ANDROID: mm: Create an new handler for extra_free_kbytes

When modifying extra_free_kbytes, user_min_free_kbytes is modified
at the same time, which will cause user_min_free_kbytes to be
modified incorrectly.
Create an new handler for extra_free_kbytes.

Bug: 201480378

Change-Id: Ib30aa846ad4ea17a1ef4d306f82500de6dc2bf10
Signed-off-by: Liangcai Fan <liangcai.fan@unisoc.com>

include/linux/mmzone.h

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 11f0106..9ac53dd9 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -961,6 +961,8 @@ static inline int is_highmem(struct zone *zone)
 struct ctl_table;
 int min_free_kbytes_sysctl_handler(struct ctl_table *, int,
 					void __user *, size_t *, loff_t *);
+int extra_free_kbytes_sysctl_handler(struct ctl_table *, int,
+					void __user *, size_t *, loff_t *);
 int watermark_boost_factor_sysctl_handler(struct ctl_table *, int,
 					void __user *, size_t *, loff_t *);
 int watermark_scale_factor_sysctl_handler(struct ctl_table *, int,

kernel/sysctl.c

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index e8f0787..8a098896 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1537,7 +1537,7 @@ static struct ctl_table vm_table[] = {
 		.data		= &extra_free_kbytes,
 		.maxlen		= sizeof(extra_free_kbytes),
 		.mode		= 0644,
-		.proc_handler	= min_free_kbytes_sysctl_handler,
+		.proc_handler	= extra_free_kbytes_sysctl_handler,
 		.extra1		= SYSCTL_ZERO,
 	},
 	{

mm/page_alloc.c

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8147f8f..a2f1ccc 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7995,8 +7995,7 @@ postcore_initcall(init_per_zone_wmark_min)
 
 /*
  * min_free_kbytes_sysctl_handler - just a wrapper around proc_dointvec() so
- *	that we can call two helper functions whenever min_free_kbytes
- *	or extra_free_kbytes changes.
+ *	that we can call two helper functions whenever min_free_kbytes changes.
  */
 int min_free_kbytes_sysctl_handler(struct ctl_table *table, int write,
 	void __user *buffer, size_t *length, loff_t *ppos)
@@ -8014,6 +8013,25 @@ int min_free_kbytes_sysctl_handler(struct ctl_table *table, int write,
 	return 0;
 }
 
+/*
+ * extra_free_kbytes_sysctl_handler - just a wrapper around proc_dointvec() so
+ * that we can call two helper functions whenever extra_free_kbytes changes.
+ */
+int extra_free_kbytes_sysctl_handler(struct ctl_table *table, int write,
+	void __user *buffer, size_t *length, loff_t *ppos)
+{
+	int rc;
+
+	rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
+	if (rc)
+		return rc;
+
+	if (write)
+		setup_per_zone_wmarks();
+
+	return 0;
+}
+
 int watermark_boost_factor_sysctl_handler(struct ctl_table *table, int write,
 	void __user *buffer, size_t *length, loff_t *ppos)
 {