[PATCH] mm: cma: support sysfs

[Minchan Kim]

Since CMA is getting used more widely, it's more important to
keep monitoring CMA statistics for system health since it's
directly related to user experience.

This patch introduces sysfs for the CMA and exposes stats below
to keep monitor for telemetric in the system.

 * the number of CMA allocation attempts
 * the number of CMA allocation failures
 * the number of CMA page allocation attempts
 * the number of CMA page allocation failures

Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
---
 Documentation/ABI/testing/sysfs-kernel-mm-cma |  39 +++++
 include/linux/cma.h                           |   1 +
 mm/Makefile                                   |   1 +
 mm/cma.c                                      |   6 +-
 mm/cma.h                                      |  20 +++
 mm/cma_sysfs.c                                | 143 ++++++++++++++++++
 6 files changed, 209 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/ABI/testing/sysfs-kernel-mm-cma
 create mode 100644 mm/cma_sysfs.c

diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-cma b/Documentation/ABI/testing/sysfs-kernel-mm-cma
new file mode 100644
index 000000000000..2a43c0aacc39
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-mm-cma
@@ -0,0 +1,39 @@
+What:		/sys/kernel/mm/cma/
+Date:		Feb 2021
+Contact:	Minchan Kim <minchan@xxxxxxxxxx>
+Description:
+		/sys/kernel/mm/cma/ contains a number of subdirectories by
+		cma-heap name. The subdirectory contains a number of files
+		to represent cma allocation statistics.
+
+		There are number of files under
+				/sys/kernel/mm/cma/<cma-heap-name> directory
+
+			- cma_alloc_attempt
+			- cma_alloc_fail
+			- alloc_pages_attempt
+			- alloc_pages_fail
+
+What:		/sys/kernel/mm/cma/<cma-heap-name>/cma_alloc_attempt
+Date:		Feb 2021
+Contact:	Minchan Kim <minchan@xxxxxxxxxx>
+Description:
+		the number of cma_alloc API attempted
+
+What:		/sys/kernel/mm/cma/<cma-heap-name>/cma_alloc_fail
+Date:		Feb 2021
+Contact:	Minchan Kim <minchan@xxxxxxxxxx>
+Description:
+		the number of CMA_alloc API failed
+
+What:		/sys/kernel/mm/cma/<cma-heap-name>/alloc_pages_attempt
+Date:		Feb 2021
+Contact:	Minchan Kim <minchan@xxxxxxxxxx>
+Description:
+		the number of pages CMA API tried to allocate
+
+What:		/sys/kernel/mm/cma/<cma-heap-name>/alloc_pages_fail
+Date:		Feb 2021
+Contact:	Minchan Kim <minchan@xxxxxxxxxx>
+Description:
+		the number of pages CMA API failed to allocate
diff --git a/include/linux/cma.h b/include/linux/cma.h
index 217999c8a762..71a28a5bb54e 100644
--- a/include/linux/cma.h
+++ b/include/linux/cma.h
@@ -49,4 +49,5 @@ extern struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
 extern bool cma_release(struct cma *cma, const struct page *pages, unsigned int count);
 
 extern int cma_for_each_area(int (*it)(struct cma *cma, void *data), void *data);
+
 #endif
diff --git a/mm/Makefile b/mm/Makefile
index b2a564eec27f..9c2c81ce3894 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -106,6 +106,7 @@ obj-$(CONFIG_ZSMALLOC)	+= zsmalloc.o
 obj-$(CONFIG_Z3FOLD)	+= z3fold.o
 obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o
 obj-$(CONFIG_CMA)	+= cma.o
+obj-$(CONFIG_SYSFS)     += cma_sysfs.o
 obj-$(CONFIG_MEMORY_BALLOON) += balloon_compaction.o
 obj-$(CONFIG_PAGE_EXTENSION) += page_ext.o
 obj-$(CONFIG_CMA_DEBUGFS) += cma_debug.o
diff --git a/mm/cma.c b/mm/cma.c
index 0ba69cd16aeb..a25068b9d012 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -448,9 +448,10 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
 	offset = cma_bitmap_aligned_offset(cma, align);
 	bitmap_maxno = cma_bitmap_maxno(cma);
 	bitmap_count = cma_bitmap_pages_to_bits(cma, count);
+	cma_sysfs_alloc_count(cma, count);
 
 	if (bitmap_count > bitmap_maxno)
-		return NULL;
+		goto out;
 
 	for (;;) {
 		mutex_lock(&cma->lock);
@@ -505,6 +506,9 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
 			__func__, count, ret);
 		cma_debug_show_areas(cma);
 	}
+out:
+	if (!page)
+		cma_sysfs_fail(cma, count);
 
 	pr_debug("%s(): returned %p\n", __func__, page);
 	return page;
diff --git a/mm/cma.h b/mm/cma.h
index 42ae082cb067..e7e31012b44e 100644
--- a/mm/cma.h
+++ b/mm/cma.h
@@ -3,6 +3,16 @@
 #define __MM_CMA_H__
 
 #include <linux/debugfs.h>
+#include <linux/kobject.h>
+
+struct cma_stat {
+	spinlock_t lock;
+	unsigned long alloc_attempt;	/* the number of CMA allocation attempts */
+	unsigned long alloc_fail;	/* the number of CMA allocation failures */
+	unsigned long pages_attempt;	/* the number of CMA page allocation attempts */
+	unsigned long pages_fail;	/* the number of CMA page allocation failures */
+	struct kobject kobj;
+};
 
 struct cma {
 	unsigned long   base_pfn;
@@ -16,6 +26,9 @@ struct cma {
 	struct debugfs_u32_array dfs_bitmap;
 #endif
 	char name[CMA_MAX_NAME];
+#ifdef CONFIG_SYSFS
+	struct cma_stat	*stat;
+#endif
 };
 
 extern struct cma cma_areas[MAX_CMA_AREAS];
@@ -26,4 +39,11 @@ static inline unsigned long cma_bitmap_maxno(struct cma *cma)
 	return cma->count >> cma->order_per_bit;
 }
 
+#ifdef CONFIG_SYSFS
+void cma_sysfs_alloc_count(struct cma *cma, size_t count);
+void cma_sysfs_fail(struct cma *cma, size_t count);
+#else
+static void cma_sysfs_alloc_count(struct cma *cma, size_t count) {};
+static void cma_sysfs_fail(struct cma *cma, size_t count) {};
+#endif
 #endif
diff --git a/mm/cma_sysfs.c b/mm/cma_sysfs.c
new file mode 100644
index 000000000000..66df292cd6ca
--- /dev/null
+++ b/mm/cma_sysfs.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * CMA SysFS Interface
+ *
+ * Copyright (c) 2021 Minchan Kim <minchan@xxxxxxxxxx>
+ */
+
+#include <linux/cma.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+
+#include "cma.h"
+
+void cma_sysfs_alloc_count(struct cma *cma, size_t count)
+{
+	spin_lock(&cma->stat->lock);
+	cma->stat->alloc_attempt++;
+	cma->stat->pages_attempt += count;
+	spin_unlock(&cma->stat->lock);
+}
+
+void cma_sysfs_fail(struct cma *cma, size_t count)
+{
+	spin_lock(&cma->stat->lock);
+	cma->stat->alloc_fail++;
+	cma->stat->pages_fail += count;
+	spin_unlock(&cma->stat->lock);
+}
+
+#define CMA_ATTR_RO(_name) \
+	static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
+
+static struct kobject *cma_kobj;
+
+static ssize_t cma_alloc_attempt_show(struct kobject *kobj,
+			struct kobj_attribute *attr, char *buf)
+{
+	unsigned long val;
+	struct cma_stat *stat = container_of(kobj, struct cma_stat, kobj);
+
+	val = stat->alloc_attempt;
+
+	return sysfs_emit(buf, "%lu\n", val);
+}
+CMA_ATTR_RO(cma_alloc_attempt);
+
+static ssize_t cma_alloc_fail_show(struct kobject *kobj,
+			struct kobj_attribute *attr, char *buf)
+{
+	unsigned long val;
+	struct cma_stat *stat = container_of(kobj, struct cma_stat, kobj);
+
+	val = stat->alloc_fail;
+
+	return sysfs_emit(buf, "%lu\n", val);
+}
+CMA_ATTR_RO(cma_alloc_fail);
+
+static ssize_t alloc_pages_attempt_show(struct kobject *kobj,
+			struct kobj_attribute *attr, char *buf)
+{
+	unsigned long val;
+	struct cma_stat *stat = container_of(kobj, struct cma_stat, kobj);
+
+	val = stat->pages_attempt;
+
+	return sysfs_emit(buf, "%lu\n", val);
+}
+CMA_ATTR_RO(alloc_pages_attempt);
+
+static ssize_t alloc_pages_fail_show(struct kobject *kobj,
+			struct kobj_attribute *attr, char *buf)
+{
+	unsigned long val;
+	struct cma_stat *stat = container_of(kobj, struct cma_stat, kobj);
+
+	val = stat->pages_fail;
+
+	return sysfs_emit(buf, "%lu\n", val);
+}
+CMA_ATTR_RO(alloc_pages_fail);
+
+static void cma_kobj_release(struct kobject *kobj)
+{
+	struct cma_stat *stat = container_of(kobj, struct cma_stat, kobj);
+
+	kfree(stat);
+}
+
+static struct attribute *cma_attrs[] = {
+	&cma_alloc_attempt_attr.attr,
+	&cma_alloc_fail_attr.attr,
+	&alloc_pages_attempt_attr.attr,
+	&alloc_pages_fail_attr.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(cma);
+
+static struct kobj_type cma_ktype = {
+	.release = cma_kobj_release,
+	.sysfs_ops = &kobj_sysfs_ops,
+	.default_groups = cma_groups
+};
+
+static int __init cma_sysfs_init(void)
+{
+	int i;
+	struct cma *cma;
+	struct cma_stat *stat;
+
+	cma_kobj = kobject_create_and_add("cma", mm_kobj);
+	if (!cma_kobj) {
+		pr_err("failed to create cma kobject\n");
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < cma_area_count; i++) {
+		cma = &cma_areas[i];
+		stat = kzalloc(sizeof(*stat), GFP_KERNEL);
+		if (!stat)
+			goto out;
+
+		cma->stat = stat;
+		spin_lock_init(&stat->lock);
+		if (kobject_init_and_add(&stat->kobj, &cma_ktype,
+					cma_kobj, "%s", cma->name)) {
+			kobject_put(&stat->kobj);
+			goto out;
+		}
+	}
+
+	return 0;
+out:
+	while (--i >= 0) {
+		cma = &cma_areas[i];
+		kobject_put(&cma->stat->kobj);
+	}
+
+	kobject_put(cma_kobj);
+
+	return -ENOMEM;
+}
+subsys_initcall(cma_sysfs_init);
-- 
2.30.0.365.g02bc693789-goog