[RFC 1/4] block: factor out bdev_init_dma_buf_io_ctx()

[Anuj Gupta <anuj1072538@gmail.com>]

From: Nitesh Shetty <nj.shetty@samsung.com>

Factor the checks and driver setup into an exported helper that takes
an explicit block device, so filesystems can initialize a dma-buf I/O
context for the device backing a regular file. The block-device file
operation becomes a wrapper using file_bdev(), so its behavior is
unchanged.

Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
---
 block/fops.c           | 12 +++++++++---
 include/linux/blkdev.h |  3 +++
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/block/fops.c b/block/fops.c
index 49ae0302f123..18a755f6e0b0 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -934,10 +934,9 @@ 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)
+int bdev_init_dma_buf_io_ctx(struct file *file, struct block_device *bdev,
+			     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))
@@ -948,6 +947,13 @@ static int blkdev_init_dma_buf_io_ctx(struct file *file,
 		return -EOPNOTSUPP;
 	return disk->fops->init_dma_buf_io_ctx(bdev, ctx);
 }
+EXPORT_SYMBOL_GPL(bdev_init_dma_buf_io_ctx);
+
+static int blkdev_init_dma_buf_io_ctx(struct file *file,
+				      struct dma_buf_io_ctx *ctx)
+{
+	return bdev_init_dma_buf_io_ctx(file, file_bdev(file), ctx);
+}
 
 const struct file_operations def_blk_fops = {
 	.open		= blkdev_open,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 2d555a992e75..a0abdf94e7d6 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1609,6 +1609,9 @@ struct block_device_operations {
 	int (*alternative_gpt_sector)(struct gendisk *disk, sector_t *sector);
 };
 
+int bdev_init_dma_buf_io_ctx(struct file *file, struct block_device *bdev,
+			     struct dma_buf_io_ctx *ctx);
+
 #ifdef CONFIG_COMPAT
 extern int blkdev_compat_ptr_ioctl(struct block_device *, blk_mode_t,
 				      unsigned int, unsigned long);
-- 
2.43.0