missing helpers: bdev_unhash(), bdev_drop()

bdev_unhash(): make block device invisible to lookups by device number
bdev_drop(): drop reference to associated inode.

Both are internal, for use by genhd and partition-related code - similar
to bdev_add().  The logics in there (especially the lifetime-related
parts of it) ought to be cleaned up, but that's a separate story; here
we just encapsulate getting to associated inode.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Author: Al Viro

block/bdev.c

@@ -451,6 +451,16 @@ void bdev_add(struct block_device *bdev, dev_t dev)
 	insert_inode_hash(bdev->bd_inode);
 }
 
+void bdev_unhash(struct block_device *bdev)
+{
+	remove_inode_hash(bdev->bd_inode);
+}
+
+void bdev_drop(struct block_device *bdev)
+{
+	iput(bdev->bd_inode);
+}
+
 long nr_blockdev_pages(void)
 {
 	struct inode *inode;

block/blk.h

@@ -428,6 +428,8 @@ static inline int blkdev_zone_mgmt_ioctl(struct block_device *bdev,
 
 struct block_device *bdev_alloc(struct gendisk *disk, u8 partno);
 void bdev_add(struct block_device *bdev, dev_t dev);
+void bdev_unhash(struct block_device *bdev);
+void bdev_drop(struct block_device *bdev);
 
 int blk_alloc_ext_minor(void);
 void blk_free_ext_minor(unsigned int minor);

block/genhd.c

@@ -656,7 +656,7 @@ void del_gendisk(struct gendisk *disk)
 	 */
 	mutex_lock(&disk->open_mutex);
 	xa_for_each(&disk->part_tbl, idx, part)
-		remove_inode_hash(part->bd_inode);
+		bdev_unhash(part);
 	mutex_unlock(&disk->open_mutex);
 
 	/*
@@ -1191,7 +1191,7 @@ static void disk_release(struct device *dev)
 	if (test_bit(GD_ADDED, &disk->state) && disk->fops->free_disk)
 		disk->fops->free_disk(disk);
 
-	iput(disk->part0->bd_inode);	/* frees the disk */
+	bdev_drop(disk->part0);	/* frees the disk */
 }
 
 static int block_uevent(const struct device *dev, struct kobj_uevent_env *env)
@@ -1381,7 +1381,7 @@ struct gendisk *__alloc_disk_node(struct request_queue *q, int node_id,
 out_destroy_part_tbl:
 	xa_destroy(&disk->part_tbl);
 	disk->part0->bd_disk = NULL;
-	iput(disk->part0->bd_inode);
+	bdev_drop(disk->part0);
 out_free_bdi:
 	bdi_put(disk->bdi);
 out_free_bioset:

block/partitions/core.c

@@ -243,7 +243,7 @@ static const struct attribute_group *part_attr_groups[] = {
 static void part_release(struct device *dev)
 {
 	put_disk(dev_to_bdev(dev)->bd_disk);
-	iput(dev_to_bdev(dev)->bd_inode);
+	bdev_drop(dev_to_bdev(dev));
 }
 
 static int part_uevent(const struct device *dev, struct kobj_uevent_env *env)
@@ -469,7 +469,7 @@ int bdev_del_partition(struct gendisk *disk, int partno)
 	 * Just delete the partition and invalidate it.
 	 */
 
-	remove_inode_hash(part->bd_inode);
+	bdev_unhash(part);
 	invalidate_bdev(part);
 	drop_partition(part);
 	ret = 0;
@@ -655,7 +655,7 @@ int bdev_disk_changed(struct gendisk *disk, bool invalidate)
 		 * it cannot be looked up any more even when openers
 		 * still hold references.
 		 */
-		remove_inode_hash(part->bd_inode);
+		bdev_unhash(part);
 
 		/*
 		 * If @disk->open_partitions isn't elevated but there's