block: add a bdev_kobj helper

Add a little helper to find the kobject for a struct block_device.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Coly Li <colyli@suse.de>		[bcache]
Acked-by: David Sterba <dsterba@suse.com>	[btrfs]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/bcache/super.c

@@ -1447,8 +1447,7 @@ static int register_bdev(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
 		goto err;
 
 	err = "error creating kobject";
-	if (kobject_add(&dc->disk.kobj, &part_to_dev(bdev->bd_part)->kobj,
-			"bcache"))
+	if (kobject_add(&dc->disk.kobj, bdev_kobj(bdev), "bcache"))
 		goto err;
 	if (bch_cache_accounting_add_kobjs(&dc->accounting, &dc->disk.kobj))
 		goto err;
@@ -2342,9 +2341,7 @@ static int register_cache(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
 		goto err;
 	}
 
-	if (kobject_add(&ca->kobj,
-			&part_to_dev(bdev->bd_part)->kobj,
-			"bcache")) {
+	if (kobject_add(&ca->kobj, bdev_kobj(bdev), "bcache")) {
 		err = "error calling kobject_add";
 		ret = -ENOMEM;
 		goto out;

drivers/md/md.c

@@ -2414,7 +2414,6 @@ EXPORT_SYMBOL(md_integrity_add_rdev);
 static int bind_rdev_to_array(struct md_rdev *rdev, struct mddev *mddev)
 {
 	char b[BDEVNAME_SIZE];
-	struct kobject *ko;
 	int err;
 
 	/* prevent duplicates */
@@ -2477,9 +2476,8 @@ static int bind_rdev_to_array(struct md_rdev *rdev, struct mddev *mddev)
 	if ((err = kobject_add(&rdev->kobj, &mddev->kobj, "dev-%s", b)))
 		goto fail;
 
-	ko = &part_to_dev(rdev->bdev->bd_part)->kobj;
 	/* failure here is OK */
-	err = sysfs_create_link(&rdev->kobj, ko, "block");
+	err = sysfs_create_link(&rdev->kobj, bdev_kobj(rdev->bdev), "block");
 	rdev->sysfs_state = sysfs_get_dirent_safe(rdev->kobj.sd, "state");
 	rdev->sysfs_unack_badblocks =
 		sysfs_get_dirent_safe(rdev->kobj.sd, "unacknowledged_bad_blocks");

fs/block_dev.c

@@ -1242,7 +1242,7 @@ int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
 	holder->disk = disk;
 	holder->refcnt = 1;
 
-	ret = add_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
+	ret = add_symlink(disk->slave_dir, bdev_kobj(bdev));
 	if (ret)
 		goto out_free;
 
@@ -1259,7 +1259,7 @@ int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
 	goto out_unlock;
 
 out_del:
-	del_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
+	del_symlink(disk->slave_dir, bdev_kobj(bdev));
 out_free:
 	kfree(holder);
 out_unlock:
@@ -1287,7 +1287,7 @@ void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)
 	holder = bd_find_holder_disk(bdev, disk);
 
 	if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) {
-		del_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
+		del_symlink(disk->slave_dir, bdev_kobj(bdev));
 		del_symlink(bdev->bd_part->holder_dir,
 			    &disk_to_dev(disk)->kobj);
 		kobject_put(bdev->bd_part->holder_dir);

fs/btrfs/sysfs.c

@@ -1232,8 +1232,6 @@ int btrfs_sysfs_add_space_info_type(struct btrfs_fs_info *fs_info,
 
 void btrfs_sysfs_remove_device(struct btrfs_device *device)
 {
-	struct hd_struct *disk;
-	struct kobject *disk_kobj;
 	struct kobject *devices_kobj;
 
 	/*
@@ -1243,11 +1241,8 @@ void btrfs_sysfs_remove_device(struct btrfs_device *device)
 	devices_kobj = device->fs_info->fs_devices->devices_kobj;
 	ASSERT(devices_kobj);
 
-	if (device->bdev) {
-		disk = device->bdev->bd_part;
-		disk_kobj = &part_to_dev(disk)->kobj;
-		sysfs_remove_link(devices_kobj, disk_kobj->name);
-	}
+	if (device->bdev)
+		sysfs_remove_link(devices_kobj, bdev_kobj(device->bdev)->name);
 
 	if (device->devid_kobj.state_initialized) {
 		kobject_del(&device->devid_kobj);
@@ -1353,11 +1348,7 @@ int btrfs_sysfs_add_device(struct btrfs_device *device)
 	nofs_flag = memalloc_nofs_save();
 
 	if (device->bdev) {
-		struct hd_struct *disk;
-		struct kobject *disk_kobj;
-
-		disk = device->bdev->bd_part;
-		disk_kobj = &part_to_dev(disk)->kobj;
+		struct kobject *disk_kobj = bdev_kobj(device->bdev);
 
 		ret = sysfs_create_link(devices_kobj, disk_kobj, disk_kobj->name);
 		if (ret) {

include/linux/blk_types.h

@@ -49,6 +49,9 @@ struct block_device {
 	struct super_block	*bd_fsfreeze_sb;
 } __randomize_layout;
 
+#define bdev_kobj(_bdev) \
+	(&part_to_dev((_bdev)->bd_part)->kobj)
+
 /*
  * Block error status values.  See block/blk-core:blk_errors for the details.
  * Alpha cannot write a byte atomically, so we need to use 32-bit value.