206 lines
5.6 KiB
C
206 lines
5.6 KiB
C
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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* DMA-BUF sysfs statistics.
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*
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* Copyright (C) 2021 Google LLC.
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*/
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#include <linux/dma-buf.h>
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#include <linux/dma-resv.h>
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#include <linux/kobject.h>
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#include <linux/printk.h>
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#include <linux/slab.h>
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#include <linux/sysfs.h>
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#include "dma-buf-sysfs-stats.h"
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#define to_dma_buf_entry_from_kobj(x) container_of(x, struct dma_buf_sysfs_entry, kobj)
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/**
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* DOC: overview
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*
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* ``/sys/kernel/debug/dma_buf/bufinfo`` provides an overview of every DMA-BUF
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* in the system. However, since debugfs is not safe to be mounted in
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* production, procfs and sysfs can be used to gather DMA-BUF statistics on
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* production systems.
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*
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* The ``/proc/<pid>/fdinfo/<fd>`` files in procfs can be used to gather
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* information about DMA-BUF fds. Detailed documentation about the interface
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* is present in Documentation/filesystems/proc.rst.
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*
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* Unfortunately, the existing procfs interfaces can only provide information
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* about the DMA-BUFs for which processes hold fds or have the buffers mmapped
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* into their address space. This necessitated the creation of the DMA-BUF sysfs
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* statistics interface to provide per-buffer information on production systems.
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*
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* The interface at ``/sys/kernel/dma-buf/buffers`` exposes information about
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* every DMA-BUF when ``CONFIG_DMABUF_SYSFS_STATS`` is enabled.
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*
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* The following stats are exposed by the interface:
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*
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* * ``/sys/kernel/dmabuf/buffers/<inode_number>/exporter_name``
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* * ``/sys/kernel/dmabuf/buffers/<inode_number>/size``
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*
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* The information in the interface can also be used to derive per-exporter
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* statistics. The data from the interface can be gathered on error conditions
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* or other important events to provide a snapshot of DMA-BUF usage.
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* It can also be collected periodically by telemetry to monitor various metrics.
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*
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* Detailed documentation about the interface is present in
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* Documentation/ABI/testing/sysfs-kernel-dmabuf-buffers.
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*/
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struct dma_buf_stats_attribute {
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struct attribute attr;
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ssize_t (*show)(struct dma_buf *dmabuf,
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struct dma_buf_stats_attribute *attr, char *buf);
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};
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#define to_dma_buf_stats_attr(x) container_of(x, struct dma_buf_stats_attribute, attr)
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static ssize_t dma_buf_stats_attribute_show(struct kobject *kobj,
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struct attribute *attr,
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char *buf)
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{
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struct dma_buf_stats_attribute *attribute;
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struct dma_buf_sysfs_entry *sysfs_entry;
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struct dma_buf *dmabuf;
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attribute = to_dma_buf_stats_attr(attr);
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sysfs_entry = to_dma_buf_entry_from_kobj(kobj);
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dmabuf = sysfs_entry->dmabuf;
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if (!dmabuf || !attribute->show)
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return -EIO;
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return attribute->show(dmabuf, attribute, buf);
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}
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static const struct sysfs_ops dma_buf_stats_sysfs_ops = {
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.show = dma_buf_stats_attribute_show,
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};
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static ssize_t exporter_name_show(struct dma_buf *dmabuf,
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struct dma_buf_stats_attribute *attr,
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char *buf)
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{
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return sysfs_emit(buf, "%s\n", dmabuf->exp_name);
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}
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static ssize_t size_show(struct dma_buf *dmabuf,
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struct dma_buf_stats_attribute *attr,
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char *buf)
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{
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return sysfs_emit(buf, "%zu\n", dmabuf->size);
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}
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static struct dma_buf_stats_attribute exporter_name_attribute =
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__ATTR_RO(exporter_name);
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static struct dma_buf_stats_attribute size_attribute = __ATTR_RO(size);
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static struct attribute *dma_buf_stats_default_attrs[] = {
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&exporter_name_attribute.attr,
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&size_attribute.attr,
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NULL,
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};
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ATTRIBUTE_GROUPS(dma_buf_stats_default);
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static void dma_buf_sysfs_release(struct kobject *kobj)
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{
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struct dma_buf_sysfs_entry *sysfs_entry;
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sysfs_entry = to_dma_buf_entry_from_kobj(kobj);
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kfree(sysfs_entry);
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}
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static struct kobj_type dma_buf_ktype = {
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.sysfs_ops = &dma_buf_stats_sysfs_ops,
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.release = dma_buf_sysfs_release,
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.default_groups = dma_buf_stats_default_groups,
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};
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void dma_buf_stats_teardown(struct dma_buf *dmabuf)
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{
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struct dma_buf_sysfs_entry *sysfs_entry;
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sysfs_entry = dmabuf->sysfs_entry;
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if (!sysfs_entry)
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return;
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kobject_del(&sysfs_entry->kobj);
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kobject_put(&sysfs_entry->kobj);
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}
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/* Statistics files do not need to send uevents. */
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static int dmabuf_sysfs_uevent_filter(struct kobject *kobj)
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{
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return 0;
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}
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static const struct kset_uevent_ops dmabuf_sysfs_no_uevent_ops = {
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.filter = dmabuf_sysfs_uevent_filter,
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};
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static struct kset *dma_buf_stats_kset;
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static struct kset *dma_buf_per_buffer_stats_kset;
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int dma_buf_init_sysfs_statistics(void)
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{
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dma_buf_stats_kset = kset_create_and_add("dmabuf",
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&dmabuf_sysfs_no_uevent_ops,
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kernel_kobj);
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if (!dma_buf_stats_kset)
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return -ENOMEM;
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dma_buf_per_buffer_stats_kset = kset_create_and_add("buffers",
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&dmabuf_sysfs_no_uevent_ops,
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&dma_buf_stats_kset->kobj);
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if (!dma_buf_per_buffer_stats_kset) {
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kset_unregister(dma_buf_stats_kset);
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return -ENOMEM;
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}
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return 0;
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}
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void dma_buf_uninit_sysfs_statistics(void)
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{
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kset_unregister(dma_buf_per_buffer_stats_kset);
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kset_unregister(dma_buf_stats_kset);
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}
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int dma_buf_stats_setup(struct dma_buf *dmabuf)
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{
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struct dma_buf_sysfs_entry *sysfs_entry;
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int ret;
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if (!dmabuf || !dmabuf->file)
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return -EINVAL;
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if (!dmabuf->exp_name) {
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pr_err("exporter name must not be empty if stats needed\n");
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return -EINVAL;
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}
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sysfs_entry = kzalloc(sizeof(struct dma_buf_sysfs_entry), GFP_KERNEL);
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if (!sysfs_entry)
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return -ENOMEM;
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sysfs_entry->kobj.kset = dma_buf_per_buffer_stats_kset;
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sysfs_entry->dmabuf = dmabuf;
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dmabuf->sysfs_entry = sysfs_entry;
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/* create the directory for buffer stats */
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ret = kobject_init_and_add(&sysfs_entry->kobj, &dma_buf_ktype, NULL,
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"%lu", file_inode(dmabuf->file)->i_ino);
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if (ret)
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goto err_sysfs_dmabuf;
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return 0;
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err_sysfs_dmabuf:
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kobject_put(&sysfs_entry->kobj);
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dmabuf->sysfs_entry = NULL;
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return ret;
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}
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