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Sender: Minchan Kim <minchan.kim@gmail.com>
From:   Minchan Kim <minchan@kernel.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-mm <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>,
        gregkh@linuxfoundation.org, surenb@google.com, joaodias@google.com,
        jhubbard@nvidia.com, willy@infradead.org, digetx@gmail.com,
        Minchan Kim <minchan@kernel.org>
Subject: [PATCH v6] mm: cma: support sysfs
Date:   Tue, 23 Mar 2021 18:05:47 -0700
Message-Id: <20210324010547.4134370-1-minchan@kernel.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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 statistics for CMA, in order to provide
some basic monitoring of the CMA allocator.

 * the number of CMA page successful allocations
 * the number of CMA page allocation failures

These two values allow the user to calculate the allocation
failure rate for each CMA area.

e.g.)
  /sys/kernel/mm/cma/WIFI/alloc_pages_[success|fail]
  /sys/kernel/mm/cma/SENSOR/alloc_pages_[success|fail]
  /sys/kernel/mm/cma/BLUETOOTH/alloc_pages_[success|fail]

The cma_stat was intentionally allocated by dynamic allocation
to harmonize with kobject lifetime management.
https://lore.kernel.org/linux-mm/YCOAmXqt6dZkCQYs@kroah.com/

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Tested-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
From v5 - https://lore.kernel.org/linux-mm/20210323195050.2577017-1-minchan@kernel.org/
 * refactoring and fix typo - digetx@

From v4 - https://lore.kernel.org/linux-mm/20210309062333.3216138-1-minchan@kernel.org/
 * fix corruption - digetx@

From v3 - https://lore.kernel.org/linux-mm/20210303205053.2906924-1-minchan@kernel.org/
 * fix ZERO_OR_NULL_PTR - kernel test robot
 * remove prefix cma - david@
 * resolve conflict with vmstat cma in mmotm - akpm@
 * rename stat name with success|fail

From v2 - https://lore.kernel.org/linux-mm/20210208180142.2765456-1-minchan@kernel.org/
 * sysfs doc and description modification - jhubbard

From v1 - https://lore.kernel.org/linux-mm/20210203155001.4121868-1-minchan@kernel.org/
 * fix sysfs build and refactoring - willy

 Documentation/ABI/testing/sysfs-kernel-mm-cma |  25 ++++
 mm/Kconfig                                    |   7 ++
 mm/Makefile                                   |   1 +
 mm/cma.c                                      |   7 +-
 mm/cma.h                                      |  23 ++++
 mm/cma_sysfs.c                                | 107 ++++++++++++++++++
 6 files changed, 168 insertions(+), 2 deletions(-)
 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..02b2bb60c296
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-mm-cma
@@ -0,0 +1,25 @@
+What:		/sys/kernel/mm/cma/
+Date:		Feb 2021
+Contact:	Minchan Kim <minchan@kernel.org>
+Description:
+		/sys/kernel/mm/cma/ contains a subdirectory for each CMA
+		heap name (also sometimes called CMA areas).
+
+		Each CMA heap subdirectory (that is, each
+		/sys/kernel/mm/cma/<cma-heap-name> directory) contains the
+		following items:
+
+			alloc_pages_success
+			alloc_pages_fail
+
+What:		/sys/kernel/mm/cma/<cma-heap-name>/alloc_pages_success
+Date:		Feb 2021
+Contact:	Minchan Kim <minchan@kernel.org>
+Description:
+		the number of pages CMA API succeeded to allocate
+
+What:		/sys/kernel/mm/cma/<cma-heap-name>/alloc_pages_fail
+Date:		Feb 2021
+Contact:	Minchan Kim <minchan@kernel.org>
+Description:
+		the number of pages CMA API failed to allocate
diff --git a/mm/Kconfig b/mm/Kconfig
index 24c045b24b95..febb7e8e24de 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -513,6 +513,13 @@ config CMA_DEBUGFS
 	help
 	  Turns on the DebugFS interface for CMA.
 
+config CMA_SYSFS
+	bool "CMA information through sysfs interface"
+	depends on CMA && SYSFS
+	help
+	  This option exposes some sysfs attributes to get information
+	  from CMA.
+
 config CMA_AREAS
 	int "Maximum count of the CMA areas"
 	depends on CMA
diff --git a/mm/Makefile b/mm/Makefile
index 72227b24a616..56968b23ed7a 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -109,6 +109,7 @@ obj-$(CONFIG_CMA)	+= cma.o
 obj-$(CONFIG_MEMORY_BALLOON) += balloon_compaction.o
 obj-$(CONFIG_PAGE_EXTENSION) += page_ext.o
 obj-$(CONFIG_CMA_DEBUGFS) += cma_debug.o
+obj-$(CONFIG_CMA_SYSFS) += cma_sysfs.o
 obj-$(CONFIG_USERFAULTFD) += userfaultfd.o
 obj-$(CONFIG_IDLE_PAGE_TRACKING) += page_idle.o
 obj-$(CONFIG_DEBUG_PAGE_REF) += debug_page_ref.o
diff --git a/mm/cma.c b/mm/cma.c
index 908f04775686..204e349a0c25 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -507,10 +507,13 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
 
 	pr_debug("%s(): returned %p\n", __func__, page);
 out:
-	if (page)
+	if (page) {
 		count_vm_event(CMA_ALLOC_SUCCESS);
-	else
+		cma_sysfs_account_success_pages(cma, count);
+	} else {
 		count_vm_event(CMA_ALLOC_FAIL);
+		cma_sysfs_account_fail_pages(cma, count);
+	}
 
 	return page;
 }
diff --git a/mm/cma.h b/mm/cma.h
index 42ae082cb067..2298a2e736a6 100644
--- a/mm/cma.h
+++ b/mm/cma.h
@@ -3,6 +3,12 @@
 #define __MM_CMA_H__
 
 #include <linux/debugfs.h>
+#include <linux/kobject.h>
+
+struct cma_kobject {
+	struct cma *cma;
+	struct kobject kobj;
+};
 
 struct cma {
 	unsigned long   base_pfn;
@@ -16,6 +22,14 @@ struct cma {
 	struct debugfs_u32_array dfs_bitmap;
 #endif
 	char name[CMA_MAX_NAME];
+#ifdef CONFIG_CMA_SYSFS
+	/* the number of CMA page successful allocations */
+	atomic64_t nr_pages_succeeded;
+	/* the number of CMA page allocation failures */
+	atomic64_t nr_pages_failed;
+	/* kobject requires dynamic object */
+	struct cma_kobject *kobj;
+#endif
 };
 
 extern struct cma cma_areas[MAX_CMA_AREAS];
@@ -26,4 +40,13 @@ static inline unsigned long cma_bitmap_maxno(struct cma *cma)
 	return cma->count >> cma->order_per_bit;
 }
 
+#ifdef CONFIG_CMA_SYSFS
+void cma_sysfs_account_success_pages(struct cma *cma, size_t count);
+void cma_sysfs_account_fail_pages(struct cma *cma, size_t count);
+#else
+static inline void cma_sysfs_account_success_pages(struct cma *cma,
+						   size_t count) {};
+static inline void cma_sysfs_account_fail_pages(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..c3791a032dc5
--- /dev/null
+++ b/mm/cma_sysfs.c
@@ -0,0 +1,107 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * CMA SysFS Interface
+ *
+ * Copyright (c) 2021 Minchan Kim <minchan@kernel.org>
+ */
+
+#include <linux/cma.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+
+#include "cma.h"
+
+void cma_sysfs_account_success_pages(struct cma *cma, size_t count)
+{
+	atomic64_add(count, &cma->nr_pages_succeeded);
+}
+
+void cma_sysfs_account_fail_pages(struct cma *cma, size_t count)
+{
+	atomic64_add(count, &cma->nr_pages_failed);
+}
+
+#define CMA_ATTR_RO(_name) \
+	static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
+
+#define to_cma_kobject(x) container_of(x, struct cma_kobject, kobj)
+
+static ssize_t alloc_pages_success_show(struct kobject *kobj,
+					struct kobj_attribute *attr, char *buf)
+{
+	struct cma_kobject *cma_kobj = to_cma_kobject(kobj);
+	struct cma *cma = cma_kobj->cma;
+
+	return sysfs_emit(buf, "%llu\n",
+			  atomic64_read(&cma->nr_pages_succeeded));
+}
+CMA_ATTR_RO(alloc_pages_success);
+
+static ssize_t alloc_pages_fail_show(struct kobject *kobj,
+				     struct kobj_attribute *attr, char *buf)
+{
+	struct cma_kobject *cma_kobj = to_cma_kobject(kobj);
+	struct cma *cma = cma_kobj->cma;
+
+	return sysfs_emit(buf, "%llu\n", atomic64_read(&cma->nr_pages_failed));
+}
+CMA_ATTR_RO(alloc_pages_fail);
+
+static void cma_kobj_release(struct kobject *kobj)
+{
+	struct cma_kobject *cma_kobj = to_cma_kobject(kobj);
+	struct cma *cma = cma_kobj->cma;
+
+	kfree(cma_kobj);
+	cma->kobj = NULL;
+}
+
+static struct attribute *cma_attrs[] = {
+	&alloc_pages_success_attr.attr,
+	&alloc_pages_fail_attr.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(cma);
+
+static struct kobject *cma_kobj_root;
+
+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)
+{
+	unsigned int i;
+
+	cma_kobj_root = kobject_create_and_add("cma", mm_kobj);
+	if (!cma_kobj_root)
+		return -ENOMEM;
+
+	for (i = 0; i < cma_area_count; i++) {
+		int err;
+		struct cma *cma;
+		struct cma_kobject *cma_kobj;
+
+		cma_kobj = kzalloc(sizeof(*cma_kobj), GFP_KERNEL);
+		if (!cma_kobj) {
+			kobject_put(cma_kobj_root);
+			return -ENOMEM;
+		}
+
+		cma = &cma_areas[i];
+		cma->kobj = cma_kobj;
+		cma_kobj->cma = cma;
+		err = kobject_init_and_add(&cma_kobj->kobj, &cma_ktype,
+					   cma_kobj_root, "%s", cma->name);
+		if (err) {
+			kobject_put(&cma_kobj->kobj);
+			kobject_put(cma_kobj_root);
+			return err;
+		}
+	}
+
+	return 0;
+}
+subsys_initcall(cma_sysfs_init);
-- 
2.31.0.291.g576ba9dcdaf-goog