/20240729143743.34236-2-davidf@vimeo.com
Signed-off-by: David Finkel <davidf@vimeo.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: Waiman Long <longman@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Linux 6.11-rc1
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Many core headers include cpumask.h for nothing. Drop it.
Link: https://lkml.kernel.org/r/20240528005648.182376-6-yury.norov@gmail.com
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Cc: Amit Daniel Kachhap <amit.kachhap@gmail.com>
Cc: Anna-Maria Behnsen <anna-maria@linutronix.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Yury Norov <yury.norov@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Factor out sched_weight_from/to_cgroup() which convert between scheduler
shares and cgroup weight. No functional change. The factored out functions
will be used by a new BPF extensible sched_class so that the weights can be
exposed to the BPF programs in a way which is consistent cgroup weights and
easier to interpret.
The weight conversions will be used regardless of cgroup usage. It's just
borrowing the cgroup weight range as it's more intuitive.
CGROUP_WEIGHT_MIN/DFL/MAX constants are moved outside CONFIG_CGROUPS so that
the conversion helpers can always be defined.
v2: The helpers are now defined regardless of COFNIG_CGROUPS.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: David Vernet <dvernet@meta.com>
Acked-by: Josh Don <joshdon@google.com>
Acked-by: Hao Luo <haoluo@google.com>
Acked-by: Barret Rhoden <brho@google.com>
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This commit enhances the ability to troubleshoot the global
cgroup_rstat_lock by introducing wrapper helper functions for the lock
along with associated tracepoints.
Although global, the cgroup_rstat_lock helper APIs and tracepoints take
arguments such as cgroup pointer and cpu_in_loop variable. This
adjustment is made because flushing occurs per cgroup despite the lock
being global. Hence, when troubleshooting, it's important to identify the
relevant cgroup. The cpu_in_loop variable is necessary because the global
lock may be released within the main flushing loop that traverses CPUs.
In the tracepoints, the cpu_in_loop value is set to -1 when acquiring the
main lock; otherwise, it denotes the CPU number processed last.
The new feature in this patchset is detecting when lock is contended. The
tracepoints are implemented with production in mind. For minimum overhead
attach to cgroup:cgroup_rstat_lock_contended, which only gets activated
when trylock detects lock is contended. A quick production check for
issues could be done via this perf commands:
perf record -g -e cgroup:cgroup_rstat_lock_contended
Next natural question would be asking how long time do lock contenders
wait for obtaining the lock. This can be answered by measuring the time
between cgroup:cgroup_rstat_lock_contended and cgroup:cgroup_rstat_locked
when args->contended is set. Like this bpftrace script:
bpftrace -e '
tracepoint:cgroup:cgroup_rstat_lock_contended {@start[tid]=nsecs}
tracepoint:cgroup:cgroup_rstat_locked {
if (args->contended) {
@wait_ns=hist(nsecs-@start[tid]); delete(@start[tid]);}}
interval:s:1 {time("%H:%M:%S "); print(@wait_ns); }'
Extending with time spend holding the lock will be more expensive as this
also looks at all the non-contended cases.
Like this bpftrace script:
bpftrace -e '
tracepoint:cgroup:cgroup_rstat_lock_contended {@start[tid]=nsecs}
tracepoint:cgroup:cgroup_rstat_locked { @locked[tid]=nsecs;
if (args->contended) {
@wait_ns=hist(nsecs-@start[tid]); delete(@start[tid]);}}
tracepoint:cgroup:cgroup_rstat_unlock {
@locked_ns=hist(nsecs-@locked[tid]); delete(@locked[tid]);}
interval:s:1 {time("%H:%M:%S "); print(@wait_ns);print(@locked_ns); }'
Signed-off-by: Jesper Dangaard Brouer <hawk@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
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A new helper is added for cgroup1 hierarchy:
- task_get_cgroup1
Acquires the associated cgroup of a task within a specific cgroup1
hierarchy. The cgroup1 hierarchy is identified by its hierarchy ID.
This helper function is added to facilitate the tracing of tasks within
a particular container or cgroup dir in BPF programs. It's important to
note that this helper is designed specifically for cgroup1 only.
tj: Use irsqsave/restore as suggested by Hou Tao <houtao@huaweicloud.com>.
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Hou Tao <houtao@huaweicloud.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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This patch makes some preparations for using css_task_iter_*() in BPF
Program.
1. Flags CSS_TASK_ITER_* are #define-s and it's not easy for bpf prog to
use them. Convert them to enum so bpf prog can take them from vmlinux.h.
2. In the next patch we will add css_task_iter_*() in common kfuncs which
is not safe. Since css_task_iter_*() does spin_unlock_irq() which might
screw up irq flags depending on the context where bpf prog is running.
So we should use irqsave/irqrestore here and the switching is harmless.
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20231018061746.111364-2-zhouchuyi@bytedance.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull mm updates from Andrew Morton:
- Yosry Ahmed brought back some cgroup v1 stats in OOM logs
- Yosry has also eliminated cgroup's atomic rstat flushing
- Nhat Pham adds the new cachestat() syscall. It provides userspace
with the ability to query pagecache status - a similar concept to
mincore() but more powerful and with improved usability
- Mel Gorman provides more optimizations for compaction, reducing the
prevalence of page rescanning
- Lorenzo Stoakes has done some maintanance work on the
get_user_pages() interface
- Liam Howlett continues with cleanups and maintenance work to the
maple tree code. Peng Zhang also does some work on maple tree
- Johannes Weiner has done some cleanup work on the compaction code
- David Hildenbrand has contributed additional selftests for
get_user_pages()
- Thomas Gleixner has contributed some maintenance and optimization
work for the vmalloc code
- Baolin Wang has provided some compaction cleanups,
- SeongJae Park continues maintenance work on the DAMON code
- Huang Ying has done some maintenance on the swap code's usage of
device refcounting
- Christoph Hellwig has some cleanups for the filemap/directio code
- Ryan Roberts provides two patch series which yield some
rationalization of the kernel's access to pte entries - use the
provided APIs rather than open-coding accesses
- Lorenzo Stoakes has some fixes to the interaction between pagecache
and directio access to file mappings
- John Hubbard has a series of fixes to the MM selftesting code
- ZhangPeng continues the folio conversion campaign
- Hugh Dickins has been working on the pagetable handling code, mainly
with a view to reducing the load on the mmap_lock
- Catalin Marinas has reduced the arm64 kmalloc() minimum alignment
from 128 to 8
- Domenico Cerasuolo has improved the zswap reclaim mechanism by
reorganizing the LRU management
- Matthew Wilcox provides some fixups to make gfs2 work better with the
buffer_head code
- Vishal Moola also has done some folio conversion work
- Matthew Wilcox has removed the remnants of the pagevec code - their
functionality is migrated over to struct folio_batch
* tag 'mm-stable-2023-06-24-19-15' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (380 commits)
mm/hugetlb: remove hugetlb_set_page_subpool()
mm: nommu: correct the range of mmap_sem_read_lock in task_mem()
hugetlb: revert use of page_cache_next_miss()
Revert "page cache: fix page_cache_next/prev_miss off by one"
mm/vmscan: fix root proactive reclaim unthrottling unbalanced node
mm: memcg: rename and document global_reclaim()
mm: kill [add|del]_page_to_lru_list()
mm: compaction: convert to use a folio in isolate_migratepages_block()
mm: zswap: fix double invalidate with exclusive loads
mm: remove unnecessary pagevec includes
mm: remove references to pagevec
mm: rename invalidate_mapping_pagevec to mapping_try_invalidate
mm: remove struct pagevec
net: convert sunrpc from pagevec to folio_batch
i915: convert i915_gpu_error to use a folio_batch
pagevec: rename fbatch_count()
mm: remove check_move_unevictable_pages()
drm: convert drm_gem_put_pages() to use a folio_batch
i915: convert shmem_sg_free_table() to use a folio_batch
scatterlist: add sg_set_folio()
...
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task_cgroup_path() is not used anymore. So remove it.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Previous patches removed the only caller of cgroup_rstat_flus |
