After we implemented default unified hierarchy, cgrp->kn can never
be NULL.
Signed-off-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Use the ONE macro instead of REG, and we can simplify proc_cgroup_show().
Signed-off-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Instead of using a global work to schedule release agent on removable
cgroups, we change to use a per-cgroup work to do this, which makes
the code much simpler.
v2: use a dedicated work instead of reusing css->destroy_work. (Tejun)
Signed-off-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
cgroup now distinguishes cftypes for the default and legacy
hierarchies more explicitly by using separate arrays and
CFTYPE_ONLY_ON_DFL and CFTYPE_INSANE should be and are used only
inside cgroup core proper. Let's make it clear that the flags are
internal by prefixing them with double underscores.
CFTYPE_INSANE is renamed to __CFTYPE_NOT_ON_DFL for consistency. The
two flags are also collected and assigned bits >= 16 so that they
aren't mixed with the published flags.
v2: Convert the extra ones in cgroup_exit_cftypes() which are added by
revision to the previous patch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Until now, cftype arrays carried files for both the default and legacy
hierarchies and the files which needed to be used on only one of them
were flagged with either CFTYPE_ONLY_ON_DFL or CFTYPE_INSANE. This
gets confusing very quickly and we may end up exposing interface files
to the default hierarchy without thinking it through.
This patch makes cgroup core provide separate sets of interfaces for
cftype handling so that the cftypes for the default and legacy
hierarchies are clearly distinguished. The previous two patches
renamed the existing ones so that they clearly indicate that they're
for the legacy hierarchies. This patch adds the interface for the
default hierarchy and apply them selectively depending on the
hierarchy type.
* cftypes added through cgroup_subsys->dfl_cftypes and
cgroup_add_dfl_cftypes() only show up on the default hierarchy.
* cftypes added through cgroup_subsys->legacy_cftypes and
cgroup_add_legacy_cftypes() only show up on the legacy hierarchies.
* cgroup_subsys->dfl_cftypes and ->legacy_cftypes can point to the
same array for the cases where the interface files are identical on
both types of hierarchies.
* This makes all the existing subsystem interface files legacy-only by
default and all subsystems will have no interface file created when
enabled on the default hierarchy. Each subsystem should explicitly
review and compose the interface for the default hierarchy.
* A boot param "cgroup__DEVEL__legacy_files_on_dfl" is added which
makes subsystems which haven't decided the interface files for the
default hierarchy to present the legacy files on the default
hierarchy so that its behavior on the default hierarchy can be
tested. As the awkward name suggests, this is for development only.
* memcg's CFTYPE_INSANE on "use_hierarchy" is noop now as the whole
array isn't used on the default hierarchy. The flag is removed.
v2: Updated documentation for cgroup__DEVEL__legacy_files_on_dfl.
v3: Clear CFTYPE_ONLY_ON_DFL and CFTYPE_INSANE when cfts are removed
as suggested by Li.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Aristeu Rozanski <aris@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Currently, cftypes added by cgroup_add_cftypes() are used for both the
unified default hierarchy and legacy ones and subsystems can mark each
file with either CFTYPE_ONLY_ON_DFL or CFTYPE_INSANE if it has to
appear only on one of them. This is quite hairy and error-prone.
Also, we may end up exposing interface files to the default hierarchy
without thinking it through.
cgroup_subsys will grow two separate cftype addition functions and
apply each only on the hierarchies of the matching type. This will
allow organizing cftypes in a lot clearer way and encourage subsystems
to scrutinize the interface which is being exposed in the new default
hierarchy.
In preparation, this patch adds cgroup_add_legacy_cftypes() which
currently is a simple wrapper around cgroup_add_cftypes() and replaces
all cgroup_add_cftypes() usages with it.
While at it, this patch drops a completely spurious return from
__hugetlb_cgroup_file_init().
This patch doesn't introduce any functional differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Currently, cgroup_subsys->base_cftypes is used for both the unified
default hierarchy and legacy ones and subsystems can mark each file
with either CFTYPE_ONLY_ON_DFL or CFTYPE_INSANE if it has to appear
only on one of them. This is quite hairy and error-prone. Also, we
may end up exposing interface files to the default hierarchy without
thinking it through.
cgroup_subsys will grow two separate cftype arrays and apply each only
on the hierarchies of the matching type. This will allow organizing
cftypes in a lot clearer way and encourage subsystems to scrutinize
the interface which is being exposed in the new default hierarchy.
In preparation, this patch renames cgroup_subsys->base_cftypes to
cgroup_subsys->legacy_cftypes. This patch is pure rename.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Aristeu Rozanski <aris@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
sane_behavior has been used as a development vehicle for the default
unified hierarchy. Now that the default hierarchy is in place, the
flag became redundant and confusing as its usage is allowed on all
hierarchies. There are gonna be either the default hierarchy or
legacy ones. Let's make that clear by removing sane_behavior support
on non-default hierarchies.
This patch replaces cgroup_sane_behavior() with cgroup_on_dfl(). The
comment on top of CGRP_ROOT_SANE_BEHAVIOR is moved to on top of
cgroup_on_dfl() with sane_behavior specific part dropped.
On the default and legacy hierarchies w/o sane_behavior, this
shouldn't cause any behavior differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
cgroup_root->flags only contains CGRP_ROOT_* flags and there's no
reason to mask the flags. Remove CGRP_ROOT_OPTION_MASK.
This doesn't cause any behavior differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, the blkio subsystem attributes all of writeback IOs to the
root. One of the issues is that there's no way to tell who originated
a writeback IO from block layer. Those IOs are usually issued
asynchronously from a task which didn't have anything to do with
actually generating the dirty pages. The memory subsystem, when
enabled, already keeps track of the ownership of each dirty page and
it's desirable for blkio to piggyback instead of adding its own
per-page tag.
blkio piggybacking on memory is an implementation detail which
preferably should be handled automatically without requiring explicit
userland action. To achieve that, this patch implements
cgroup_subsys->depends_on which contains the mask of subsystems which
should be enabled together when the subsystem is enabled.
The previous patches already implemented the support for enabled but
invisible subsystems and cgroup_subsys->depends_on can be easily
implemented by updating cgroup_refresh_child_subsys_mask() so that it
calculates cgroup->child_subsys_mask considering
cgroup_subsys->depends_on of the explicitly enabled subsystems.
Documentation/cgroups/unified-hierarchy.txt is updated to explain that
subsystems may not become immediately available after being unused
from userland and that dependency could be a factor in it. As
subsystems may already keep residual references, this doesn't
significantly change how subsystem rebinding can be used.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
cgroup is implementing support for subsystem dependency which would
require a way to enable a subsystem even when it's not directly
configured through "cgroup.subtree_control".
The previous patches added support for explicitly and implicitly
enabled subsystems and showing/hiding their interface files. An
explicitly enabled subsystem may become implicitly enabled if it's
turned off through "cgroup.subtree_control" but there are subsystems
depending on it. In such cases, the subsystem, as it's turned off
when seen from userland, shouldn't enforce any resource control.
Also, the subsystem may be explicitly turned on later again and its
interface files should be as close to the intial state as possible.
This patch adds cgroup_subsys->css_reset() which is invoked when a css
is hidden. The callback should disable resource control and reset the
state to the vanilla state.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
cgroup is implementing support for subsystem dependency which would
require a way to enable a subsystem even when it's not directly
configured through "cgroup.subtree_control".
The preceding patch distinguished cgroup->subtree_control and
->child_subsys_mask where the former is the subsystems explicitly
configured by the userland and the latter is all enabled subsystems
currently is equal to the former but will include subsystems
implicitly enabled through dependency.
Subsystems which are enabled due to dependency shouldn't be visible to
userland. This patch updates cgroup_subtree_control_write() and
create_css() such that interface files are not created for implicitly
enabled subsytems.
* @visible paramter is added to create_css(). Interface files are
created only when true.
* If an already implicitly enabled subsystem is turned on through
"cgroup.subtree_control", the existing css should be used. css
draining is skipped.
* cgroup_subtree_control_write() computes the new target
cgroup->child_subsys_mask and create/kill or show/hide csses
accordingly.
As the two subsystem masks are still kept identical, this patch
doesn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
cgroup is implementing support for subsystem dependency which would
require a way to enable a subsystem even when it's not directly
configured through "cgroup.subtree_control".
Previously, cgroup->child_subsys_mask directly reflected
"cgroup.subtree_control" and the enabled subsystems in the child
cgroups. This patch adds cgroup->subtree_control which
"cgroup.subtree_control" operates on. cgroup->child_subsys_mask is
now calculated from cgroup->subtree_control by
cgroup_refresh_child_subsys_mask(), which sets it identical to
cgroup->subtree_control for now.
This will allow using cgroup->child_subsys_mask for all the enabled
subsystems including the implicit ones and ->subtree_control for
tracking the explicitly requested ones. This patch keeps the two
masks identical and doesn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
The debug controller, as its name suggests, exposes cgroup core
internals to userland to aid debugging. Unfortunately, except for the
name, there's no provision to prevent its usage in production
configurations and the controller is widely enabled and mounted
leaking internal details to userland. Like most other debug
information, the information exposed by debug isn't interesting even
for debugging itself once the related parts are working reliably.
This controller has no reason for existing. This patch implements
cgrp_dfl_root_inhibit_ss_mask which can suppress specific subsystems
on the default hierarchy and adds the debug subsystem to it so that it
can be gradually deprecated as usages move towards the unified
hierarchy.
Signed-off-by: Tejun Heo <tj@kernel.org>
Implement css_tryget() which tries to grab a cgroup_subsys_state's
reference as long as it already hasn't reached zero. Combined with
the recent css iterator changes to include offline && !released csses
during traversal, this can be used to access csses regardless of its
online state.
v2: Take the new flag CSS_NO_REF into account.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Now that cgroup liveliness and css onliness are the same state,
convert cgroup_has_live_children() into css_has_online_children() so
that it can be used for actual csses too. The function now uses
css_for_each_child() for iteration and is published.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Use CSS_ONLINE on the self css to indicate whether a cgroup has been
killed instead of CGRP_DEAD. This will allow re-using css online test
for cgroup liveliness test. This doesn't introduce any functional
change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, css_next_child() is implemented as finding the next child
cgroup which has the css enabled, which used to be the only way to do
it as only cgroups participated in sibling lists and thus could be
iteratd. This works as long as what's required during iteration is
not missing online csses; however, it turns out that there are use
cases where offlined but not yet released csses need to be iterated.
This is difficult to implement through cgroup iteration the unified
hierarchy as there may be multiple dying csses for the same subsystem
associated with single cgroup.
After the recent changes, the cgroup self and regular csses behave
identically in how they're linked and unlinked from the sibling lists
including assertion of CSS_RELEASED and css_next_child() can simply
switch to iterating csses directly. This both simplifies the logic
and ensures that all visible non-released csses are included in the
iteration whether there are multiple dying csses for a subsystem or
not.
As all other iterators depend on css_next_child() for sibling
iteration, this changes behaviors of all css iterators. Add and
update explanations on the css states which are included in traversal
to all iterators.
As css iteration could always contain offlined csses, this shouldn't
break any of the current users and new usages which need iteration of
all on and offline csses can make use of the new semantics.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
css iterations allow the caller to drop RCU read lock. As long as the
caller keeps the current position accessible, it can simply re-grab
RCU read lock later and continue iteration. This is achieved by using
CGRP_DEAD to detect whether the current positions next pointer is safe
to dereference and if not re-iterate from the beginning to the next
position using ->serial_nr.
CGRP_DEAD is used as the marker to invalidate the next pointer and the
only requirement is that the marker is set before the next sibling
starts its RCU grace period. Because CGRP_DEAD is set at the end of
cgroup_destroy_locked() but the cgroup is unlinked when the reference
count reaches zero, we currently have a rather large window where this
fallback re-iteration logic can be triggered.
This patch introduces CSS_RELEASED which is set when a css is unlinked
from its sibling list. This still keeps the re-iteration logic
working while drastically reducing the window of its activation.
While at it, rewrite the comment in css_next_child() to reflect the
new flag and better explain the synchronization.
This will also enable iterating csses directly instead of through
cgroups.
v2: CSS_RELEASED now assigned to 1 << 2 as 1 << 0 is used by
CSS_NO_REF.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
We're moving towards using cgroup_subsys_states as the fundamental
structural blocks. All csses including the cgroup->self and actual
ones now form trees through css->children and ->sibling which follow
the same rules as what cgroup->children and ->sibling followed. This
patch moves cgroup->serial_nr which is used to implement css iteration
into css.
Note that all csses, regardless of their types, allocate their serial
numbers from the same monotonically increasing counter. This doesn't
affect the ordering needed by css iteration or cause any other
material behavior changes. This will be used to update css iteration.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
We're moving towards using cgroup_subsys_states as the fundamental
structural blocks. Let's move cgroup->sibling and ->children into
cgroup_subsys_state. This is pure move without functional change and
only cgroup->self's fields are actually used. Other csses will make
use of the fields later.
While at it, update init_and_link_css() so that it zeroes the whole
css before initializing it and remove explicit zeroing of ->flags.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup->parent is redundant as cgroup->self.parent can also be used to
determine the parent cgroup and we're moving towards using
cgroup_subsys_states as the fundamental structural blocks. This patch
introduces cgroup_parent() which follows cgroup->self.parent and
removes cgroup->parent.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup in general is moving towards using cgroup_subsys_state as the
fundamental structural component and css_parent() was introduced to
convert from using cgroup->parent to css->parent. It was quite some
time ago and we're moving forward with making css more prominent.
This patch drops the trivial wrapper css_parent() and let the users
dereference css->parent. While at it, explicitly mark fields of css
which are public and immutable.
v2: New usage from device_cgroup.c converted.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: "David S. Miller" <davem@davemloft.net>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Johannes Weiner <hannes@cmpxchg.org>
9395a45004 ("cgroup: enable refcnting for root csses") enabled
reference counting for root csses (cgroup_subsys_states) so that
cgroup's self csses can be used to manage the lifetime of the
containing cgroups.
Unfortunately, this change was incorrect. During early init,
cgrp_dfl_root self css refcnt is used. percpu_ref can't initialized
during early init and its initialization is deferred till
cgroup_init() time. This means that cpu was using percpu_ref which
wasn't properly initialized. Due to the way percpu variables are laid
out on x86, this didn't blow up immediately on x86 but ended up
incrementing and decrementing the percpu variable at offset zero,
whatever it may be; however, on other archs, this caused fault and
early boot failure.
As cgroup self csses for root cgroups of non-dfl hierarchies need
working refcounting, we can't revert 9395a45004. This patch adds
CSS_NO_REF which explicitly inhibits reference counting on the css and
sets it on all normal (non-self) csses and cgroup_dfl_root self css.
v2: cgrp_dfl_root.self is the offending one. Set the flag on it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Stephen Warren <swarren@nvidia.com>
Fixes: 9395a45004 ("cgroup: enable refcnting for root csses")
Currently cgroup implements refcnting separately using atomic_t
cgroup->refcnt. The destruction paths of cgroup and css are rather
complex and bear a lot of similiarities including the use of RCU and
bouncing to a work item.
This patch makes cgroup use the refcnt of self css for refcnting
instead of using its own. This makes cgroup refcnting use css's
percpu refcnt and share the destruction mechanism.
* css_release_work_fn() and css_free_work_fn() are updated to handle
both csses and cgroups. This is a bit messy but should do until we
can make cgroup->self a full css, which currently can't be done
thanks to multiple hierarchies.
* cgroup_destroy_locked() now performs
percpu_ref_kill(&cgrp->self.refcnt) instead of cgroup_put(cgrp).
* Negative refcnt sanity check in cgroup_get() is no longer necessary
as percpu_ref already handles it.
* Similarly, as a cgroup which hasn't been killed will never be
released regardless of its refcnt value and percpu_ref has sanity
check on kill, cgroup_is_dead() sanity check in cgroup_put() is no
longer necessary.
* As whether a refcnt reached zero or not can only be decided after
the reference count is killed, cgroup_root->cgrp's refcnting can no
longer be used to decide whether to kill the root or not. Let's
make cgroup_kill_sb() explicitly initiate destruction if the root
doesn't have any children. This makes sense anyway as unmounted
cgroup hierarchy without any children should be destroyed.
While this is a bit messy, this will allow pushing more bookkeeping
towards cgroup->self and thus handling cgroups and csses in more
uniform way. In the very long term, it should be possible to
introduce a base subsystem and convert the self css to a proper one
making things whole lot simpler and unified.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, css_get(), css_tryget() and css_tryget_online() are noops
for root csses as an optimization; however, we're planning to use css
refcnts to track of cgroup lifetime too and root cgroups also need to
be reference counted. Since css has been converted to percpu_refcnt,
the overhead of refcnting is miniscule and this optimization isn't too
meaningful anymore. Furthermore, controllers which optimize the root
cgroup often never even invoke these functions in their hot paths.
This patch enables refcnting for root csses too. This makes CSS_ROOT
flag unused and removes it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup_destroy_css_killed() is cgroup destruction stage which happens
after all csses are offlined. After the recent updates, it no longer
does anything other than putting the base reference. This patch
removes the function and makes cgroup_destroy_locked() put the base
ref at the end isntead.
This also makes cgroup->nr_css unnecessary. Removed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup->dummy_css is used as the placeholder css when performing css
oriended operations on the cgroup. We're gonna shift more cgroup
management to this css. Let's rename it to ->self and move it to the
top.
This is pure rename and field relocation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Now that cgroup_subtree_control_write() has access to the associated
kernfs_open_file and thus the kernfs_node, there's no need to cache it
in cgroup->control_kn on creation. Remove cgroup->control_kn and use
@of->kn directly.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cftype->trigger() is pointless. It's trivial to ignore the input
buffer from a regular ->write() operation. Convert all ->trigger()
users to ->write() and remove ->trigger().
This patch doesn't introduce any visible behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Convert all cftype->write_string() users to the new cftype->write()
which maps directly to kernfs write operation and has full access to
kernfs and cgroup contexts. The conversions are mostly mechanical.
* @css and @cft are accessed using of_css() and of_cft() accessors
respectively instead of being specified as arguments.
* Should return @nbytes on success instead of 0.
* @buf is not trimmed automatically. Trim if necessary. Note that
blkcg and netprio don't need this as the parsers already handle
whitespaces.
cftype->write_string() has no user left after the conversions and
removed.
While at it, remove unnecessary local variable @p in
cgroup_subtree_control_write() and stale comment about
CGROUP_LOCAL_BUFFER_SIZE in cgroup_freezer.c.
This patch doesn't introduce any visible behavior changes.
v2: netprio was missing from conversion. Converted.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Aristeu Rozanski <arozansk@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: "David S. Miller" <davem@davemloft.net>
During the recent conversion to kernfs, cftype's seq_file operations
are updated so that they are directly mapped to kernfs operations and
thus can fully access the associated kernfs and cgroup contexts;
however, write path hasn't seen similar updates and none of the
existing write operations has access to, for example, the associated
kernfs_open_file.
Let's introduce a new operation cftype->write() which maps directly to
the kernfs write operation and has access to all the arguments and
contexts. This will replace ->write_string() and ->trigger() and ease
manipulation of kernfs active protection from cgroup file operations.
Two accessors - of_cft() and of_css() - are introduced to enable
accessing the associated cgroup context from cftype->write() which
only takes kernfs_open_file for the context information. The
accessors for seq_file operations - seq_cft() and seq_css() - are
rewritten to wrap the of_ accessors.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Unlike the more usual refcnting, what css_tryget() provides is the
distinction between online and offline csses instead of protection
against upping a refcnt which already reached zero. cgroup is
planning to provide actual tryget which fails if the refcnt already
reached zero. Let's rename the existing trygets so that they clearly
indicate that they're onliness.
I thought about keeping the existing names as-are and introducing new
names for the planned actual tryget; however, given that each
controller participates in the synchronization of the online state, it
seems worthwhile to make it explicit that these functions are about
on/offline state.
Rename css_tryget() to css_tryget_online() and css_tryget_from_dir()
to css_tryget_online_from_dir(). This is pure rename.
v2: cgroup_freezer grew new usages of css_tryget(). Update
accordingly.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Pull to receive e37a06f109 ("cgroup: fix the retry path of
cgroup_mount()") to avoid unnecessary conflicts with planned
cgroup_tree_mutex removal and also to be able to remove the temp fix
added by 36c38fb714 ("blkcg: use trylock on blkcg_pol_mutex in
blkcg_reset_stats()") afterwards.
Signed-off-by: Tejun Heo <tj@kernel.org>
Determining the css of a task usually requires RCU read lock as that's
the only thing which keeps the returned css accessible till its
reference is acquired; however, testing whether a task belongs to the
root can be performed without dereferencing the returned css by
comparing the returned pointer against the root one in init_css_set[]
which never changes.
Implement task_css_is_root() which can be invoked in any context.
This will be used by the scheduled cgroup_freezer change.
v2: cgroup no longer supports modular controllers. No need to export
init_css_set. Pointed out by Li.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
percpu_ref_tryget() is different from the usual tryget semantics in
that it fails if the refcnt is in its dying stage even if the refcnt
hasn't reached zero yet. We're about to introduce the more
conventional tryget and the current one has only one user. Let's
rename it to percpu_ref_tryget_live() so that it explicitly signifies
the peculiarities of its semantics.
This is pure rename.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Kent Overstreet <kmo@daterainc.com>
Until now, cgroup->id has been used to identify all the associated
csses and css_from_id() takes cgroup ID and returns the matching css
by looking up the cgroup and then dereferencing the css associated
with it; however, now that the lifetimes of cgroup and css are
separate, this is incorrect and breaks on the unified hierarchy when a
controller is disabled and enabled back again before the previous
instance is released.
This patch adds css->id which is a subsystem-unique ID and converts
css_from_id() to look up by the new css->id instead. memcg is the
only user of css_from_id() and also converted to use css->id instead.
For traditional hierarchies, this shouldn't make any functional
difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jianyu Zhan <nasa4836@gmail.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, cgroup->id is allocated from 0, which is always assigned to
the root cgroup; unfortunately, memcg wants to use ID 0 to indicate
invalid IDs and ends up incrementing all IDs by one.
It's reasonable to reserve 0 for special purposes. This patch updates
cgroup core so that ID 0 is not used and the root cgroups get ID 1.
The ID incrementing is removed form memcg.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Li Zefan <lizefan@huawei.com>
There's no reason to use atomic bitops for cgroup_subsys_state->flags,
cgroup_root->flags and various subsys_masks. This patch updates those
to use bitwise and/or operations instead and converts them form
unsigned long to unsigned int.
This makes the fields occupy (marginally) smaller space and makes it
clear that they don't require atomicity.
This patch doesn't cause any behavior difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup users often need a way to determine when a cgroup's
subhierarchy becomes empty so that it can be cleaned up. cgroup
currently provides release_agent for it; unfortunately, this mechanism
is riddled with issues.
* It delivers events by forking and execing a userland binary
specified as the release_agent. This is a long deprecated method of
notification delivery. It's extremely heavy, slow and cumbersome to
integrate with larger infrastructure.
* There is single monitoring point at the root. There's no way to
delegate management of a subtree.
* The event isn't recursive. It triggers when a cgroup doesn't have
any tasks or child cgroups. Events for internal nodes trigger only
after all children are removed. This again makes it impossible to
delegate management of a subtree.
* Events are filtered from the kernel side. "notify_on_release" file
is used to subscribe to or suppress release event. This is
unnecessarily complicated and probably done this way because event
delivery itself was expensive.
This patch implements interface file "cgroup.populated" which can be
used to monitor whether the cgroup's subhierarchy has tasks in it or
not. Its value is 0 if there is no task in the cgroup and its
descendants; otherwise, 1, and kernfs_notify() notificaiton is
triggers when the value changes, which can be monitored through poll
and [di]notify.
This is a lot ligther and simpler and trivially allows delegating
management of subhierarchy - subhierarchy monitoring can block further
propgation simply by putting itself or another process in the root of
the subhierarchy and monitor events that it's interested in from there
without interfering with monitoring higher in the tree.
v2: Patch description updated as per Serge.
v3: "cgroup.subtree_populated" renamed to "cgroup.populated". The
subtree_ prefix was a bit confusing because
"cgroup.subtree_control" uses it to denote the tree rooted at the
cgroup sans the cgroup itself while the populated state includes
the cgroup itself.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Lennart Poettering <lennart@poettering.net>
cgroup is switching away from multiple hierarchies and will use one
unified default hierarchy where controllers can be dynamically enabled
and disabled per subtree. The default hierarchy will serve as the
unified hierarchy to which all controllers are attached and a css on
the default hierarchy would need to also serve the tasks of descendant
cgroups which don't have the controller enabled - ie. the tree may be
collapsed from leaf towards root when viewed from specific
controllers. This has been implemented through effective css in the
previous patches.
This patch finally implements dynamic subtree controller
enable/disable on the default hierarchy via a new knob -
"cgroup.subtree_control" which controls which controllers are enabled
on the child cgroups. Let's assume a hierarchy like the following.
root - A - B - C
\ D
root's "cgroup.subtree_control" determines which controllers are
enabled on A. A's on B. B's on C and D. This coincides with the
fact that controllers on the immediate sub-level are used to
distribute the resources of the parent. In fact, it's natural to
assume that resource control knobs of a child belong to its parent.
Enabling a controller in "cgroup.subtree_control" declares that
distribution of the respective resources of the cgroup will be
controlled. Note that this means that controller enable states are
shared among siblings.
The default hierarchy has an extra restriction - only cgroups which
don't contain any task may have controllers enabled in
"cgroup.subtree_control". Combined with the other properties of the
default hierarchy, this guarantees that, from the view point of
controllers, tasks are only on the leaf cgroups. In other words, only
leaf csses may contain tasks. This rules out situations where child
cgroups compete against internal tasks of the parent, which is a
competition between two different types of entities without any clear
way to determine resource distribution between the two. Different
controllers handle it differently and all the implemented behaviors
are ambiguous, ad-hoc, cumbersome and/or just wrong. Having this
structural constraints imposed from cgroup core removes the burden
from controller implementations and enables showing one consistent
behavior across all controllers.
When a controller is enabled or disabled, css associations for the
controller in the subtrees of each child should be updated. After
enabling, the whole subtree of a child should point to the new css of
the child. After disabling, the whole subtree of a child should point
to the cgroup's css. This is implemented by first updating cgroup
states such that cgroup_e_css() result points to the appropriate css
and then invoking cgroup_update_dfl_csses() which migrates all tasks
in the affected subtrees to the self cgroup on the default hierarchy.
* When read, "cgroup.subtree_control" lists all the currently enabled
controllers on the children of the cgroup.
* White-space separated list of controller names prefixed with either
'+' or '-' can be written to "cgroup.subtree_control". The ones
prefixed with '+' are enabled on the controller and '-' disabled.
* A controller can be enabled iff the parent's
"cgroup.subtree_control" enables it and disabled iff no child's
"cgroup.subtree_control" has it enabled.
* If a cgroup has tasks, no controller can be enabled via
"cgroup.subtree_control". Likewise, if "cgroup.subtree_control" has
some controllers enabled, tasks can't be migrated into the cgroup.
* All controllers which aren't bound on other hierarchies are
automatically associated with the root cgroup of the default
hierarchy. All the controllers which are bound to the default
hierarchy are listed in the read-only file "cgroup.controllers" in
the root directory.
* "cgroup.controllers" in all non-root cgroups is read-only file whose
content is equal to that of "cgroup.subtree_control" of the parent.
This indicates which controllers can be used in the cgroup's
"cgroup.subtree_control".
This is still experimental and there are some holes, one of which is
that ->can_attach() failure during cgroup_update_dfl_csses() may leave
the cgroups in an undefined state. The issues will be addressed by
future patches.
v2: Non-root cgroups now also have "cgroup.controllers".
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
To implement the unified hierarchy behavior, we'll need to be able to
determine the associated cgroup on the default hierarchy from css_set.
Let's add css_set->dfl_cgrp so that it can be accessed conveniently
and efficiently.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, css_task_iter iterates tasks associated with a css by
visiting each css_set associated with the owning cgroup and walking
tasks of each of them. This works fine for !unified hierarchies as
each cgroup has its own css for each associated subsystem on the
hierarchy; however, on the planned unified hierarchy, a cgroup may not
have csses associated and its tasks would be considered associated
with the matching css of the nearest ancestor which has the subsystem
enabled.
This means that on the default unified hierarchy, just walking all
tasks associated with a cgroup isn't enough to walk all tasks which
are associated with the specified css. If any of its children doesn't
have the matching css enabled, task iteration should also include all
tasks from the subtree. We already added cgroup->e_csets[] to list
all css_sets effectively associated with a given css and walk css_sets
on that list instead to achieve such iteration.
This patch updates css_task_iter iteration such that it walks css_sets
on cgroup->e_csets[] instead of cgroup->cset_links if iteration is
requested on an non-dummy css. Thanks to the previous iteration
update, this change can be achieved with the addition of
css_task_iter->ss and minimal updates to css_advance_task_iter() and
css_task_iter_start().
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This patch reorganizes css_task_iter so that adding effective css
support is easier.
* s/->cset_link/->cset_pos/ and s/->task/->task_pos/ for consistency
* ->origin_css is used to determine whether the iteration reached the
last css_set. Replace it with explicit ->cset_head so that
css_advance_task_iter() doesn't have to know the termination
condition directly.
* css_task_iter_next() currently assumes that it's walking list of
cgrp_cset_link and reaches into the current cset through the current
link to determine the termination conditions for task walking. As
this won't always be true for effective css walking, add
->tasks_head and ->mg_tasks_head and use them to control task
walking so that css_task_iter_next() doesn't have to know how
css_sets are being walked.
This patch doesn't make any behavior changes. The iteration logic
stays unchanged after the patch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
On the default unified hierarchy, a cgroup may be associated with
csses of its ancestors, which means that a css of a given cgroup may
be associated with css_sets of descendant cgroups. This means that we
can't walk all tasks associated with a css by iterating the css_sets
associated with the cgroup as there are css_sets which are pointing to
the css but linked on the descendants.
This patch adds per-subsystem list heads cgroup->e_csets[]. Any
css_set which is pointing to a css is linked to
css->cgroup->e_csets[$SUBSYS_ID] through
css_set->e_cset_node[$SUBSYS_ID]. The lists are protected by
css_set_rwsem and will allow us to walk all css_sets associated with a
given css so that we can find out all associated tasks.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
944196278d ("cgroup: move ->subsys_mask from cgroupfs_root to
cgroup") moved ->subsys_mask from cgroup_root to cgroup to prepare for
the unified hierarhcy; however, it turns out that carrying the
subsys_mask of the children in the parent, instead of itself, is a lot
more natural. This patch restores cgroup_root->subsys_mask and morphs
cgroup->subsys_mask into cgroup->child_subsys_mask.
* Uses of root->cgrp.subsys_mask are restored to root->subsys_mask.
* Remove automatic setting and clearing of cgrp->subsys_mask and
instead just inherit ->child_subsys_mask from the parent during
cgroup creation. Note that this doesn't affect any current
behaviors.
* Undo __kill_css() separation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This cftype flag makes the file only appear on the default hierarchy.
This will later be used for cgroup.controllers file.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgrp_dfl_root will be used as the default unified hierarchy. This
patch makes cgrp_dfl_root mountable by making the following changes.
* cgroup_init_early() now initializes cgrp_dfl_root w/
CGRP_ROOT_SANE_BEHAVIOR. The default hierarchy is always sane.
* parse_cgroupfs_options() and cgroup_mount() are updated such that
cgrp_dfl_root is mounted if sane_behavior is specified w/o any
subsystems.
* rebind_subsystems() now populates the root directory of
cgrp_dfl_root. Note that the function still guarantees success of
rebinding subsystems to cgrp_dfl_root. If populating fails while
rebinding to cgrp_dfl_root, it whines but ignores the error.
* For backward compatibility, the default hierarchy shows up in
/proc/$PID/cgroup only after it's explicitly mounted so that
userland which doesn't make use of it doesn't see any change.
* "current_css_set_cg_links" file of debug cgroup now treats the
default hierarchy the same as other hierarchies. This is visible to
userland. Given that it's for debug controller, this should be
fine.
* While at it, implement cgroup_on_dfl() which tests whether a give
cgroup is on the default hierarchy or not.
The above changes make cgrp_dfl_root mostly equivalent to other
controllers but the actual unified hierarchy behaviors are not
implemented yet. Let's plug child cgroup creation in cgrp_dfl_root
from create_cgroup() for now.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cftype->write_string() just passes on the writeable buffer from kernfs
and there's no reason to add const restriction on the buffer. The
only thing const achieves is unnecessarily complicating parsing of the
buffer. Drop const from @buffer.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
The dummy root will be repurposed to serve as the default unified
hierarchy. Let's rename things in preparation.
* s/cgroup_dummy_root/cgrp_dfl_root/
* s/cgroupfs_root/cgroup_root/ as we don't do fs part directly anymore
* s/cgroup_root->top_cgroup/cgroup_root->cgrp/ for brevity
This is pure rename.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroupfs_root->subsys_mask represents the controllers attached to the
hierarchy. This patch moves the field to cgroup. Subsystem
initialization and rebinding updates the top cgroup's subsys_mask.
For !root cgroups, the subsys_mask bits are set from create_css() and
cleared from kill_css(), which effectively means that all cgroups will
have the same subsys_mask as the top cgroup.
While this doesn't make any difference now, this will help
implementation of the default unified hierarchy where !root cgroups
may have subsets of the top_cgroup's subsys_mask.
While at it, __kill_css() is split out of kill_css(). The former
doesn't care about the subsys_mask while the latter becomes noop if
the controller is already killed and clears the matching bit if not
before proceeding to killing the css. This will be used later by the
default unified hierarchy implementation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
The dummy hierarchy is now a fully functional one and dummy_top has a
kernfs_node associated with it. Drop the NULL checks in
[pr_cont_]cont_{name|path}() which are no longer necessary.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
For optimization, task_lock() is additionally used to protect
task->cgroups. The optimization is pretty dubious as either
css_set_rwsem is grabbed anyway or PF_EXITING already protects
task->cgroups. It adds only overhead and confusion at this point.
Let's drop task_[un]lock() and update comments accordingly.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, process / task migration is a single operation which may
fail depending on memory pressure or the involved controllers'
->can_attach() callbacks. One problem with this approach is migration
of multiple targets. It's impossible to tell whether a given target
will be successfully migrated beforehand and cgroup core can't keep
track of enough states to roll back after intermediate failure.
This is already an issue with cgroup_transfer_tasks(). Also, we're
gonna need multiple target migration for unified hierarchy.
This patch splits migration into four stages -
cgroup_migrate_add_src(), cgroup_migrate_prepare_dst(),
cgroup_migrate() and cgroup_migrate_finish(), where
cgroup_migrate_prepare_dst() performs all the operations which may
fail due to allocation failure without actually migrating the target.
The four separate stages mean that, disregarding ->can_attach()
failures, the success or failure of multi target migration can be
determined before performing any actual migration. If preparations of
all targets succeed, the whole thing will succeed. If not, the whole
operation can fail without any side-effect.
Since the previous patch to use css_set->mg_tasks to keep track of
migration targets, the only thing which may need memory allocation
during migration is the target css_sets. cgroup_migrate_prepare()
pins all source and target css_sets and link them up. Note that this
can be performed without holding threadgroup_lock even if the target
is a process. As long as cgroup_mutex is held, no new css_set can be
put into play.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, while migrating tasks from one cgroup to another,
cgroup_attach_task() builds a flex array of all target tasks;
unfortunately, this has a couple issues.
* Flex array has size limit. On 64bit, struct task_and_cgroup is
24bytes making the flex element limit around 87k. It is a high
number but not impossible to hit. This means that the current
cgroup implementation can't migrate a process with more than 87k
threads.
* Process migration involves memory allocation whose size is dependent
on the number of threads the process has. This means that cgroup
core can't guarantee success or failure of multi-process migrations
as memory allocation failure can happen in the middle. This is in
part because cgroup can't grab threadgroup locks of multiple
processes at the same time, so when there are multiple processes to
migrate, it is imposible to tell how many tasks are to be migrated
beforehand.
Note that this already affects cgroup_transfer_tasks(). cgroup
currently cannot guarantee atomic success or failure of the
operation. It may fail in the middle and after such failure cgroup
doesn't have enough information to roll back properly. It just
aborts with some tasks migrated and others not.
To resolve the situation, this patch updates the migration path to use
task->cg_list to track target tasks. The previous patch already added
css_set->mg_tasks and updated iterations in non-migration paths to
include them during task migration. This patch updates migration path
to actually make use of it.
Instead of putting onto a flex_array, each target task is moved from
its css_set->tasks list to css_set->mg_tasks and the migration path
keeps trace of all the source css_sets and the associated cgroups.
Once all source css_sets are determined, the destination css_set for
each is determined, linked to the matching source css_set and put on a
separate list.
To iterate the target tasks, migration path just needs to iterat
through either the source or target css_sets, depending on whether
migration has been committed or not, and the tasks on their ->mg_tasks
lists. cgroup_taskset is updated to contain the list_heads for source
and target css_sets and the iteration cursor. cgroup_taskset_*() are
accordingly updated to walk through css_sets and their ->mg_tasks.
This resolves the above listed issues with moderate additional
complexity.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, while migrating tasks from one cgroup to another,
cgroup_attach_task() builds a flex array of all target tasks;
unfortunately, this has a couple issues.
* Flex array has size limit. On 64bit, struct task_and_cgroup is
24bytes making the flex element limit around 87k. It is a high
number but not impossible to hit. This means that the current
cgroup implementation can't migrate a process with more than 87k
threads.
* Process migration involves memory allocation whose size is dependent
on the number of threads the process has. This means that cgroup
core can't guarantee success or failure of multi-process migrations
as memory allocation failure can happen in the middle. This is in
part because cgroup can't grab threadgroup locks of multiple
processes at the same time, so when there are multiple processes to
migrate, it is imposible to tell how many tasks are to be migrated
beforehand.
Note that this already affects cgroup_transfer_tasks(). cgroup
currently cannot guarantee atomic success or failure of the
operation. It may fail in the middle and after such failure cgroup
doesn't have enough information to roll back properly. It just
aborts with some tasks migrated and others not.
To resolve the situation, we're going to use task->cg_list during
migration too. Instead of building a separate array, target tasks
will be linked into a dedicated migration list_head on the owning
css_set. Tasks on the migration list are treated the same as tasks on
the usual tasks list; however, being on a separate list allows cgroup
migration code path to keep track of the target tasks by simply
keeping the list of css_sets with tasks being migrated, making
unpredictable dynamic allocation unnecessary.
In prepartion of such migration path update, this patch introduces
css_set->mg_tasks list and updates css_set task iterations so that
they walk both css_set->tasks and ->mg_tasks. Note that ->mg_tasks
isn't used yet.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
My kernel fails to boot, because blkcg calls cgroup_path() while
cgroupfs is not mounted.
Fix both cgroup_name() and cgroup_path().
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The two functions don't have any users left. Remove them along with
cgroup_taskset->cur_cgrp.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
If !NULL, @skip_css makes cgroup_taskset_for_each() skip the matching
css. The intention of the interface is to make it easy to skip css's
(cgroup_subsys_states) which already match the migration target;
however, this is entirely unnecessary as migration taskset doesn't
include tasks which are already in the target cgroup. Drop @skip_css
from cgroup_taskset_for_each().
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Daniel Borkmann <dborkman@redhat.com>
cgroup_task_count() read-locks css_set_lock and walks all tasks to
count them and then returns the result. The only thing all the users
want is determining whether the cgroup is empty or not. This patch
implements cgroup_has_tasks() which tests whether cgroup->cset_links
is empty, replaces all cgroup_task_count() usages and unexports it.
Note that the test isn't synchronized. This is the same as before.
The test has always been racy.
This will help planned css_set locking update.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Before kernfs conversion, due to the way super_block lookup works,
cgroup roots were created and made visible before being fully
initialized. This in turn required a special flag to mark that the
root hasn't been fully initialized so that the destruction path can
tell fully bound ones from half initialized.
That flag is CGRP_ROOT_SUBSYS_BOUND and no longer necessary after the
kernfs conversion as the lookup and creation of new root are atomic
w.r.t. cgroup_mutex. This patch removes the flag and passes the
requests subsystem mask to cgroup_setup_root() so that it can set the
respective mask bits as subsystems are bound.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Disallow more mount options if sane_behavior. Note that xattr used to
generate warning.
While at it, simplify option check in cgroup_mount() and update
sane_behavior comment in cgroup.h.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, cgroupfs_root and its ->top_cgroup are separated reference
counted and the latter's is ignored. There's no reason to do this
separately. This patch removes cgroupfs_root->refcnt and destroys
cgroupfs_root when the top_cgroup is released.
* cgroup_put() updated to ignore cgroup_is_dead() test for top
cgroups. cgroup_free_fn() updated to handle root destruction when
releasing a top cgroup.
* As root destruction is now bounced through cgroup destruction, it is
asynchronous. Update cgroup_mount() so that it waits for pending
release which is currently implemented using msleep(). Converting
this to proper wait_queue isn't hard but likely unnecessary.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
root->number_of_cgroups is currently an integer protected with
cgroup_mutex. Except for sanity checks and proc reporting, the only
place it's used is to check whether the root has any child during
remount; however, this is a bit flawed as the counter is not
decremented when the cgroup is unlinked but when it's released,
meaning that there could be an extended period where all cgroups are
removed but remount is still not allowed because some internal objects
are lingering. While not perfect either, it'd be better to use
emptiness test on root->top_cgroup.children.
This patch updates cgroup_remount() to test top_cgroup's children
instead, which makes number_of_cgroups only actual usage statistics
printing in proc implemented in proc_cgroupstats_show(). Let's
shorten its name and make it an atomic_t so that we don't have to
worry about its synchronization. It's purely auxiliary at this point.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup->name handling became quite complicated over time involving
dedicated struct cgroup_name for RCU protection. Now that cgroup is
on kernfs, we can drop all of it and simply use kernfs_name/path() and
friends. Replace cgroup->name and all related code with kernfs
name/path constructs.
* Reimplement cgroup_name() and cgroup_path() as thin wrappers on top
of kernfs counterparts, which involves semantic changes.
pr_cont_cgroup_name() and pr_cont_cgroup_path() added.
* cgroup->name handling dropped from cgroup_rename().
* All users of cgroup_name/path() updated to the new semantics. Users
which were formatting the string just to printk them are converted
to use pr_cont_cgroup_name/path() instead, which simplifies things
quite a bit. As cgroup_name() no longer requires RCU read lock
around it, RCU lockings which were protecting only cgroup_name() are
removed.
v2: Comment above oom_info_lock updated as suggested by Michal.
v3: dummy_top doesn't have a kn associated and
pr_cont_cgroup_name/path() ended up calling the matching kernfs
functions with NULL kn leading to oops. Test for NULL kn and
print "/" if so. This issue was reported by Fengguang Wu.
v4: Rebased on top of 0ab02ca8f8 ("cgroup: protect modifications to
cgroup_idr with cgroup_mutex").
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
cftype_set was added primarily to allow registering the same cftype
array more than once for different subsystems. Nobody uses or needs
such thing and it's already broken because each cftype has ->ss
pointer which is initialized during registration.
Let's add list_head ->node to cftype and use the first cftype entry in
the array to link them instead of allocating separate cftype_set.
While at it, trigger WARN if cft seems previously initialized during
registration.
This simplifies cftype handling a bit.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Mount option "xattr" is no longer necessary as it's enabled by default
on kernfs. Warn if "xattr" is specified with "sane_behavior" so that
the option can be removed in the future.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup filesystem code was derived from the original sysfs
implementation which was heavily intertwined with vfs objects and
locking with the goal of re-using the existing vfs infrastructure.
That experiment turned out rather disastrous and sysfs switched, a
long time ago, to distributed filesystem model where a separate
representation is maintained which is queried by vfs. Unfortunately,
cgroup stuck with the failed experiment all these years and
accumulated even more problems over time.
Locking and object lifetime management being entangled with vfs is
probably the most egregious. vfs is never designed to be misused like
this and cgroup ends up jumping through various convoluted dancing to
make things work. Even then, operations across multiple cgroups can't
be done safely as it'll deadlock with rename locking.
Recently, kernfs is separated out from sysfs so that it can be used by
users other than sysfs. This patch converts cgroup to use kernfs,
which will bring the following benefits.
* Separation from vfs internals. Locking and object lifetime
management is contained in cgroup proper making things a lot
simpler. This removes significant amount of locking convolutions,
hairy object lifetime rules and the restriction on multi-cgroup
operations.
* Can drop a lot of code to implement filesystem interface as most are
provided by kernfs.
* Proper "severing" semantics, which allows controllers to not worry
about lingering file accesses after offline.
While the preceding patches did as much as possible to make the
transition less painful, large part of the conversion has to be one
discrete step making this patch rather large. The rest of the commit
message lists notable changes in different areas.
Overall
-------
* vfs constructs replaced with kernfs ones. cgroup->dentry w/ ->kn,
cgroupfs_root->sb w/ ->kf_root.
* All dentry accessors are removed. Helpers to map from kernfs
constructs are added.
* All vfs plumbing around dentry, inode and bdi removed.
* cgroup_mount() now directly looks for matching root and then
proceeds to create a new one if not found.
Synchronization and object lifetime
-----------------------------------
* vfs inode locking removed. Among other things, this removes the
need for the convolution in cgroup_cfts_commit(). Future patches
will further simplify it.
* vfs refcnting replaced with cgroup internal ones. cgroup->refcnt,
cgroupfs_root->refcnt added. cgroup_put_root() now directly puts
root->refcnt and when it reaches zero proceeds to destroy it thus
merging cgroup_put_root() and the former cgroup_kill_sb().
Simliarly, cgroup_put() now directly schedules cgroup_free_rcu()
when refcnt reaches zero.
* Unlike before, kernfs objects don't hold onto cgroup objects. When
cgroup destroys a kernfs node, all existing operations are drained
and the association is broken immediately. The same for
cgroupfs_roots and mounts.
* All operations which come through kernfs guarantee that the
associated cgroup is and stays valid for the duration of operation;
however, there are two paths which need to find out the associated
cgroup from dentry without going through kernfs -
css_tryget_from_dir() and cgroupstats_build(). For these two,
kernfs_node->priv is RCU managed so that they can dereference it
under RCU read lock.
File and directory handling
---------------------------
* File and directory operations converted to kernfs_ops and
kernfs_syscall_ops.
* xattrs is implicitly supported by kernfs. No need to worry about it
from cgroup. This means that "xattr" mount option is no longer
necessary. A future patch will add a deprecated warning message
when sane_behavior.
* When cftype->max_write_len > PAGE_SIZE, it's necessary to make a
private copy of one of the kernfs_ops to set its atomic_write_len.
cftype->kf_ops is added and cgroup_init/exit_cftypes() are updated
to handle it.
* cftype->lockdep_key added so that kernfs lockdep annotation can be
per cftype.
* Inidividual file entries and open states are now managed by kernfs.
No need to worry about them from cgroup. cfent, cgroup_open_file
and their friends are removed.
* kernfs_nodes are created deactivated and kernfs_activate()
invocations added to places where creation of new nodes are
committed.
* cgroup_rmdir() uses kernfs_[un]break_active_protection() for
self-removal.
v2: - Li pointed out in an earlier patch that specifying "name="
during mount without subsystem specification should succeed if
there's an existing hierarchy with a matching name although it
should fail with -EINVAL if a new hierarchy should be created.
Prior to the conversion, this used by handled by deferring
failure from NULL return from cgroup_root_from_opts(), which was
necessary because root was being created before checking for
existing ones. Note that cgroup_root_from_opts() returned an
ERR_PTR() value for error conditions which require immediate
mount failure.
As we now have separate search and creation steps, deferring
failure from cgroup_root_from_opts() is no longer necessary.
cgroup_root_from_opts() is updated to always return ERR_PTR()
value on failure.
- The logic to match existing roots is updated so that a mount
attempt with a matching name but different subsys_mask are
rejected. This was handled by a separate matching loop under
the comment "Check for name clashes with existing mounts" but
got lost during conversion. Merge the check into the main
search loop.
- Add __rcu __force casting in RCU_INIT_POINTER() in
cgroup_destroy_locked() to avoid the sparse address space
warning reported by kbuild test bot. Maybe we want an explicit
interface to use kn->priv as RCU protected pointer?
v3: Make CONFIG_CGROUPS select CONFIG_KERNFS.
v4: Rebased on top of 0ab02ca8f8 ("cgroup: protect modifications to
cgroup_idr with cgroup_mutex").
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: kbuild test robot fengguang.wu@intel.com>
* Un-inline seq_css(). After kernfs conversion, the function will
need to dereference internal data structures.
* Add cgroup_get/put_root() and replace direct super_block->s_active
manipulatinos with them. These will be converted to kernfs_root
refcnting.
* Add cgroup_get/put() and replace dget/put() on cgrp->dentry with
them. These will be converted to kernfs refcnting.
* Update current_css_set_cg_links_read() to use cgroup_name() instead
of reaching into the dentry name. The end result is the same.
These changes don't make functional differences but will make
transition to kernfs easier.
v2: Rebased on top of 0ab02ca8f8 ("cgroup: protect modifications to
cgroup_idr with cgroup_mutex").
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
mm/memory-failure.c::hwpoison_filter_task() has been reaching into
cgroup to extract the associated ino to be used as a filtering
criterion. This is an implementation detail which shouldn't be
depended upon from outside cgroup proper and is about to change with
the scheduled kernfs conversion.
This patch introduces a proper interface to determine the associated
ino, cgroup_ino(), and updates hwpoison_filter_task() to use it
instead of reaching directly into cgroup.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
cftype->max_write_len is used to extend the maximum size of writes.
It's interpreted in such a way that the actual maximum size is one
less than the specified value. The default size is defined by
CGROUP_LOCAL_BUFFER_SIZE. Its interpretation is quite confusing - its
value is decremented by 1 and then compared for equality with max
size, which means that the actual default size is
CGROUP_LOCAL_BUFFER_SIZE - 2, which is 62 chars.
There's no point in having a limit that low. Update its definition so
that it means the actual string length sans termination and anything
below PAGE_SIZE-1 is treated as PAGE_SIZE-1.
.max_write_len for "release_agent" is updated to PATH_MAX-1 and
cgroup_release_agent_write() is updated so that the redundant strlen()
check is removed and it uses strlcpy() instead of strcpy().
.max_write_len initializations in blk-throttle.c and cfq-iosched.c are
no longer necessary and removed. The one in cpuset is kept unchanged
as it's an approximated value to begin with.
This will also make transition to kernfs smoother.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, cgroup_subsys->base_cftypes registration is different from
dynamic cftypes registartion. Instead of going through
cgroup_add_cftypes(), cgroup_init_subsys() invokes
cgroup_init_cftsets() which makes use of cgroup_subsys->base_cftset
which doesn't involve dynamic allocation.
While avoiding dynamic allocation is somewhat nice, having two
separate paths for cftypes registration is nasty, especially as we're
planning to add more operations during cftypes registration.
This patch drops cgroup_init_cftsets() and cgroup_subsys->base_cftset
and registers base_cftypes using cgroup_add_cftypes(). This is done
as a separate step in cgroup_init() instead of a part of
cgroup_init_subsys(). This is because cgroup_init_subsys() can be
called very early during boot when kmalloc() isn't available yet.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
css_from_dir() returns the matching css (cgroup_subsys_state) given a
dentry and subsystem. The function doesn't pin the css before
returning and requires the caller to be holding RCU read lock or
cgroup_mutex and handling pinning on the caller side.
Given that users of the function are likely to want to pin the
returned css (both existing users do) and that getting and putting
css's are very cheap, there's no reason for the interface to be tricky
like this.
Rename css_from_dir() to css_tryget_from_dir() and make it try to pin
the found css and return it only if pinning succeeded. The callers
are updated so that they no longer do RCU locking and pinning around
the function and just use the returned css.
This will also ease converting cgroup to kernfs.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Pull for-3.14-fixes to receive 0ab02ca8f8 ("cgroup: protect
modifications to cgroup_idr with cgroup_mutex") prior to kernfs
conversion series to avoid non-trivial conflicts.
Signed-off-by: Tejun Heo <tj@kernel.org>
Setup cgroupfs like this:
# mount -t cgroup -o cpuacct xxx /cgroup
# mkdir /cgroup/sub1
# mkdir /cgroup/sub2
Then run these two commands:
# for ((; ;)) { mkdir /cgroup/sub1/tmp && rmdir /mnt/sub1/tmp; } &
# for ((; ;)) { mkdir /cgroup/sub2/tmp && rmdir /mnt/sub2/tmp; } &
After seconds you may see this warning:
------------[ cut here ]------------
WARNING: CPU: 1 PID: 25243 at lib/idr.c:527 sub_remove+0x87/0x1b0()
idr_remove called for id=6 which is not allocated.
...
Call Trace:
[<ffffffff8156063c>] dump_stack+0x7a/0x96
[<ffffffff810591ac>] warn_slowpath_common+0x8c/0xc0
[<ffffffff81059296>] warn_slowpath_fmt+0x46/0x50
[<ffffffff81300aa7>] sub_remove+0x87/0x1b0
[<ffffffff810f3f02>] ? css_killed_work_fn+0x32/0x1b0
[<ffffffff81300bf5>] idr_remove+0x25/0xd0
[<ffffffff810f2bab>] cgroup_destroy_css_killed+0x5b/0xc0
[<ffffffff810f4000>] css_killed_work_fn+0x130/0x1b0
[<ffffffff8107cdbc>] process_one_work+0x26c/0x550
[<ffffffff8107eefe>] worker_thread+0x12e/0x3b0
[<ffffffff81085f96>] kthread+0xe6/0xf0
[<ffffffff81570bac>] ret_from_fork+0x7c/0xb0
---[ end trace 2d1577ec10cf80d0 ]---
It's because allocating/removing cgroup ID is not properly synchronized.
The bug was introduced when we converted cgroup_ida to cgroup_idr.
While synchronization is already done inside ida_simple_{get,remove}(),
users are responsible for concurrent calls to idr_{alloc,remove}().
tj: Refreshed on top of b58c89986a ("cgroup: fix error return from
cgroup_create()").
Fixes: 4e96ee8e98 ("cgroup: convert cgroup_ida to cgroup_idr")
Cc: <stable@vger.kernel.org> #3.12+
Reported-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
It's no longer referenced outside cgroup core, so renaming is easy.
Let's rename it for consistency & brevity.
This patch is pure rename.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup_subsys is a bit messier than it needs to be.
* The name of a subsys can be different from its internal identifier
defined in cgroup_subsys.h. Most subsystems use the matching name
but three - cpu, memory and perf_event - use different ones.
* cgroup_subsys_id enums are postfixed with _subsys_id and each
cgroup_subsys is postfixed with _subsys. cgroup.h is widely
included throughout various subsystems, it doesn't and shouldn't
have claim on such generic names which don't have any qualifier
indicating that they belong to cgroup.
* cgroup_subsys->subsys_id should always equal the matching
cgroup_subsys_id enum; however, we require each controller to
initialize it and then BUG if they don't match, which is a bit
silly.
This patch cleans up cgroup_subsys names and initialization by doing
the followings.
* cgroup_subsys_id enums are now postfixed with _cgrp_id, and each
cgroup_subsys with _cgrp_subsys.
* With the above, renaming subsys identifiers to match the userland
visible names doesn't cause any naming conflicts. All non-matching
identifiers are renamed to match the official names.
cpu_cgroup -> cpu
mem_cgroup -> memory
perf -> perf_event
* controllers no longer need to initialize ->subsys_id and ->name.
They're generated in cgroup core and set automatically during boot.
* Redundant cgroup_subsys declarations removed.
* While updating BUG_ON()s in cgroup_init_early(), convert them to
WARN()s. BUGging that early during boot is stupid - the kernel
can't print anything, even through serial console and the trap
handler doesn't even link stack frame properly for back-tracing.
This patch doesn't introduce any behavior changes.
v2: Rebased on top of fe1217c4f3 ("net: net_cls: move cgroupfs
classid handling into core").
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: "David S. Miller" <davem@davemloft.net>
Acked-by: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Acked-by: Ingo Molnar <mingo@redhat.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Serge E. Hallyn <serue@us.ibm.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Thomas Graf <tgraf@suug.ch>
With module supported dropped from net_prio, no controller is using
cgroup module support. None of actual resource controllers can be
built as a module and we aren't gonna add new controllers which don't
control resources. This patch drops module support from cgroup.
* cgroup_[un]load_subsys() and cgroup_subsys->module removed.
* As there's no point in distinguishing IS_BUILTIN() and IS_MODULE(),
cgroup_subsys.h now uses IS_ENABLED() directly.
* enum cgroup_subsys_id now exactly matches the list of enabled
controllers as ordered in cgroup_subsys.h.
* cgroup_subsys[] is now a contiguously occupied array. Size
specification is no longer necessary and dropped.
* for_each_builtin_subsys() is removed and for_each_subsys() is
updated to not require any locking.
* module ref handling is removed from rebind_subsystems().
* Module related comments dropped.
v2: Rebased on top of fe1217c4f3 ("net: net_cls: move cgroupfs
classid handling into core").
v3: Added {} around the if (need_forkexit_callback) block in
cgroup_post_fork() for readability as suggested by Li.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Trivial: remove the few stray references to css_id, which itself
was removed in v3.13's 2ff2a7d03b "cgroup: kill css_id".
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
After the previous patch which introduced for_each_css(),
for_each_root_subsys() only has two users left. This patch replaces
it with for_each_subsys() + explicit subsys_mask testing and remove
for_each_root_subsys() along with cgroupfs_root->subsys_list handling.
This patch doesn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
In preparation of conversion to kernfs, cgroup file handling is
updated so that it can be easily mapped to kernfs. With the previous
changes, the difference between pidlist and other files are very
small. Both are served by seq_file in a pretty standard way with the
only difference being !pidlist files use single_open().
This patch adds cftype->seq_start(), ->seq_next and ->seq_stop() and
implements the matching cgroup_seqfile_start/next/stop() which either
emulates single_open() behavior or invokes cftype->seq_*() operations
if specified. This allows using single seq_operations for both
pidlist and other files and makes cgroup_pidlist_operations and
cgorup_pidlist_open() no longer necessary. As cgroup_pidlist_open()
was the only user of cftype->open(), the method is dropped together.
This brings cftype file interface very close to kernfs interface and
mapping shouldn't be too difficult. Once converted to kernfs, most of
the plumbing code including cgroup_seqfile_*() will be removed as
kernfs provides those facilities.
This patch does not introduce any behavior changes.
v2: Refreshed on top of the updated "cgroup: introduce struct
cgroup_pidlist_open_file".
v3: Refreshed on top of the updated "cgroup: attach cgroup_open_file
to all cgroup files".
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
In preparation of conversion to kernfs, cgroup file handling is
updated so that it can be easily mapped to kernfs. This patch
replaces cftype->read_seq_string() with cftype->seq_show() which is
not limited to single_open() operation and will map directcly to
kernfs seq_file interface.
The conversions are mechanical. As ->seq_show() doesn't have @css and
@cft, the functions which make use of them are converted to use
seq_css() and seq_cft() respectively. In several occassions, e.f. if
it has seq_string in its name, the function name is updated to fit the
new method better.
This patch does not introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Aristeu Rozanski <arozansk@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
In preparation of conversion to kernfs, cgroup file handling is
updated so that it can be easily mapped to kernfs. This patch
attaches cgroup_open_file, which used to be attached to pidlist files,
to all cgroup files, introduces seq_css/cft() accessors to determine
the cgroup_subsys_state and cftype associated with a given cgroup
seq_file, exports them as public interface.
This doesn't cause any behavior changes but unifies cgroup file
handling across different file types and will help converting them to
kernfs seq_show() interface.
v2: Li pointed out that the original patch was using
single_open_size() incorrectly assuming that the size param is
private data size. Fix it by allocating @of separately and
passing it to single_open() and explicitly freeing it in the
release path. This isn't the prettiest but this path is gonna be
restructured by the following patches pretty soon.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
In preparation of conversion to kernfs, cgroup file handling is being
consolidated so that it can be easily mapped to the seq_file based
interface of kernfs.
After recent updates, ->read() and ->read_map() don't have any user
left and ->write() never had any user. Remove them.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
For some reason, tasks and cgroup.procs guarantee that the result is
sorted. This is the only reason this whole pidlist logic is necessary
instead of just iterating through sorted member tasks. We can't do
anything about the existing interface but at least ensure that such
expectation doesn't exist for the new interface so that pidlist logic
may be removed in the distant future.
This patch scrambles the sort order if sane_behavior so that the
output is usually not sorted in the new interface.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Now that pidlist files don't use cftype->release(), it doesn't have
any user left. Remove it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Merge v3.12 based patch series to move cgroup_event implementation to
memcg into for-3.14. The following two commits cause a conflict in
kernel/cgroup.c
2ff2a7d03b ("cgroup: kill css_id")
79bd9814e5 ("cgroup, memcg: move cgroup_event implementation to memcg")
Each patch removes a struct definition from kernel/cgroup.c. As the
two are adjacent, they cause a context conflict. Easily resolved by
removing both structs.
Signed-off-by: Tejun Heo <tj@kernel.org>
Now that cgroup_event is made memcg specific, the temporarily exported
functions are no longer necessary. Unexport cgroup_css() and remove
__file_cft() which doesn't have any user left.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
cgroup_event is being moved from cgroup core to memcg and the
implementation is already moved by the previous patch. This patch
moves the data fields and callbacks.
* cgroup->event_list[_lock] are moved to mem_cgroup.
* cftype->[un]register_event() are moved to cgroup_event. This makes
it impossible for individual cftype definitions to specify their
event callbacks. This is worked around by simply hard-coding
filename to event callback mapping in cgroup_write_event_control().
This is awkward and inflexible, which is actually desirable given
that we don't want to grow more usages of this feature.
* eventfd_ctx declaration is removed from cgroup.h, which makes
vmpressure.h miss eventfd_ctx declaration. Include eventfd.h from
vmpressure.h.
v2: Use file name from dentry instead of cftype. This will allow
removing all cftype handling in the function.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
cgroup_event is way over-designed and tries to build a generic
flexible event mechanism into cgroup - fully customizable event
specification for each user of the interface. This is utterly
unnecessary and overboard especially in the light of the planned
unified hierarchy as there's gonna be single agent. Simply generating
events at fixed points, or if that's too restrictive, configureable
cadence or single set of configureable points should be enough.
Thankfully, memcg is the only user and gets to keep it. Replacing it
with something simpler on sane_behavior is strongly recommended.
This patch moves cgroup_event and "cgroup.event_control"
implementation to mm/memcontrol.c. Clearing of events on cgroup
destruction is moved from cgroup_destroy_locked() to
mem_cgroup_css_offline(), which shouldn't make any noticeable
difference.
cgroup_css() and __file_cft() are exported to enable the move;
however, this will soon be reverted once the event code is updated to
be memcg specific.
Note that "cgroup.event_control" will now exist only on the hierarchy
with memcg attached to it. While this change is visible to userland,
it is unlikely to be noticeable as the file has never been meaningful
outside memcg.
Aside from the above change, this is pure code relocation.
v2: Per Li Zefan's comments, init/Kconfig updated accordingly and
poll.h inclusion moved from cgroup.c to memcontrol.c.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
The only user of css_id was memcg, and it has been convered to use
cgroup->id, so kill css_id.
Signed-off-by: Li Zefan <lizefan@huwei.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
When cgroup files are created, cgroup core automatically prepends the
name of the subsystem as prefix. This patch adds CFTYPE_NO_ which
disables the automatic prefix. This is to work around historical
baggages and shouldn't be used for new files.
This will be used to move "cgroup.event_control" from cgroup core to
memcg.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Glauber Costa <glommer@gmail.com>
cgroup_css_from_dir() will grow another user. In preparation, make
the following changes.
* All css functions are prefixed with just "css_", rename it to
css_from_dir().
* Take dentry * instead of file * as dentry is what ultimately
identifies a cgroup and file may not always be available. Note that
the function now checkes whether @dentry->d_inode is NULL as the
caller now may specify a negative dentry.
* Make it take cgroup_subsys * instead of integer subsys_id. This
simplifies the function and allows specifying no subsystem for
cgroup->dummy_css.
* Make return section a bit less verbose.
This patch doesn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Now we want cgroup core to always provide the css to use to the
subsystems, so change this API to css_from_id().
Uninline css_from_id(), because it's getting bigger and cgroup_css()
has been unexported.
While at it, remove the #ifdef, and shuffle the order of the args.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
With the planned unified hierarchy, individual css's will be created
and destroyed dynamically across the lifetime of a cgroup. To enable
such usages, css destruction is being decoupled from cgroup
destruction. Most of the destruction path has been decoupled but the
actual free of css still depends on cgroup free path.
When all css refs are drained, css_release() kicks off
css_free_work_fn() which puts the cgroup. When the cgroup refcnt
reaches zero, cgroup_diput() is invoked which in turn schedules RCU
free of the cgroup. After a grace period, all css's are freed along
with the cgroup itself.
This patch moves the RCU grace period and css freeing from cgroup
release path to css release path. css_release(), instead of kicking
off css_free_work_fn() directly, schedules RCU callback
css_free_rcu_fn() which in turn kicks off css_free_work_fn() after a
RCU grace period. css_free_work_fn() is updated to free the css
directly.
The five-way punting - percpu ref kill confirmation, a work item,
percpu ref release, RCU grace period, and again a work item - is quite
hairy but the work items are there only to provide process context and
the actual sequence is kill confirm -> release -> RCU free, which
isn't simple but not too crazy.
This removes cgroup_css() usage after offline_css() allowing clearing
cgroup->subsys[] from offline_css(), which makes it consistent with
online_css() and brings it closer to proper lifetime management for
individual css's.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, css (cgroup_subsys_state) lifetime is tied to that of the
associated cgroup. css's are created when the associated cgroup is
created and destroyed when it gets destroyed. Also, individual css's
aren't RCU protected but the whole cgroup is. With the planned
unified hierarchy, css's will need to be dynamically created and
destroyed within the lifetime of a cgroup.
To enable such usages, this patch decouples css destruction from
cgroup destruction - offline_css() invocation and the final css_put()
are moved from cgroup_destroy_css_killed() to css_killed_work_fn().
Now each css is individually offlined and put as its reference count
is killed instead of waiting for all css's attached to the cgroup to
finish refcnt killing and then proceeding to offlining and putting
them together.
While this changes the order of destruction operations, the changes
shouldn't be noticeable to cgroup subsystems or userland.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, css (cgroup_subsys_state) lifetime is tied to that of the
associated cgroup. With the planned unified hierarchy, css's will be
dynamically created and destroyed within the lifetime of a cgroup. To
enable such usages, css's will be individually RCU protected instead
of being tied to the cgroup.
cgroup->css_kill_cnt is used during cgroup destruction to wait for css
reference count disable; however, this model doesn't work once css's
lifetimes are managed separately from cgroup's. This patch replaces
it with cgroup->nr_css which is an cgroup_mutex protected integer
counting the number of attached css's. The count is incremented from
online_css() and decremented after refcnt kill is confirmed. If the
count reaches zero and the cgroup is marked dead, the second stage of
cgroup destruction is kicked off. If a cgroup doesn't have any css
attached at the time of rmdir, cgroup_destroy_locked() now invokes the
second stage directly as no css kill confirmation would happen.
cgroup_offline_fn() - the second step of cgroup destruction - is
renamed to cgroup_destroy_css_killed() and now expects to be called
with cgroup_mutex held.
While this patch changes how css destruction is punted to work items,
it shouldn't change any visible behavior.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
For the planned unified hierarchy, each css (cgroup_subsys_state) will
be RCU protected so that it can be created and destroyed individually
while allowing RCU accesses. Previous changes ensured that all
cgroup->subsys[] accesses use the cgroup_css() accessor. This patch
adds __rcu modifier to cgroup->subsys[], add matching RCU dereference
in cgroup_css() and convert all assignments to either
rcu_assign_pointer() or RCU_INIT_POINTER().
This change prepares for the actual RCUfication of css's and doesn't
introduce any visible behavior change. The conversion is verified
with sparse and all accesses are properly RCU annotated.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
With the planned unified hierarchy, css's (cgroup_subsys_state) will
be RCU protected and allowed to be attached and detached dynamically
over the course of a cgroup's lifetime. This means that css's will
stay accessible after being detached from its cgroup - the matching
pointer in cgroup->subsys[] cleared - for ref draining and RCU grace
period.
cgroup core still wants to guarantee that the parent css is never
destroyed before its children and css_parent() always returns the
parent regardless of the state of the child css as long as it's
accessible.
This patch makes css's hold onto their parents and adds css->parent so
that the parent css is never detroyed before its children and can be
determined without consulting the cgroups.
cgroup->dummy_css is also updated to point to the parent dummy_css;
however, it doesn't need to worry about object lifetime as the parent
cgroup is already pinned by the child.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
css (cgroup_subsys_state) will become RCU protected and there will be
two stages which require punting to work item during release. To
prepare for using the work item for multiple times, rename
css->dput_work to css->destroy_work and css_dput_fn() to
css_free_work_fn() and move work item initialization from css init to
right before the actual usage.
This reorganization doesn't introduce any behavior change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Previously, all css descendant iterators didn't include the origin
(root of subtree) css in the iteration. The reasons were maintaining
consistency with css_for_each_child() and that at the time of
introduction more use cases needed skipping the origin anyway;
however, given that css_is_descendant() considers self to be a
descendant, omitting the origin css has become more confusing and
looking at the accumulated use cases rather clearly indicates that
including origin would result in simpler code overall.
While this is a change which can easily lead to subtle bugs, cgroup
API including the iterators has recently gone through major
restructuring and no out-of-tree changes will be applicable without
adjustments making this a relatively acceptable opportunity for this
type of change.
The conversions are mostly straight-forward. If the iteration block
had explicit origin handling before or after, it's moved inside the
iteration. If not, if (pos == origin) continue; is added. Some
conversions add extra reference get/put around origin handling by
consolidating origin handling and the rest. While the extra ref
operations aren't strictly necessary, this shouldn't cause any
noticeable difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
cgroup_css() no longer has any user left outside cgroup.c proper and
we don't want subsystems to grow new usages of the function. cgroup
core should always provide the css to use to the subsystems, which
will make dynamic creation and destruction of css's across the
lifetime of a cgroup much more manageable than exposing the cgroup
directly to subsystems and let them dereference css's from it.
Make cgroup_css() a static function in cgroup.c.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup is in the process of converting to css (cgroup_subsys_state)
from cgroup as the principal subsystem interface handle. This is
mostly to prepare for the unified hierarchy support where css's will
be created and destroyed dynamically but also helps cleaning up
subsystem implementations as css is usually what they are interested
in anyway.
cgroup_taskset which is used by the subsystem attach methods is the
last cgroup subsystem API which isn't using css as the handle. Update
cgroup_taskset_cur_cgroup() to cgroup_taskset_cur_css() and
cgroup_taskset_for_each() to take @skip_css instead of @skip_cgrp.
The conversions are pretty mechanical. One exception is
cpuset::cgroup_cs(), which lost its last user and got removed.
This patch shouldn't introduce any functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
cgroup is in the process of converting to css (cgroup_subsys_state)
from cgroup as the principal subsystem interface handle. This is
mostly to prepare for the unified hierarchy support where css's will
be created and destroyed dynamically but also helps cleaning up
subsystem implementations as css is usually what they are interested
in anyway.
cftype->[un]register_event() is among the remaining couple interfaces
which still use struct cgroup. Convert it to cgroup_subsys_state.
The conversion is mostly mechanical and removes the last users of
mem_cgroup_from_cont() and cg_to_vmpressure(), which are removed.
v2: indentation update as suggested by Li Zefan.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
cgroup is in the process of converting to css (cgroup_subsys_state)
from cgroup as the principal subsystem interface handle. This is
mostly to prepare for the unified hierarchy support where css's will
be created and destroyed dynamically but also helps cleaning up
subsystem implementations as css is usually what they are interested
in anyway.
This patch converts task iterators to deal with css instead of cgroup.
Note that under unified hierarchy, different sets of tasks will be
considered belonging to a given cgroup depending on the subsystem in
question and making the iterators deal with css instead cgroup
provides them with enough information about the iteration.
While at it, fix several function comment formats in cpuset.c.
This patch doesn't introduce any behavior differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
cgroup_scan_tasks() takes a pointer to struct cgroup_scanner as its
sole argument and the only function of that struct is packing the
arguments of the function call which are consisted of five fields.
It's not too unusual to pack parameters into a struct when the number
of arguments gets excessive or the whole set needs to be passed around
a lot, but neither holds here making it just weird.
Drop struct cgroup_scanner and pass the params directly to
cgroup_scan_tasks(). Note that struct cpuset_change_nodemask_arg was
added to cpuset.c to pass both ->cs and ->newmems pointer to
cpuset_change_nodemask() using single data pointer.
This doesn't make any functional differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently all cgroup_task_iter functions require @cgrp to be passed
in, which is superflous and increases chance of usage error. Make
cgroup_task_iter remember the cgroup being iterated and drop @cgrp
argument from next and end functions.
This patch doesn't introduce any behavior differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
cgroup now has multiple iterators and it's quite confusing to have
something which walks over tasks of a single cgroup named cgroup_iter.
Let's rename it to cgroup_task_iter.
While at it, reformat / update comments and replace the overview
comment above the interface function decls with proper function
comments. Such overview can be useful but function comments should be
more than enough here.
This is pure rename and doesn't introduce any functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
cgroup is currently in the process of transitioning to using css
(cgroup_subsys_state) as the primary handle instead of cgroup in
subsystem API. For hierarchy iterators, this is beneficial because
* In most cases, css is the only thing subsystems care about anyway.
* On the planned unified hierarchy, iterations for different
subsystems will need to skip over different subtrees of the
hierarchy depending on which subsystems are enabled on each cgroup.
Passing around css makes it unnecessary to explicitly specify the
subsystem in question as css is intersection between cgroup and
subsystem
* For the planned unified hierarchy, css's would need to be created
and destroyed dynamically independent from cgroup hierarchy. Having
cgroup core manage css iteration makes enforcing deref rules a lot
easier.
Most subsystem conversions are straight-forward. Noteworthy changes
are
* blkio: cgroup_to_blkcg() is no longer used. Removed.
* freezer: cgroup_freezer() is no longer used. Removed.
* devices: cgroup_to_devcgroup() is no longer used. Removed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Jens Axboe <axboe@kernel.dk>
There are several places where the children list is accessed directly.
This patch converts those places to use cgroup_next_child(). This
will help updating the hierarchy iterators to use @css instead of
@cgrp.
While cgroup_next_child() can be heavy in pathological cases - e.g. a
lot of dead children, this shouldn't cause any noticeable behavior
differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup is transitioning to using css (cgroup_subsys_state) as the main
subsys interface handle instead of cgroup and the iterators will be
updated to use css too. The iterators need to walk the cgroup
hierarchy and return the css's matching the origin css, which is a bit
cumbersome to open code.
This patch converts cgroup_next_sibling() to cgroup_next_child() so
that it can handle all steps of direct child iteration. This will be
used to update iterators to take @css instead of @cgrp. In addition
to the new iteration init handling, cgroup_next_child() is
restructured so that the different branches share the end of iteration
condition check.
This patch doesn't change any behavior.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup is currently in the process of transitioning to using struct
cgroup_subsys_state * as the primary handle instead of struct cgroup.
Please see the previous commit which converts the subsystem methods
for rationale.
This patch converts all cftype file operations to take @css instead of
@cgroup. cftypes for the cgroup core files don't have their subsytem
pointer set. These will automatically use the dummy_css added by the
previous patch and can be converted the same way.
Most subsystem conversions are straight forwards but there are some
interesting ones.
* freezer: update_if_frozen() is also converted to take @css instead
of @cgroup for consistency. This will make the code look simpler
too once iterators are converted to use css.
* memory/vmpressure: mem_cgroup_from_css() needs to be exported to
vmpressure while mem_cgroup_from_cont() can be made static.
Updated accordingly.
* cpu: cgroup_tg() doesn't have any user left. Removed.
* cpuacct: cgroup_ca() doesn't have any user left. Removed.
* hugetlb: hugetlb_cgroup_form_cgroup() doesn't have any user left.
Removed.
* net_cls: cgrp_cls_state() doesn't have any user left. Removed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Steven Rostedt <rostedt@goodmis.org>
cgroup subsystem API is being converted to use css
(cgroup_subsys_state) as the main handle, which makes things a bit
awkward for subsystem agnostic core features - the "cgroup.*"
interface files and various iterations - a bit awkward as they don't
have a css to use.
This patch adds cgroup->dummy_css which has NULL ->ss and whose only
role is pointing back to the cgroup. This will be used to support
subsystem agnostic features on the coming css based API.
css_parent() is updated to handle dummy_css's. Note that css will
soon grow its own ->parent field and css_parent() will be made
trivial.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup is transitioning to using css (cgroup_subsys_state) instead of
cgroup as the primary subsystem handle. The cgroupfs file interface
will be converted to use css's which requires finding out the
subsystem from cftype so that the matching css can be determined from
the cgroup.
This patch adds cftype->ss which points to the subsystem the file
belongs to. The field is initialized while a cftype is being
registered. This makes it unnecessary to explicitly specify the
subsystem for other cftype handling functions. @ss argument dropped
from various cftype handling functions.
This patch shouldn't introduce any behavior differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
cgroup is currently in the process of transitioning to using struct
cgroup_subsys_state * as the primary handle instead of struct cgroup *
in subsystem implementations for the following reasons.
* With unified hierarchy, subsystems will be dynamically bound and
unbound from cgroups and thus css's (cgroup_subsys_state) may be
created and destroyed dynamically over the lifetime of a cgroup,
which is different from the current state where all css's are
allocated and destroyed together with the associated cgroup. This
in turn means that cgroup_css() should be synchronized and may
return NULL, making it more cumbersome to use.
* Differing levels of per-subsystem granularity in the unified
hierarchy means that the task and descendant iterators should behave
differently depending on the specific subsystem the iteration is
being performed for.
* In majority of the cases, subsystems only care about its part in the
cgroup hierarchy - ie. the hierarchy of css's. Subsystem methods
often obtain the matching css pointer from the cgroup and don't
bother with the cgroup pointer itself. Passing around css fits
much better.
This patch converts all cgroup_subsys methods to take @css instead of
@cgroup. The conversions are mostly straight-forward. A few
noteworthy changes are
* ->css_alloc() now takes css of the parent cgroup rather than the
pointer to the new cgroup as the css for the new cgroup doesn't
exist yet. Knowing the parent css is enough for all the existing
subsystems.
* In kernel/cgroup.c::offline_css(), unnecessary open coded css
dereference is replaced with local variable access.
This patch shouldn't cause any behavior differences.
v2: Unnecessary explicit cgrp->subsys[] deref in css_online() replaced
with local variable @css as suggested by Li Zefan.
Rebased on top of new for-3.12 which includes for-3.11-fixes so
that ->css_free() invocation added by da0a12caff ("cgroup: fix a
leak when percpu_ref_init() fails") is converted too. Suggested
by Li Zefan.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Steven Rostedt <rostedt@goodmis.org>
Currently, controllers have to explicitly follow the cgroup hierarchy
to find the parent of a given css. cgroup is moving towards using
cgroup_subsys_state as the main controller interface construct, so
let's provide a way to climb the hierarchy using just csses.
This patch implements css_parent() which, given a css, returns its
parent. The function is guarnateed to valid non-NULL parent css as
long as the target css is not at the top of the hierarchy.
freezer, cpuset, cpu, cpuacct, hugetlb, memory, net_cls and devices
are converted to use css_parent() instead of accessing cgroup->parent
directly.
* __parent_ca() is dropped from cpuacct and its usage is replaced with
parent_ca(). The only difference between the two was NULL test on
cgroup->parent which is now embedded in css_parent() making the
distinction moot. Note that eventually a css->parent field will be
added to css and the NULL check in css_parent() will go away.
This patch shouldn't cause any behavior differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, given a cgroup_subsys_state, there's no way to find out
which subsystem the css is for, which we'll need to convert the cgroup
controller API to primarily use @css instead of @cgroup. This patch
adds cgroup_subsys_state->ss which points to the subsystem the @css
belongs to.
While at it, remove the comment about accessing @css->cgroup to
determine the hierarchy. cgroup core will provide API to traverse
hierarchy of css'es and we don't want subsystems to directly walk
cgroup hierarchies anymore.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
The names of the two struct cgroup_subsys_state accessors -
cgroup_subsys_state() and task_subsys_state() - are somewhat awkward.
The former clashes with the type name and the latter doesn't even
indicate it's somehow related to cgroup.
We're about to revamp large portion of cgroup API, so, let's rename
them so that they're less awkward. Most per-controller usages of the
accessors are localized in accessor wrappers and given the amount of
scheduled changes, this isn't gonna add any noticeable headache.
Rename cgroup_subsys_state() to cgroup_css() and task_subsys_state()
to task_css(). This patch is pure rename.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
for-3.12 branch is about to receive invasive updates which are
dependent on da0a12caff ("cgroup: fix a leak when percpu_ref_init()
fails"). Given the amount of scheduled changes, I think it'd less
painful to pull in for-3.11-fixes as preparation. Pull in
for-3.11-fixes into for-3.12.
Signed-off-by: Tejun Heo <tj@kernel.org>
This will be used as a replacement for css_lookup().
There's a difference with cgroup id and css id. cgroup id starts with 0,
while css id starts with 1.
v4:
- also check if cggroup_mutex is held.
- make it an inline function.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Tejun Heo <tj@kernel.org>
As cgroup id has been used in netprio cgroup and will be used in memcg,
it's important to make it clear how a cgroup id is allocated.
For example, in netprio cgroup, the id is used as index of anarray.
Signed-off-by: Li Zefan <lizefan@huwei.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Tejun Heo <tj@kernel.org>
This enables us to lookup a cgroup by its id.
v4:
- add a comment for idr_remove() in cgroup_offline_fn().
v3:
- on success, idr_alloc() returns the id but not 0, so fix the BUG_ON()
in cgroup_init().
- pass the right value to idr_alloc() so that the id for dummy cgroup is 0.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Tejun Heo <tj@kernel.org>
Constantly use @cset for css_set variables and use @cgrp as cgroup
variables.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
task_cgroup_path_from_hierarchy() was added for the planned new users
and none of the currently planned users wants to know about multiple
hierarchies. This patch drops the multiple hierarchy part and makes
it always return the path in the first non-dummy hierarchy.
As unified hierarchy will always have id 1, this is guaranteed to
return the path for the unified hierarchy if mounted; otherwise, it
will return the path from the hierarchy which happens to occupy the
lowest hierarchy id, which will usually be the first hierarchy mounted
after boot.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Jan Kaluža <jkaluza@redhat.com>
Pull core block IO updates from Jens Axboe:
"Here are the core IO block bits for 3.11. It contains:
- A tweak to the reserved tag logic from Jan, for weirdo devices with
just 3 free tags. But for those it improves things substantially
for random writes.
- Periodic writeback fix from Jan. Marked for stable as well.
- Fix for a race condition in IO scheduler switching from Jianpeng.
- The hierarchical blk-cgroup support from Tejun. This is the grunt
of the series.
- blk-throttle fix from Vivek.
Just a note that I'm in the middle of a relocation, whole family is
flying out tomorrow. Hence I will be awal the remainder of this week,
but back at work again on Monday the 15th. CC'ing Tejun, since any
potential "surprises" will most likely be from the blk-cgroup work.
But it's been brewing for a while and sitting in my tree and
linux-next for a long time, so should be solid."
* 'for-3.11/core' of git://git.kernel.dk/linux-block: (36 commits)
elevator: Fix a race in elevator switching
block: Reserve only one queue tag for sync IO if only 3 tags are available
writeback: Fix periodic writeback after fs mount
blk-throttle: implement proper hierarchy support
blk-throttle: implement throtl_grp->has_rules[]
blk-throttle: Account for child group's start time in parent while bio climbs up
blk-throttle: add throtl_qnode for dispatch fairness
blk-throttle: make throtl_pending_timer_fn() ready for hierarchy
blk-throttle: make tg_dispatch_one_bio() ready for hierarchy
blk-throttle: make blk_throtl_bio() ready for hierarchy
blk-throttle: make blk_throtl_drain() ready for hierarchy
blk-throttle: dispatch from throtl_pending_timer_fn()
blk-throttle: implement dispatch looping
blk-throttle: separate out throtl_service_queue->pending_timer from throtl_data->dispatch_work
blk-throttle: set REQ_THROTTLED from throtl_charge_bio() and gate stats update with it
blk-throttle: implement sq_to_tg(), sq_to_td() and throtl_log()
blk-throttle: add throtl_service_queue->parent_sq
blk-throttle: generalize update_disptime optimization in blk_throtl_bio()
blk-throttle: dispatch to throtl_data->service_queue.bio_lists[]
blk-throttle: move bio_lists[] and friends to throtl_service_queue
...
Pull cpuset changes from Tejun Heo:
"cpuset has always been rather odd about its configurations - a cgroup
right after creation didn't allow any task executions before
configuration, changing configuration in the parent modifies the
descendants irreversibly and so on. These behaviors are inherently
nasty and almost hostile against sharing the hierarchy with other
controllers making it very difficult to use in unified hierarchy.
Li is currently in the process of updating the behaviors for
__DEVEL__sane_behavior which is the bulk of changes in this pull
request. It isn't complete yet and the behaviors will change further
but all changes are gated behind sane_behavior. In the process, the
rather hairy work-item punting which was used to work around the
limitations of cgroup descendant iterator was simplified."
* 'for-3.11-cpuset' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cpuset: rename @cont to @cgrp
cpuset: fix to migrate mm correctly in a corner case
cpuset: allow to move tasks to empty cpusets
cpuset: allow to keep tasks in empty cpusets
cpuset: introduce effective_{cpumask|nodemask}_cpuset()
cpuset: record old_mems_allowed in struct cpuset
cpuset: remove async hotplug propagation work
cpuset: let hotplug propagation work wait for task attaching
cpuset: re-structure update_cpumask() a bit
cpuset: remove cpuset_test_cpumask()
cpuset: remove unnecessary variable in cpuset_attach()
cpuset: cleanup guarantee_online_{cpus|mems}()
cpuset: remove redundant check in cpuset_cpus_allowed_fallback()
1672d04070 ("cgroup: fix cgroupfs_root early destruction path")
introduced CGRP_ROOT_SUBSYS_BOUND which is used to mark completion of
subsys binding on a new root; however, this broke remounts.
cgroup_remount() doesn't allow changing root options via remount and
CGRP_ROOT_SUBSYS_BOUND, which is set on all fully initialized roots,
makes the function reject all remounts.
Fix it by putting the options part in the lower 16 bits of root->flags
and masking the comparions. While at it, make cgroup_remount() emit
an error message explaining why it's rejecting a remount request, so
that it's less of a mystery.
Signed-off-by: Tejun Heo <tj@kernel.org>
task->cgroups is a RCU pointer pointing to struct css_set. A task
switches to a different css_set on cgroup migration but a css_set
doesn't change once created and its pointers to cgroup_subsys_states
aren't RCU protected.
task_subsys_state[_check]() is the macro to acquire css given a task
and subsys_id pair. It RCU-dereferences task->cgroups->subsys[] not
task->cgroups, so the RCU pointer task->cgroups ends up being
dereferenced without read_barrier_depends() after it. It's broken.
Fix it by introducing task_css_set[_check]() which does
RCU-dereference on task->cgroups. task_subsys_state[_check]() is
reimplemented to directly dereference ->subsys[] of the css_set
returned from task_css_set[_check]().
This removes some of sparse RCU warnings in cgroup.
v2: Fixed unbalanced parenthsis and there's no need to use
rcu_dereference_raw() when !CONFIG_PROVE_RCU. Both spotted by Li.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: stable@vger.kernel.org
cgroupfs_root used to have ->actual_subsys_mask in addition to
->subsys_mask. a8a648c4ac ("cgroup: remove
cgroup->actual_subsys_mask") removed it noting that the subsys_mask is
essentially temporary and doesn't belong in cgroupfs_root; however,
the patch made it impossible to tell whether a cgroupfs_root actually
has the subsystems bound or just have the bits set leading to the
following BUG when trying to mount with subsystems which are already
mounted elsewhere.
kernel BUG at kernel/cgroup.c:1038!
invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
...
CPU: 1 PID: 7973 Comm: mount Tainted: G W 3.10.0-rc7-next-20130625-sasha-00011-g1c1dc0e #1105
task: ffff880fc0ae8000 ti: ffff880fc0b9a000 task.ti: ffff880fc0b9a000
RIP: 0010:[<ffffffff81249b29>] [<ffffffff81249b29>] rebind_subsystems+0x409/0x5f0
...
Call Trace:
[<ffffffff8124bd4f>] cgroup_kill_sb+0xff/0x210
[<ffffffff813d21af>] deactivate_locked_super+0x4f/0x90
[<ffffffff8124f3b3>] cgroup_mount+0x673/0x6e0
[<ffffffff81257169>] cpuset_mount+0xd9/0x110
[<ffffffff813d2580>] mount_fs+0xb0/0x2d0
[<ffffffff81404afd>] vfs_kern_mount+0xbd/0x180
[<ffffffff814070b5>] do_new_mount+0x145/0x2c0
[<ffffffff814085d6>] do_mount+0x356/0x3c0
[<ffffffff8140873d>] SyS_mount+0xfd/0x140
[<ffffffff854eb600>] tracesys+0xdd/0xe2
We still want rebind_subsystems() to take added/removed masks, so
let's fix it by marking whether a cgroupfs_root has finished binding
or not. Also, document what's going on around ->subsys_mask
initialization so that similar mistakes aren't repeated.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup curiously has two subsystem masks, ->subsys_mask and
->actual_subsys_mask. The latter only exists because the new target
subsys_mask is passed into rebind_subsystems() via @root>subsys_mask.
rebind_subsystems() needs to know what the current mask is to decide
how to reach the target mask so ->actual_subsys_mask is used as the
temp location to remember the current state.
Adding a temporary field to a permanent data structure is rather silly
and can be misleading. Update rebind_subsystems() to take @added_mask
and @removed_mask instead and remove @root->actual_subsys_mask.
This patch shouldn't introduce any behavior changes.
v2: Comment and description updated as suggested by Li.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cont is short for container. control group was named process container
at first, but then people found container already has a meaning in
linux kernel.
Clean up the leftover variable name @cont.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
We used root->allcg_list to iterate cgroup hierarchy because at that time
cgroup_for_each_descendant_pre() hasn't been invented.
tj: In cgroup_cfts_commit(), s/@serial_nr/@update_upto/, move the
assignment right above releasing cgroup_mutex and explain what's
going on there.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
cgroup's rename(2) isn't a proper migration implementation - it can't
move the cgroup to a different parent in the hierarchy. All it can do
is swapping the name string for that cgroup. This isn't useful and
can mislead users to think that cgroup supports proper cgroup-level
migration. Disallow rename(2) if sane_behavior.
v2: Fail with -EPERM instead of -EINVAL so that it matches the vfs
return value when ->rename is not implemented as suggested by Li.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
f12dc02014 ("cgroup: mark "tasks" cgroup file as insane") and
cc5943a781 ("cgroup: mark "notify_on_release" and "release_agent"
cgroup files insane") forgot to update the changed behavior
documentation in cgroup.h. Update it.
Signed-off-by: Tejun Heo <tj@kernel.org>
A css (cgroup_subsys_state) is how each cgroup is represented to a
controller. As such, it can be used in hot paths across the various
subsystems different controllers are associated with.
One of the common operations is reference counting, which up until now
has been implemented using a global atomic counter and can have
significant adverse impact on scalability. For example, css refcnt
can be gotten and put multiple times by blkcg for each IO request.
For highops configurations which try to do as much per-cpu as
possible, the global frequent refcnting can be very expensive.
In general, given the various and hugely diverse paths css's end up
being used from, we need to make it cheap and highly scalable. In its
usage, css refcnting isn't very different from module refcnting.
This patch converts css refcnting to use the recently added
percpu_ref. css_get/tryget/put() directly maps to the matching
percpu_ref operations and the deactivation logic is no longer
necessary as percpu_ref already has refcnt killing.
The only complication is that as the refcnt is per-cpu,
percpu_ref_kill() in itself doesn't ensure that further tryget
operations will fail, which we need to guarantee before invoking
->css_offline()'s. This is resolved collecting kill confirmation
using percpu_ref_kill_and_confirm() and initiating the offline phase
of destruction after all css refcnt's are confirmed to be seen as
killed on all CPUs. The previous patches already splitted destruction
into two phases, so percpu_ref_kill_and_confirm() can be hooked up
easily.
This patch removes css_refcnt() which is used for rcu dereference
sanity check in css_id(). While we can add a percpu refcnt API to ask
the same question, css_id() itself is scheduled to be removed fairly
soon, so let's not bother with it. Just drop the sanity check and use
rcu_dereference_raw() instead.
v2: - init_cgroup_css() was calling percpu_ref_init() without checking
the return value. This causes two problems - the obvious lack
of error handling and percpu_ref_init() being called from
cgroup_init_subsys() before the allocators are up, which
triggers warnings but doesn't cause actual problems as the
refcnt isn't used for roots anyway. Fix both by moving
percpu_ref_init() to cgroup_create().
- The base references were put too early by
percpu_ref_kill_and_confirm() and cgroup_offline_fn() put the
refs one extra time. This wasn't noticeable because css's go
through another RCU grace period before being freed. Update
cgroup_destroy_locked() to grab an extra reference before
killing the refcnts. This problem was noticed by Kent.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Kent Overstreet <koverstreet@google.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: "Alasdair G. Kergon" <agk@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Glauber Costa <glommer@gmail.com>
Split cgroup_destroy_locked() into two steps and put the latter half
into cgroup_offline_fn() which is executed from a work item. The
latter half is responsible for offlining the css's, removing the
cgroup from internal lists, and propagating release notification to
the parent. The separation is to allow using percpu refcnt for css.
Note that this allows for other cgroup operations to happen between
the first and second halves of destruction, including creating a new
cgroup with the same name. As the target cgroup is marked DEAD in the
first half and cgroup internals don't care about the names of cgroups,
this should be fine. A comment explaining this will be added by the
next patch which implements the actual percpu refcnting.
As RCU freeing is guaranteed to happen after the second step of
destruction, we can use the same work item for both. This patch
renames cgroup->free_work to ->destroy_work and uses it for both
purposes. INIT_WORK() is now performed right before queueing the work
item.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup->count tracks the number of css_sets associated with the cgroup
and used only to verify that no css_set is associated when the cgroup
is being destroyed. It's superflous as the destruction path can
simply check whether cgroup->cset_links is empty instead.
Drop cgroup->count and check ->cset_links directly from
cgroup_destroy_locked().
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
We will add another flag indicating that the cgroup is in the process
of being killed. REMOVING / REMOVED is more difficult to distinguish
and cgroup_is_removing()/cgroup_is_removed() are a bit awkward. Also,
later percpu_ref usage will involve "kill"ing the refcnt.
s/CGRP_REMOVED/CGRP_DEAD/
s/cgroup_is_removed()/cgroup_is_dead()
This patch is purely cosmetic.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
* __css_get() isn't used by anyone. Fold it into css_get().
* Add proper function comments to all css reference functions.
This patch is purely cosmetic.
v2: Typo fix as per Li.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroups and css_sets are mapped M:N and this M:N mapping is
represented by struct cg_cgroup_link which forms linked lists on both
sides. The naming around this mapping is already confusing and struct
cg_cgroup_link exacerbates the situation quite a bit.
>From cgroup side, it starts off ->css_sets and runs through
->cgrp_link_list. From css_set side, it starts off ->cg_links and
runs through ->cg_link_list. This is rather reversed as
cgrp_link_list is used to iterate css_sets and cg_link_list cgroups.
Also, this is the only place which is still using the confusing "cg"
for css_sets. This patch cleans it up a bit.
* s/cgroup->css_sets/cgroup->cset_links/
s/css_set->cg_links/css_set->cgrp_links/
s/cgroup_iter->cg_link/cgroup_iter->cset_link/
* s/cg_cgroup_link/cgrp_cset_link/
* s/cgrp_cset_link->cg/cgrp_cset_link->cset/
s/cgrp_cset_link->cgrp_link_list/cgrp_cset_link->cset_link/
s/cgrp_cset_link->cg_link_list/cgrp_cset_link->cgrp_link/
* s/init_css_set_link/init_cgrp_cset_link/
s/free_cg_links/free_cgrp_cset_links/
s/allocate_cg_links/allocate_cgrp_cset_links/
* s/cgl[12]/link[12]/ in compare_css_sets()
* s/saved_link/tmp_link/ s/tmp/tmp_links/ and a couple similar
adustments.
* Comment and whiteline adjustments.
After the changes, we have
list_for_each_entry(link, &cont->cset_links, cset_link) {
struct css_set *cset = link->cset;
instead of
list_for_each_entry(link, &cont->css_sets, cgrp_link_list) {
struct css_set *cset = link->cg;
This patch is purely cosmetic.
v2: Fix broken sentences in the patch description.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently some cpuset behaviors are not friendly when cpuset is co-mounted
with other cgroup controllers.
Now with this patchset if cpuset is mounted with sane_behavior option,
it behaves differently:
- Tasks will be kept in empty cpusets when hotplug happens and take
masks of ancestors with non-empty cpus/mems, instead of being moved to
an ancestor.
- A task can be moved into an empty cpuset, and again it takes masks of
ancestors, so the user can drop a task into a newly created cgroup without
having to do anything for it.
As tasks can reside in empy cpusets, here're some rules:
- They can be moved to another cpuset, regardless it's empty or not.
- Though it takes masks from ancestors, it takes other configs from the
empty cpuset.
- If the ancestors' masks are changed, those tasks will also be updated
to take new masks.
v2: add documentation in include/linux/cgroup.h
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
To achieve this:
- We call update_tasks_cpumask/nodemask() for empty cpusets when
hotplug happens, instead of moving tasks out of them.
- When a cpuset's masks are changed by writing cpuset.cpus/mems,
we also update tasks in child cpusets which are empty.
v3:
- do propagation work in one place for both hotplug and unplug
v2:
- drop rcu_read_lock before calling update_task_nodemask() and
update_task_cpumask(), instead of using workqueue.
- add documentation in include/linux/cgroup.h
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This patch converts cgroup_for_each_child(),
cgroup_next_descendant_pre/post() and thus
cgroup_for_each_descendant_pre/post() to use cgroup_next_sibling()
instead of manually dereferencing ->sibling.next.
The only reason the iterators couldn't allow dropping RCU read lock
while iteration is in progress was because they couldn't determine the
next sibling safely once RCU read lock is dropped. Using
cgroup_next_sibling() removes that problem and enables all iterators
to allow dropping RCU read lock in the middle. Comments are updated
accordingly.
This makes the iterators easier to use and will simplify controllers.
Note that @cgroup argument is renamed to @cgrp in
cgroup_for_each_child() because it conflicts with "struct cgroup" used
in the new macro body.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
