[RFC PATCH 1/3] proc/meminfo: introduce extra meminfo

[Jaewon Kim]

Provide APIs to drivers so that they can show its memory usage on
/proc/meminfo.

int register_extra_meminfo(atomic_long_t *val, int shift,
			   const char *name);
int unregister_extra_meminfo(atomic_long_t *val);

Signed-off-by: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>
---
 fs/proc/meminfo.c  | 103 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/mm.h |   4 +++
 lib/show_mem.c     |   1 +
 3 files changed, 108 insertions(+)

diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index 8c1f1bb1a5ce..12b1f77b091b 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -13,6 +13,7 @@
 #include <linux/vmstat.h>
 #include <linux/atomic.h>
 #include <linux/vmalloc.h>
+#include <linux/slab.h>
 #ifdef CONFIG_CMA
 #include <linux/cma.h>
 #endif
@@ -30,6 +31,106 @@ static void show_val_kb(struct seq_file *m, const char *s, unsigned long num)
 	seq_write(m, " kB\n", 4);
 }
 
+static LIST_HEAD(meminfo_head);
+static DEFINE_SPINLOCK(meminfo_lock);
+
+#define NAME_SIZE      15
+#define NAME_BUF_SIZE  (NAME_SIZE + 2) /* ':' and '\0' */
+
+struct extra_meminfo {
+	struct list_head list;
+	atomic_long_t *val;
+	int shift_for_page;
+	char name[NAME_BUF_SIZE];
+	char name_pad[NAME_BUF_SIZE];
+};
+
+int register_extra_meminfo(atomic_long_t *val, int shift, const char *name)
+{
+	struct extra_meminfo *meminfo, *memtemp;
+	int len;
+	int error = 0;
+
+	meminfo = kzalloc(sizeof(*meminfo), GFP_KERNEL);
+	if (!meminfo) {
+		error = -ENOMEM;
+		goto out;
+	}
+
+	meminfo->val = val;
+	meminfo->shift_for_page = shift;
+	strncpy(meminfo->name, name, NAME_SIZE);
+	len = strlen(meminfo->name);
+	meminfo->name[len] = ':';
+	strncpy(meminfo->name_pad, meminfo->name, NAME_BUF_SIZE);
+	while (++len < NAME_BUF_SIZE - 1)
+		meminfo->name_pad[len] = ' ';
+
+	spin_lock(&meminfo_lock);
+	list_for_each_entry(memtemp, &meminfo_head, list) {
+		if (memtemp->val == val) {
+			error = -EINVAL;
+			break;
+		}
+	}
+	if (!error)
+		list_add_tail(&meminfo->list, &meminfo_head);
+	spin_unlock(&meminfo_lock);
+	if (error)
+		kfree(meminfo);
+out:
+
+	return error;
+}
+EXPORT_SYMBOL(register_extra_meminfo);
+
+int unregister_extra_meminfo(atomic_long_t *val)
+{
+	struct extra_meminfo *memtemp, *memtemp2;
+	int error = -EINVAL;
+
+	spin_lock(&meminfo_lock);
+	list_for_each_entry_safe(memtemp, memtemp2, &meminfo_head, list) {
+		if (memtemp->val == val) {
+			list_del(&memtemp->list);
+			error = 0;
+			break;
+		}
+	}
+	spin_unlock(&meminfo_lock);
+	kfree(memtemp);
+
+	return error;
+}
+EXPORT_SYMBOL(unregister_extra_meminfo);
+
+static void __extra_meminfo(struct seq_file *m)
+{
+	struct extra_meminfo *memtemp;
+	unsigned long nr_page;
+
+	spin_lock(&meminfo_lock);
+	list_for_each_entry(memtemp, &meminfo_head, list) {
+		nr_page = (unsigned long)atomic_long_read(memtemp->val);
+		nr_page = nr_page >> memtemp->shift_for_page;
+		if (m)
+			show_val_kb(m, memtemp->name_pad, nr_page);
+		else
+			pr_cont("%s%lukB ", memtemp->name, nr_page);
+	}
+	spin_unlock(&meminfo_lock);
+}
+
+void extra_meminfo_log(void)
+{
+	__extra_meminfo(NULL);
+}
+
+static void extra_meminfo_proc(struct seq_file *m)
+{
+	__extra_meminfo(m);
+}
+
 static int meminfo_proc_show(struct seq_file *m, void *v)
 {
 	struct sysinfo i;
@@ -148,6 +249,8 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 
 	arch_report_meminfo(m);
 
+	extra_meminfo_proc(m);
+
 	return 0;
 }
 
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c54fb96cb1e6..457570ddd17c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2902,6 +2902,10 @@ void __init setup_nr_node_ids(void);
 static inline void setup_nr_node_ids(void) {}
 #endif
 
+void extra_meminfo_log(void);
+int register_extra_meminfo(atomic_long_t *val, int shift, const char *name);
+int unregister_extra_meminfo(atomic_long_t *val);
+
 extern int memcmp_pages(struct page *page1, struct page *page2);
 
 static inline int pages_identical(struct page *page1, struct page *page2)
diff --git a/lib/show_mem.c b/lib/show_mem.c
index 1c26c14ffbb9..48be5afaca0a 100644
--- a/lib/show_mem.c
+++ b/lib/show_mem.c
@@ -14,6 +14,7 @@ void show_mem(unsigned int filter, nodemask_t *nodemask)
 	unsigned long total = 0, reserved = 0, highmem = 0;
 
 	printk("Mem-Info:\n");
+	extra_meminfo_log();
 	show_free_areas(filter, nodemask);
 
 	for_each_online_pgdat(pgdat) {
-- 
2.13.7