cgroup: drop @skip_css from cgroup_taskset_for_each()

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>

8 files changed, 11 insertions, 15 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 1cef07cf9c21..4aefd46d7d95 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -894,7 +894,7 @@ static int blkcg_can_attach(struct cgroup_subsys_state *css,
         int ret = 0;
 
         /* task_lock() is needed to avoid races with exit_io_context() */
-        cgroup_taskset_for_each(task, css, tset) {
+        cgroup_taskset_for_each(task, tset) {
                 task_lock(task);
                 ioc = task->io_context;
                 if (ioc && atomic_read(&ioc->nr_tasks) > 1)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 3bd0a7138371..581a124c7bc8 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -535,15 +535,11 @@ int cgroup_taskset_size(struct cgroup_taskset *tset);
 /**
  * cgroup_taskset_for_each - iterate cgroup_taskset
  * @task: the loop cursor
- * @skip_css: skip if task's css matches this, %NULL to iterate through all
  * @tset: taskset to iterate
  */
-#define cgroup_taskset_for_each(task, skip_css, tset)                   \
+#define cgroup_taskset_for_each(task, tset)                             \
         for ((task) = cgroup_taskset_first((tset)); (task);             \
-             (task) = cgroup_taskset_next((tset)))                      \
-                if (!(skip_css) ||                                      \
-                    cgroup_taskset_cur_css((tset),                      \
-                        (skip_css)->ss->id) != (skip_css))
+             (task) = cgroup_taskset_next((tset)))
 
 /*
  * Control Group subsystem type.
diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index 98ea26a99076..7201a637c405 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -187,7 +187,7 @@ static void freezer_attach(struct cgroup_subsys_state *new_css,
          * current state before executing the following - !frozen tasks may
          * be visible in a FROZEN cgroup and frozen tasks in a THAWED one.
          */
-        cgroup_taskset_for_each(task, new_css, tset) {
+        cgroup_taskset_for_each(task, tset) {
                 if (!(freezer->state & CGROUP_FREEZING)) {
                         __thaw_task(task);
                 } else {
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 65ae0bdf4af8..bf20e4ac2f75 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1398,7 +1398,7 @@ static int cpuset_can_attach(struct cgroup_subsys_state *css,
             (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed)))
                 goto out_unlock;
 
-        cgroup_taskset_for_each(task, css, tset) {
+        cgroup_taskset_for_each(task, tset) {
                 /*
                  * Kthreads which disallow setaffinity shouldn't be moved
                  * to a new cpuset; we don't want to change their cpu
@@ -1467,7 +1467,7 @@ static void cpuset_attach(struct cgroup_subsys_state *css,
 
         guarantee_online_mems(mems_cs, &cpuset_attach_nodemask_to);
 
-        cgroup_taskset_for_each(task, css, tset) {
+        cgroup_taskset_for_each(task, tset) {
                 /*
                  * can_attach beforehand should guarantee that this doesn't
                  * fail.  TODO: have a better way to handle failure here
diff --git a/kernel/events/core.c b/kernel/events/core.c
index a3c3ab50271a..6dd714955b04 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8021,7 +8021,7 @@ static void perf_cgroup_attach(struct cgroup_subsys_state *css,
 {
         struct task_struct *task;
 
-        cgroup_taskset_for_each(task, css, tset)
+        cgroup_taskset_for_each(task, tset)
                 task_function_call(task, __perf_cgroup_move, task);
 }
 
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d4cfc5561830..ba386a06ab11 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7600,7 +7600,7 @@ static int cpu_cgroup_can_attach(struct cgroup_subsys_state *css,
 {
         struct task_struct *task;
 
-        cgroup_taskset_for_each(task, css, tset) {
+        cgroup_taskset_for_each(task, tset) {
 #ifdef CONFIG_RT_GROUP_SCHED
                 if (!sched_rt_can_attach(css_tg(css), task))
                         return -EINVAL;
@@ -7618,7 +7618,7 @@ static void cpu_cgroup_attach(struct cgroup_subsys_state *css,
 {
         struct task_struct *task;
 
-        cgroup_taskset_for_each(task, css, tset)
+        cgroup_taskset_for_each(task, tset)
                 sched_move_task(task);
 }
 
diff --git a/net/core/netclassid_cgroup.c b/net/core/netclassid_cgroup.c
index b865662fba71..22931e1b99b4 100644
--- a/net/core/netclassid_cgroup.c
+++ b/net/core/netclassid_cgroup.c
@@ -73,7 +73,7 @@ static void cgrp_attach(struct cgroup_subsys_state *css,
         void *v = (void *)(unsigned long)cs->classid;
         struct task_struct *p;
 
-        cgroup_taskset_for_each(p, css, tset) {
+        cgroup_taskset_for_each(p, tset) {
                 task_lock(p);
                 iterate_fd(p->files, 0, update_classid, v);
                 task_unlock(p);
diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index d7d23e28fafd..f9f3a40d3350 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -224,7 +224,7 @@ static void net_prio_attach(struct cgroup_subsys_state *css,
         struct task_struct *p;
         void *v = (void *)(unsigned long)css->cgroup->id;
 
-        cgroup_taskset_for_each(p, css, tset) {
+        cgroup_taskset_for_each(p, tset) {
                 task_lock(p);
                 iterate_fd(p->files, 0, update_netprio, v);
                 task_unlock(p);