block: move .bd_inode into 1st cacheline of block_device

The .bd_inode field of block_device is used in IO fast path of
blkdev_write_iter() and blkdev_llseek(), so it is more efficient to keep
it into the 1st cacheline.

.bd_openers is only touched in open()/close(), and .bd_size_lock is only
for updating bdev capacity, which is in slow path too.

So swap .bd_inode layout with .bd_openers & .bd_size_lock to move
.bd_inode into the 1st cache line.

Cc: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20231128123027.971610-2-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Ming Lei

include/linux/blk_types.h

@@ -49,9 +49,10 @@ struct block_device {
 	bool			bd_write_holder;
 	bool			bd_has_submit_bio;
 	dev_t			bd_dev;
+	struct inode		*bd_inode;	/* will die */
+
 	atomic_t		bd_openers;
 	spinlock_t		bd_size_lock; /* for bd_inode->i_size updates */
-	struct inode *		bd_inode;	/* will die */
 	void *			bd_claiming;
 	void *			bd_holder;
 	const struct blk_holder_ops *bd_holder_ops;