Information processing device including host device and semiconductor memory device having a block rearrangement to secure free blocks

A device includes a host including a main memory, and semiconductor memory including a nonvolatile semiconductor memory, memory unit, and controller. The nonvolatile semiconductor memory stores first address information. The memory unit stores second address information as part of the first address information. The controller accesses the nonvolatile semiconductor memory based on the second address information. Third address information is stored in the main memory, and is part or all of the first address information. The controller uses the third address information when accessing the nonvolatile semiconductor memory if address information to be referred is not stored in the second address information.