block: Provide bdev_open_* functions

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@lst.de>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230927093442.25915-1-jack@suse.cz
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/block/bdev.c b/block/bdev.c
index f3b13aa1b7d4289a4ce3ec8a9b63abed4e0094ec..bdc7d739882bb04486a83e0a27630fb933c348f5 100644 (file)
--- 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 eef450f259828d933f1f4b96d5515aed3d7eb3c5..03d3adc3ff347d129b6b9b844ffa0cd12f8c4e80 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1479,14 +1479,24 @@ 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);