[PATCH] ksm: Expose configuration via sysctl

[Alexander Graf]

Configuration of tunables and Linux virtual memory settings has traditionally
happened via sysctl. Thanks to that there are well established ways to make
sysctl configuration bits persistent (sysctl.conf).

KSM introduced a sysfs based configuration path which is not covered by user
space persistent configuration frameworks.

In order to make life easy for sysadmins, this patch adds all access to all
KSM tunables via sysctl as well. That way sysctl.conf works for KSM as well,
giving us a streamlined way to make KSM configuration persistent.

Reported-by: Sasche Peilicke <speilicke@xxxxxxxx>
Signed-off-by: Alexander Graf <agraf@xxxxxxx>
---
 kernel/sysctl.c |   10 +++++++
 mm/ksm.c        |   78 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 88 insertions(+), 0 deletions(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 332cefc..2169a00 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -217,6 +217,9 @@ extern struct ctl_table random_table[];
 #ifdef CONFIG_EPOLL
 extern struct ctl_table epoll_table[];
 #endif
+#ifdef CONFIG_KSM
+extern struct ctl_table ksm_table[];
+#endif
 
 #ifdef HAVE_ARCH_PICK_MMAP_LAYOUT
 int sysctl_legacy_va_layout;
@@ -1279,6 +1282,13 @@ static struct ctl_table vm_table[] = {
 	},
 
 #endif /* CONFIG_COMPACTION */
+#ifdef CONFIG_KSM
+	{
+		.procname	= "ksm",
+		.mode		= 0555,
+		.child		= ksm_table,
+	},
+#endif
 	{
 		.procname	= "min_free_kbytes",
 		.data		= &min_free_kbytes,
diff --git a/mm/ksm.c b/mm/ksm.c
index 3df141e..df93989 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2306,6 +2306,84 @@ static struct attribute_group ksm_attr_group = {
 };
 #endif /* CONFIG_SYSFS */
 
+#ifdef CONFIG_SYSCTL
+static int fill_from_user(char *buf, char __user *ubuf, size_t len)
+{
+	if (len > 15)
+		return -EINVAL;
+
+	if (copy_from_user(buf, ubuf, len))
+		return -EFAULT;
+
+	buf[len] = 0;
+	return 0;
+}
+
+static int sysctl_ksm(struct ctl_table *ctl, int write, void __user *buffer,
+		      size_t *lenp, loff_t *fpos)
+{
+	int r;
+	char buf[16];
+
+	if (!write)
+		return proc_dointvec(ctl, write, buffer, lenp, fpos);
+
+	r = fill_from_user(buf, buffer, *lenp);
+	if (r)
+		return r;
+
+	if (ctl->data == &ksm_run)
+		r = run_store(NULL, NULL, buf, *lenp);
+	else if (ctl->data == &ksm_thread_sleep_millisecs)
+		r = sleep_millisecs_store(NULL, NULL, buf, *lenp);
+	else if (ctl->data == &ksm_thread_pages_to_scan)
+		r = pages_to_scan_store(NULL, NULL, buf, *lenp);
+#ifdef CONFIG_NUMA
+	else if (ctl->data == &ksm_merge_across_nodes)
+		r = merge_across_nodes_store(NULL, NULL, buf, *lenp);
+#endif
+	else
+		r = -EINVAL;
+
+	return r;
+}
+
+struct ctl_table ksm_table[] =
+{
+	{
+		.procname	= "run",
+		.data		= &ksm_run,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= sysctl_ksm,
+	},
+	{
+		.procname	= "sleep_millisecs",
+		.data		= &ksm_thread_sleep_millisecs,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= sysctl_ksm,
+	},
+	{
+		.procname	= "pages_to_scan",
+		.data		= &ksm_thread_pages_to_scan,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= sysctl_ksm,
+	},
+#ifdef CONFIG_NUMA
+	{
+		.procname	= "merge_across_nodes",
+		.data		= &ksm_merge_across_nodes,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= sysctl_ksm,
+	},
+#endif /* CONFIG_NUMA */
+	{ }
+};
+#endif /* CONFIG_SYSCTL */
+
 static int __init ksm_init(void)
 {
 	struct task_struct *ksm_thread;
-- 
1.6.0.2

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