alinux: mm,memcg: export memory.high to v1

Export "memory.high" from cgroup v2 to v1 which can be used to archive
some memory QoS.

This is also a way of migrating to v2 gradually.
Signed-off-by: NXu Yu <xuyu@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
Reviewed-by: NYang Shi <yang.shi@linux.alibaba.com>

mm/memcontrol.c

@@ -4751,6 +4751,48 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
 	return ret;
 }
 
+static int memory_high_show(struct seq_file *m, void *v)
+{
+	struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));
+	unsigned long high = READ_ONCE(memcg->high);
+
+	if (high == PAGE_COUNTER_MAX)
+		seq_puts(m, "max\n");
+	else
+		seq_printf(m, "%llu\n", (u64)high * PAGE_SIZE);
+
+	return 0;
+}
+
+static ssize_t memory_high_write(struct kernfs_open_file *of,
+				 char *buf, size_t nbytes, loff_t off)
+{
+	struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
+	unsigned long nr_pages;
+	unsigned long high;
+	int err;
+
+	buf = strstrip(buf);
+	err = page_counter_memparse(buf, "max", &high);
+	if (err)
+		return err;
+
+	memcg->high = high;
+
+	nr_pages = page_counter_read(&memcg->memory);
+	if (nr_pages > high)
+		try_to_free_mem_cgroup_pages(memcg, nr_pages - high,
+					     GFP_KERNEL, true);
+
+	setup_memcg_wmark(memcg);
+
+	if (!is_wmark_ok(memcg, true))
+		queue_work(memcg_wmark_wq, &memcg->wmark_work);
+
+	memcg_wb_domain_size_changed(memcg);
+	return nbytes;
+}
+
 static struct cftype mem_cgroup_legacy_files[] = {
 	{
 		.name = "usage_in_bytes",
@@ -4910,6 +4952,12 @@ static struct cftype mem_cgroup_legacy_files[] = {
 		.write = mem_cgroup_idle_page_stats_write,
 	},
 #endif
+	{
+		.name = "high",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.seq_show = memory_high_show,
+		.write = memory_high_write,
+	},
 	{ },	/* terminate */
 };
 
@@ -6095,48 +6143,6 @@ static ssize_t memory_low_write(struct kernfs_open_file *of,
 	return nbytes;
 }
 
-static int memory_high_show(struct seq_file *m, void *v)
-{
-	struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));
-	unsigned long high = READ_ONCE(memcg->high);
-
-	if (high == PAGE_COUNTER_MAX)
-		seq_puts(m, "max\n");
-	else
-		seq_printf(m, "%llu\n", (u64)high * PAGE_SIZE);
-
-	return 0;
-}
-
-static ssize_t memory_high_write(struct kernfs_open_file *of,
-				 char *buf, size_t nbytes, loff_t off)
-{
-	struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
-	unsigned long nr_pages;
-	unsigned long high;
-	int err;
-
-	buf = strstrip(buf);
-	err = page_counter_memparse(buf, "max", &high);
-	if (err)
-		return err;
-
-	memcg->high = high;
-
-	nr_pages = page_counter_read(&memcg->memory);
-	if (nr_pages > high)
-		try_to_free_mem_cgroup_pages(memcg, nr_pages - high,
-					     GFP_KERNEL, true);
-
-	setup_memcg_wmark(memcg);
-
-	if (!is_wmark_ok(memcg, true))
-		queue_work(memcg_wmark_wq, &memcg->wmark_work);
-
-	memcg_wb_domain_size_changed(memcg);
-	return nbytes;
-}
-
 static int memory_wmark_low_show(struct seq_file *m, void *v)
 {
 	struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));