threadgroup_change_begin()/end() is a pointless wrapper around
cgroup_threadgroup_change_begin()/end(), minus a might_sleep()
in the !CONFIG_CGROUPS=y case.

Remove the wrappery, move the might_sleep() (the down_read()
already has a might_sleep() check).

This debloats <linux/sched.h> a bit and simplifies this API.

Update all call sites.

No change in functionality.
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Along with the write access to the cgroup.procs or tasks file, cgroup
has required the writer's euid, unless root, to match [s]uid of the
target process or task.  On cgroup v1, this is necessary because
there's nothing preventing a delegatee from pulling in tasks or
processes from all over the system.

If a user has a cgroup subdirectory delegated to it, the user would
have write access to the cgroup.procs or tasks file.  If there are no
further checks than file write access check, the user would be able to
pull processes from all over the system into its subhierarchy which is
clearly not the intended behavior.  The matching [s]uid requirement
partially prevents this problem by allowing a delegatee to pull in the
processes that belongs to it.  This isn't a sufficient protection
however, because a user would still be able to jump processes across
two disjoint sub-hierarchies that has been delegated to them.

cgroup v2 resolves the issue by requiring the writer to have access to
the common ancestor of the cgroup.procs file of the source and target
cgroups.  This confines each delegatee to their own sub-hierarchy
proper and bases all permission decisions on the cgroup filesystem
rather than having to pull in explicit uid matching.

cgroup v2 has still been applying the matching [s]uid requirement just
for historical reasons.  On cgroup2, the requirement doesn't serve any
purpose while unnecessarily complicating the permission model.  Let's
drop it.
Signed-off-by: NTejun Heo <tj@kernel.org>

* cgrp_dfl_implicit_ss_mask is ulong instead of u16 unlike other
  ss_masks.  Make it a u16.

* Move have_canfork_callback together with other callback ss_masks.
Signed-off-by: NTejun Heo <tj@kernel.org>

Currently, subsys->*attach() callbacks are called for all subsystems
which are attached to the hierarchy on which the migration is taking
place.

With cgroup_migrate_prepare_dst() filtering out identity migrations,
v1 hierarchies can avoid spurious ->*attach() callback invocations
where the source and destination csses are identical; however, this
isn't enough on v2 as only a subset of the attached controllers can be
affected on controller enable/disable.

While spurious ->*attach() invocations aren't critically broken,
they're unnecessary overhead and can lead to temporary overcharges on
certain controllers.  Fix it by tracking which subsystems are affected
by a migration and invoking ->*attach() callbacks only on those
subsystems.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NZefan Li <lizefan@huawei.com>

cgroup migration is performed in four steps - css_set preloading,
addition of target tasks, actual migration, and clean up.  A list
named preloaded_csets is used to track the preloading.  This is a bit
too restricted and the code is already depending on the subtlety that
all source css_sets appear before destination ones.

Let's create struct cgroup_mgctx which keeps track of everything
during migration.  Currently, it has separate preload lists for source
and destination csets and also embeds cgroup_taskset which is used
during the actual migration.  This moves struct cgroup_taskset
definition to cgroup-internal.h.

This patch doesn't cause any functional changes.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NZefan Li <lizefan@huawei.com>

cgroup_taskset_add() was using list_add_tail() when for source csets
but list_move_tail() for destination.  As the operations are gated by
list_empty() test, list_move_tail() is equivalent to list_add_tail()
here.  Use list_add_tail() too for destination csets too.

This doesn't cause any functional changes.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NZefan Li <lizefan@huawei.com>

Fixed warning reported by kbuild test robot.
When reading current resource usage value, when no resources are
allocated, its possible that it can report a uninitialized value
for current resource usage.
This fix avoids it by initializing it to zero as no resource is
allocated.
Signed-off-by: NParav Pandit <pandit.parav@gmail.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

Added rdma cgroup controller that does accounting, limit enforcement
on rdma/IB resources.

Added rdma cgroup header file which defines its APIs to perform
charging/uncharging functionality. It also defined APIs for RDMA/IB
stack for device registration. Devices which are registered will
participate in controller functions of accounting and limit
enforcements. It define rdmacg_device structure to bind IB stack
and RDMA cgroup controller.

RDMA resources are tracked using resource pool. Resource pool is per
device, per cgroup entity which allows setting up accounting limits
on per device basis.

Currently resources are defined by the RDMA cgroup.

Resource pool is created/destroyed dynamically whenever
charging/uncharging occurs respectively and whenever user
configuration is done. Its a tradeoff of memory vs little more code
space that creates resource pool object whenever necessary, instead of
creating them during cgroup creation and device registration time.
Signed-off-by: NParav Pandit <pandit.parav@gmail.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

kn->priv which is a void * is used as a RCU pointer by cgroup.  When
dereferencing it, it was passing kn->priv to rcu_derefreence() without
casting it into a RCU pointer triggering address space mismatch
warning from sparse.  Fix them.
Signed-off-by: NTejun Heo <tj@kernel.org>
Reported-by: NFengguang Wu <fengguang.wu@intel.com>
Acked-by: NAcked-by: Zefan Li <lizefan@huawei.com>

get/put_css_set() get exposed in cgroup-internal.h in the process.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NAcked-by: Zefan Li <lizefan@huawei.com>

Now that v1 functions are separated out, rename some functions for
consistency.

 cgroup_dfl_base_files		-> cgroup_base_files
 cgroup_legacy_base_files	-> cgroup1_base_files
 cgroup_ssid_no_v1()		-> cgroup1_ssid_disabled()
 cgroup_pidlist_destroy_all	-> cgroup1_pidlist_destroy_all()
 cgroup_release_agent()		-> cgroup1_release_agent()
 check_for_release()		-> cgroup1_check_for_release()
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NAcked-by: Zefan Li <lizefan@huawei.com>

Now that the v1 mount code is split into separate functions, move them
to kernel/cgroup/cgroup-v1.c along with the mount option handling
code.  As this puts all v1-only kernfs_syscall_ops in cgroup-v1.c,
move cgroup1_kf_syscall_ops to cgroup-v1.c too.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NAcked-by: Zefan Li <lizefan@huawei.com>

Currently, cgroup_kf_syscall_ops is shared by v1 and v2 and the
specific methods test the version and take different actions.  Split
out v1 functions and put them in cgroup1_kf_syscall_ops and remove the
now unnecessary explicit branches in specific methods.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NAcked-by: Zefan Li <lizefan@huawei.com>

While sharing some mechanisms, the mount paths of v1 and v2 are
substantially different.  Their implementations were mixed in
cgroup_mount().  This patch splits them out so that they're easier to
follow and organize.

This patch causes one functional change - the WARN_ON(new_sb) gets
lost.  This is because the actual mounting gets moved to
cgroup_do_mount() and thus @new_sb is no longer accessible by default
to cgroup1_mount().  While we can add it as an explicit out parameter
to cgroup_do_mount(), this part of code hasn't changed and the warning
hasn't triggered for quite a while.  Dropping it should be fine.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NAcked-by: Zefan Li <lizefan@huawei.com>

cgroup.c is getting too unwieldy.  Let's move out cgroup v1 specific
code along with the debug controller into kernel/cgroup/cgroup-v1.c.

v2: cgroup_mutex and css_set_lock made available in cgroup-internal.h
    regardless of CONFIG_PROVE_RCU.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NAcked-by: Zefan Li <lizefan@huawei.com>

They're growing to be too many and planned to get split further.  Move
them under their own directory.

 kernel/cgroup.c		-> kernel/cgroup/cgroup.c
 kernel/cgroup_freezer.c	-> kernel/cgroup/freezer.c
 kernel/cgroup_pids.c		-> kernel/cgroup/pids.c
 kernel/cpuset.c		-> kernel/cgroup/cpuset.c
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NAcked-by: Zefan Li <lizefan@huawei.com>