[PATCH 01/29] block: Provide bdev_open_* functions

[Jan Kara <jack@xxxxxxx>]

Create struct bdev_handle that contains all parameters that need to be
passed to blkdev_put() and provide bdev_open_* functions that return
this structure instead of plain bdev pointer. This will eventually allow
us to pass one more argument to blkdev_put() (renamed to bdev_release())
without too much hassle.

Acked-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
 block/bdev.c           | 48 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/blkdev.h | 10 +++++++++
 2 files changed, 58 insertions(+)

diff --git a/block/bdev.c b/block/bdev.c
index a20263fa27a4..fce150f9e66d 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -829,6 +829,25 @@ struct block_device *blkdev_get_by_dev(dev_t dev, blk_mode_t mode, void *holder,
 }
 EXPORT_SYMBOL(blkdev_get_by_dev);
 
+struct bdev_handle *bdev_open_by_dev(dev_t dev, blk_mode_t mode, void *holder,
+				     const struct blk_holder_ops *hops)
+{
+	struct bdev_handle *handle = kmalloc(sizeof(*handle), GFP_KERNEL);
+	struct block_device *bdev;
+
+	if (!handle)
+		return ERR_PTR(-ENOMEM);
+	bdev = blkdev_get_by_dev(dev, mode, holder, hops);
+	if (IS_ERR(bdev)) {
+		kfree(handle);
+		return ERR_CAST(bdev);
+	}
+	handle->bdev = bdev;
+	handle->holder = holder;
+	return handle;
+}
+EXPORT_SYMBOL(bdev_open_by_dev);
+
 /**
  * blkdev_get_by_path - open a block device by name
  * @path: path to the block device to open
@@ -867,6 +886,28 @@ struct block_device *blkdev_get_by_path(const char *path, blk_mode_t mode,
 }
 EXPORT_SYMBOL(blkdev_get_by_path);
 
+struct bdev_handle *bdev_open_by_path(const char *path, blk_mode_t mode,
+		void *holder, const struct blk_holder_ops *hops)
+{
+	struct bdev_handle *handle;
+	dev_t dev;
+	int error;
+
+	error = lookup_bdev(path, &dev);
+	if (error)
+		return ERR_PTR(error);
+
+	handle = bdev_open_by_dev(dev, mode, holder, hops);
+	if (!IS_ERR(handle) && (mode & BLK_OPEN_WRITE) &&
+	    bdev_read_only(handle->bdev)) {
+		bdev_release(handle);
+		return ERR_PTR(-EACCES);
+	}
+
+	return handle;
+}
+EXPORT_SYMBOL(bdev_open_by_path);
+
 void blkdev_put(struct block_device *bdev, void *holder)
 {
 	struct gendisk *disk = bdev->bd_disk;
@@ -903,6 +944,13 @@ void blkdev_put(struct block_device *bdev, void *holder)
 }
 EXPORT_SYMBOL(blkdev_put);
 
+void bdev_release(struct bdev_handle *handle)
+{
+	blkdev_put(handle->bdev, handle->holder);
+	kfree(handle);
+}
+EXPORT_SYMBOL(bdev_release);
+
 /**
  * lookup_bdev() - Look up a struct block_device by name.
  * @pathname: Name of the block device in the filesystem.
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index fa462d48ee96..6a942ec773b6 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1478,14 +1478,24 @@ extern const struct blk_holder_ops fs_holder_ops;
 #define sb_open_mode(flags) \
 	(BLK_OPEN_READ | (((flags) & SB_RDONLY) ? 0 : BLK_OPEN_WRITE))
 
+struct bdev_handle {
+	struct block_device *bdev;
+	void *holder;
+};
+
 struct block_device *blkdev_get_by_dev(dev_t dev, blk_mode_t mode, void *holder,
 		const struct blk_holder_ops *hops);
 struct block_device *blkdev_get_by_path(const char *path, blk_mode_t mode,
 		void *holder, const struct blk_holder_ops *hops);
+struct bdev_handle *bdev_open_by_dev(dev_t dev, blk_mode_t mode, void *holder,
+		const struct blk_holder_ops *hops);
+struct bdev_handle *bdev_open_by_path(const char *path, blk_mode_t mode,
+		void *holder, const struct blk_holder_ops *hops);
 int bd_prepare_to_claim(struct block_device *bdev, void *holder,
 		const struct blk_holder_ops *hops);
 void bd_abort_claiming(struct block_device *bdev, void *holder);
 void blkdev_put(struct block_device *bdev, void *holder);
+void bdev_release(struct bdev_handle *handle);
 
 /* just for blk-cgroup, don't use elsewhere */
 struct block_device *blkdev_get_no_open(dev_t dev);
-- 
2.35.3