From 839231d193932ca0d592c2859669066f7c43731c Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Wed, 14 Oct 2026 12:02:03 +0100 Subject: [PATCH] block: add dma-buf support for raw bdev Add a simple proxy implementation of init_dma_buf_io_ctx() forwarding the call to a new struct block_device_operations operation. Also reject dma-buf backed iterators for buffered IO. Reviewed-by: Christoph Hellwig [pavel: reject dma-buf without O_DIRECT] Signed-off-by: Pavel Begunkov Link: https://patch.msgid.link/c01c4709dc55a12fb0f2fe1ec847b5f1f0c92789.1791975048.git.asml.silence@gmail.com Signed-off-by: Jens Axboe --- block/fops.c | 24 ++++++++++++++++++++++++ include/linux/blkdev.h | 2 ++ 2 files changed, 26 insertions(+) diff --git a/block/fops.c b/block/fops.c index eb4f588bb4f7..49ae0302f123 100644 --- a/block/fops.c +++ b/block/fops.c @@ -709,6 +709,9 @@ blkdev_direct_write(struct kiocb *iocb, struct iov_iter *from) static ssize_t blkdev_buffered_write(struct kiocb *iocb, struct iov_iter *from) { + if (unlikely(iov_iter_is_dmabuf_map(from))) + return -EOPNOTSUPP; + return iomap_file_buffered_write(iocb, from, &blkdev_iomap_ops, NULL, NULL); } @@ -823,6 +826,11 @@ static ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to) if (ret < 0 || !count) goto reexpand; } + if (unlikely(iov_iter_is_dmabuf_map(to))) { + if (!ret) + ret = -EOPNOTSUPP; + goto reexpand; + } /* * Take i_rwsem and invalidate_lock to avoid racing with set_blocksize @@ -926,6 +934,21 @@ static int blkdev_mmap_prepare(struct vm_area_desc *desc) return generic_file_mmap_prepare(desc); } +static int blkdev_init_dma_buf_io_ctx(struct file *file, + struct dma_buf_io_ctx *ctx) +{ + struct block_device *bdev = file_bdev(file); + struct gendisk *disk = bdev->bd_disk; + + if (!(file->f_flags & O_DIRECT)) + return -EINVAL; + if (!disk->fops->init_dma_buf_io_ctx) + return -EOPNOTSUPP; + if (bdev_has_integrity_csum(bdev)) + return -EOPNOTSUPP; + return disk->fops->init_dma_buf_io_ctx(bdev, ctx); +} + const struct file_operations def_blk_fops = { .open = blkdev_open, .release = blkdev_release, @@ -944,6 +967,7 @@ const struct file_operations def_blk_fops = { .fallocate = blkdev_fallocate, .uring_cmd = blkdev_uring_cmd, .fop_flags = FOP_BUFFER_RASYNC | FOP_DONTCACHE, + .init_dma_buf_io_ctx = blkdev_init_dma_buf_io_ctx, }; static __init int blkdev_init(void) diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 4f7905c3412b..2d555a992e75 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1596,6 +1596,8 @@ struct block_device_operations { /* returns the length of the identifier or a negative errno: */ int (*get_unique_id)(struct gendisk *disk, u8 id[16], enum blk_unique_id id_type); + int (*init_dma_buf_io_ctx)(struct block_device *, + struct dma_buf_io_ctx *); struct module *owner; const struct pr_ops *pr_ops;