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Wed, 29 Jul 2026 13:30:47 +0000 (GMT) Message-ID: <583fdfb2-5368-467f-a388-6d388859c995@samsung.com> Date: Wed, 29 Jul 2026 19:00:46 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 14/14] io_uring/rsrc: add dmabuf backed registered buffers To: Pavel Begunkov , 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: Alexander Viro , Christian Brauner , Andrew Morton , Sumit Semwal , =?UTF-8?Q?Christian_K=C3=B6nig?= , Nitesh Shetty , Kanchan Joshi , Jason Gunthorpe , Damien Le Moal , Alasdair Kergon , Mike Snitzer , Mikulas Patocka , Benjamin Marzinski , David Sterba , Ilya Dryomov , dm-devel@lists.linux.dev, nvdimm@lists.linux.dev, linux-btrfs@vger.kernel.org, ceph-devel@vger.kernel.org Content-Language: en-US From: Anuj Gupta/Anuj Gupta In-Reply-To: <26dcd0ae5c87a3ada5710b14b6894ef343cec6fe.1785274111.git.asml.silence@gmail.com> Content-Transfer-Encoding: 7bit X-CMS-MailID: 20260729133052epcas5p21fab8c8ffc58e9b13b267e5af8bbbb63 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" CMS-TYPE: 105P cpgsPolicy: CPGSC10-542,Y X-CFilter-Loop: Reflected X-CMS-RootMailID: 20260728213020epcas5p1721e72ba5544abf0b61482da005120d9 References: <26dcd0ae5c87a3ada5710b14b6894ef343cec6fe.1785274111.git.asml.silence@gmail.com> On 7/29/2026 2:59 AM, Pavel Begunkov wrote: > +static struct io_rsrc_node *io_register_dmabuf(struct io_ring_ctx *ctx, > + struct io_uring_regbuf_desc *desc) > +{ > + struct io_rsrc_node *node = NULL; > + struct io_mapped_ubuf *imu = NULL; > + struct io_regbuf_dma *regbuf = NULL; > + struct file *target_file = NULL; > + struct dma_buf *dmabuf = NULL; > + int ret; > + > + if (!IS_ENABLED(CONFIG_DMA_SHARED_BUFFER)) > + return ERR_PTR(-EOPNOTSUPP); > + if (ctx->flags & IORING_SETUP_IOPOLL) > + return ERR_PTR(-EOPNOTSUPP); > + if (desc->uaddr || desc->size) > + return ERR_PTR(-EINVAL); > + > + ret = -ENOMEM; > + node = io_rsrc_node_alloc(ctx, IORING_RSRC_BUFFER); > + if (!node) > + return ERR_PTR(-ENOMEM); > + imu = io_alloc_imu(ctx, 0); > + if (!imu) > + goto err; > + regbuf = kzalloc(sizeof(*regbuf), GFP_KERNEL); > + if (!regbuf) > + goto err; > + > + ret = -EBADF; > + target_file = fget(desc->target_fd); > + if (!target_file) > + goto err; > + > + dmabuf = dma_buf_get(desc->dmabuf_fd); > + if (IS_ERR(dmabuf)) { > + ret = PTR_ERR(dmabuf); > + dmabuf = NULL; > + goto err; > + } > + if (dmabuf->size > SZ_1G) { > + ret = -EINVAL; > + goto err; > + } > + > + ret = dma_buf_io_ctx_create(target_file, ®buf->ctx, dmabuf, > + DMA_BIDIRECTIONAL); > + if (ret) > + goto err; > + > + regbuf->target_file = target_file; > + imu->nr_bvecs = 1; There is no bvec backing a dmabuf imu - should this be 0? > + imu->ubuf = 0; > + imu->len = dmabuf->size; > + imu->folio_shift = 0; > + imu->release = io_release_reg_dmabuf; > + imu->priv = regbuf; > + imu->flags = IO_REGBUF_F_DMABUF; > + imu->dir = IO_IMU_DEST | IO_IMU_SOURCE; > + refcount_set(&imu->refs, 1); > + node->buf = imu; > + dma_buf_put(dmabuf); > + return node; > +err: > + kfree(regbuf); > + if (imu) > + io_free_imu(ctx, imu); > + if (node) > + io_cache_free(&ctx->node_cache, node); > + if (target_file) > + fput(target_file); > + if (dmabuf) > + dma_buf_put(dmabuf); > + return ERR_PTR(ret); > +} > + > + nit: extra newline here > +static int io_import_dmabuf(struct io_kiocb *req, > + int ddir, struct iov_iter *iter, > + struct io_mapped_ubuf *imu, > + size_t len, size_t offset, > + unsigned issue_flags) > +{ > + struct io_regbuf_dma *db = imu->priv; > + struct dma_buf_io_map *map; > + > + if (!IS_ENABLED(CONFIG_DMA_SHARED_BUFFER)) > + return -EOPNOTSUPP; > + if (!len) > + return -EFAULT; > + if (req->file != db->target_file) > + return -EBADF; > + > + if (req->flags & REQ_F_DROP_DMABUF) { > + map = req->dmabuf_map; > + goto init_iter; > + } O_DIRECT is checked only during registration; we should recheck (file->f_flags & O_DIRECT) per request.