From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Fri, 26 Aug 2022 11:48:29 +0900
Subject: cgroup: Use cgroup_attach_{lock,unlock}() from
 cgroup_attach_task_all()
Git-commit: 075b593f54f0f3883532cb750081cae6917bc8fe
Patch-mainline: v6.1-rc1
References: bsc#1212563

No behavior changes; preparing for potential locking changes in future.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by:Mukesh Ojha <quic_mojha@quicinc.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Koutný <mkoutny@suse.com>
---
 kernel/cgroup/cgroup-internal.h | 2 ++
 kernel/cgroup/cgroup-v1.c       | 6 ++----
 kernel/cgroup/cgroup.c          | 4 ++--
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h
index 36b740cb3d59..2c7ecca226be 100644
--- a/kernel/cgroup/cgroup-internal.h
+++ b/kernel/cgroup/cgroup-internal.h
@@ -250,6 +250,8 @@ int cgroup_migrate(struct task_struct *leader, bool threadgroup,
 
 int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader,
 		       bool threadgroup);
+void cgroup_attach_lock(bool lock_threadgroup);
+void cgroup_attach_unlock(bool lock_threadgroup);
 struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup,
 					     bool *locked)
 	__acquires(&cgroup_threadgroup_rwsem);
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index ff6a8099eb2a..52bb5a74a23b 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -59,8 +59,7 @@ int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
 	int retval = 0;
 
 	mutex_lock(&cgroup_mutex);
-	cpus_read_lock();
-	percpu_down_write(&cgroup_threadgroup_rwsem);
+	cgroup_attach_lock(true);
 	for_each_root(root) {
 		struct cgroup *from_cgrp;
 
@@ -72,8 +71,7 @@ int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
 		if (retval)
 			break;
 	}
-	percpu_up_write(&cgroup_threadgroup_rwsem);
-	cpus_read_unlock();
+	cgroup_attach_unlock(true);
 	mutex_unlock(&cgroup_mutex);
 
 	return retval;
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 65497a1a44fa..0005de2e2ed9 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -2393,7 +2393,7 @@ EXPORT_SYMBOL_GPL(task_cgroup_path);
  * write-locking cgroup_threadgroup_rwsem. This allows ->attach() to assume that
  * CPU hotplug is disabled on entry.
  */
-static void cgroup_attach_lock(bool lock_threadgroup)
+void cgroup_attach_lock(bool lock_threadgroup)
 {
 	cpus_read_lock();
 	if (lock_threadgroup)
@@ -2404,7 +2404,7 @@ static void cgroup_attach_lock(bool lock_threadgroup)
  * cgroup_attach_unlock - Undo cgroup_attach_lock()
  * @lock_threadgroup: whether to up_write cgroup_threadgroup_rwsem
  */
-static void cgroup_attach_unlock(bool lock_threadgroup)
+void cgroup_attach_unlock(bool lock_threadgroup)
 {
 	if (lock_threadgroup)
 		percpu_up_write(&cgroup_threadgroup_rwsem);