On 5/5/25 00:41, T.J. Mercier wrote:
> I think Android is probably the only remaining user of the dmabuf sysfs
> files. The BPF infrastructure added earlier in this series will allow us
> to get the same information much more cheaply.
>
> This patch is a RFC because I'd like to keep this for at least one more
> longterm stable release (6.18?) before actually removing it so that we
> can have one longterm stable kernel version that supports both options
> to facilitate a transition from the sysfs files to a BPF program.
Sounds like a plan to me.
>
> Signed-off-by: T.J. Mercier <tjmerc...@google.com>
Acked-by: Christian König <christian.koe...@amd.com>
> ---
> .../ABI/testing/sysfs-kernel-dmabuf-buffers | 24 ---
> Documentation/driver-api/dma-buf.rst | 5 -
> drivers/dma-buf/Kconfig | 15 --
> drivers/dma-buf/Makefile | 1 -
> drivers/dma-buf/dma-buf-sysfs-stats.c | 202 ------------------
> drivers/dma-buf/dma-buf-sysfs-stats.h | 35 ---
> drivers/dma-buf/dma-buf.c | 18 --
> 7 files changed, 300 deletions(-)
> delete mode 100644 Documentation/ABI/testing/sysfs-kernel-dmabuf-buffers
> delete mode 100644 drivers/dma-buf/dma-buf-sysfs-stats.c
> delete mode 100644 drivers/dma-buf/dma-buf-sysfs-stats.h
>
> diff --git a/Documentation/ABI/testing/sysfs-kernel-dmabuf-buffers
> b/Documentation/ABI/testing/sysfs-kernel-dmabuf-buffers
> deleted file mode 100644
> index 5d3bc997dc64..000000000000
> --- a/Documentation/ABI/testing/sysfs-kernel-dmabuf-buffers
> +++ /dev/null
> @@ -1,24 +0,0 @@
> -What: /sys/kernel/dmabuf/buffers
> -Date: May 2021
> -KernelVersion: v5.13
> -Contact: Hridya Valsaraju <hri...@google.com>
> -Description: The /sys/kernel/dmabuf/buffers directory contains a
> - snapshot of the internal state of every DMA-BUF.
> - /sys/kernel/dmabuf/buffers/<inode_number> will contain the
> - statistics for the DMA-BUF with the unique inode number
> - <inode_number>
> -Users: kernel memory tuning/debugging tools
> -
> -What: /sys/kernel/dmabuf/buffers/<inode_number>/exporter_name
> -Date: May 2021
> -KernelVersion: v5.13
> -Contact: Hridya Valsaraju <hri...@google.com>
> -Description: This file is read-only and contains the name of the exporter of
> - the DMA-BUF.
> -
> -What: /sys/kernel/dmabuf/buffers/<inode_number>/size
> -Date: May 2021
> -KernelVersion: v5.13
> -Contact: Hridya Valsaraju <hri...@google.com>
> -Description: This file is read-only and specifies the size of the DMA-BUF in
> - bytes.
> diff --git a/Documentation/driver-api/dma-buf.rst
> b/Documentation/driver-api/dma-buf.rst
> index 29abf1eebf9f..2f36c21d9948 100644
> --- a/Documentation/driver-api/dma-buf.rst
> +++ b/Documentation/driver-api/dma-buf.rst
> @@ -125,11 +125,6 @@ Implicit Fence Poll Support
> .. kernel-doc:: drivers/dma-buf/dma-buf.c
> :doc: implicit fence polling
>
> -DMA-BUF statistics
> -~~~~~~~~~~~~~~~~~~
> -.. kernel-doc:: drivers/dma-buf/dma-buf-sysfs-stats.c
> - :doc: overview
> -
> DMA Buffer ioctls
> ~~~~~~~~~~~~~~~~~
>
> diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig
> index fee04fdb0822..03e38c0d1fff 100644
> --- a/drivers/dma-buf/Kconfig
> +++ b/drivers/dma-buf/Kconfig
> @@ -76,21 +76,6 @@ menuconfig DMABUF_HEAPS
> allows userspace to allocate dma-bufs that can be shared
> between drivers.
>
> -menuconfig DMABUF_SYSFS_STATS
> - bool "DMA-BUF sysfs statistics (DEPRECATED)"
> - depends on DMA_SHARED_BUFFER
> - help
> - Choose this option to enable DMA-BUF sysfs statistics
> - in location /sys/kernel/dmabuf/buffers.
> -
> - /sys/kernel/dmabuf/buffers/<inode_number> will contain
> - statistics for the DMA-BUF with the unique inode number
> - <inode_number>.
> -
> - This option is deprecated and should sooner or later be removed.
> - Android is the only user of this and it turned out that this resulted
> - in quite some performance problems.
> -
> source "drivers/dma-buf/heaps/Kconfig"
>
> endmenu
> diff --git a/drivers/dma-buf/Makefile b/drivers/dma-buf/Makefile
> index 70ec901edf2c..8ab2bfecb1c9 100644
> --- a/drivers/dma-buf/Makefile
> +++ b/drivers/dma-buf/Makefile
> @@ -6,7 +6,6 @@ obj-$(CONFIG_DMABUF_HEAPS) += heaps/
> obj-$(CONFIG_SYNC_FILE) += sync_file.o
> obj-$(CONFIG_SW_SYNC) += sw_sync.o sync_debug.o
> obj-$(CONFIG_UDMABUF) += udmabuf.o
> -obj-$(CONFIG_DMABUF_SYSFS_STATS) += dma-buf-sysfs-stats.o
>
> dmabuf_selftests-y := \
> selftest.o \
> diff --git a/drivers/dma-buf/dma-buf-sysfs-stats.c
> b/drivers/dma-buf/dma-buf-sysfs-stats.c
> deleted file mode 100644
> index b5b62e40ccc1..000000000000
> --- a/drivers/dma-buf/dma-buf-sysfs-stats.c
> +++ /dev/null
> @@ -1,202 +0,0 @@
> -// 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) container_of(x, struct
> dma_buf_sysfs_entry, kobj)
> -
> -/**
> - * 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 {
> - struct attribute attr;
> - ssize_t (*show)(struct dma_buf *dmabuf,
> - struct dma_buf_stats_attribute *attr, char *buf);
> -};
> -#define to_dma_buf_stats_attr(x) container_of(x, struct
> dma_buf_stats_attribute, attr)
> -
> -static ssize_t dma_buf_stats_attribute_show(struct kobject *kobj,
> - struct attribute *attr,
> - char *buf)
> -{
> - struct dma_buf_stats_attribute *attribute;
> - struct dma_buf_sysfs_entry *sysfs_entry;
> - struct dma_buf *dmabuf;
> -
> - attribute = to_dma_buf_stats_attr(attr);
> - sysfs_entry = to_dma_buf_entry_from_kobj(kobj);
> - dmabuf = sysfs_entry->dmabuf;
> -
> - if (!dmabuf || !attribute->show)
> - return -EIO;
> -
> - return attribute->show(dmabuf, attribute, buf);
> -}
> -
> -static const struct sysfs_ops dma_buf_stats_sysfs_ops = {
> - .show = dma_buf_stats_attribute_show,
> -};
> -
> -static ssize_t exporter_name_show(struct dma_buf *dmabuf,
> - struct dma_buf_stats_attribute *attr,
> - char *buf)
> -{
> - return sysfs_emit(buf, "%s\n", dmabuf->exp_name);
> -}
> -
> -static ssize_t size_show(struct dma_buf *dmabuf,
> - struct dma_buf_stats_attribute *attr,
> - char *buf)
> -{
> - return sysfs_emit(buf, "%zu\n", dmabuf->size);
> -}
> -
> -static struct dma_buf_stats_attribute exporter_name_attribute =
> - __ATTR_RO(exporter_name);
> -static struct dma_buf_stats_attribute size_attribute = __ATTR_RO(size);
> -
> -static struct attribute *dma_buf_stats_default_attrs[] = {
> - &exporter_name_attribute.attr,
> - &size_attribute.attr,
> - NULL,
> -};
> -ATTRIBUTE_GROUPS(dma_buf_stats_default);
> -
> -static void dma_buf_sysfs_release(struct kobject *kobj)
> -{
> - struct dma_buf_sysfs_entry *sysfs_entry;
> -
> - sysfs_entry = to_dma_buf_entry_from_kobj(kobj);
> - kfree(sysfs_entry);
> -}
> -
> -static const struct kobj_type dma_buf_ktype = {
> - .sysfs_ops = &dma_buf_stats_sysfs_ops,
> - .release = dma_buf_sysfs_release,
> - .default_groups = dma_buf_stats_default_groups,
> -};
> -
> -void dma_buf_stats_teardown(struct dma_buf *dmabuf)
> -{
> - struct dma_buf_sysfs_entry *sysfs_entry;
> -
> - sysfs_entry = dmabuf->sysfs_entry;
> - if (!sysfs_entry)
> - return;
> -
> - kobject_del(&sysfs_entry->kobj);
> - kobject_put(&sysfs_entry->kobj);
> -}
> -
> -
> -/* Statistics files do not need to send uevents. */
> -static int dmabuf_sysfs_uevent_filter(const struct kobject *kobj)
> -{
> - return 0;
> -}
> -
> -static const struct kset_uevent_ops dmabuf_sysfs_no_uevent_ops = {
> - .filter = dmabuf_sysfs_uevent_filter,
> -};
> -
> -static struct kset *dma_buf_stats_kset;
> -static struct kset *dma_buf_per_buffer_stats_kset;
> -int dma_buf_init_sysfs_statistics(void)
> -{
> - dma_buf_stats_kset = kset_create_and_add("dmabuf",
> - &dmabuf_sysfs_no_uevent_ops,
> - kernel_kobj);
> - if (!dma_buf_stats_kset)
> - return -ENOMEM;
> -
> - dma_buf_per_buffer_stats_kset = kset_create_and_add("buffers",
> -
> &dmabuf_sysfs_no_uevent_ops,
> -
> &dma_buf_stats_kset->kobj);
> - if (!dma_buf_per_buffer_stats_kset) {
> - kset_unregister(dma_buf_stats_kset);
> - return -ENOMEM;
> - }
> -
> - return 0;
> -}
> -
> -void dma_buf_uninit_sysfs_statistics(void)
> -{
> - kset_unregister(dma_buf_per_buffer_stats_kset);
> - kset_unregister(dma_buf_stats_kset);
> -}
> -
> -int dma_buf_stats_setup(struct dma_buf *dmabuf, struct file *file)
> -{
> - struct dma_buf_sysfs_entry *sysfs_entry;
> - int ret;
> -
> - if (!dmabuf->exp_name) {
> - pr_err("exporter name must not be empty if stats needed\n");
> - return -EINVAL;
> - }
> -
> - sysfs_entry = kzalloc(sizeof(struct dma_buf_sysfs_entry), GFP_KERNEL);
> - if (!sysfs_entry)
> - return -ENOMEM;
> -
> - sysfs_entry->kobj.kset = dma_buf_per_buffer_stats_kset;
> - sysfs_entry->dmabuf = dmabuf;
> -
> - dmabuf->sysfs_entry = sysfs_entry;
> -
> - /* create the directory for buffer stats */
> - ret = kobject_init_and_add(&sysfs_entry->kobj, &dma_buf_ktype, NULL,
> - "%lu", file_inode(file)->i_ino);
> - if (ret)
> - goto err_sysfs_dmabuf;
> -
> - return 0;
> -
> -err_sysfs_dmabuf:
> - kobject_put(&sysfs_entry->kobj);
> - dmabuf->sysfs_entry = NULL;
> - return ret;
> -}
> diff --git a/drivers/dma-buf/dma-buf-sysfs-stats.h
> b/drivers/dma-buf/dma-buf-sysfs-stats.h
> deleted file mode 100644
> index 7a8a995b75ba..000000000000
> --- a/drivers/dma-buf/dma-buf-sysfs-stats.h
> +++ /dev/null
> @@ -1,35 +0,0 @@
> -/* SPDX-License-Identifier: GPL-2.0-only */
> -/*
> - * DMA-BUF sysfs statistics.
> - *
> - * Copyright (C) 2021 Google LLC.
> - */
> -
> -#ifndef _DMA_BUF_SYSFS_STATS_H
> -#define _DMA_BUF_SYSFS_STATS_H
> -
> -#ifdef CONFIG_DMABUF_SYSFS_STATS
> -
> -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);
> -
> -void dma_buf_stats_teardown(struct dma_buf *dmabuf);
> -#else
> -
> -static inline int dma_buf_init_sysfs_statistics(void)
> -{
> - return 0;
> -}
> -
> -static inline void dma_buf_uninit_sysfs_statistics(void) {}
> -
> -static inline int dma_buf_stats_setup(struct dma_buf *dmabuf, struct file
> *file)
> -{
> - return 0;
> -}
> -
> -static inline void dma_buf_stats_teardown(struct dma_buf *dmabuf) {}
> -#endif
> -#endif // _DMA_BUF_SYSFS_STATS_H
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index 7260bdd77c75..adc6a0c96641 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -31,8 +31,6 @@
> #include <uapi/linux/dma-buf.h>
> #include <uapi/linux/magic.h>
>
> -#include "dma-buf-sysfs-stats.h"
> -
> static inline int is_dma_buf_file(struct file *);
>
> DEFINE_MUTEX(dmabuf_list_mutex);
> @@ -88,7 +86,6 @@ static void dma_buf_release(struct dentry *dentry)
> */
> BUG_ON(dmabuf->cb_in.active || dmabuf->cb_out.active);
>
> - dma_buf_stats_teardown(dmabuf);
> dmabuf->ops->release(dmabuf);
>
> if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
> @@ -671,10 +668,6 @@ struct dma_buf *dma_buf_export(const struct
> dma_buf_export_info *exp_info)
> dmabuf->resv = resv;
> }
>
> - ret = dma_buf_stats_setup(dmabuf, file);
> - if (ret)
> - goto err_dmabuf;
> -
> file->private_data = dmabuf;
> file->f_path.dentry->d_fsdata = dmabuf;
> dmabuf->file = file;
> @@ -683,10 +676,6 @@ struct dma_buf *dma_buf_export(const struct
> dma_buf_export_info *exp_info)
>
> return dmabuf;
>
> -err_dmabuf:
> - if (!resv)
> - dma_resv_fini(dmabuf->resv);
> - kfree(dmabuf);
> err_file:
> fput(file);
> err_module:
> @@ -1717,12 +1706,6 @@ static inline void dma_buf_uninit_debugfs(void)
>
> static int __init dma_buf_init(void)
> {
> - int ret;
> -
> - ret = dma_buf_init_sysfs_statistics();
> - if (ret)
> - return ret;
> -
> dma_buf_mnt = kern_mount(&dma_buf_fs_type);
> if (IS_ERR(dma_buf_mnt))
> return PTR_ERR(dma_buf_mnt);
> @@ -1736,6 +1719,5 @@ static void __exit dma_buf_deinit(void)
> {
> dma_buf_uninit_debugfs();
> kern_unmount(dma_buf_mnt);
> - dma_buf_uninit_sysfs_statistics();
> }
> __exitcall(dma_buf_deinit);
