block: move bd_part_count to struct gendisk

The bd_part_count value only makes sense for whole devices, so move it
to struct gendisk and give it a more descriptive name.
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/20210525061301.2242282-7-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/ioctl.c

@@ -89,7 +89,7 @@ static int blkdev_reread_part(struct block_device *bdev, fmode_t mode)
 		return -EINVAL;
 	if (!capable(CAP_SYS_ADMIN))
 		return -EACCES;
-	if (bdev->bd_part_count)
+	if (bdev->bd_disk->open_partitions)
 		return -EBUSY;
 
 	/*

fs/block_dev.c

@@ -1253,7 +1253,7 @@ int bdev_disk_changed(struct block_device *bdev, bool invalidate)
 		return -ENXIO;
 
 rescan:
-	if (bdev->bd_part_count)
+	if (disk->open_partitions)
 		return -EBUSY;
 	sync_blockdev(bdev);
 	invalidate_bdev(bdev);
@@ -1348,7 +1348,7 @@ static int blkdev_get_part(struct block_device *part, fmode_t mode)
 	if (!bdev_nr_sectors(part))
 		goto out_blkdev_put;
 
-	whole->bd_part_count++;
+	disk->open_partitions++;
 	set_init_blocksize(part);
 	if (part->bd_bdi == &noop_backing_dev_info)
 		part->bd_bdi = bdi_get(disk->queue->backing_dev_info);
@@ -1370,7 +1370,7 @@ static void blkdev_put_part(struct block_device *part, fmode_t mode)
 	if (--part->bd_openers)
 		return;
 	blkdev_flush_mapping(part);
-	whole->bd_part_count--;
+	whole->bd_disk->open_partitions--;
 	blkdev_put_whole(whole, mode);
 	bdput(whole);
 }

include/linux/blk_types.h

@@ -39,9 +39,6 @@ struct block_device {
 #endif
 	struct kobject		*bd_holder_dir;
 	u8			bd_partno;
-	/* number of times partitions within this device have been opened. */
-	unsigned		bd_part_count;
-
 	spinlock_t		bd_size_lock; /* for bd_inode->i_size updates */
 	struct gendisk *	bd_disk;
 	struct backing_dev_info *bd_bdi;

include/linux/genhd.h

@@ -156,6 +156,7 @@ struct gendisk {
 #define GD_QUEUE_REF			2
 
 	struct mutex open_mutex;	/* open/close mutex */
+	unsigned open_partitions;	/* number of open partitions */
 
 	struct kobject *slave_dir;