[PATCH v5 3/6] vhost: Add the cgroup related function

[Cindy Lu <lulu@redhat.com>]

Reintroduce the previously removed functions vhost_attach_cgroups_work()
and vhost_attach_cgroups() to support kthread mode. Rename
vhost_attach_cgroups() to vhost_attach_task_to_cgroups(), and include
the implementation of the old function vhost_dev_flush() in this
new function.

These function was removed in
commit 6e890c5d5021 ("vhost: use vhost_tasks for worker threads")

Signed-off-by: Cindy Lu <lulu@redhat.com>
---
 drivers/vhost/vhost.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 1feba29abf95..812dfd218bc2 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -22,6 +22,7 @@
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/kthread.h>
+#include <linux/cgroup.h>
 #include <linux/module.h>
 #include <linux/sort.h>
 #include <linux/sched/mm.h>
@@ -620,6 +621,38 @@ long vhost_dev_check_owner(struct vhost_dev *dev)
 }
 EXPORT_SYMBOL_GPL(vhost_dev_check_owner);
 
+struct vhost_attach_cgroups_struct {
+	struct vhost_work work;
+	struct task_struct *owner;
+	int ret;
+};
+
+static void vhost_attach_cgroups_work(struct vhost_work *work)
+{
+	struct vhost_attach_cgroups_struct *s;
+
+	s = container_of(work, struct vhost_attach_cgroups_struct, work);
+	s->ret = cgroup_attach_task_all(s->owner, current);
+}
+
+static int vhost_attach_task_to_cgroups(struct vhost_worker *worker)
+{
+	struct vhost_flush_struct flush;
+	struct vhost_attach_cgroups_struct attach;
+
+	attach.owner = current;
+
+	vhost_work_init(&attach.work, vhost_attach_cgroups_work);
+	vhost_worker_queue(worker, &attach.work);
+
+	init_completion(&flush.wait_event);
+	vhost_work_init(&flush.work, vhost_flush_work);
+	vhost_worker_queue(worker, &flush.work);
+	wait_for_completion(&flush.wait_event);
+
+	return attach.ret;
+}
+
 /* Caller should have device mutex */
 bool vhost_dev_has_owner(struct vhost_dev *dev)
 {
-- 
2.45.0