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[PATCH] dma-buf: Remove DMA-BUF sysfs stats

by T.J. Mercier

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(a)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(a)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(a)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(a)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-goog

1 week

Re: [PATCH rdma-next 2/2] RDMA/mlx5: Implement DMABUF export ops

by Jason Gunthorpe

On Thu, Jan 08, 2026 at 01:11:15PM +0200, Edward Srouji wrote: > +static int phys_addr_to_bar(struct pci_dev *pdev, phys_addr_t pa) > +{ > + resource_size_t start, end; > + int bar; > + > + for (bar = 0; bar < PCI_STD_NUM_BARS; bar++) { > + /* Skip BARs not present or not memory-mapped */ > + if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM)) > + continue; > + > + start = pci_resource_start(pdev, bar); > + end = pci_resource_end(pdev, bar); > + > + if (!start || !end) > + continue; > + > + if (pa >= start && pa <= end) > + return bar; > + } Don't we know which of the two BARs the mmap entry came from based on its type? This seems like overkill.. Jason

1 week, 1 day

[PATCH v2 0/4] dma-buf: document revoke mechanism to invalidate shared buffers

by Leon Romanovsky

Changelog: v2: * Changed series to document the revoke semantics instead of implementing it. v1: https://patch.msgid.link/20260111-dmabuf-revoke-v1-0-fb4bcc8c259b@nvidia.com ------------------------------------------------------------------------- This series documents a dma-buf “revoke” mechanism: to allow a dma-buf exporter to explicitly invalidate (“kill”) a shared buffer after it has been distributed to importers, so that further CPU and device access is prevented and importers reliably observe failure. The change in this series is to properly document and use existing core “revoked” state on the dma-buf object and a corresponding exporter-triggered revoke operation. Once a dma-buf is revoked, new access paths are blocked so that attempts to DMA-map, vmap, or mmap the buffer fail in a consistent way. Thanks Cc: linux-media(a)vger.kernel.org Cc: dri-devel(a)lists.freedesktop.org Cc: linaro-mm-sig(a)lists.linaro.org Cc: linux-kernel(a)vger.kernel.org Cc: amd-gfx(a)lists.freedesktop.org Cc: virtualization(a)lists.linux.dev Cc: intel-xe(a)lists.freedesktop.org Cc: linux-rdma(a)vger.kernel.org Cc: iommu(a)lists.linux.dev Cc: kvm(a)vger.kernel.org To: Sumit Semwal <sumit.semwal(a)linaro.org> To: Christian König <christian.koenig(a)amd.com> To: Alex Deucher <alexander.deucher(a)amd.com> To: David Airlie <airlied(a)gmail.com> To: Simona Vetter <simona(a)ffwll.ch> To: Gerd Hoffmann <kraxel(a)redhat.com> To: Dmitry Osipenko <dmitry.osipenko(a)collabora.com> To: Gurchetan Singh <gurchetansingh(a)chromium.org> To: Chia-I Wu <olvaffe(a)gmail.com> To: Maarten Lankhorst <maarten.lankhorst(a)linux.intel.com> To: Maxime Ripard <mripard(a)kernel.org> To: Thomas Zimmermann <tzimmermann(a)suse.de> To: Lucas De Marchi <lucas.demarchi(a)intel.com> To: Thomas Hellström <thomas.hellstrom(a)linux.intel.com> To: Rodrigo Vivi <rodrigo.vivi(a)intel.com> To: Jason Gunthorpe <jgg(a)ziepe.ca> To: Leon Romanovsky <leon(a)kernel.org> To: Kevin Tian <kevin.tian(a)intel.com> To: Joerg Roedel <joro(a)8bytes.org> To: Will Deacon <will(a)kernel.org> To: Robin Murphy <robin.murphy(a)arm.com> To: Alex Williamson <alex(a)shazbot.org> --- Leon Romanovsky (4): dma-buf: Rename .move_notify() callback to a clearer identifier dma-buf: Document revoke semantics iommufd: Require DMABUF revoke semantics vfio: Add pinned interface to perform revoke semantics drivers/dma-buf/dma-buf.c | 6 +++--- drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 4 ++-- drivers/gpu/drm/virtio/virtgpu_prime.c | 2 +- drivers/gpu/drm/xe/tests/xe_dma_buf.c | 6 +++--- drivers/gpu/drm/xe/xe_dma_buf.c | 2 +- drivers/infiniband/core/umem_dmabuf.c | 4 ++-- drivers/infiniband/hw/mlx5/mr.c | 2 +- drivers/iommu/iommufd/pages.c | 11 +++++++++-- drivers/vfio/pci/vfio_pci_dmabuf.c | 16 ++++++++++++++++ include/linux/dma-buf.h | 25 ++++++++++++++++++++++--- 10 files changed, 60 insertions(+), 18 deletions(-) --- base-commit: 9ace4753a5202b02191d54e9fdf7f9e3d02b85eb change-id: 20251221-dmabuf-revoke-b90ef16e4236 Best regards, -- Leon Romanovsky <leonro(a)nvidia.com>

1 week, 1 day

Re: [PATCH v3 0/2] dma-buf: system_heap: account for system heap allocation in memcg

by Maxime Ripard

On Fri, 16 Jan 2026 15:05:37 -0500, Eric Chanudet wrote: > Capture dmabuf system heap allocations in memcg following prior > conversations[1][2]. Disable this behavior by default unless configured > by "dma_heap.mem_accounting" module parameter. > > [1] https://lore.kernel.org/dri-devel/Z-5GZ3kJDbhgVBPG@phenom.ffwll.local/ > > [ ... ] Reviewed-by: Maxime Ripard <mripard(a)kernel.org> Thanks! Maxime

1 week, 2 days

Re: [PATCH v3 1/2] dma-buf: heaps: add parameter to account allocations using cgroup

by T.J. Mercier

On Fri, Jan 16, 2026 at 12:06 PM Eric Chanudet <echanude(a)redhat.com> wrote: > > Add a parameter to enable dma-buf heaps allocation accounting using > cgroup for heaps that implement it. It is disabled by default as doing > so incurs caveats based on how memcg currently accounts for shared > buffers. > > Signed-off-by: Eric Chanudet <echanude(a)redhat.com> Reviewed-by: T.J. Mercier <tjmercier(a)google.com>

1 week, 2 days

Re: [PATCH v3 2/2] dma-buf: system_heap: account for system heap allocation in memcg

by T.J. Mercier

On Fri, Jan 16, 2026 at 12:06 PM Eric Chanudet <echanude(a)redhat.com> wrote: > > The system dma-buf heap lets userspace allocate buffers from the page > allocator. However, these allocations are not accounted for in memcg, > allowing processes to escape limits that may be configured. > > Pass __GFP_ACCOUNT for system heap allocations, based on the > dma_heap.mem_accounting parameter, to use memcg and account for them. > > Signed-off-by: Eric Chanudet <echanude(a)redhat.com> Reviewed-by: T.J. Mercier <tjmercier(a)google.com>

1 week, 2 days

Re: [PATCH v2 2/4] dma-buf: Document revoke semantics

by Leon Romanovsky

On Sun, Jan 18, 2026 at 11:32:20PM -0800, John Hubbard wrote: > On 1/18/26 11:25 PM, Leon Romanovsky wrote: > > On Sun, Jan 18, 2026 at 01:40:11PM -0800, John Hubbard wrote: > > > On 1/18/26 4:08 AM, Leon Romanovsky wrote: > > > > From: Leon Romanovsky <leonro(a)nvidia.com> > > > ... > > > > +/** > > > > + * dma_buf_attachment_is_revoke - check if a DMA-buf importer implements > > > > + * revoke semantics. > > > > + * @attach: the DMA-buf attachment to check > > > > + * > > > > + * Returns true if DMA-buf importer honors revoke semantics, which is > > > > + * negotiated with the exporter, by making sure that importer implements > > > > + * .invalidate_mappings() callback and calls to dma_buf_pin() after > > > > + * DMA-buf attach. > > > > + */ > > > > +static inline bool > > > > +dma_buf_attachment_is_revoke(struct dma_buf_attachment *attach) > > > > > > Maybe a slight rename, to dma_buf_attachment_is_revocable()? > > > > I can do that. The issue is that even "dma_buf_attachment_is_revoke" > > is already too long. :) > > > > If you're really pressed for space for some reason, Mainly aesthetics. > maybe dma_buf_attach_revocable() ? > > Just trying to hang on to the "revocable" part of the name, as > I think it's an improvement. Sure > > thanks, > -- > John Hubbard > >

1 week, 2 days

Re: [PATCH v2 2/4] dma-buf: Document revoke semantics

by Leon Romanovsky

On Sun, Jan 18, 2026 at 01:40:11PM -0800, John Hubbard wrote: > On 1/18/26 4:08 AM, Leon Romanovsky wrote: > > From: Leon Romanovsky <leonro(a)nvidia.com> > ... > > +/** > > + * dma_buf_attachment_is_revoke - check if a DMA-buf importer implements > > + * revoke semantics. > > + * @attach: the DMA-buf attachment to check > > + * > > + * Returns true if DMA-buf importer honors revoke semantics, which is > > + * negotiated with the exporter, by making sure that importer implements > > + * .invalidate_mappings() callback and calls to dma_buf_pin() after > > + * DMA-buf attach. > > + */ > > +static inline bool > > +dma_buf_attachment_is_revoke(struct dma_buf_attachment *attach) > > Maybe a slight rename, to dma_buf_attachment_is_revocable()? I can do that. The issue is that even "dma_buf_attachment_is_revoke" is already too long. :) Thanks > > > thanks, > -- > John Hubbard >

1 week, 2 days

Re: types: reuse common phys_vec type instead of DMABUF open‑coded variant

by Leon Romanovsky

On Fri, Jan 16, 2026 at 10:14:55AM -0700, Alex Williamson wrote: > On Wed, 14 Jan 2026 14:18:19 +0200 > Leon Romanovsky <leon(a)kernel.org> wrote: > > > On Wed, Jan 07, 2026 at 11:14:14AM +0200, Leon Romanovsky wrote: > > > From: Leon Romanovsky <leonro(a)nvidia.com> > > > > > > After commit fcf463b92a08 ("types: move phys_vec definition to common header"), > > > we can use the shared phys_vec type instead of the DMABUF‑specific > > > dma_buf_phys_vec, which duplicated the same structure and semantics. > > > > > > Signed-off-by: Leon Romanovsky <leonro(a)nvidia.com> > > > --- > > > Alex, > > > > > > According to diffstat, VFIO is the subsystem with the largest set of changes, > > > so it would be great if you could take it through your tree. > > > > > > The series is based on the for-7.0/blk-pvec shared branch from Jens: > > > https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git/log/?h=for-… > > > > > > Thanks > > > --- > > > > Alex, > > > > Could you please move this patch forward? We have the RDMA series [1] that > > depends on this rename, and I would like to base it on the shared branch. > > > > [1] https://lore.kernel.org/all/20260108-dmabuf-export-v1-0-6d47d46580d3@nvidia… > > I tried to ping Jens regarding why the branch with this code hasn't > been merged into their for-next branch, maybe you have more traction. It is in block/for-next now, commit df73d3c618b4 ("Merge branch 'for-7.0/blk-pvec' into for-7.0/block". Thanks > Thanks, > > Alex >

1 week, 3 days

Re: [PATCH v2 0/2] dma-buf: system_heap: account for system heap allocation in memcg

by T.J. Mercier

On Tue, Jan 13, 2026 at 1:33 PM Eric Chanudet <echanude(a)redhat.com> wrote: > > Capture dmabuf system heap allocations in memcg following prior > conversations[1][2]. Disable this behavior by default unless configured > by "dma_heap.mem_accounting" module parameter. > > [1] https://lore.kernel.org/dri-devel/Z-5GZ3kJDbhgVBPG@phenom.ffwll.local/ > [2] https://lore.kernel.org/all/CABdmKX2_UOENujpW0dXe0Z0x+4V3onfGDmHf1DMOXfDha6… > > Changes in v2: > - Add a module parameter to enable dma-buf cgroup accounting, disabled > by default. > - Split system_heap logic in its own commit. > - Link to v1: https://lore.kernel.org/lkml/20251211193106.755485-2-echanude@redhat.com/ > > Signed-off-by: Eric Chanudet <echanude(a)redhat.com> > --- > Eric Chanudet (2): > dma-buf: heaps: add parameter to account allocations using cgroup > dma-buf: system_heap: account for system heap allocation in memcg > > drivers/dma-buf/dma-heap.c | 5 +++++ > drivers/dma-buf/heaps/system_heap.c | 9 +++++++-- > 2 files changed, 12 insertions(+), 2 deletions(-) > --- > base-commit: b71e635feefc852405b14620a7fc58c4c80c0f73 > change-id: 20260102-dmabuf-heap-system-memcg-c86a381d663a > > Best regards, > -- > Eric Chanudet <echanude(a)redhat.com> Thanks for adding the param, LGTM. Looking forward to v3.

1 week, 5 days

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