freezer_cg: remove redundant check in freezer_can_attach()

It is sufficient to check if @task is frozen, and no need to check if the
original freezer is frozen.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Cedric Le Goater <clg@fr.ibm.com>
Acked-by: Matt Helsley <matthltc@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index 7f54d1c..e9c856a 100644 (file)
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -162,9 +162,13 @@ static int freezer_can_attach(struct cgroup_subsys *ss,
                              struct task_struct *task)
 {
        struct freezer *freezer;
-       int retval;
 
-       /* Anything frozen can't move or be moved to/from */
+       /*
+        * Anything frozen can't move or be moved to/from.
+        *
+        * Since orig_freezer->state == FROZEN means that @task has been
+        * frozen, so it's sufficient to check the latter condition.
+        */
 
        if (is_task_frozen_enough(task))
                return -EBUSY;
@@ -173,13 +177,7 @@ static int freezer_can_attach(struct cgroup_subsys *ss,
        if (freezer->state == CGROUP_FROZEN)
                return -EBUSY;
 
-       retval = 0;
-       task_lock(task);
-       freezer = task_freezer(task);
-       if (freezer->state == CGROUP_FROZEN)
-               retval = -EBUSY;
-       task_unlock(task);
-       return retval;
+       return 0;
 }
 
 static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)