Unlike other drivers, rd.c wants block size to be set once an
forever (for everybody else setting block size as high as possible and
letting filesystems change it with set_blocksize() is OK; rd.c treats
invalidate_buffers() as "kill the ramdisk contents".
if (rd_bdev[unit] == NULL) {
rd_bdev[unit] = bdget(kdev_t_to_nr(inode->i_rdev));
rd_bdev[unit]->bd_openers++;
+ rd_bdev[unit]->bd_block_size = rd_blocksize;
rd_bdev[unit]->bd_inode->i_mapping->a_ops = &ramdisk_aops;
}