linux-toradex.git/kernel/cgroup_freezer.c, branch v3.14.4

cgroup: replace cftype->read_seq_string() with cftype->seq_show()

2013-12-05T17:28:04+00:00

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 
Acked-by: Aristeu Rozanski 
Acked-by: Vivek Goyal 
Acked-by: Michal Hocko 
Acked-by: Daniel Wagner 
Acked-by: Li Zefan 
Cc: Jens Axboe 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Johannes Weiner 
Cc: Balbir Singh 
Cc: KAMEZAWA Hiroyuki 
Cc: Neil Horman

cgroup: make css_for_each_descendant() and friends include the origin css in the iteration

2013-08-09T00:11:27+00:00

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 
Acked-by: Li Zefan 
Acked-by: Vivek Goyal 
Acked-by: Aristeu Rozanski 
Acked-by: Michal Hocko 
Cc: Jens Axboe 
Cc: Matt Helsley 
Cc: Johannes Weiner 
Cc: Balbir Singh

cgroup: make cgroup_taskset deal with cgroup_subsys_state instead of cgroup

2013-08-09T00:11:27+00:00

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 
Acked-by: Li Zefan 
Acked-by: Daniel Wagner 
Cc: Ingo Molnar 
Cc: Matt Helsley 
Cc: Steven Rostedt

cgroup: make task iterators deal with cgroup_subsys_state instead of cgroup

2013-08-09T00:11:26+00:00

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 
Acked-by: Li Zefan 
Acked-by: Michal Hocko 
Cc: Johannes Weiner 
Cc: Balbir Singh 
Cc: Matt Helsley

cgroup: make cgroup_task_iter remember the cgroup being iterated

2013-08-09T00:11:26+00:00

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 
Acked-by: Li Zefan 
Acked-by: Michal Hocko 
Cc: Matt Helsley 
Cc: Johannes Weiner 
Cc: Balbir Singh

cgroup: rename cgroup_iter to cgroup_task_iter

2013-08-09T00:11:26+00:00

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 
Acked-by: Li Zefan 
Acked-by: Michal Hocko 
Cc: Matt Helsley 
Cc: Johannes Weiner 
Cc: Balbir Singh

cgroup: make hierarchy iterators deal with cgroup_subsys_state instead of cgroup

2013-08-09T00:11:25+00:00

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 
Acked-by: Li Zefan 
Acked-by: Michal Hocko 
Acked-by: Vivek Goyal 
Acked-by: Aristeu Rozanski 
Cc: Johannes Weiner 
Cc: Balbir Singh 
Cc: Matt Helsley 
Cc: Jens Axboe

cgroup: pass around cgroup_subsys_state instead of cgroup in file methods

2013-08-09T00:11:24+00:00

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 
Acked-by: Li Zefan 
Acked-by: Michal Hocko 
Acked-by: Vivek Goyal 
Acked-by: Aristeu Rozanski 
Acked-by: Daniel Wagner 
Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Cc: Johannes Weiner 
Cc: Balbir Singh 
Cc: Matt Helsley 
Cc: Jens Axboe 
Cc: Steven Rostedt

cgroup: pass around cgroup_subsys_state instead of cgroup in subsystem methods

2013-08-09T00:11:23+00:00

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 
Acked-by: Li Zefan 
Acked-by: Michal Hocko 
Acked-by: Vivek Goyal 
Acked-by: Aristeu Rozanski 
Acked-by: Daniel Wagner 
Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Cc: Johannes Weiner 
Cc: Balbir Singh 
Cc: Matt Helsley 
Cc: Jens Axboe 
Cc: Steven Rostedt

cgroup: add css_parent()

2013-08-09T00:11:23+00:00

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 
Acked-by: Li Zefan