mm/sharepool: Add sp_group_sem protection.

hulk inclusion
category: other
bugzilla: https://gitee.com/openeuler/kernel/issues/I6GI0X

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In sp_update_process_stat, traverse node_list
and lock protection is required.
Signed-off-by: NXu Qiang <xuqiang36@huawei.com>

mm/share_pool.c

@@ -841,8 +841,11 @@ static void sp_update_process_stat(struct task_struct *tsk, bool inc,
 	unsigned long size = spa->real_size;
 	enum spa_type type = spa->type;
 
+	down_read(&sp_group_sem);
 	spg_node = find_spg_node_by_spg(tsk->mm, spa->spg);
-	update_mem_usage(size, inc, spa->is_hugepage, spg_node, type);
+	if (spg_node != NULL)
+		update_mem_usage(size, inc, spa->is_hugepage, spg_node, type);
+	up_read(&sp_group_sem);
 }
 
 static inline void check_interrupt_context(void)