cgroup: cosmetic updates to cgroup_attach_task()

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>

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a9d9bbb12310159b28bf95a237e692de951d3df8..9a890a2e58fc8ef126c6ef55200da0eb9ef4ddec 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -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;
 }
 
 /*