fs.h: remove 8 bytes of padding from block_device on 64bit builds

Re-ordering struct block_inode to remove 8 bytes of padding on 64 bit
builds, which also shrinks bdev_inode by 8 bytes (776 -> 768) allowing it
to fit into one fewer cache lines.

Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/fs.h

@@ -662,9 +662,9 @@ struct address_space {
 
 struct block_device {
 	dev_t			bd_dev;  /* not a kdev_t - it's a search key */
+	int			bd_openers;
 	struct inode *		bd_inode;	/* will die */
 	struct super_block *	bd_super;
-	int			bd_openers;
 	struct mutex		bd_mutex;	/* open/close mutex */
 	struct list_head	bd_inodes;
 	void *			bd_claiming;