mm: export symbol find_get_task_by_vpid

hulk inclusion
category: feature
bugzilla: 14369
CVE: NA
-------------------

Userspace drivers implemented with VFIO might want to bind sub-processes
to their devices. In a VFIO ioctl, they provide a pid that is used to find
a task and its mm. Since VFIO can be built as a module, export the
find_get_task_by_vpid symbol.

Cc: akpm@linux-foundation.org
Signed-off-by: NJean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: NFang Lijun <fanglijun3@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Reviewed-by: NZhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

kernel/pid.c

@@ -365,6 +365,7 @@ struct task_struct *find_get_task_by_vpid(pid_t nr)
 
 	return task;
 }
+EXPORT_SYMBOL_GPL(find_get_task_by_vpid);
 
 struct pid *get_task_pid(struct task_struct *task, enum pid_type type)
 {