[PATCH 3/4] block: use bd_prepare_to_claim directly in the loop driver

[Christoph Hellwig <hch@xxxxxx>]

The arcane magic in bd_start_claiming is only needed to be able to claim
a block_device that hasn't been fully set up.  Switch the loop driver
that claims from the ioctl path with a fully set up struct block_device
to just use the much simpler bd_prepare_to_claim directly.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 drivers/block/loop.c   | 7 +++----
 fs/block_dev.c         | 9 +++++----
 include/linux/blkdev.h | 3 ++-
 3 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index a943207705ddf1..d181601462260b 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1090,11 +1090,10 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
 	 * here to avoid changing device under exclusive owner.
 	 */
 	if (!(mode & FMODE_EXCL)) {
-		claimed_bdev = bd_start_claiming(bdev, loop_configure);
-		if (IS_ERR(claimed_bdev)) {
-			error = PTR_ERR(claimed_bdev);
+		claimed_bdev = bdev->bd_contains;
+		error = bd_prepare_to_claim(bdev, claimed_bdev, loop_configure);
+		if (error)
 			goto out_putf;
-		}
 	}
 
 	error = mutex_lock_killable(&loop_ctl_mutex);
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 1c9da1f08011b0..7075004d36997b 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1027,8 +1027,8 @@ static bool bd_may_claim(struct block_device *bdev, struct block_device *whole,
  * RETURNS:
  * 0 if @bdev can be claimed, -EBUSY otherwise.
  */
-static int bd_prepare_to_claim(struct block_device *bdev,
-			       struct block_device *whole, void *holder)
+int bd_prepare_to_claim(struct block_device *bdev, struct block_device *whole,
+		void *holder)
 {
 retry:
 	spin_lock(&bdev_lock);
@@ -1055,6 +1055,7 @@ static int bd_prepare_to_claim(struct block_device *bdev,
 	spin_unlock(&bdev_lock);
 	return 0;
 }
+EXPORT_SYMBOL_GPL(bd_prepare_to_claim); /* only for the loop driver */
 
 static struct gendisk *bdev_get_gendisk(struct block_device *bdev, int *partno)
 {
@@ -1100,7 +1101,8 @@ static struct gendisk *bdev_get_gendisk(struct block_device *bdev, int *partno)
  * Pointer to the block device containing @bdev on success, ERR_PTR()
  * value on failure.
  */
-struct block_device *bd_start_claiming(struct block_device *bdev, void *holder)
+static struct block_device *bd_start_claiming(struct block_device *bdev,
+		void *holder)
 {
 	struct gendisk *disk;
 	struct block_device *whole;
@@ -1141,7 +1143,6 @@ struct block_device *bd_start_claiming(struct block_device *bdev, void *holder)
 
 	return whole;
 }
-EXPORT_SYMBOL(bd_start_claiming);
 
 static void bd_clear_claiming(struct block_device *whole, void *holder)
 {
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 408eb66a82fdc7..6489a0c478165b 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1921,7 +1921,8 @@ int blkdev_get(struct block_device *bdev, fmode_t mode, void *holder);
 struct block_device *blkdev_get_by_path(const char *path, fmode_t mode,
 		void *holder);
 struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder);
-struct block_device *bd_start_claiming(struct block_device *bdev, void *holder);
+int bd_prepare_to_claim(struct block_device *bdev, struct block_device *whole,
+		void *holder);
 void bd_abort_claiming(struct block_device *bdev, struct block_device *whole,
 		void *holder);
 void blkdev_put(struct block_device *bdev, fmode_t mode);
-- 
2.26.2