.../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 -- include/linux/dma-buf.h | 12 -- 8 files changed, 312 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
Commit bdb8d06dfefd ("dmabuf: Add the capability to expose DMA-BUF stats
in sysfs") added dmabuf statistics to sysfs in 2021 under
CONFIG_DMABUF_SYSFS_STATS. After being used in production, performance
problems were discovered leading to its deprecation in 2022 in commit
e0a9f1fe206a ("dma-buf: deprecate DMABUF_SYSFS_STATS"). Some of the
problems with this interface were discussed in my LPC 2025 talk. [1][2]
Android was probably the last user of the interface, which has since
been migrated to use the dmabuf BPF iterator [3] to obtain the same
information more cheaply. As promised in that series, now that the
longterm stable 6.18 kernel has been released let's remove the sysfs
dmabuf statistics from the kernel.
[1] https://www.youtube.com/watch?v=D83qygudq9c
[2] https://lpc.events/event/19/contributions/2118/
[3] https://lore.kernel.org/all/20250522230429.941193-1-tjmercier@google.com/
Signed-off-by: T.J. Mercier <tjmercier@google.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 --
include/linux/dma-buf.h | 12 --
8 files changed, 312 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 <hridya@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 <hridya@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 <hridya@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 fdd823e446cc..012d22e941d6 100644
--- a/drivers/dma-buf/Kconfig
+++ b/drivers/dma-buf/Kconfig
@@ -75,21 +75,6 @@ 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 2008fb7481b3..7a85565d906b 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 a4d8f2ff94e4..8e23580f1754 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -33,8 +33,6 @@
#include <uapi/linux/dma-buf.h>
#include <uapi/linux/magic.h>
-#include "dma-buf-sysfs-stats.h"
-
#define CREATE_TRACE_POINTS
#include <trace/events/dma_buf.h>
@@ -184,7 +182,6 @@ 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])
@@ -765,10 +762,6 @@ 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;
@@ -779,10 +772,6 @@ 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:
@@ -1802,12 +1791,6 @@ 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);
@@ -1821,6 +1804,5 @@ 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);
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index 0bc492090237..91f4939db89b 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -429,18 +429,6 @@ struct dma_buf {
__poll_t active;
} cb_in, cb_out;
-#ifdef CONFIG_DMABUF_SYSFS_STATS
- /**
- * @sysfs_entry:
- *
- * For exposing information about this buffer in sysfs. See also
- * `DMA-BUF statistics`_ for the uapi this enables.
- */
- struct dma_buf_sysfs_entry {
- struct kobject kobj;
- struct dma_buf *dmabuf;
- } *sysfs_entry;
-#endif
};
/**
base-commit: 26b4309a3ab82a0697751cde52eb336c29c19035
--
2.52.0.457.g6b5491de43-googOn 1/16/26 20:05, T.J. Mercier wrote:
> Commit bdb8d06dfefd ("dmabuf: Add the capability to expose DMA-BUF stats
> in sysfs") added dmabuf statistics to sysfs in 2021 under
> CONFIG_DMABUF_SYSFS_STATS. After being used in production, performance
> problems were discovered leading to its deprecation in 2022 in commit
> e0a9f1fe206a ("dma-buf: deprecate DMABUF_SYSFS_STATS"). Some of the
> problems with this interface were discussed in my LPC 2025 talk. [1][2]
>
> Android was probably the last user of the interface, which has since
> been migrated to use the dmabuf BPF iterator [3] to obtain the same
> information more cheaply. As promised in that series, now that the
> longterm stable 6.18 kernel has been released let's remove the sysfs
> dmabuf statistics from the kernel.
>
> [1] https://www.youtube.com/watch?v=D83qygudq9c
> [2] https://lpc.events/event/19/contributions/2118/
> [3] https://lore.kernel.org/all/20250522230429.941193-1-tjmercier@google.com/
>
> Signed-off-by: T.J. Mercier <tjmercier@google.com>
Oh yes please :)
Reviewed-by: Christian König <christian.koenig@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 --
> include/linux/dma-buf.h | 12 --
> 8 files changed, 312 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 <hridya@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 <hridya@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 <hridya@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 fdd823e446cc..012d22e941d6 100644
> --- a/drivers/dma-buf/Kconfig
> +++ b/drivers/dma-buf/Kconfig
> @@ -75,21 +75,6 @@ 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 2008fb7481b3..7a85565d906b 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 a4d8f2ff94e4..8e23580f1754 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -33,8 +33,6 @@
> #include <uapi/linux/dma-buf.h>
> #include <uapi/linux/magic.h>
>
> -#include "dma-buf-sysfs-stats.h"
> -
> #define CREATE_TRACE_POINTS
> #include <trace/events/dma_buf.h>
>
> @@ -184,7 +182,6 @@ 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])
> @@ -765,10 +762,6 @@ 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;
> @@ -779,10 +772,6 @@ 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:
> @@ -1802,12 +1791,6 @@ 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);
> @@ -1821,6 +1804,5 @@ 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);
> diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> index 0bc492090237..91f4939db89b 100644
> --- a/include/linux/dma-buf.h
> +++ b/include/linux/dma-buf.h
> @@ -429,18 +429,6 @@ struct dma_buf {
>
> __poll_t active;
> } cb_in, cb_out;
> -#ifdef CONFIG_DMABUF_SYSFS_STATS
> - /**
> - * @sysfs_entry:
> - *
> - * For exposing information about this buffer in sysfs. See also
> - * `DMA-BUF statistics`_ for the uapi this enables.
> - */
> - struct dma_buf_sysfs_entry {
> - struct kobject kobj;
> - struct dma_buf *dmabuf;
> - } *sysfs_entry;
> -#endif
> };
>
> /**
>
> base-commit: 26b4309a3ab82a0697751cde52eb336c29c19035
Hi T J,
On Mon, 19 Jan 2026 at 15:15, Christian König <christian.koenig@amd.com> wrote:
>
> On 1/16/26 20:05, T.J. Mercier wrote:
> > Commit bdb8d06dfefd ("dmabuf: Add the capability to expose DMA-BUF stats
> > in sysfs") added dmabuf statistics to sysfs in 2021 under
> > CONFIG_DMABUF_SYSFS_STATS. After being used in production, performance
> > problems were discovered leading to its deprecation in 2022 in commit
> > e0a9f1fe206a ("dma-buf: deprecate DMABUF_SYSFS_STATS"). Some of the
> > problems with this interface were discussed in my LPC 2025 talk. [1][2]
> >
> > Android was probably the last user of the interface, which has since
> > been migrated to use the dmabuf BPF iterator [3] to obtain the same
> > information more cheaply. As promised in that series, now that the
> > longterm stable 6.18 kernel has been released let's remove the sysfs
> > dmabuf statistics from the kernel.
> >
> > [1] https://www.youtube.com/watch?v=D83qygudq9c
> > [2] https://lpc.events/event/19/contributions/2118/
> > [3] https://lore.kernel.org/all/20250522230429.941193-1-tjmercier@google.com/
> >
> > Signed-off-by: T.J. Mercier <tjmercier@google.com>
>
> Oh yes please :)
>
> Reviewed-by: Christian König <christian.koenig@amd.com>
Thank you for your patch, LGTM :)
If its not pushed yet, I'll push it tonight.
Best,
Sumit
>
> > ---
> > .../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 --
> > include/linux/dma-buf.h | 12 --
> > 8 files changed, 312 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 <hridya@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 <hridya@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 <hridya@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 fdd823e446cc..012d22e941d6 100644
> > --- a/drivers/dma-buf/Kconfig
> > +++ b/drivers/dma-buf/Kconfig
> > @@ -75,21 +75,6 @@ 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 2008fb7481b3..7a85565d906b 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 a4d8f2ff94e4..8e23580f1754 100644
> > --- a/drivers/dma-buf/dma-buf.c
> > +++ b/drivers/dma-buf/dma-buf.c
> > @@ -33,8 +33,6 @@
> > #include <uapi/linux/dma-buf.h>
> > #include <uapi/linux/magic.h>
> >
> > -#include "dma-buf-sysfs-stats.h"
> > -
> > #define CREATE_TRACE_POINTS
> > #include <trace/events/dma_buf.h>
> >
> > @@ -184,7 +182,6 @@ 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])
> > @@ -765,10 +762,6 @@ 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;
> > @@ -779,10 +772,6 @@ 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:
> > @@ -1802,12 +1791,6 @@ 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);
> > @@ -1821,6 +1804,5 @@ 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);
> > diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> > index 0bc492090237..91f4939db89b 100644
> > --- a/include/linux/dma-buf.h
> > +++ b/include/linux/dma-buf.h
> > @@ -429,18 +429,6 @@ struct dma_buf {
> >
> > __poll_t active;
> > } cb_in, cb_out;
> > -#ifdef CONFIG_DMABUF_SYSFS_STATS
> > - /**
> > - * @sysfs_entry:
> > - *
> > - * For exposing information about this buffer in sysfs. See also
> > - * `DMA-BUF statistics`_ for the uapi this enables.
> > - */
> > - struct dma_buf_sysfs_entry {
> > - struct kobject kobj;
> > - struct dma_buf *dmabuf;
> > - } *sysfs_entry;
> > -#endif
> > };
> >
> > /**
> >
> > base-commit: 26b4309a3ab82a0697751cde52eb336c29c19035
>
On Mon, Jan 19, 2026 at 5:08 AM Sumit Semwal <sumit.semwal@linaro.org> wrote:
>
> Hi T J,
>
> On Mon, 19 Jan 2026 at 15:15, Christian König <christian.koenig@amd.com> wrote:
> >
> > On 1/16/26 20:05, T.J. Mercier wrote:
> > > Commit bdb8d06dfefd ("dmabuf: Add the capability to expose DMA-BUF stats
> > > in sysfs") added dmabuf statistics to sysfs in 2021 under
> > > CONFIG_DMABUF_SYSFS_STATS. After being used in production, performance
> > > problems were discovered leading to its deprecation in 2022 in commit
> > > e0a9f1fe206a ("dma-buf: deprecate DMABUF_SYSFS_STATS"). Some of the
> > > problems with this interface were discussed in my LPC 2025 talk. [1][2]
> > >
> > > Android was probably the last user of the interface, which has since
> > > been migrated to use the dmabuf BPF iterator [3] to obtain the same
> > > information more cheaply. As promised in that series, now that the
> > > longterm stable 6.18 kernel has been released let's remove the sysfs
> > > dmabuf statistics from the kernel.
> > >
> > > [1] https://www.youtube.com/watch?v=D83qygudq9c
> > > [2] https://lpc.events/event/19/contributions/2118/
> > > [3] https://lore.kernel.org/all/20250522230429.941193-1-tjmercier@google.com/
> > >
> > > Signed-off-by: T.J. Mercier <tjmercier@google.com>
> >
> > Oh yes please :)
> >
> > Reviewed-by: Christian König <christian.koenig@amd.com>
> Thank you for your patch, LGTM :)
>
> If its not pushed yet, I'll push it tonight.
>
> Best,
> Sumit
Thanks Sumit and Christian!
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