linux/drivers/dma-buf/dma-buf-sysfs-stats.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * DMA-BUF sysfs statistics.
 *
 * Copyright (C) 2021 Google LLC.
 */

#include <linux/dma-buf.h>
#include <linux/dma-resv.h>
#include <linux/kobject.h>
#include <linux/printk.h>
#include <linux/slab.h>
#include <linux/sysfs.h>

#include "dma-buf-sysfs-stats.h"

#define to_dma_buf_entry_from_kobj(x) …

/**
 * DOC: overview
 *
 * ``/sys/kernel/debug/dma_buf/bufinfo`` provides an overview of every DMA-BUF
 * in the system. However, since debugfs is not safe to be mounted in
 * production, procfs and sysfs can be used to gather DMA-BUF statistics on
 * production systems.
 *
 * The ``/proc/<pid>/fdinfo/<fd>`` files in procfs can be used to gather
 * information about DMA-BUF fds. Detailed documentation about the interface
 * is present in Documentation/filesystems/proc.rst.
 *
 * Unfortunately, the existing procfs interfaces can only provide information
 * about the DMA-BUFs for which processes hold fds or have the buffers mmapped
 * into their address space. This necessitated the creation of the DMA-BUF sysfs
 * statistics interface to provide per-buffer information on production systems.
 *
 * The interface at ``/sys/kernel/dmabuf/buffers`` exposes information about
 * every DMA-BUF when ``CONFIG_DMABUF_SYSFS_STATS`` is enabled.
 *
 * The following stats are exposed by the interface:
 *
 * * ``/sys/kernel/dmabuf/buffers/<inode_number>/exporter_name``
 * * ``/sys/kernel/dmabuf/buffers/<inode_number>/size``
 *
 * The information in the interface can also be used to derive per-exporter
 * statistics. The data from the interface can be gathered on error conditions
 * or other important events to provide a snapshot of DMA-BUF usage.
 * It can also be collected periodically by telemetry to monitor various metrics.
 *
 * Detailed documentation about the interface is present in
 * Documentation/ABI/testing/sysfs-kernel-dmabuf-buffers.
 */

struct dma_buf_stats_attribute { … };
#define to_dma_buf_stats_attr(x) …

static ssize_t dma_buf_stats_attribute_show(struct kobject *kobj,
					    struct attribute *attr,
					    char *buf)
{ … }

static const struct sysfs_ops dma_buf_stats_sysfs_ops = …;

static ssize_t exporter_name_show(struct dma_buf *dmabuf,
				  struct dma_buf_stats_attribute *attr,
				  char *buf)
{ … }

static ssize_t size_show(struct dma_buf *dmabuf,
			 struct dma_buf_stats_attribute *attr,
			 char *buf)
{ … }

static struct dma_buf_stats_attribute exporter_name_attribute = …;
static struct dma_buf_stats_attribute size_attribute = …;

static struct attribute *dma_buf_stats_default_attrs[] = …;
ATTRIBUTE_GROUPS(…);

static void dma_buf_sysfs_release(struct kobject *kobj)
{ … }

static const struct kobj_type dma_buf_ktype = …;

void dma_buf_stats_teardown(struct dma_buf *dmabuf)
{ … }


/* Statistics files do not need to send uevents. */
static int dmabuf_sysfs_uevent_filter(const struct kobject *kobj)
{ … }

static const struct kset_uevent_ops dmabuf_sysfs_no_uevent_ops = …;

static struct kset *dma_buf_stats_kset;
static struct kset *dma_buf_per_buffer_stats_kset;
int dma_buf_init_sysfs_statistics(void)
{ … }

void dma_buf_uninit_sysfs_statistics(void)
{ … }

int dma_buf_stats_setup(struct dma_buf *dmabuf, struct file *file)
{ … }