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cgroup: cosmetic updates to cgroup_attach_task()

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cgroup_attach_task() is planned to go through restructuring.  Let's
tidy it up a bit in preparation.

* Update cgroup_attach_task() to receive the target task argument in
  @leader instead of @tsk.

* Rename @tsk to @task.

* Rename @retval to @ret.

This is purely cosmetic.

v2: get_nr_threads() was using uninitialized @task instead of @leader.
    Fixed.  Reported by Dan Carpenter.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
This commit is contained in:
Tejun Heo 2014-02-13 06:58:43 -05:00
parent bc668c7519
commit 9db8de3722
1 changed files with 23 additions and 22 deletions
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45
kernel/cgroup.c
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@ -1728,20 +1728,20 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp,
/**
* cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
* @cgrp: the cgroup to attach to
* @tsk: the task or the leader of the threadgroup to be attached
* @leader: the task or the leader of the threadgroup to be attached
* @threadgroup: attach the whole threadgroup?
*
* Call holding cgroup_mutex and the group_rwsem of the leader. Will take
* task_lock of @tsk or each thread in the threadgroup individually in turn.
*/
static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *leader,
bool threadgroup)
{
int retval, i, group_size;
int ret, i, group_size;
struct cgroupfs_root *root = cgrp->root;
struct cgroup_subsys_state *css, *failed_css = NULL;
/* threadgroup list cursor and array */
struct task_struct *leader = tsk;
struct task_struct *task;
struct task_and_cgroup *tc;
struct flex_array *group;
struct cgroup_taskset tset = { };
@ -1754,7 +1754,7 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
* threads exit, this will just be an over-estimate.
*/
if (threadgroup)
group_size = get_nr_threads(tsk);
group_size = get_nr_threads(leader);
else
group_size = 1;
/* flex_array supports very large thread-groups better than kmalloc. */
@ -1762,8 +1762,8 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
if (!group)
return -ENOMEM;
/* pre-allocate to guarantee space while iterating in rcu read-side. */
retval = flex_array_prealloc(group, 0, group_size, GFP_KERNEL);
if (retval)
ret = flex_array_prealloc(group, 0, group_size, GFP_KERNEL);
if (ret)
goto out_free_group_list;
i = 0;
@ -1774,17 +1774,18 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
*/
down_read(&css_set_rwsem);
rcu_read_lock();
task = leader;
do {
struct task_and_cgroup ent;
/* @tsk either already exited or can't exit until the end */
if (tsk->flags & PF_EXITING)
/* @task either already exited or can't exit until the end */
if (task->flags & PF_EXITING)
goto next;
/* as per above, nr_threads may decrease, but not increase. */
BUG_ON(i >= group_size);
ent.task = tsk;
ent.cgrp = task_cgroup_from_root(tsk, root);
ent.task = task;
ent.cgrp = task_cgroup_from_root(task, root);
/* nothing to do if this task is already in the cgroup */
if (ent.cgrp == cgrp)
goto next;
@ -1792,13 +1793,13 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
* saying GFP_ATOMIC has no effect here because we did prealloc
* earlier, but it's good form to communicate our expectations.
*/
retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
BUG_ON(retval != 0);
ret = flex_array_put(group, i, &ent, GFP_ATOMIC);
BUG_ON(ret != 0);
i++;
next:
if (!threadgroup)
break;
} while_each_thread(leader, tsk);
} while_each_thread(leader, task);
rcu_read_unlock();
up_read(&css_set_rwsem);
/* remember the number of threads in the array for later. */
@ -1807,7 +1808,7 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
tset.tc_array_len = group_size;
/* methods shouldn't be called if no task is actually migrating */
retval = 0;
ret = 0;
if (!group_size)
goto out_free_group_list;
@ -1816,8 +1817,8 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
*/
for_each_css(css, i, cgrp) {
if (css->ss->can_attach) {
retval = css->ss->can_attach(css, &tset);
if (retval) {
ret = css->ss->can_attach(css, &tset);
if (ret) {
failed_css = css;
goto out_cancel_attach;
}
@ -1835,7 +1836,7 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
old_cset = task_css_set(tc->task);
tc->cset = find_css_set(old_cset, cgrp);
if (!tc->cset) {
retval = -ENOMEM;
ret = -ENOMEM;
goto out_put_css_set_refs;
}
}
@ -1863,9 +1864,9 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
/*
* step 5: success! and cleanup
*/
retval = 0;
ret = 0;
out_put_css_set_refs:
if (retval) {
if (ret) {
for (i = 0; i < group_size; i++) {
tc = flex_array_get(group, i);
if (!tc->cset)
@ -1874,7 +1875,7 @@ out_put_css_set_refs:
}
}
out_cancel_attach:
if (retval) {
if (ret) {
for_each_css(css, i, cgrp) {
if (css == failed_css)
break;
@ -1884,7 +1885,7 @@ out_cancel_attach:
}
out_free_group_list:
flex_array_free(group);
return retval;
return ret;
}
/*