block: move holder_dir from disk to part0

Move disk->holder_dir to part0->holder_dir.  Kill now mostly
superflous bdev_get_holder().

While at it, kill superflous kobject_get/put() around holder_dir,
slave_dir and cmd_filter creation and collapse
disk_sysfs_add_subdirs() into register_disk().  These serve no purpose
but obfuscating the code.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block/cmd-filter.c

@@ -211,14 +211,10 @@ int blk_register_filter(struct gendisk *disk)
 {
 	int ret;
 	struct blk_cmd_filter *filter = &disk->queue->cmd_filter;
-	struct kobject *parent = kobject_get(disk->holder_dir->parent);
 
-	if (!parent)
-		return -ENODEV;
-
-	ret = kobject_init_and_add(&filter->kobj, &rcf_ktype, parent,
+	ret = kobject_init_and_add(&filter->kobj, &rcf_ktype,
+				   &disk_to_dev(disk)->kobj,
 				   "%s", "cmd_filter");
-
 	if (ret < 0)
 		return ret;
 
@@ -231,7 +227,6 @@ void blk_unregister_filter(struct gendisk *disk)
 	struct blk_cmd_filter *filter = &disk->queue->cmd_filter;
 
 	kobject_put(&filter->kobj);
-	kobject_put(disk->holder_dir->parent);
 }
 EXPORT_SYMBOL(blk_unregister_filter);
 #endif

fs/block_dev.c

@@ -548,14 +548,6 @@ static struct kobject *bdev_get_kobj(struct block_device *bdev)
 		return kobject_get(&disk_to_dev(bdev->bd_disk)->kobj);
 }
 
-static struct kobject *bdev_get_holder(struct block_device *bdev)
-{
-	if (bdev->bd_contains != bdev)
-		return kobject_get(bdev->bd_part->holder_dir);
-	else
-		return kobject_get(bdev->bd_disk->holder_dir);
-}
-
 static int add_symlink(struct kobject *from, struct kobject *to)
 {
 	if (!from || !to)
@@ -608,7 +600,7 @@ static int bd_holder_grab_dirs(struct block_device *bdev,
 	if (!bo->sdev)
 		goto fail_put_hdev;
 
-	bo->hdir = bdev_get_holder(bdev);
+	bo->hdir = kobject_get(bdev->bd_part->holder_dir);
 	if (!bo->hdir)
 		goto fail_put_sdev;
 

fs/partitions/check.c

@@ -305,16 +305,6 @@ struct device_type part_type = {
 	.release	= part_release,
 };
 
-static inline void disk_sysfs_add_subdirs(struct gendisk *disk)
-{
-	struct kobject *k;
-
-	k = kobject_get(&disk_to_dev(disk)->kobj);
-	disk->holder_dir = kobject_create_and_add("holders", k);
-	disk->slave_dir = kobject_create_and_add("slaves", k);
-	kobject_put(k);
-}
-
 static void delete_partition_rcu_cb(struct rcu_head *head)
 {
 	struct hd_struct *part = container_of(head, struct hd_struct, rcu_head);
@@ -464,7 +454,8 @@ void register_disk(struct gendisk *disk)
 		return;
 	}
 #endif
-	disk_sysfs_add_subdirs(disk);
+	disk->part0.holder_dir = kobject_create_and_add("holders", &ddev->kobj);
+	disk->slave_dir = kobject_create_and_add("slaves", &ddev->kobj);
 
 	/* No minors to use for partitions */
 	if (!disk_partitionable(disk))
@@ -592,7 +583,7 @@ void del_gendisk(struct gendisk *disk)
 	disk_stat_set_all(disk, 0);
 	disk->stamp = 0;
 
-	kobject_put(disk->holder_dir);
+	kobject_put(disk->part0.holder_dir);
 	kobject_put(disk->slave_dir);
 	disk->driverfs_dev = NULL;
 #ifndef CONFIG_SYSFS_DEPRECATED

include/linux/genhd.h

@@ -141,7 +141,6 @@ struct gendisk {
 
 	int flags;
 	struct device *driverfs_dev;  // FIXME: remove
-	struct kobject *holder_dir;
 	struct kobject *slave_dir;
 
 	struct timer_rand_state *random;