Commit Graph

473 Commits

Author SHA1 Message Date
Linus Torvalds
11f00074f7 cgroup: Fixes for v7.1-rc2
- During v6.19, cgroup task unlink was moved from do_exit() to after the
   final task switch to satisfy a controller invariant. That left the kernel
   seeing tasks past exit_signals() longer than userspace expected, and
   several v7.0 follow-ups tried to bridge the gap by making rmdir wait for
   the kernel side. None held up. The latest is an A-A deadlock when rmdir
   is invoked by the reaper of zombies whose pidns teardown the rmdir itself
   is waiting on, which points at the synchronizing approach being
   fundamentally wrong:
 
   - Take a different approach: drop the wait, leave rmdir's user-visible
     side returning as soon as cgroup.procs is empty, and defer the css
     percpu_ref kill that drives ->css_offline() until the cgroup is fully
     depopulated.
 
   - Tagged for stable. Somewhat invasive but contained. The hope is that
     fixing forward sticks. If not, the fallback is to revert the entire
     chain and rework on the development branch.
 
   - Doesn't plug a pre-existing analogous race in
     cgroup_apply_control_disable() (controller disable via subtree_control).
     Not a regression. The development branch will do the more invasive
     restructuring needed for that.
 
 - Documentation update for cgroup-v1 charge-commit section that still
   referenced functions removed when the memcg hugetlb try-commit-cancel
   protocol was retired.
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Merge tag 'cgroup-for-7.1-rc2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup fixes from Tejun Heo:

 - During v6.19, cgroup task unlink was moved from do_exit() to after the
   final task switch to satisfy a controller invariant. That left the kernel
   seeing tasks past exit_signals() longer than userspace expected, and
   several v7.0 follow-ups tried to bridge the gap by making rmdir wait for
   the kernel side. None held up.

   The latest is an A-A deadlock when rmdir is invoked by the reaper of
   zombies whose pidns teardown the rmdir itself is waiting on, which
   points at the synchronizing approach being fundamentally wrong.

   Take a different approach: drop the wait, leave rmdir's user-visible
   side returning as soon as cgroup.procs is empty, and defer the css
   percpu_ref kill that drives ->css_offline() until the cgroup is fully
   depopulated.

   Tagged for stable. Somewhat invasive but contained. The hope is that
   fixing forward sticks. If not, the fallback is to revert the entire
   chain and rework on the development branch.

   Note that this doesn't plug a pre-existing analogous race in
   cgroup_apply_control_disable() (controller disable via
   subtree_control). Not a regression. The development branch will do
   the more invasive restructuring needed for that.

 - Documentation update for cgroup-v1 charge-commit section that still
   referenced functions removed when the memcg hugetlb try-commit-cancel
   protocol was retired.

* tag 'cgroup-for-7.1-rc2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  docs: cgroup-v1: Update charge-commit section
  cgroup: Defer css percpu_ref kill on rmdir until cgroup is depopulated
2026-05-05 15:43:32 -07:00
Linus Torvalds
de95ad90fb sched_ext: Fixes for v7.1-rc2
- Fix idle CPU selection returning prev_cpu outside the task's cpus_ptr
   when the BPF caller's allowed mask was wider. Stable backport.
 
 - Two opposite-direction gaps in scx_task_iter's cgroup-scoped mode
   versus the global mode:
 
   - Tasks past exit_signals() are filtered by the cgroup walk but kept by
     global. Sub-scheduler enable abort leaked __scx_init_task() state.
     Add a CSS_TASK_ITER_WITH_DEAD flag to cgroup's task iterator
     (scx_task_iter is its only user) and use it.
 
   - Tasks past sched_ext_dead() are still returned, tripping
     WARN_ON_ONCE() in callers or making them touch torn-down state. Mark
     and skip under the per-task rq lock.
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Merge tag 'sched_ext-for-7.1-rc2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

Pull sched_ext fixes from Tejun Heo:

 - Fix idle CPU selection returning prev_cpu outside the task's cpus_ptr
   when the BPF caller's allowed mask was wider. Stable backport.

 - Two opposite-direction gaps in scx_task_iter's cgroup-scoped mode
   versus the global mode:

    - Tasks past exit_signals() are filtered by the cgroup walk but kept
      by global. Sub-scheduler enable abort leaked __scx_init_task()
      state. Add a CSS_TASK_ITER_WITH_DEAD flag to cgroup's task
      iterator (scx_task_iter is its only user) and use it.

    - Tasks past sched_ext_dead() are still returned, tripping
      WARN_ON_ONCE() in callers or making them touch torn-down state.
      Mark and skip under the per-task rq lock.

* tag 'sched_ext-for-7.1-rc2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
  sched_ext: idle: Recheck prev_cpu after narrowing allowed mask
  sched_ext: Skip past-sched_ext_dead() tasks in scx_task_iter_next_locked()
  cgroup, sched_ext: Include exiting tasks in cgroup iter
2026-05-05 15:22:04 -07:00
Tejun Heo
60f21a2649 cgroup, sched_ext: Include exiting tasks in cgroup iter
a72f73c4dd ("cgroup: Don't expose dead tasks in cgroup") made
css_task_iter_advance() skip exiting tasks so cgroup.procs stays consistent
with waitpid() visibility. Unfortunately, this broke scx_task_iter.

scx_task_iter walks either scx_tasks (global) or a cgroup subtree via
css_task_iter() and the two modes are expected to cover the same set of
tasks. After the above change the cgroup-scoped mode silently skips tasks
past exit_signals() that are still on scx_tasks.

scx_sub_enable_workfn()'s abort path is one of the symptoms: an exiting
SCX_TASK_SUB_INIT task can race past the cgroup iter leaking
__scx_init_task() state. Other iterations share the same gap.

Add CSS_TASK_ITER_WITH_DEAD to opt out of the skip and use it from
scx_task_iter().

Fixes: b0e4c2f8a0 ("sched_ext: Implement cgroup subtree iteration for scx_task_iter")
Reported-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
2026-05-04 09:06:03 -10:00
Tejun Heo
93618edf75 cgroup: Defer css percpu_ref kill on rmdir until cgroup is depopulated
A chain of commits going back to v7.0 reworked rmdir to satisfy the
controller invariant that a subsystem's ->css_offline() must not run while
tasks are still doing kernel-side work in the cgroup.

[1] d245698d72 ("cgroup: Defer task cgroup unlink until after the task is done switching out")
[2] a72f73c4dd ("cgroup: Don't expose dead tasks in cgroup")
[3] 1b164b876c ("cgroup: Wait for dying tasks to leave on rmdir")
[4] 4c56a8ac68 ("cgroup: Fix cgroup_drain_dying() testing the wrong condition")
[5] 13e786b64b ("cgroup: Increment nr_dying_subsys_* from rmdir context")

[1] moved task cset unlink from do_exit() to finish_task_switch() so a
task's cset link drops only after the task has fully stopped scheduling.
That made tasks past exit_signals() linger on cset->tasks until their final
context switch, which led to a series of problems as what userspace expected
to see after rmdir diverged from what the kernel needs to wait for. [2]-[5]
tried to bridge that divergence: [2] filtered the exiting tasks from
cgroup.procs; [3] had rmdir(2) sleep in TASK_UNINTERRUPTIBLE for them; [4]
fixed the wait's condition; [5] made nr_dying_subsys_* visible
synchronously.

The cgroup_drain_dying() wait in [3] turned out to be a dead end. When the
rmdir caller is also the reaper of a zombie that pins a pidns teardown (e.g.
host PID 1 systemd reaping orphan pids that were re-parented to it during
the same teardown), rmdir blocks in TASK_UNINTERRUPTIBLE waiting for those
pids to free, the pids can't free because PID 1 is the reaper and it's stuck
in rmdir, and the system A-A deadlocks. No internal lock ordering breaks
this; the wait itself is the bug.

The css killing side that drove the original reorder, however, can be made
cleanly asynchronous: ->css_offline() is already async, run from
css_killed_work_fn() driven by percpu_ref_kill_and_confirm(). The fix is to
make that chain start only after all tasks have left the cgroup. rmdir's
user-visible side then returns as soon as cgroup.procs and friends are
empty, while ->css_offline() still runs only after the cgroup is fully
drained.

Verified by the original reproducer (pidns teardown + zombie reaper, runs
under vng) which hangs vanilla and succeeds here, and by per-commit
deterministic repros for [2], [3], [4], [5] with a boot parameter that
widens the post-exit_signals() window so each state is reliably reachable.
Some stress tests on top of that.

cgroup_apply_control_disable() has the same shape of pre-existing race:
when a controller is disabled via subtree_control, kill_css() ran
synchronously while tasks past exit_signals() could still be linked to
the cgroup's csets, and ->css_offline() could fire before they drained.
This patch preserves the existing synchronous behavior at that call site
(kill_css_sync() + kill_css_finish() back-to-back) and a follow-up patch
will defer kill_css_finish() there using a per-css trigger.

This seems like the right approach and I don't see problems with it. The
changes are somewhat invasive but not excessively so, so backporting to
-stable should be okay. If something does turn out to be wrong, the fallback
is to revert the entire chain ([1]-[5]) and rework in the development branch
instead.

v2: Pin cgrp across the deferred destroy work with explicit
    cgroup_get()/cgroup_put() around queue_work() and the work_fn. v1
    wasn't actually broken (ordered cgroup_offline_wq + queue_work order
    in cgroup_task_dead() saved it) but the explicit ref removes the
    dependency on those non-obvious invariants. Also note the
    pre-existing cgroup_apply_control_disable() race in the description;
    a follow-up will defer kill_css_finish() there.

Fixes: 1b164b876c ("cgroup: Wait for dying tasks to leave on rmdir")
Cc: stable@vger.kernel.org # v7.0+
Reported-and-tested-by: Martin Pitt <martin@piware.de>
Link: https://lore.kernel.org/all/afHNg2VX2jy9bW7y@piware.de/
Link: https://lore.kernel.org/all/35e0670adb4abeab13da2c321582af9f@kernel.org/
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2026-05-04 08:52:26 -10:00
Linus Torvalds
3b3bea6d4b cgroup: Fixes for v7.1-rc1
- Fix UAF race in psi pressure_write() against cgroup file release by
   extending cgroup_mutex coverage and ordering of->priv access after
   cgroup_kn_lock_live().
 
 - Fix integer overflow in rdmacg_try_charge() when usage equals INT_MAX
   by performing the increment in s64.
 
 - Fix asymmetric DL bandwidth accounting on cpuset attach rollback by
   recording the CPU used by dl_bw_alloc() so cancel_attach() returns
   the reservation to the same root domain.
 
 - Fix nr_dying_subsys_* race that briefly showed 0 in cgroup.stat after
   rmdir by incrementing from kill_css() instead of offline_css().
 
 - Typo fix in cgroup-v2 documentation.
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Merge tag 'cgroup-for-7.1-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup fixes from Tejun Heo:

 - Fix UAF race in psi pressure_write() against cgroup file release by
   extending cgroup_mutex coverage and ordering of->priv access after
   cgroup_kn_lock_live()

 - Fix integer overflow in rdmacg_try_charge() when usage equals INT_MAX
   by performing the increment in s64

 - Fix asymmetric DL bandwidth accounting on cpuset attach rollback by
   recording the CPU used by dl_bw_alloc() so cancel_attach() returns
   the reservation to the same root domain

 - Fix nr_dying_subsys_* race that briefly showed 0 in cgroup.stat after
   rmdir by incrementing from kill_css() instead of offline_css()

 - Typo fix in cgroup-v2 documentation

* tag 'cgroup-for-7.1-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  docs: cgroup: fix typo 'protetion' -> 'protection'
  cgroup: Increment nr_dying_subsys_* from rmdir context
  cgroup/cpuset: record DL BW alloc CPU for attach rollback
  cgroup/rdma: fix integer overflow in rdmacg_try_charge()
  sched/psi: fix race between file release and pressure write
2026-04-27 16:51:27 -07:00
Petr Malat
13e786b64b cgroup: Increment nr_dying_subsys_* from rmdir context
Incrementing nr_dying_subsys_* in offline_css(), which is executed by
cgroup_offline_wq worker, leads to a race where user can see the value
to be 0 if he reads cgroup.stat after calling rmdir and before the worker
executes. This makes the user wrongly expect resources released by the
removed cgroup to be available for a new assignment.

Increment nr_dying_subsys_* from kill_css(), which is called from the
cgroup_rmdir() context.

Fixes: ab03125268 ("cgroup: Show # of subsystem CSSes in cgroup.stat")
Signed-off-by: Petr Malat <oss@malat.biz>
Signed-off-by: Tejun Heo <tj@kernel.org>
2026-04-23 07:37:40 -10:00
Linus Torvalds
40735a683b mm.git review status for linus..mm-stable
Everything:
 
 Total patches:       121
 Reviews/patch:       2.11
 Reviewed rate:       90%
 
 Excluding DAMON:
 
 Total patches:       113
 Reviews/patch:       2.25
 Reviewed rate:       96%
 
 - The 33 patch series "Eliminate Dying Memory Cgroup" from Qi Zheng and
   Muchun Song addresses the longstanding "dying memcg problem".  A
   situation wherein a no-longer-used memory control group will hang around
   for an extended period pointlessly consuming memory.  The [0/N]
   changelog has a good overview of this work.
 
 - The 3 patch series "fix unexpected type conversions and potential
   overflows" from Qi Zheng fixes a couple of potential 32-bit/64-bit
   issues which were identified during review of the "Eliminate Dying
   Memory Cgroup" series.
 
 - The 6 patch series "kho: history: track previous kernel version and
   kexec boot count" from Breno Leitao uses Kexec Handover (KHO) to pass
   the previous kernel's version string and the number of kexec reboots
   since the last cold boot to the next kernel, and prints it at boot time.
 
 - The 4 patch series "liveupdate: prevent double preservation" from
   Pasha Tatashin teaches LUO to avoid managing the same file across
   different active sessions.
 
 - The 10 patch series "liveupdate: Fix module unloading and unregister
   API" from Pasha Tatashin addresses an issue with how LUO handles module
   reference counting and unregistration during module unloading.
 
 - The 2 patch series "zswap pool per-CPU acomp_ctx simplifications" from
   Kanchana Sridhar simplifies and cleans up the zswap crypto compression
   handling and improves the lifecycle management of zswap pool's per-CPU
   acomp_ctx resources.
 
 - The 2 patch series "mm/damon/core: fix damon_call()/damos_walk() vs
   kdmond exit race" from SeongJae Park addresses unlikely but possible
   leaks and deadlocks in damon_call() and damon_walk().
 
 - The 2 patch series "mm/damon/core: validate damos_quota_goal->nid"
   from SeongJae Park fixes a couple of root-only wild pointer
   dereferences.
 
 - The 2 patch series "Docs/admin-guide/mm/damon: warn commit_inputs vs
   other params race" from SeongJae Park updates the DAMON documentation to
   warn operators about potential races which can occur if the
   commit_inputs parameter is altered at the wrong time.
 
 - The 3 patch series "Minor hmm_test fixes and cleanups" from Alistair
   Popple implements two bugfixes a cleanup for the HMM kernel selftests.
 
 - The 6 patch series "Modify memfd_luo code" from Chenghao Duan provides
   cleanups, simplifications and speedups in the memfd_lou code.
 
 - The 4 patch series "mm, kvm: allow uffd support in guest_memfd" from
   Mike Rapoport enables support for userfaultfd in guest_memfd.
 
 - The 6 patch series "selftests/mm: skip several tests when thp is not
   available" from Chunyu Hu fixes several issues in the selftests code
   which were causing breakage when the tests were run on CONFIG_THP=n
   kernels.
 
 - The 2 patch series "mm/mprotect: micro-optimization work" from Pedro
   Falcato implements a couple of nice speedups for mprotect().
 
 - The 3 patch series "MAINTAINERS: update KHO and LIVE UPDATE entries"
   from Pratyush Yadav reflects upcoming changes in the maintenance of KHO,
   LUO, memfd_luo, kexec, crash, kdump and probably other kexec-based
   things - they are being moved out of mm.git and into a new git tree.
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Merge tag 'mm-stable-2026-04-18-02-14' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull more MM updates from Andrew Morton:

 - "Eliminate Dying Memory Cgroup" (Qi Zheng and Muchun Song)

   Address the longstanding "dying memcg problem". A situation wherein a
   no-longer-used memory control group will hang around for an extended
   period pointlessly consuming memory

 - "fix unexpected type conversions and potential overflows" (Qi Zheng)

   Fix a couple of potential 32-bit/64-bit issues which were identified
   during review of the "Eliminate Dying Memory Cgroup" series

 - "kho: history: track previous kernel version and kexec boot count"
   (Breno Leitao)

   Use Kexec Handover (KHO) to pass the previous kernel's version string
   and the number of kexec reboots since the last cold boot to the next
   kernel, and print it at boot time

 - "liveupdate: prevent double preservation" (Pasha Tatashin)

   Teach LUO to avoid managing the same file across different active
   sessions

 - "liveupdate: Fix module unloading and unregister API" (Pasha
   Tatashin)

   Address an issue with how LUO handles module reference counting and
   unregistration during module unloading

 - "zswap pool per-CPU acomp_ctx simplifications" (Kanchana Sridhar)

   Simplify and clean up the zswap crypto compression handling and
   improve the lifecycle management of zswap pool's per-CPU acomp_ctx
   resources

 - "mm/damon/core: fix damon_call()/damos_walk() vs kdmond exit race"
   (SeongJae Park)

   Address unlikely but possible leaks and deadlocks in damon_call() and
   damon_walk()

 - "mm/damon/core: validate damos_quota_goal->nid" (SeongJae Park)

   Fix a couple of root-only wild pointer dereferences

 - "Docs/admin-guide/mm/damon: warn commit_inputs vs other params race"
   (SeongJae Park)

   Update the DAMON documentation to warn operators about potential
   races which can occur if the commit_inputs parameter is altered at
   the wrong time

 - "Minor hmm_test fixes and cleanups" (Alistair Popple)

   Bugfixes and a cleanup for the HMM kernel selftests

 - "Modify memfd_luo code" (Chenghao Duan)

   Cleanups, simplifications and speedups to the memfd_lou code

 - "mm, kvm: allow uffd support in guest_memfd" (Mike Rapoport)

   Support for userfaultfd in guest_memfd

 - "selftests/mm: skip several tests when thp is not available" (Chunyu
   Hu)

   Fix several issues in the selftests code which were causing breakage
   when the tests were run on CONFIG_THP=n kernels

 - "mm/mprotect: micro-optimization work" (Pedro Falcato)

   A couple of nice speedups for mprotect()

 - "MAINTAINERS: update KHO and LIVE UPDATE entries" (Pratyush Yadav)

   Document upcoming changes in the maintenance of KHO, LUO, memfd_luo,
   kexec, crash, kdump and probably other kexec-based things - they are
   being moved out of mm.git and into a new git tree

* tag 'mm-stable-2026-04-18-02-14' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (121 commits)
  MAINTAINERS: add page cache reviewer
  mm/vmscan: avoid false-positive -Wuninitialized warning
  MAINTAINERS: update Dave's kdump reviewer email address
  MAINTAINERS: drop include/linux/liveupdate from LIVE UPDATE
  MAINTAINERS: drop include/linux/kho/abi/ from KHO
  MAINTAINERS: update KHO and LIVE UPDATE maintainers
  MAINTAINERS: update kexec/kdump maintainers entries
  mm/migrate_device: remove dead migration entry check in migrate_vma_collect_huge_pmd()
  selftests: mm: skip charge_reserved_hugetlb without killall
  userfaultfd: allow registration of ranges below mmap_min_addr
  mm/vmstat: fix vmstat_shepherd double-scheduling vmstat_update
  mm/hugetlb: fix early boot crash on parameters without '=' separator
  zram: reject unrecognized type= values in recompress_store()
  docs: proc: document ProtectionKey in smaps
  mm/mprotect: special-case small folios when applying permissions
  mm/mprotect: move softleaf code out of the main function
  mm: remove '!root_reclaim' checking in should_abort_scan()
  mm/sparse: fix comment for section map alignment
  mm/page_io: use sio->len for PSWPIN accounting in sio_read_complete()
  selftests/mm: transhuge_stress: skip the test when thp not available
  ...
2026-04-19 08:01:17 -07:00
Qi Zheng
8285917d6f mm: memcontrol: prepare for reparenting non-hierarchical stats
To resolve the dying memcg issue, we need to reparent LRU folios of child
memcg to its parent memcg.  This could cause problems for non-hierarchical
stats.

As Yosry Ahmed pointed out:

In short, if memory is charged to a dying cgroup at the time of
reparenting, when the memory gets uncharged the stats updates will occur
at the parent. This will update both hierarchical and non-hierarchical
stats of the parent, which would corrupt the parent's non-hierarchical
stats (because those counters were never incremented when the memory was
charged).

Now we have the following two types of non-hierarchical stats, and they
are only used in CONFIG_MEMCG_V1:

a. memcg->vmstats->state_local[i]
b. pn->lruvec_stats->state_local[i]

To ensure that these non-hierarchical stats work properly, we need to
reparent these non-hierarchical stats after reparenting LRU folios. To
this end, this commit makes the following preparations:

1. implement reparent_state_local() to reparent non-hierarchical stats
2. make css_killed_work_fn() to be called in rcu work, and implement
   get_non_dying_memcg_start() and get_non_dying_memcg_end() to avoid race
   between mod_memcg_state()/mod_memcg_lruvec_state()
   and reparent_state_local()

Link: https://lore.kernel.org/e862995c45a7101a541284b6ebee5e5c32c89066.1772711148.git.zhengqi.arch@bytedance.com
Co-developed-by: Yosry Ahmed <yosry@kernel.org>
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Allen Pais <apais@linux.microsoft.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Chen Ridong <chenridong@huawei.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
Cc: Harry Yoo <harry.yoo@oracle.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Imran Khan <imran.f.khan@oracle.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <Liam.Howlett@oracle.com>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2026-04-18 00:10:47 -07:00
Edward Adam Davis
a5b98009f1 sched/psi: fix race between file release and pressure write
A potential race condition exists between pressure write and cgroup file
release regarding the priv member of struct kernfs_open_file, which
triggers the uaf reported in [1].

Consider the following scenario involving execution on two separate CPUs:

   CPU0					CPU1
   ====					====
					vfs_rmdir()
					kernfs_iop_rmdir()
					cgroup_rmdir()
					cgroup_kn_lock_live()
					cgroup_destroy_locked()
					cgroup_addrm_files()
					cgroup_rm_file()
					kernfs_remove_by_name()
					kernfs_remove_by_name_ns()
 vfs_write()				__kernfs_remove()
 new_sync_write()			kernfs_drain()
 kernfs_fop_write_iter()		kernfs_drain_open_files()
 cgroup_file_write()			kernfs_release_file()
 pressure_write()			cgroup_file_release()
 ctx = of->priv;
					kfree(ctx);
 					of->priv = NULL;
					cgroup_kn_unlock()
 cgroup_kn_lock_live()
 cgroup_get(cgrp)
 cgroup_kn_unlock()
 if (ctx->psi.trigger)  // here, trigger uaf for ctx, that is of->priv

The cgroup_rmdir() is protected by the cgroup_mutex, it also safeguards
the memory deallocation of of->priv performed within cgroup_file_release().
However, the operations involving of->priv executed within pressure_write()
are not entirely covered by the protection of cgroup_mutex. Consequently,
if the code in pressure_write(), specifically the section handling the
ctx variable executes after cgroup_file_release() has completed, a uaf
vulnerability involving of->priv is triggered.

Therefore, the issue can be resolved by extending the scope of the
cgroup_mutex lock within pressure_write() to encompass all code paths
involving of->priv, thereby properly synchronizing the race condition
occurring between cgroup_file_release() and pressure_write().

And, if an live kn lock can be successfully acquired while executing
the pressure write operation, it indicates that the cgroup deletion
process has not yet reached its final stage; consequently, the priv
pointer within open_file cannot be NULL. Therefore, the operation to
retrieve the ctx value must be moved to a point *after* the live kn
lock has been successfully acquired.

In another situation, specifically after entering cgroup_kn_lock_live()
but before acquiring cgroup_mutex, there exists a different class of
race condition:

CPU0: write memory.pressure               CPU1: write cgroup.pressure=0
===========================		  =============================

kernfs_fop_write_iter()
 kernfs_get_active_of(of)
 pressure_write()
   cgroup_kn_lock_live(memory.pressure)
     cgroup_tryget(cgrp)
     kernfs_break_active_protection(kn)
     ... blocks on cgroup_mutex

                                     	  cgroup_pressure_write()
                                     	  cgroup_kn_lock_live(cgroup.pressure)
                                     	  cgroup_file_show(memory.pressure, false)
                                     	    kernfs_show(false)
                                     	      kernfs_drain_open_files()
                                     	        cgroup_file_release(of)
                                     	          kfree(ctx)
                                     	            of->priv = NULL
                                     	  cgroup_kn_unlock()

   ... acquires cgroup_mutex
   ctx = of->priv;        // may now be NULL
   if (ctx->psi.trigger)  // NULL dereference

Consequently, there is a possibility that of->priv is NULL, the pressure
write needs to check for this.

Now that the scope of the cgroup_mutex has been expanded, the original
explicit cgroup_get/put operations are no longer necessary, this is
because acquiring/releasing the live kn lock inherently executes a
cgroup get/put operation.

[1]
BUG: KASAN: slab-use-after-free in pressure_write+0xa4/0x210 kernel/cgroup/cgroup.c:4011
Call Trace:
 pressure_write+0xa4/0x210 kernel/cgroup/cgroup.c:4011
 cgroup_file_write+0x36f/0x790 kernel/cgroup/cgroup.c:4311
 kernfs_fop_write_iter+0x3b0/0x540 fs/kernfs/file.c:352

Allocated by task 9352:
 cgroup_file_open+0x90/0x3a0 kernel/cgroup/cgroup.c:4256
 kernfs_fop_open+0x9eb/0xcb0 fs/kernfs/file.c:724
 do_dentry_open+0x83d/0x13e0 fs/open.c:949

Freed by task 9353:
 cgroup_file_release+0xd6/0x100 kernel/cgroup/cgroup.c:4283
 kernfs_release_file fs/kernfs/file.c:764 [inline]
 kernfs_drain_open_files+0x392/0x720 fs/kernfs/file.c:834
 kernfs_drain+0x470/0x600 fs/kernfs/dir.c:525

Fixes: 0e94682b73 ("psi: introduce psi monitor")
Reported-by: syzbot+33e571025d88efd1312c@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=33e571025d88efd1312c
Tested-by: syzbot+33e571025d88efd1312c@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
Reviewed-by: Chen Ridong <chenridong@huaweicloud.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
2026-04-17 07:25:09 -10:00
Linus Torvalds
b71f0be2d2 cgroup: Changes for v7.1
- cgroup_file_notify() locking converted from a global lock to
   per-cgroup_file spinlock with a lockless fast-path when no notification
   is needed.
 
 - Misc changes including exposing cgroup helpers for sched_ext and minor
   fixes.
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Merge tag 'cgroup-for-7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:

 - cgroup_file_notify() locking converted from a global lock to
   per-cgroup_file spinlock with a lockless fast-path when no
   notification is needed

 - Misc changes including exposing cgroup helpers for sched_ext and
   minor fixes

* tag 'cgroup-for-7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup/rdma: fix swapped arguments in pr_warn() format string
  cgroup/dmem: remove region parameter from dmemcg_parse_limit
  cgroup: replace global cgroup_file_kn_lock with per-cgroup_file lock
  cgroup: add lockless fast-path checks to cgroup_file_notify()
  cgroup: reduce cgroup_file_kn_lock hold time in cgroup_file_notify()
  cgroup: Expose some cgroup helpers
2026-04-15 10:18:49 -07:00
Tejun Heo
4c56a8ac68 cgroup: Fix cgroup_drain_dying() testing the wrong condition
cgroup_drain_dying() was using cgroup_is_populated() to test whether there are
dying tasks to wait for. cgroup_is_populated() tests nr_populated_csets,
nr_populated_domain_children and nr_populated_threaded_children, but
cgroup_drain_dying() only needs to care about this cgroup's own tasks - whether
there are children is cgroup_destroy_locked()'s concern.

This caused hangs during shutdown. When systemd tried to rmdir a cgroup that had
no direct tasks but had a populated child, cgroup_drain_dying() would enter its
wait loop because cgroup_is_populated() was true from
nr_populated_domain_children. The task iterator found nothing to wait for, yet
the populated state never cleared because it was driven by live tasks in the
child cgroup.

Fix it by using cgroup_has_tasks() which only tests nr_populated_csets.

v3: Fix cgroup_is_populated() -> cgroup_has_tasks() (Sebastian).

v2: https://lore.kernel.org/r/20260323200205.1063629-1-tj@kernel.org

Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Fixes: 1b164b876c ("cgroup: Wait for dying tasks to leave on rmdir")
Signed-off-by: Tejun Heo <tj@kernel.org>
Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2026-03-25 14:08:04 -10:00
Tejun Heo
1b164b876c cgroup: Wait for dying tasks to leave on rmdir
a72f73c4dd ("cgroup: Don't expose dead tasks in cgroup") hid PF_EXITING
tasks from cgroup.procs so that systemd doesn't see tasks that have already
been reaped via waitpid(). However, the populated counter (nr_populated_csets)
is only decremented when the task later passes through cgroup_task_dead() in
finish_task_switch(). This means cgroup.procs can appear empty while the
cgroup is still populated, causing rmdir to fail with -EBUSY.

Fix this by making cgroup_rmdir() wait for dying tasks to fully leave. If the
cgroup is populated but all remaining tasks have PF_EXITING set (the task
iterator returns none due to the existing filter), wait for a kick from
cgroup_task_dead() and retry. The wait is brief as tasks are removed from the
cgroup's css_set between PF_EXITING assertion in do_exit() and
cgroup_task_dead() in finish_task_switch().

v2: cgroup_is_populated() true to false transition happens under css_set_lock
    not cgroup_mutex, so retest under css_set_lock before sleeping to avoid
    missed wakeups (Sebastian).

Fixes: a72f73c4dd ("cgroup: Don't expose dead tasks in cgroup")
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202603222104.2c81684e-lkp@intel.com
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Bert Karwatzki <spasswolf@web.de>
Cc: Michal Koutny <mkoutny@suse.com>
Cc: cgroups@vger.kernel.org
2026-03-24 10:21:40 -10:00
Shakeel Butt
4ef420b345 cgroup: replace global cgroup_file_kn_lock with per-cgroup_file lock
Replace the global cgroup_file_kn_lock with a per-cgroup_file spinlock
to eliminate cross-cgroup contention as it is not really protecting
data shared between different cgroups.

The lock is initialized in cgroup_add_file() alongside timer_setup().
No lock acquisition is needed during initialization since the cgroup
directory is being populated under cgroup_mutex and no concurrent
accessors exist at that point.

Reported-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Tejun Heo <tj@kernel.org>
2026-03-11 12:16:21 -10:00
Shakeel Butt
4616120fca cgroup: add lockless fast-path checks to cgroup_file_notify()
Add lockless checks before acquiring cgroup_file_kn_lock:

1. READ_ONCE(cfile->kn) NULL check to skip torn-down files.
2. READ_ONCE(cfile->notified_at) rate-limit check to skip when
   within the notification interval.  If within the interval, arm
   the deferred timer via timer_reduce() and confirm it is pending
   before returning -- if the timer fired in between, fall through
   to the lock path so the notification is not lost.

Both checks have safe error directions -- a stale read can only
cause unnecessary lock acquisition, never a missed notification.

The critical section is simplified to just taking a kernfs_get()
reference and updating notified_at.

Annotate cfile->kn and cfile->notified_at write sites with
WRITE_ONCE() to pair with the lockless readers.

Reported-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Tejun Heo <tj@kernel.org>
2026-03-11 12:16:21 -10:00
Shakeel Butt
05070cd654 cgroup: reduce cgroup_file_kn_lock hold time in cgroup_file_notify()
cgroup_file_notify() calls kernfs_notify() while holding the global
cgroup_file_kn_lock.  kernfs_notify() does non-trivial work including
wake_up_interruptible() and acquisition of a second global spinlock
(kernfs_notify_lock), inflating the hold time.

Take a kernfs_get() reference under the lock and call kernfs_notify()
after dropping it, following the pattern from cgroup_file_show().

Reported-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Tejun Heo <tj@kernel.org>
2026-03-11 12:16:21 -10:00
Sebastian Andrzej Siewior
a72f73c4dd cgroup: Don't expose dead tasks in cgroup
Once a task exits it has its state set to TASK_DEAD and then it is
removed from the cgroup it belonged to. The last step happens on the task
gets out of its last schedule() invocation and is delayed on PREEMPT_RT
due to locking constraints.

As a result it is possible to receive a pid via waitpid() of a task
which is still listed in cgroup.procs for the cgroup it belonged
to. This is something that systemd does not expect and as a result it
waits for its exit until a time out occurs.
This can also be reproduced on !PREEMPT_RT kernel with a significant
delay in do_exit() after exit_notify().

Hide the task from the output which have PF_EXITING set which is done
before the parent is notified. Keeping zombies with live threads
shouldn't break anything (suggested by Tejun).

Reported-by: Bert Karwatzki <spasswolf@web.de>
Closes: https://lore.kernel.org/all/20260219164648.3014-1-spasswolf@web.de/
Tested-by: Bert Karwatzki <spasswolf@web.de>
Fixes: 9311e6c29b ("cgroup: Fix sleeping from invalid context warning on PREEMPT_RT")
Cc: stable@vger.kernel.org # v6.19+
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
2026-03-06 12:43:25 -10:00
Tejun Heo
5b30afc20b cgroup: Expose some cgroup helpers
Expose the following through cgroup.h:

- cgroup_on_dfl()
- cgroup_is_dead()
- cgroup_for_each_live_child()
- cgroup_for_each_live_descendant_pre()
- cgroup_for_each_live_descendant_post()

Until now, these didn't need to be exposed because controllers only cared
about the css hierarchy. The planned sched_ext hierarchical scheduler
support will be based on the default cgroup hierarchy, which is in line
with the existing BPF cgroup support, and thus needs these exposed.

Signed-off-by: Tejun Heo <tj@kernel.org>
2026-03-05 18:15:58 -10:00
Linus Torvalds
0031c06807 cgroup: Fixes for v7.0-rc2
- Fix circular locking dependency in cpuset partition code by deferring
   housekeeping_update() calls to a workqueue instead of calling them
   directly under cpus_read_lock.
 
 - Fix null-ptr-deref in rebuild_sched_domains_cpuslocked() when
   generate_sched_domains() returns NULL due to kmalloc failure.
 
 - Fix incorrect cpuset behavior for effective_xcpus in
   partition_xcpus_del() and cpuset_update_tasks_cpumask() in
   update_cpumasks_hier().
 
 - Fix race between task migration and cgroup iteration.
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Merge tag 'cgroup-for-7.0-rc2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup fixes from Tejun Heo:

 - Fix circular locking dependency in cpuset partition code by
   deferring housekeeping_update() calls to a workqueue instead
   of calling them directly under cpus_read_lock

 - Fix null-ptr-deref in rebuild_sched_domains_cpuslocked() when
   generate_sched_domains() returns NULL due to kmalloc failure

 - Fix incorrect cpuset behavior for effective_xcpus in
   partition_xcpus_del() and cpuset_update_tasks_cpumask()
   in update_cpumasks_hier()

 - Fix race between task migration and cgroup iteration

* tag 'cgroup-for-7.0-rc2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup/cpuset: fix null-ptr-deref in rebuild_sched_domains_cpuslocked
  cgroup/cpuset: Call housekeeping_update() without holding cpus_read_lock
  cgroup/cpuset: Defer housekeeping_update() calls from CPU hotplug to workqueue
  cgroup/cpuset: Move housekeeping_update()/rebuild_sched_domains() together
  kselftest/cgroup: Simplify test_cpuset_prs.sh by removing "S+" command
  cgroup/cpuset: Set isolated_cpus_updating only if isolated_cpus is changed
  cgroup/cpuset: Clarify exclusion rules for cpuset internal variables
  cgroup/cpuset: Fix incorrect use of cpuset_update_tasks_cpumask() in update_cpumasks_hier()
  cgroup/cpuset: Fix incorrect change to effective_xcpus in partition_xcpus_del()
  cgroup: fix race between task migration and iteration
2026-03-03 14:25:18 -08:00
Linus Torvalds
323bbfcf1e Convert 'alloc_flex' family to use the new default GFP_KERNEL argument
This is the exact same thing as the 'alloc_obj()' version, only much
smaller because there are a lot fewer users of the *alloc_flex()
interface.

As with alloc_obj() version, this was done entirely with mindless brute
force, using the same script, except using 'flex' in the pattern rather
than 'objs*'.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2026-02-21 17:09:51 -08:00
Linus Torvalds
bf4afc53b7 Convert 'alloc_obj' family to use the new default GFP_KERNEL argument
This was done entirely with mindless brute force, using

    git grep -l '\<k[vmz]*alloc_objs*(.*, GFP_KERNEL)' |
        xargs sed -i 's/\(alloc_objs*(.*\), GFP_KERNEL)/\1)/'

to convert the new alloc_obj() users that had a simple GFP_KERNEL
argument to just drop that argument.

Note that due to the extreme simplicity of the scripting, any slightly
more complex cases spread over multiple lines would not be triggered:
they definitely exist, but this covers the vast bulk of the cases, and
the resulting diff is also then easier to check automatically.

For the same reason the 'flex' versions will be done as a separate
conversion.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2026-02-21 17:09:51 -08:00
Kees Cook
69050f8d6d treewide: Replace kmalloc with kmalloc_obj for non-scalar types
This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:

Single allocations:	kmalloc(sizeof(TYPE), ...)
are replaced with:	kmalloc_obj(TYPE, ...)

Array allocations:	kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with:	kmalloc_objs(TYPE, COUNT, ...)

Flex array allocations:	kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with:	kmalloc_flex(*PTR, FAM, COUNT, ...)

(where TYPE may also be *VAR)

The resulting allocations no longer return "void *", instead returning
"TYPE *".

Signed-off-by: Kees Cook <kees@kernel.org>
2026-02-21 01:02:28 -08:00
Qingye Zhao
5ee01f1a73 cgroup: fix race between task migration and iteration
When a task is migrated out of a css_set, cgroup_migrate_add_task()
first moves it from cset->tasks to cset->mg_tasks via:

    list_move_tail(&task->cg_list, &cset->mg_tasks);

If a css_task_iter currently has it->task_pos pointing to this task,
css_set_move_task() calls css_task_iter_skip() to keep the iterator
valid. However, since the task has already been moved to ->mg_tasks,
the iterator is advanced relative to the mg_tasks list instead of the
original tasks list. As a result, remaining tasks on cset->tasks, as
well as tasks queued on cset->mg_tasks, can be skipped by iteration.

Fix this by calling css_set_skip_task_iters() before unlinking
task->cg_list from cset->tasks. This advances all active iterators to
the next task on cset->tasks, so iteration continues correctly even
when a task is concurrently being migrated.

This race is hard to hit in practice without instrumentation, but it
can be reproduced by artificially slowing down cgroup_procs_show().
For example, on an Android device a temporary
/sys/kernel/cgroup/cgroup_test knob can be added to inject a delay
into cgroup_procs_show(), and then:

  1) Spawn three long-running tasks (PIDs 101, 102, 103).
  2) Create a test cgroup and move the tasks into it.
  3) Enable a large delay via /sys/kernel/cgroup/cgroup_test.
  4) In one shell, read cgroup.procs from the test cgroup.
  5) Within the delay window, in another shell migrate PID 102 by
     writing it to a different cgroup.procs file.

Under this setup, cgroup.procs can intermittently show only PID 101
while skipping PID 103. Once the migration completes, reading the
file again shows all tasks as expected.

Note that this change does not allow removing the existing
css_set_skip_task_iters() call in css_set_move_task(). The new call
in cgroup_migrate_add_task() only handles iterators that are racing
with migration while the task is still on cset->tasks. Iterators may
also start after the task has been moved to cset->mg_tasks. If we
dropped css_set_skip_task_iters() from css_set_move_task(), such
iterators could keep task_pos pointing to a migrating task, causing
css_task_iter_advance() to malfunction on the destination css_set,
up to and including crashes or infinite loops.

The race window between migration and iteration is very small, and
css_task_iter is not on a hot path. In the worst case, when an
iterator is positioned on the first thread of the migrating process,
cgroup_migrate_add_task() may have to skip multiple tasks via
css_set_skip_task_iters(). However, this only happens when migration
and iteration actually race, so the performance impact is negligible
compared to the correctness fix provided here.

Fixes: b636fd38dc ("cgroup: Implement css_task_iter_skip()")
Cc: stable@vger.kernel.org # v5.2+
Signed-off-by: Qingye Zhao <zhaoqingye@honor.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
2026-02-12 07:25:09 -10:00
Linus Torvalds
ff661eeee2 cgroup: Changes for v6.20
- cpuset changes:
 
   - Continue separating v1 and v2 implementations by moving more
     v1-specific logic into cpuset-v1.c.
 
   - Improve partition handling. Sibling partitions are no longer
     invalidated on cpuset.cpus conflict, cpuset.cpus changes no longer
     fail in v2, and effective_xcpus computation is made consistent.
 
   - Fix partition effective CPUs overlap that caused a warning on cpuset
     removal when sibling partitions shared CPUs.
 
 - Increase the maximum cgroup subsystem count from 16 to 32 to
   accommodate future subsystem additions.
 
 - Misc cleanups and selftest improvements including switching to
   css_is_online() helper, removing dead code and stale documentation
   references, using lockdep_assert_cpuset_lock_held() consistently,
   and adding polling helpers for asynchronously updated cgroup
   statistics.
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Merge tag 'cgroup-for-6.20' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:

 - cpuset changes:

    - Continue separating v1 and v2 implementations by moving more
      v1-specific logic into cpuset-v1.c

    - Improve partition handling. Sibling partitions are no longer
      invalidated on cpuset.cpus conflict, cpuset.cpus changes no longer
      fail in v2, and effective_xcpus computation is made consistent

    - Fix partition effective CPUs overlap that caused a warning on
      cpuset removal when sibling partitions shared CPUs

 - Increase the maximum cgroup subsystem count from 16 to 32 to
   accommodate future subsystem additions

 - Misc cleanups and selftest improvements including switching to
   css_is_online() helper, removing dead code and stale documentation
   references, using lockdep_assert_cpuset_lock_held() consistently, and
   adding polling helpers for asynchronously updated cgroup statistics

* tag 'cgroup-for-6.20' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (21 commits)
  cpuset: fix overlap of partition effective CPUs
  cgroup: increase maximum subsystem count from 16 to 32
  cgroup: Remove stale cpu.rt.max reference from documentation
  cpuset: replace direct lockdep_assert_held() with lockdep_assert_cpuset_lock_held()
  cgroup/cpuset: Move the v1 empty cpus/mems check to cpuset1_validate_change()
  cgroup/cpuset: Don't invalidate sibling partitions on cpuset.cpus conflict
  cgroup/cpuset: Don't fail cpuset.cpus change in v2
  cgroup/cpuset: Consistently compute effective_xcpus in update_cpumasks_hier()
  cgroup/cpuset: Streamline rm_siblings_excl_cpus()
  cpuset: remove dead code in cpuset-v1.c
  cpuset: remove v1-specific code from generate_sched_domains
  cpuset: separate generate_sched_domains for v1 and v2
  cpuset: move update_domain_attr_tree to cpuset_v1.c
  cpuset: add cpuset1_init helper for v1 initialization
  cpuset: add cpuset1_online_css helper for v1-specific operations
  cpuset: add lockdep_assert_cpuset_lock_held helper
  cpuset: Remove unnecessary checks in rebuild_sched_domains_locked
  cgroup: switch to css_is_online() helper
  selftests: cgroup: Replace sleep with cg_read_key_long_poll() for waiting on nr_dying_descendants
  selftests: cgroup: make test_memcg_sock robust against delayed sock stats
  ...
2026-02-11 13:20:50 -08:00
Chen Ridong
5eab8c588b cgroup: increase maximum subsystem count from 16 to 32
The current cgroup subsystem limit of 16 is insufficient, as the number of
existing subsystems has already reached this limit. When adding a new
subsystem that is not yet in the mainline kernel, building with
`make allmodconfig` requires first bypassing the
`BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16)` restriction to allow compilation
to succeed. However, the kernel still fails to boot afterward.

This patch increases the maximum number of supported cgroup subsystems from
16 to 32, providing enough room for future subsystem additions.

Signed-off-by: Chen Ridong <chenridong@huawei.com>
Acked-by: Waiman Long <longman@redhat.com>
Tested-by: JP Kobryn <inwardvessel@gmail.com>
Acked-by: JP Kobryn <inwardvessel@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
2026-02-01 06:34:15 -10:00
Tim Bird
a1b3421a02 kernel: cgroup: Add SPDX-License-Identifier lines
Add GPL-2.0 SPDX license id lines to a few old
files, replacing the reference to the COPYING file.

The COPYING file at the time of creation of these files
(2007 and 2005) was GPL-v2.0, with an additional clause
indicating that only v2 applied.

Signed-off-by: Tim Bird <tim.bird@sony.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
2026-01-15 22:03:09 -10:00
Michal Koutný
ef56578274 cgroup: Eliminate cgrp_ancestor_storage in cgroup_root
The cgrp_ancestor_storage has two drawbacks:
- it's not guaranteed that the member immediately follows struct cgrp in
  cgroup_root (root cgroup's ancestors[0] might thus point to a padding
  and not in cgrp_ancestor_storage proper),
- this idiom raises warnings with -Wflex-array-member-not-at-end.

Instead of relying on the auxiliary member in cgroup_root, define the
0-th level ancestor inside struct cgroup (needed for static allocation
of cgrp_dfl_root), deeper cgroups would allocate flexible
_low_ancestors[].  Unionized alias through ancestors[] will
transparently join the two ranges.

The above change would still leave the flexible array at the end of
struct cgroup inside cgroup_root, so move cgrp also towards the end of
cgroup_root to resolve the -Wflex-array-member-not-at-end.

Link: https://lore.kernel.org/r/5fb74444-2fbb-476e-b1bf-3f3e279d0ced@embeddedor.com/
Reported-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Closes: https://lore.kernel.org/r/b3eb050d-9451-4b60-b06c-ace7dab57497@embeddedor.com/
Cc: David Laight <david.laight.linux@gmail.com>
Acked-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
2026-01-07 15:11:03 -10:00
Chen Ridong
82d7e59ea7 cgroup: switch to css_is_online() helper
Use the new css_is_online() helper that has been introduced to check css
online state, instead of testing the CSS_ONLINE flag directly. This
improves readability and centralizes the state check logic.

No functional changes intended.

Signed-off-by: Chen Ridong <chenridong@huawei.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Tejun Heo <tj@kernel.org>
2025-12-08 09:02:38 -10:00
Linus Torvalds
7203ca412f Significant patch series in this merge are as follows:
- The 10 patch series "__vmalloc()/kvmalloc() and no-block support" from
   Uladzislau Rezki reworks the vmalloc() code to support non-blocking
   allocations (GFP_ATOIC, GFP_NOWAIT).
 
 - The 2 patch series "ksm: fix exec/fork inheritance" from xu xin fixes
   a rare case where the KSM MMF_VM_MERGE_ANY prctl state is not inherited
   across fork/exec.
 
 - The 4 patch series "mm/zswap: misc cleanup of code and documentations"
   from SeongJae Park does some light maintenance work on the zswap code.
 
 - The 5 patch series "mm/page_owner: add debugfs files 'show_handles'
   and 'show_stacks_handles'" from Mauricio Faria de Oliveira enhances the
   /sys/kernel/debug/page_owner debug feature.  It adds unique identifiers
   to differentiate the various stack traces so that userspace monitoring
   tools can better match stack traces over time.
 
 - The 2 patch series "mm/page_alloc: pcp->batch cleanups" from Joshua
   Hahn makes some minor alterations to the page allocator's per-cpu-pages
   feature.
 
 - The 2 patch series "Improve UFFDIO_MOVE scalability by removing
   anon_vma lock" from Lokesh Gidra addresses a scalability issue in
   userfaultfd's UFFDIO_MOVE operation.
 
 - The 2 patch series "kasan: cleanups for kasan_enabled() checks" from
   Sabyrzhan Tasbolatov performs some cleanup in the KASAN code.
 
 - The 2 patch series "drivers/base/node: fold node register and
   unregister functions" from Donet Tom cleans up the NUMA node handling
   code a little.
 
 - The 4 patch series "mm: some optimizations for prot numa" from Kefeng
   Wang provides some cleanups and small optimizations to the NUMA
   allocation hinting code.
 
 - The 5 patch series "mm/page_alloc: Batch callers of
   free_pcppages_bulk" from Joshua Hahn addresses long lock hold times at
   boot on large machines.  These were causing (harmless) softlockup
   warnings.
 
 - The 2 patch series "optimize the logic for handling dirty file folios
   during reclaim" from Baolin Wang removes some now-unnecessary work from
   page reclaim.
 
 - The 10 patch series "mm/damon: allow DAMOS auto-tuned for per-memcg
   per-node memory usage" from SeongJae Park enhances the DAMOS auto-tuning
   feature.
 
 - The 2 patch series "mm/damon: fixes for address alignment issues in
   DAMON_LRU_SORT and DAMON_RECLAIM" from Quanmin Yan fixes DAMON_LRU_SORT
   and DAMON_RECLAIM with certain userspace configuration.
 
 - The 15 patch series "expand mmap_prepare functionality, port more
   users" from Lorenzo Stoakes enhances the new(ish)
   file_operations.mmap_prepare() method and ports additional callsites
   from the old ->mmap() over to ->mmap_prepare().
 
 - The 8 patch series "Fix stale IOTLB entries for kernel address space"
   from Lu Baolu fixes a bug (and possible security issue on non-x86) in
   the IOMMU code.  In some situations the IOMMU could be left hanging onto
   a stale kernel pagetable entry.
 
 - The 4 patch series "mm/huge_memory: cleanup __split_unmapped_folio()"
   from Wei Yang cleans up and optimizes the folio splitting code.
 
 - The 5 patch series "mm, swap: misc cleanup and bugfix" from Kairui
   Song implements some cleanups and a minor fix in the swap discard code.
 
 - The 8 patch series "mm/damon: misc documentation fixups" from SeongJae
   Park does as advertised.
 
 - The 9 patch series "mm/damon: support pin-point targets removal" from
   SeongJae Park permits userspace to remove a specific monitoring target
   in the middle of the current targets list.
 
 - The 2 patch series "mm: MISC follow-up patches for linux/pgalloc.h"
   from Harry Yoo implements a couple of cleanups related to mm header file
   inclusion.
 
 - The 2 patch series "mm/swapfile.c: select swap devices of default
   priority round robin" from Baoquan He improves the selection of swap
   devices for NUMA machines.
 
 - The 3 patch series "mm: Convert memory block states (MEM_*) macros to
   enums" from Israel Batista changes the memory block labels from macros
   to enums so they will appear in kernel debug info.
 
 - The 3 patch series "ksm: perform a range-walk to jump over holes in
   break_ksm" from Pedro Demarchi Gomes addresses an inefficiency when KSM
   unmerges an address range.
 
 - The 22 patch series "mm/damon/tests: fix memory bugs in kunit tests"
   from SeongJae Park fixes leaks and unhandled malloc() failures in DAMON
   userspace unit tests.
 
 - The 2 patch series "some cleanups for pageout()" from Baolin Wang
   cleans up a couple of minor things in the page scanner's
   writeback-for-eviction code.
 
 - The 2 patch series "mm/hugetlb: refactor sysfs/sysctl interfaces" from
   Hui Zhu moves hugetlb's sysfs/sysctl handling code into a new file.
 
 - The 9 patch series "introduce VM_MAYBE_GUARD and make it sticky" from
   Lorenzo Stoakes makes the VMA guard regions available in /proc/pid/smaps
   and improves the mergeability of guarded VMAs.
 
 - The 2 patch series "mm: perform guard region install/remove under VMA
   lock" from Lorenzo Stoakes reduces mmap lock contention for callers
   performing VMA guard region operations.
 
 - The 2 patch series "vma_start_write_killable" from Matthew Wilcox
   starts work in permitting applications to be killed when they are
   waiting on a read_lock on the VMA lock.
 
 - The 11 patch series "mm/damon/tests: add more tests for online
   parameters commit" from SeongJae Park adds additional userspace testing
   of DAMON's "commit" feature.
 
 - The 9 patch series "mm/damon: misc cleanups" from SeongJae Park does
   that.
 
 - The 2 patch series "make VM_SOFTDIRTY a sticky VMA flag" from Lorenzo
   Stoakes addresses the possible loss of a VMA's VM_SOFTDIRTY flag when
   that VMA is merged with another.
 
 - The 16 patch series "mm: support device-private THP" from Balbir Singh
   introduces support for Transparent Huge Page (THP) migration in zone
   device-private memory.
 
 - The 3 patch series "Optimize folio split in memory failure" from Zi
   Yan optimizes folio split operations in the memory failure code.
 
 - The 2 patch series "mm/huge_memory: Define split_type and consolidate
   split support checks" from Wei Yang provides some more cleanups in the
   folio splitting code.
 
 - The 16 patch series "mm: remove is_swap_[pte, pmd]() + non-swap
   entries, introduce leaf entries" from Lorenzo Stoakes cleans up our
   handling of pagetable leaf entries by introducing the concept of
   'software leaf entries', of type softleaf_t.
 
 - The 4 patch series "reparent the THP split queue" from Muchun Song
   reparents the THP split queue to its parent memcg.  This is in
   preparation for addressing the long-standing "dying memcg" problem,
   wherein dead memcg's linger for too long, consuming memory resources.
 
 - The 3 patch series "unify PMD scan results and remove redundant
   cleanup" from Wei Yang does a little cleanup in the hugepage collapse
   code.
 
 - The 6 patch series "zram: introduce writeback bio batching" from
   Sergey Senozhatsky improves zram writeback efficiency by introducing
   batched bio writeback support.
 
 - The 4 patch series "memcg: cleanup the memcg stats interfaces" from
   Shakeel Butt cleans up our handling of the interrupt safety of some
   memcg stats.
 
 - The 4 patch series "make vmalloc gfp flags usage more apparent" from
   Vishal Moola cleans up vmalloc's handling of incoming GFP flags.
 
 - The 6 patch series "mm: Add soft-dirty and uffd-wp support for RISC-V"
   from Chunyan Zhang teches soft dirty and userfaultfd write protect
   tracking to use RISC-V's Svrsw60t59b extension.
 
 - The 5 patch series "mm: swap: small fixes and comment cleanups" from
   Youngjun Park fixes a small bug and cleans up some of the swap code.
 
 - The 4 patch series "initial work on making VMA flags a bitmap" from
   Lorenzo Stoakes starts work on converting the vma struct's flags to a
   bitmap, so we stop running out of them, especially on 32-bit.
 
 - The 2 patch series "mm/swapfile: fix and cleanup swap list iterations"
   from Youngjun Park addresses a possible bug in the swap discard code and
   cleans things up a little.
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Merge tag 'mm-stable-2025-12-03-21-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull MM updates from Andrew Morton:

  "__vmalloc()/kvmalloc() and no-block support" (Uladzislau Rezki)
     Rework the vmalloc() code to support non-blocking allocations
     (GFP_ATOIC, GFP_NOWAIT)

  "ksm: fix exec/fork inheritance" (xu xin)
     Fix a rare case where the KSM MMF_VM_MERGE_ANY prctl state is not
     inherited across fork/exec

  "mm/zswap: misc cleanup of code and documentations" (SeongJae Park)
     Some light maintenance work on the zswap code

  "mm/page_owner: add debugfs files 'show_handles' and 'show_stacks_handles'" (Mauricio Faria de Oliveira)
     Enhance the /sys/kernel/debug/page_owner debug feature by adding
     unique identifiers to differentiate the various stack traces so
     that userspace monitoring tools can better match stack traces over
     time

  "mm/page_alloc: pcp->batch cleanups" (Joshua Hahn)
     Minor alterations to the page allocator's per-cpu-pages feature

  "Improve UFFDIO_MOVE scalability by removing anon_vma lock" (Lokesh Gidra)
     Address a scalability issue in userfaultfd's UFFDIO_MOVE operation

  "kasan: cleanups for kasan_enabled() checks" (Sabyrzhan Tasbolatov)

  "drivers/base/node: fold node register and unregister functions" (Donet Tom)
     Clean up the NUMA node handling code a little

  "mm: some optimizations for prot numa" (Kefeng Wang)
     Cleanups and small optimizations to the NUMA allocation hinting
     code

  "mm/page_alloc: Batch callers of free_pcppages_bulk" (Joshua Hahn)
     Address long lock hold times at boot on large machines. These were
     causing (harmless) softlockup warnings

  "optimize the logic for handling dirty file folios during reclaim" (Baolin Wang)
     Remove some now-unnecessary work from page reclaim

  "mm/damon: allow DAMOS auto-tuned for per-memcg per-node memory usage" (SeongJae Park)
     Enhance the DAMOS auto-tuning feature

  "mm/damon: fixes for address alignment issues in DAMON_LRU_SORT and DAMON_RECLAIM" (Quanmin Yan)
     Fix DAMON_LRU_SORT and DAMON_RECLAIM with certain userspace
     configuration

  "expand mmap_prepare functionality, port more users" (Lorenzo Stoakes)
     Enhance the new(ish) file_operations.mmap_prepare() method and port
     additional callsites from the old ->mmap() over to ->mmap_prepare()

  "Fix stale IOTLB entries for kernel address space" (Lu Baolu)
     Fix a bug (and possible security issue on non-x86) in the IOMMU
     code. In some situations the IOMMU could be left hanging onto a
     stale kernel pagetable entry

  "mm/huge_memory: cleanup __split_unmapped_folio()" (Wei Yang)
     Clean up and optimize the folio splitting code

  "mm, swap: misc cleanup and bugfix" (Kairui Song)
     Some cleanups and a minor fix in the swap discard code

  "mm/damon: misc documentation fixups" (SeongJae Park)

  "mm/damon: support pin-point targets removal" (SeongJae Park)
     Permit userspace to remove a specific monitoring target in the
     middle of the current targets list

  "mm: MISC follow-up patches for linux/pgalloc.h" (Harry Yoo)
     A couple of cleanups related to mm header file inclusion

  "mm/swapfile.c: select swap devices of default priority round robin" (Baoquan He)
     improve the selection of swap devices for NUMA machines

  "mm: Convert memory block states (MEM_*) macros to enums" (Israel Batista)
     Change the memory block labels from macros to enums so they will
     appear in kernel debug info

  "ksm: perform a range-walk to jump over holes in break_ksm" (Pedro Demarchi Gomes)
     Address an inefficiency when KSM unmerges an address range

  "mm/damon/tests: fix memory bugs in kunit tests" (SeongJae Park)
     Fix leaks and unhandled malloc() failures in DAMON userspace unit
     tests

  "some cleanups for pageout()" (Baolin Wang)
     Clean up a couple of minor things in the page scanner's
     writeback-for-eviction code

  "mm/hugetlb: refactor sysfs/sysctl interfaces" (Hui Zhu)
     Move hugetlb's sysfs/sysctl handling code into a new file

  "introduce VM_MAYBE_GUARD and make it sticky" (Lorenzo Stoakes)
     Make the VMA guard regions available in /proc/pid/smaps and
     improves the mergeability of guarded VMAs

  "mm: perform guard region install/remove under VMA lock" (Lorenzo Stoakes)
     Reduce mmap lock contention for callers performing VMA guard region
     operations

  "vma_start_write_killable" (Matthew Wilcox)
     Start work on permitting applications to be killed when they are
     waiting on a read_lock on the VMA lock

  "mm/damon/tests: add more tests for online parameters commit" (SeongJae Park)
     Add additional userspace testing of DAMON's "commit" feature

  "mm/damon: misc cleanups" (SeongJae Park)

  "make VM_SOFTDIRTY a sticky VMA flag" (Lorenzo Stoakes)
     Address the possible loss of a VMA's VM_SOFTDIRTY flag when that
     VMA is merged with another

  "mm: support device-private THP" (Balbir Singh)
     Introduce support for Transparent Huge Page (THP) migration in zone
     device-private memory

  "Optimize folio split in memory failure" (Zi Yan)

  "mm/huge_memory: Define split_type and consolidate split support checks" (Wei Yang)
     Some more cleanups in the folio splitting code

  "mm: remove is_swap_[pte, pmd]() + non-swap entries, introduce leaf entries" (Lorenzo Stoakes)
     Clean up our handling of pagetable leaf entries by introducing the
     concept of 'software leaf entries', of type softleaf_t

  "reparent the THP split queue" (Muchun Song)
     Reparent the THP split queue to its parent memcg. This is in
     preparation for addressing the long-standing "dying memcg" problem,
     wherein dead memcg's linger for too long, consuming memory
     resources

  "unify PMD scan results and remove redundant cleanup" (Wei Yang)
     A little cleanup in the hugepage collapse code

  "zram: introduce writeback bio batching" (Sergey Senozhatsky)
     Improve zram writeback efficiency by introducing batched bio
     writeback support

  "memcg: cleanup the memcg stats interfaces" (Shakeel Butt)
     Clean up our handling of the interrupt safety of some memcg stats

  "make vmalloc gfp flags usage more apparent" (Vishal Moola)
     Clean up vmalloc's handling of incoming GFP flags

  "mm: Add soft-dirty and uffd-wp support for RISC-V" (Chunyan Zhang)
     Teach soft dirty and userfaultfd write protect tracking to use
     RISC-V's Svrsw60t59b extension

  "mm: swap: small fixes and comment cleanups" (Youngjun Park)
     Fix a small bug and clean up some of the swap code

  "initial work on making VMA flags a bitmap" (Lorenzo Stoakes)
     Start work on converting the vma struct's flags to a bitmap, so we
     stop running out of them, especially on 32-bit

  "mm/swapfile: fix and cleanup swap list iterations" (Youngjun Park)
     Address a possible bug in the swap discard code and clean things
     up a little

[ This merge also reverts commit ebb9aeb980 ("vfio/nvgrace-gpu:
  register device memory for poison handling") because it looks
  broken to me, I've asked for clarification   - Linus ]

* tag 'mm-stable-2025-12-03-21-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (321 commits)
  mm: fix vma_start_write_killable() signal handling
  mm/swapfile: use plist_for_each_entry in __folio_throttle_swaprate
  mm/swapfile: fix list iteration when next node is removed during discard
  fs/proc/task_mmu.c: fix make_uffd_wp_huge_pte() huge pte handling
  mm/kfence: add reboot notifier to disable KFENCE on shutdown
  memcg: remove inc/dec_lruvec_kmem_state helpers
  selftests/mm/uffd: initialize char variable to Null
  mm: fix DEBUG_RODATA_TEST indentation in Kconfig
  mm: introduce VMA flags bitmap type
  tools/testing/vma: eliminate dependency on vma->__vm_flags
  mm: simplify and rename mm flags function for clarity
  mm: declare VMA flags by bit
  zram: fix a spelling mistake
  mm/page_alloc: optimize lowmem_reserve max lookup using its semantic monotonicity
  mm/vmscan: skip increasing kswapd_failures when reclaim was boosted
  pagemap: update BUDDY flag documentation
  mm: swap: remove scan_swap_map_slots() references from comments
  mm: swap: change swap_alloc_slow() to void
  mm, swap: remove redundant comment for read_swap_cache_async
  mm, swap: use SWP_SOLIDSTATE to determine if swap is rotational
  ...
2025-12-05 13:52:43 -08:00
Linus Torvalds
8449d3252c cgroup: Changes for v6.19
- Defer task cgroup unlink until after the dying task's final context switch
   so that controllers see the cgroup properly populated until the task is
   truly gone.
 
 - cpuset cleanups and simplifications. Enforce that domain isolated CPUs
   stay in root or isolated partitions and fail if isolated+nohz_full would
   leave no housekeeping CPU. Fix sched/deadline root domain handling during
   CPU hot-unplug and race for tasks in attaching cpusets.
 
 - Misc fixes including memory reclaim protection documentation and selftest
   KTAP conformance.
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Merge tag 'cgroup-for-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:

 - Defer task cgroup unlink until after the dying task's final context
   switch so that controllers see the cgroup properly populated until
   the task is truly gone

 - cpuset cleanups and simplifications.

   Enforce that domain isolated CPUs stay in root or isolated partitions
   and fail if isolated+nohz_full would leave no housekeeping CPU. Fix
   sched/deadline root domain handling during CPU hot-unplug and race
   for tasks in attaching cpusets

 - Misc fixes including memory reclaim protection documentation and
   selftest KTAP conformance

* tag 'cgroup-for-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (21 commits)
  cpuset: Treat cpusets in attaching as populated
  sched/deadline: Walk up cpuset hierarchy to decide root domain when hot-unplug
  cgroup/cpuset: Introduce cpuset_cpus_allowed_locked()
  docs: cgroup: No special handling of unpopulated memcgs
  docs: cgroup: Note about sibling relative reclaim protection
  docs: cgroup: Explain reclaim protection target
  selftests/cgroup: conform test to KTAP format output
  cpuset: remove need_rebuild_sched_domains
  cpuset: remove global remote_children list
  cpuset: simplify node setting on error
  cgroup: include missing header for struct irq_work
  cgroup: Fix sleeping from invalid context warning on PREEMPT_RT
  cgroup/cpuset: Globally track isolated_cpus update
  cgroup/cpuset: Ensure domain isolated CPUs stay in root or isolated partition
  cgroup/cpuset: Move up prstate_housekeeping_conflict() helper
  cgroup/cpuset: Fail if isolated and nohz_full don't leave any housekeeping
  cgroup/cpuset: Rename update_unbound_workqueue_cpumask() to update_isolation_cpumasks()
  cgroup: Defer task cgroup unlink until after the task is done switching out
  cgroup: Move dying_tasks cleanup from cgroup_task_release() to cgroup_task_free()
  cgroup: Rename cgroup lifecycle hooks to cgroup_task_*()
  ...
2025-12-03 13:04:07 -08:00
Linus Torvalds
1d18101a64 kernel-6.19-rc1.cred
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Merge tag 'kernel-6.19-rc1.cred' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull cred guard updates from Christian Brauner:
 "This contains substantial credential infrastructure improvements
  adding guard-based credential management that simplifies code and
  eliminates manual reference counting in many subsystems.

  Features:

   - Kernel Credential Guards

     Add with_kernel_creds() and scoped_with_kernel_creds() guards that
     allow using the kernel credentials without allocating and copying
     them. This was requested by Linus after seeing repeated
     prepare_kernel_creds() calls that duplicate the kernel credentials
     only to drop them again later.

     The new guards completely avoid the allocation and never expose the
     temporary variable to hold the kernel credentials anywhere in
     callers.

   - Generic Credential Guards

     Add scoped_with_creds() guards for the common override_creds() and
     revert_creds() pattern. This builds on earlier work that made
     override_creds()/revert_creds() completely reference count free.

   - Prepare Credential Guards

     Add prepare credential guards for the more complex pattern of
     preparing a new set of credentials and overriding the current
     credentials with them:
      - prepare_creds()
      - modify new creds
      - override_creds()
      - revert_creds()
      - put_cred()

  Cleanups:

   - Make init_cred static since it should not be directly accessed

   - Add kernel_cred() helper to properly access the kernel credentials

   - Fix scoped_class() macro that was introduced two cycles ago

   - coredump: split out do_coredump() from vfs_coredump() for cleaner
     credential handling

   - coredump: move revert_cred() before coredump_cleanup()

   - coredump: mark struct mm_struct as const

   - coredump: pass struct linux_binfmt as const

   - sev-dev: use guard for path"

* tag 'kernel-6.19-rc1.cred' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (36 commits)
  trace: use override credential guard
  trace: use prepare credential guard
  coredump: use override credential guard
  coredump: use prepare credential guard
  coredump: split out do_coredump() from vfs_coredump()
  coredump: mark struct mm_struct as const
  coredump: pass struct linux_binfmt as const
  coredump: move revert_cred() before coredump_cleanup()
  sev-dev: use override credential guards
  sev-dev: use prepare credential guard
  sev-dev: use guard for path
  cred: add prepare credential guard
  net/dns_resolver: use credential guards in dns_query()
  cgroup: use credential guards in cgroup_attach_permissions()
  act: use credential guards in acct_write_process()
  smb: use credential guards in cifs_get_spnego_key()
  nfs: use credential guards in nfs_idmap_get_key()
  nfs: use credential guards in nfs_local_call_write()
  nfs: use credential guards in nfs_local_call_read()
  erofs: use credential guards
  ...
2025-12-01 13:45:41 -08:00
Shakeel Butt
d929525c2e memcg: net: track network throttling due to memcg memory pressure
The kernel can throttle network sockets if the memory cgroup associated
with the corresponding socket is under memory pressure.  The throttling
actions include clamping the transmit window, failing to expand receive or
send buffers, aggressively prune out-of-order receive queue, FIN deferred
to a retransmitted packet and more.  Let's add memcg metric to track such
throttling actions.

At the moment memcg memory pressure is defined through vmpressure and in
future it may be defined using PSI or we may add more flexible way for the
users to define memory pressure, maybe through ebpf.  However the
potential throttling actions will remain the same, so this newly
introduced metric will continue to track throttling actions irrespective
of how memcg memory pressure is defined.

Link: https://lkml.kernel.org/r/20251016161035.86161-1-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Daniel Sedlak <daniel.sedlak@cdn77.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kacinski <kuba@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2025-11-16 17:28:06 -08:00
Bert Karwatzki
01a743550b cgroup: include missing header for struct irq_work
To compile cgroup.c with PREEMPT_RT=y include header which declares
struct irq_work.

Fixes: 9311e6c29b ("cgroup: Fix sleeping from invalid context warning on PREEMPT_RT")

Signed-off-by: Bert Karwatzki <spasswolf@web.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
2025-11-11 08:52:42 -10:00
Christian Brauner
c2bbd2db52
ns: drop custom reference count initialization for initial namespaces
Initial namespaces don't modify their reference count anymore.
They remain fixed at one so drop the custom refcount initializations.

Link: https://patch.msgid.link/20251110-work-namespace-nstree-fixes-v1-16-e8a9264e0fb9@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
2025-11-11 10:01:32 +01:00
Christian Brauner
a67ee4e2ba
Merge branch 'kbuild-6.19.fms.extension'
Bring in the shared branch with the kbuild tree to enable
'-fms-extensions' for 6.19. Further namespace cleanup work
requires this extension.

Signed-off-by: Christian Brauner <brauner@kernel.org>
2025-11-11 09:59:08 +01:00
Tejun Heo
9311e6c29b cgroup: Fix sleeping from invalid context warning on PREEMPT_RT
cgroup_task_dead() is called from finish_task_switch() which runs with
preemption disabled and doesn't allow scheduling even on PREEMPT_RT. The
function needs to acquire css_set_lock which is a regular spinlock that can
sleep on RT kernels, leading to "sleeping function called from invalid
context" warnings.

css_set_lock is too large in scope to convert to a raw_spinlock. However,
the unlinking operations don't need to run synchronously - they just need
to complete after the task is done running.

On PREEMPT_RT, defer the work through irq_work. While the work doesn't need
to happen immediately, it can't be delayed indefinitely either as the dead
task pins the cgroup and task_struct can be pinned indefinitely. Use the
lazy version of irq_work to allow batching and lower impact while ensuring
timely completion.

v2: Use IRQ_WORK_INIT_LAZY instead of immediate irq_work and add explanation
    for why the work can't be delayed indefinitely (Sebastian Andrzej Siewior).

Fixes: d245698d72 ("cgroup: Defer task cgroup unlink until after the task is done switching out")
Reported-by: Calvin Owens <calvin@wbinvd.org>
Link: https://lore.kernel.org/r/20251104181114.489391-1-calvin@wbinvd.org
Signed-off-by: Tejun Heo <tj@kernel.org>
2025-11-06 12:52:26 -10:00
Christian Brauner
b66c7af4d8
cgroup: use credential guards in cgroup_attach_permissions()
Use credential guards for scoped credential override with automatic
restoration on scope exit.

Link: https://patch.msgid.link/20251103-work-creds-guards-simple-v1-15-a3e156839e7f@kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
2025-11-04 12:36:50 +01:00
Tejun Heo
d245698d72 cgroup: Defer task cgroup unlink until after the task is done switching out
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>
2025-11-03 11:46:18 -10:00
Tejun Heo
260fbcb92b cgroup: Move dying_tasks cleanup from cgroup_task_release() to cgroup_task_free()
Currently, cgroup_task_exit() adds thread group leaders with live member
threads to their css_set's dying_tasks list (so cgroup.procs iteration can
still see the leader), and cgroup_task_release() later removes them with
list_del_init(&task->cg_list).

An upcoming patch will defer the dying_tasks list addition, moving it from
cgroup_task_exit() (called from do_exit()) to a new function called from
finish_task_switch(). However, release_task() (which calls
cgroup_task_release()) can run either before or after finish_task_switch(),
creating a race where cgroup_task_release() might try to remove the task from
dying_tasks before or while it's being added.

Move the list_del_init() from cgroup_task_release() to cgroup_task_free() to
fix this race. cgroup_task_free() runs from __put_task_struct(), which is
always after both paths, making the cleanup safe.

Cc: Dan Schatzberg <dschatzberg@meta.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2025-11-03 11:46:18 -10:00
Tejun Heo
16dad7801a cgroup: Rename cgroup lifecycle hooks to cgroup_task_*()
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>
2025-11-03 11:46:18 -10:00
Christian Brauner
4b06b70c82
ns: rename to exit_nsproxy_namespaces()
The current naming is very misleading as this really isn't exiting all
of the task's namespaces. It is only exiting the namespaces that hang of
off nsproxy. Reflect that in the name.

Link: https://patch.msgid.link/20251029-work-namespace-nstree-listns-v4-10-2e6f823ebdc0@kernel.org
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
2025-11-03 17:41:17 +01:00
Christian Brauner
0b1765830c
ns: use NS_COMMON_INIT() for all namespaces
Now that we have a common initializer use it for all static namespaces.

Signed-off-by: Christian Brauner <brauner@kernel.org>
2025-11-03 17:41:16 +01:00
Nirbhay Sharma
93a4b36ef3 cgroup: Fix seqcount lockdep assertion in cgroup freezer
The commit afa3701c0e ("cgroup: cgroup.stat.local time accounting")
introduced a seqcount to track freeze timing but initialized it as a
plain seqcount_t using seqcount_init().

However, the write-side critical section in cgroup_do_freeze() holds
the css_set_lock spinlock while calling write_seqcount_begin(). On
PREEMPT_RT kernels, spinlocks do not disable preemption, causing the
lockdep assertion for a plain seqcount_t, which checks for preemption
being disabled, to fail.

This triggers the following warning:
  WARNING: CPU: 0 PID: 9692 at include/linux/seqlock.h:221

Fix this by changing the type to seqcount_spinlock_t and initializing
it with seqcount_spinlock_init() to associate css_set_lock with the
seqcount. This allows lockdep to correctly validate that the spinlock
is held during write operations, resolving the assertion failure on all
kernel configurations.

Reported-by: syzbot+27a2519eb4dad86d0156@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=27a2519eb4dad86d0156
Fixes: afa3701c0e ("cgroup: cgroup.stat.local time accounting")
Signed-off-by: Nirbhay Sharma <nirbhay.lkd@gmail.com>
Link: https://lore.kernel.org/r/20251002165510.KtY3IT--@linutronix.de/
Acked-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
2025-10-03 04:30:28 -10:00
Linus Torvalds
ae28ed4578 bpf-next-6.18
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Merge tag 'bpf-next-6.18' of 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
  ...
2025-09-30 17:58:11 -07:00
Linus Torvalds
755fa5b4fb cgroup: Changes for v6.18
- 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.
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Merge tag 'cgroup-for-6.18' of 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
  ...
2025-09-30 09:55:41 -07:00
Linus Torvalds
18b19abc37 namespace-6.18-rc1
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Merge tag 'namespace-6.18-rc1' of 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
  ...
2025-09-29 11:20:29 -07:00
Christian Brauner
4055526d35
ns: move ns type into struct ns_common
It's misplaced in struct proc_ns_operations and ns->ops might be NULL if
the namespace is compiled out but we still want to know the type of the
namespace for the initial namespace struct.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
2025-09-25 09:23:54 +02:00
Christian Brauner
7cf7303211
ns: use inode initializer for initial namespaces
Just use the common helper we have.

Signed-off-by: Christian Brauner <brauner@kernel.org>
2025-09-19 16:22:38 +02:00
Christian Brauner
024596a4e2
ns: rename to __ns_ref
Make it easier to grep and rename to ns_count.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
2025-09-19 16:22:38 +02:00
Christian Brauner
7c60593985
cgroup: support ns lookup
Support the generic ns lookup infrastructure to support file handles for
namespaces.

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
2025-09-19 14:26:15 +02:00
pengdonglin
3ee4211ef8 cgroup: Remove redundant rcu_read_lock/unlock() in spin_lock
Since commit a8bb74acd8 ("rcu: Consolidate RCU-sched update-side function definitions")
there is no difference between rcu_read_lock(), rcu_read_lock_bh() and
rcu_read_lock_sched() in terms of RCU read section and the relevant grace
period. That means that spin_lock(), which implies rcu_read_lock_sched(),
also implies rcu_read_lock().

There is no need no explicitly start a RCU read section if one has already
been started implicitly by spin_lock().

Simplify the code and remove the inner rcu_read_lock() invocation.

Cc: Tejun Heo <tj@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Waiman Long <longman@redhat.com>
Signed-off-by: pengdonglin <pengdonglin@xiaomi.com>
Signed-off-by: pengdonglin <dolinux.peng@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
2025-09-16 08:36:14 -10:00