block: remove bdget_disk

Just opencode the xa_load in the callers, as none of them actually
needs a reference to the bdev.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210525061301.2242282-9-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/genhd.c

@@ -676,32 +676,6 @@ void blk_request_module(dev_t devt)
 		request_module("block-major-%d", MAJOR(devt));
 }
 
-/**
- * bdget_disk - do bdget() by gendisk and partition number
- * @disk: gendisk of interest
- * @partno: partition number
- *
- * Find partition @partno from @disk, do bdget() on it.
- *
- * CONTEXT:
- * Don't care.
- *
- * RETURNS:
- * Resulting block_device on success, NULL on failure.
- */
-struct block_device *bdget_disk(struct gendisk *disk, int partno)
-{
-	struct block_device *bdev = NULL;
-
-	rcu_read_lock();
-	bdev = xa_load(&disk->part_tbl, partno);
-	if (bdev && !bdgrab(bdev))
-		bdev = NULL;
-	rcu_read_unlock();
-
-	return bdev;
-}
-
 /*
  * print a full list of all partitions - intended for places where the root
  * filesystem can't be mounted and thus to give the victim some idea of what
@@ -1229,13 +1203,14 @@ module_init(proc_genhd_init);
 
 dev_t part_devt(struct gendisk *disk, u8 partno)
 {
-	struct block_device *part = bdget_disk(disk, partno);
+	struct block_device *part;
 	dev_t devt = 0;
 
-	if (part) {
+	rcu_read_lock();
+	part = xa_load(&disk->part_tbl, partno);
+	if (part)
 		devt = part->bd_dev;
-		bdput(part);
-	}
+	rcu_read_unlock();
 
 	return devt;
 }

block/partitions/core.c

@@ -326,6 +326,8 @@ static struct block_device *add_partition(struct gendisk *disk, int partno,
 	const char *dname;
 	int err;
 
+	lockdep_assert_held(&disk->open_mutex);
+
 	if (partno >= disk_max_parts(disk))
 		return ERR_PTR(-EINVAL);
 
@@ -467,14 +469,13 @@ int bdev_add_partition(struct block_device *bdev, int partno,
 
 int bdev_del_partition(struct block_device *bdev, int partno)
 {
-	struct block_device *part;
-	int ret;
-
-	part = bdget_disk(bdev->bd_disk, partno);
-	if (!part)
-		return -ENXIO;
+	struct block_device *part = NULL;
+	int ret = -ENXIO;
 
 	mutex_lock(&bdev->bd_disk->open_mutex);
+	part = xa_load(&bdev->bd_disk->part_tbl, partno);
+	if (!part)
+		goto out_unlock;
 
 	ret = -EBUSY;
 	if (part->bd_openers)
@@ -484,21 +485,20 @@ int bdev_del_partition(struct block_device *bdev, int partno)
 	ret = 0;
 out_unlock:
 	mutex_unlock(&bdev->bd_disk->open_mutex);
-	bdput(part);
 	return ret;
 }
 
 int bdev_resize_partition(struct block_device *bdev, int partno,
 		sector_t start, sector_t length)
 {
-	struct block_device *part;
-	int ret = 0;
+	struct block_device *part = NULL;
+	int ret = -ENXIO;
 
-	part = bdget_disk(bdev->bd_disk, partno);
+	mutex_lock(&bdev->bd_disk->open_mutex);
+	part = xa_load(&bdev->bd_disk->part_tbl, partno);
 	if (!part)
-		return -ENXIO;
+		goto out_unlock;
 
-	mutex_lock(&bdev->bd_disk->open_mutex);
 	ret = -EINVAL;
 	if (start != part->bd_start_sect)
 		goto out_unlock;
@@ -512,7 +512,6 @@ int bdev_resize_partition(struct block_device *bdev, int partno,
 	ret = 0;
 out_unlock:
 	mutex_unlock(&bdev->bd_disk->open_mutex);
-	bdput(part);
 	return ret;
 }
 

include/linux/genhd.h

@@ -223,7 +223,6 @@ static inline void add_disk_no_queue_reg(struct gendisk *disk)
 }
 
 extern void del_gendisk(struct gendisk *gp);
-extern struct block_device *bdget_disk(struct gendisk *disk, int partno);
 
 void set_disk_ro(struct gendisk *disk, bool read_only);