block: remove the bd_block_size field from struct block_device

We can trivially calculate the block size from the inodes i_blkbits
variable.  Use that instead of keeping two redundant copies of the
information in slightly different formats.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/block_dev.c

@@ -105,10 +105,7 @@ EXPORT_SYMBOL(invalidate_bdev);
 
 static void set_init_blocksize(struct block_device *bdev)
 {
-	unsigned bsize = bdev_logical_block_size(bdev);
-
-	bdev->bd_block_size = bsize;
-	bdev->bd_inode->i_blkbits = blksize_bits(bsize);
+	bdev->bd_inode->i_blkbits = blksize_bits(bdev_logical_block_size(bdev));
 }
 
 int set_blocksize(struct block_device *bdev, int size)
@@ -122,9 +119,8 @@ int set_blocksize(struct block_device *bdev, int size)
 		return -EINVAL;
 
 	/* Don't change the size if it is same as current */
-	if (bdev->bd_block_size != size) {
+	if (bdev->bd_inode->i_blkbits != blksize_bits(size)) {
 		sync_blockdev(bdev);
-		bdev->bd_block_size = size;
 		bdev->bd_inode->i_blkbits = blksize_bits(size);
 		kill_bdev(bdev);
 	}
@@ -889,7 +885,6 @@ struct block_device *bdget(dev_t dev)
 		bdev->bd_contains = NULL;
 		bdev->bd_super = NULL;
 		bdev->bd_inode = inode;
-		bdev->bd_block_size = i_blocksize(inode);
 		bdev->bd_part_count = 0;
 		bdev->bd_invalidated = 0;
 		inode->i_mode = S_IFBLK;

include/linux/blk_types.h

@@ -33,7 +33,6 @@ struct block_device {
 	struct list_head	bd_holder_disks;
 #endif
 	struct block_device *	bd_contains;
-	unsigned		bd_block_size;
 	u8			bd_partno;
 	struct hd_struct *	bd_part;
 	/* number of times partitions within this device have been opened. */

include/linux/blkdev.h

@@ -1543,7 +1543,7 @@ static inline unsigned int blksize_bits(unsigned int size)
 
 static inline unsigned int block_size(struct block_device *bdev)
 {
-	return bdev->bd_block_size;
+	return 1 << bdev->bd_inode->i_blkbits;
 }
 
 int kblockd_schedule_work(struct work_struct *work);