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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * DMA-BUF sysfs statistics.4 *5 * Copyright (C) 2021 Google LLC.6 */7 8#include <linux/dma-buf.h>9#include <linux/dma-resv.h>10#include <linux/kobject.h>11#include <linux/printk.h>12#include <linux/slab.h>13#include <linux/sysfs.h>14 15#include "dma-buf-sysfs-stats.h"16 17#define to_dma_buf_entry_from_kobj(x) container_of(x, struct dma_buf_sysfs_entry, kobj)18 19/**20 * DOC: overview21 *22 * ``/sys/kernel/debug/dma_buf/bufinfo`` provides an overview of every DMA-BUF23 * in the system. However, since debugfs is not safe to be mounted in24 * production, procfs and sysfs can be used to gather DMA-BUF statistics on25 * production systems.26 *27 * The ``/proc/<pid>/fdinfo/<fd>`` files in procfs can be used to gather28 * information about DMA-BUF fds. Detailed documentation about the interface29 * is present in Documentation/filesystems/proc.rst.30 *31 * Unfortunately, the existing procfs interfaces can only provide information32 * about the DMA-BUFs for which processes hold fds or have the buffers mmapped33 * into their address space. This necessitated the creation of the DMA-BUF sysfs34 * statistics interface to provide per-buffer information on production systems.35 *36 * The interface at ``/sys/kernel/dmabuf/buffers`` exposes information about37 * every DMA-BUF when ``CONFIG_DMABUF_SYSFS_STATS`` is enabled.38 *39 * The following stats are exposed by the interface:40 *41 * * ``/sys/kernel/dmabuf/buffers/<inode_number>/exporter_name``42 * * ``/sys/kernel/dmabuf/buffers/<inode_number>/size``43 *44 * The information in the interface can also be used to derive per-exporter45 * statistics. The data from the interface can be gathered on error conditions46 * or other important events to provide a snapshot of DMA-BUF usage.47 * It can also be collected periodically by telemetry to monitor various metrics.48 *49 * Detailed documentation about the interface is present in50 * Documentation/ABI/testing/sysfs-kernel-dmabuf-buffers.51 */52 53struct dma_buf_stats_attribute {54 struct attribute attr;55 ssize_t (*show)(struct dma_buf *dmabuf,56 struct dma_buf_stats_attribute *attr, char *buf);57};58#define to_dma_buf_stats_attr(x) container_of(x, struct dma_buf_stats_attribute, attr)59 60static ssize_t dma_buf_stats_attribute_show(struct kobject *kobj,61 struct attribute *attr,62 char *buf)63{64 struct dma_buf_stats_attribute *attribute;65 struct dma_buf_sysfs_entry *sysfs_entry;66 struct dma_buf *dmabuf;67 68 attribute = to_dma_buf_stats_attr(attr);69 sysfs_entry = to_dma_buf_entry_from_kobj(kobj);70 dmabuf = sysfs_entry->dmabuf;71 72 if (!dmabuf || !attribute->show)73 return -EIO;74 75 return attribute->show(dmabuf, attribute, buf);76}77 78static const struct sysfs_ops dma_buf_stats_sysfs_ops = {79 .show = dma_buf_stats_attribute_show,80};81 82static ssize_t exporter_name_show(struct dma_buf *dmabuf,83 struct dma_buf_stats_attribute *attr,84 char *buf)85{86 return sysfs_emit(buf, "%s\n", dmabuf->exp_name);87}88 89static ssize_t size_show(struct dma_buf *dmabuf,90 struct dma_buf_stats_attribute *attr,91 char *buf)92{93 return sysfs_emit(buf, "%zu\n", dmabuf->size);94}95 96static struct dma_buf_stats_attribute exporter_name_attribute =97 __ATTR_RO(exporter_name);98static struct dma_buf_stats_attribute size_attribute = __ATTR_RO(size);99 100static struct attribute *dma_buf_stats_default_attrs[] = {101 &exporter_name_attribute.attr,102 &size_attribute.attr,103 NULL,104};105ATTRIBUTE_GROUPS(dma_buf_stats_default);106 107static void dma_buf_sysfs_release(struct kobject *kobj)108{109 struct dma_buf_sysfs_entry *sysfs_entry;110 111 sysfs_entry = to_dma_buf_entry_from_kobj(kobj);112 kfree(sysfs_entry);113}114 115static const struct kobj_type dma_buf_ktype = {116 .sysfs_ops = &dma_buf_stats_sysfs_ops,117 .release = dma_buf_sysfs_release,118 .default_groups = dma_buf_stats_default_groups,119};120 121void dma_buf_stats_teardown(struct dma_buf *dmabuf)122{123 struct dma_buf_sysfs_entry *sysfs_entry;124 125 sysfs_entry = dmabuf->sysfs_entry;126 if (!sysfs_entry)127 return;128 129 kobject_del(&sysfs_entry->kobj);130 kobject_put(&sysfs_entry->kobj);131}132 133 134/* Statistics files do not need to send uevents. */135static int dmabuf_sysfs_uevent_filter(const struct kobject *kobj)136{137 return 0;138}139 140static const struct kset_uevent_ops dmabuf_sysfs_no_uevent_ops = {141 .filter = dmabuf_sysfs_uevent_filter,142};143 144static struct kset *dma_buf_stats_kset;145static struct kset *dma_buf_per_buffer_stats_kset;146int dma_buf_init_sysfs_statistics(void)147{148 dma_buf_stats_kset = kset_create_and_add("dmabuf",149 &dmabuf_sysfs_no_uevent_ops,150 kernel_kobj);151 if (!dma_buf_stats_kset)152 return -ENOMEM;153 154 dma_buf_per_buffer_stats_kset = kset_create_and_add("buffers",155 &dmabuf_sysfs_no_uevent_ops,156 &dma_buf_stats_kset->kobj);157 if (!dma_buf_per_buffer_stats_kset) {158 kset_unregister(dma_buf_stats_kset);159 return -ENOMEM;160 }161 162 return 0;163}164 165void dma_buf_uninit_sysfs_statistics(void)166{167 kset_unregister(dma_buf_per_buffer_stats_kset);168 kset_unregister(dma_buf_stats_kset);169}170 171int dma_buf_stats_setup(struct dma_buf *dmabuf, struct file *file)172{173 struct dma_buf_sysfs_entry *sysfs_entry;174 int ret;175 176 if (!dmabuf->exp_name) {177 pr_err("exporter name must not be empty if stats needed\n");178 return -EINVAL;179 }180 181 sysfs_entry = kzalloc(sizeof(struct dma_buf_sysfs_entry), GFP_KERNEL);182 if (!sysfs_entry)183 return -ENOMEM;184 185 sysfs_entry->kobj.kset = dma_buf_per_buffer_stats_kset;186 sysfs_entry->dmabuf = dmabuf;187 188 dmabuf->sysfs_entry = sysfs_entry;189 190 /* create the directory for buffer stats */191 ret = kobject_init_and_add(&sysfs_entry->kobj, &dma_buf_ktype, NULL,192 "%lu", file_inode(file)->i_ino);193 if (ret)194 goto err_sysfs_dmabuf;195 196 return 0;197 198err_sysfs_dmabuf:199 kobject_put(&sysfs_entry->kobj);200 dmabuf->sysfs_entry = NULL;201 return ret;202}203