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Tue, 28 Jul 2026 14:29:41 -0700 (PDT) Received: from 127.mynet ([2a01:4b00:bd21:4f00:7cc6:d3ca:494:116c]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47fb6ac44bcsm2245329f8f.11.2026.07.28.14.29.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Jul 2026 14:29:40 -0700 (PDT) From: Pavel Begunkov To: Jens Axboe , Keith Busch , Christoph Hellwig , Sagi Grimberg , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org Cc: asml.silence@gmail.com, Alexander Viro , Christian Brauner , Andrew Morton , Sumit Semwal , =?UTF-8?q?Christian=20K=C3=B6nig?= , Nitesh Shetty , Kanchan Joshi , Anuj Gupta , Tushar Gohad , William Power , Phil Cayton , Jason Gunthorpe , Damien Le Moal , Alasdair Kergon , Mike Snitzer , Mikulas Patocka , Benjamin Marzinski , Vishal Verma , David Sterba , Ilya Dryomov , dm-devel@lists.linux.dev, nvdimm@lists.linux.dev, linux-btrfs@vger.kernel.org, ceph-devel@vger.kernel.org Subject: [PATCH v4 00/14] Add dmabuf read/write via io_uring Date: Tue, 28 Jul 2026 22:29:12 +0100 Message-ID: X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The patch set allows to register a dmabuf to an io_uring instance for a specified file and use it with io_uring read / write requests. The infrastructure is not tied to io_uring and there could be more users in the future. A similar idea was attempted some years ago by Keith [1], from where I borrowed a good number of changes, and later was brough up by Tushar and Vishal. It's an opt-in feature for files, and they need to implement a new file operation to use it. Only NVMe block devices are supported in this series. The user API is built on top of io_uring's "registered buffers", where a dmabuf is registered in a special way, but after it can be used as any other "registered buffer" with IORING_OP_{READ,WRITE}_FIXED requests. It's created via a new file operation and the resulted map is then passed through the I/O stack in a new iterator type. There is some additional infrastructure to glue it together, count requests, manage lifetime and implement invalidation. Tushar, William, Phil as well as Kanchan, Anuj and Nitesh did a lot of testing and experimentation with different devices. Some earlier benchmarks by Anuj for IOMMU optimisations with udmabuf showed: STRICT: before = 570 KIOPS, after = 5.01 MIOPS LAZY: before = 1.93 MIOPS, after = 5.01 MIOPS PASSTHROUGH: before = 5.01 MIOPS, after = 5.01 MIOPS # Patch set structure: - Patches 1-2 introduce internal API and infrastructure mediating io_uring and target subsystem / devices - Patches 3-7: block layer support + prep patches - Patches 8-9 implement NVMe support - Patches 10-14 add io_uring support and uapi. Patch 14 specifically enables dma-buf support, the rest are preparation patches. There are some liburing tests that can serve as an example: git: https://github.com/isilence/liburing.git rw-dmabuf-tests-v4 url: https://github.com/isilence/liburing/tree/rw-dmabuf-tests-v4 [1] https://lore.kernel.org/io-uring/20220805162444.3985535-1-kbusch@fb.com/ v4: - Add sgl support from Anuj - Move it under drivers/dma-buf/ and rename - Fix mis-sized allocations - Fix io_uring re-import mishandling - Drop map before io_uring "task work" - Move blk-mq callback to block_device_operations - Convert bio flag to REQ_OP* - Other small changes v3: https://lore.kernel.org/io-uring/cover.1777475843.git.asml.silence@gmail.com/ - Rework io_uring registration - Move token/map infrastructure code out of blk-mq - Simplify callbacks: remove a separate blk-mq table, which was mostly just forwarding calls (to nvme). - Don't skip dma sync depending on request direction - Fix a couple of hangs - Rename s/dma/dmabuf/ - Other small changes v2: - Don't pass raw dma addresses, wrap it into a driver specific object - Split into two objects: token and map - Implement move_notify Anuj Gupta (1): nvme-pci: add SGL support for the dmabuf path Pavel Begunkov (13): dma-buf: introduce initial file I/O infrastructure iov_iter: add iterator type for dmabuf maps block: rename bi_bvec_done block: always adjust bi_offset on bio_advance_iter block: move bvec init into __bio_clone block: introduce dma map backed bio type block: forward init_dma_buf_io_ctx to drivers nvme-pci: implement dma_token backed requests io_uring/rsrc: introduce buf registration structure io_uring/rsrc: extend buffer update io_uring/rsrc: add uncloneable regbuf flag io_uring/rsrc: add regbuf import flags io_uring/rsrc: add dmabuf backed registered buffers Documentation/block/biovecs.rst | 8 +- block/bio.c | 30 ++- block/blk-merge.c | 23 +- block/blk-mq-dma.c | 2 +- block/blk.h | 2 +- block/fops.c | 16 ++ drivers/block/loop.c | 2 +- drivers/block/zloop.c | 2 +- drivers/dma-buf/Makefile | 2 +- drivers/dma-buf/dma-buf-io.c | 275 ++++++++++++++++++++ drivers/md/dm-io-rewind.c | 16 +- drivers/md/dm-pcache/segment.c | 4 +- drivers/nvdimm/btt.c | 2 +- drivers/nvme/host/core.c | 12 + drivers/nvme/host/nvme.h | 2 + drivers/nvme/host/pci.c | 448 +++++++++++++++++++++++++++++++- drivers/nvme/host/tcp.c | 2 +- fs/btrfs/misc.h | 2 +- include/linux/bio.h | 22 +- include/linux/blk-mq.h | 7 + include/linux/blk_types.h | 14 +- include/linux/blkdev.h | 2 + include/linux/bvec.h | 17 +- include/linux/dma-buf-io.h | 91 +++++++ include/linux/fs.h | 2 + include/linux/io_uring_types.h | 5 + include/linux/uio.h | 11 + include/uapi/linux/io_uring.h | 31 ++- io_uring/io_uring.c | 3 +- io_uring/net.c | 4 +- io_uring/rsrc.c | 281 +++++++++++++++++--- io_uring/rsrc.h | 45 +++- io_uring/rw.c | 6 +- lib/iov_iter.c | 31 ++- net/ceph/messenger.c | 4 +- 35 files changed, 1315 insertions(+), 111 deletions(-) create mode 100644 drivers/dma-buf/dma-buf-io.c create mode 100644 include/linux/dma-buf-io.h -- 2.54.0