pagecache: Use correct 'cpu' to deal with the background work.

euler inclusion
category: bugfix
CVE: NA
Bugzilla: 13084

---------------------------

When user modify the cache_reclaim_s, cache_reclaim_sysctl_handler
will modify the work delay time. we fail to initialize the 'cpu'.

The patch should mod_delayed_work instead of mod_delayed_work to
fix the issue.
Signed-off-by: Nzhong jiang <zhongjiang@huawei.com>
Reviewed-by: NJing Xiangfeng <jingxiangfeng@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

mm/vmscan.c

@@ -4049,14 +4049,14 @@ int cache_reclaim_enable_handler(struct ctl_table *table, int write,
 int cache_reclaim_sysctl_handler(struct ctl_table *table, int write,
 			void __user *buffer, size_t *length, loff_t *ppos)
 {
-	int ret, cpu;
+	int ret;
 
 	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
 	if (ret)
 		return ret;
 
 	if (write)
-		mod_delayed_work_on(cpu, system_wq, &shepherd,
+		mod_delayed_work(system_wq, &shepherd,
 				round_jiffies_relative(
 				(unsigned long)vm_cache_reclaim_s * HZ));