Make sure you understand construct the relationships between ip-> addrs[], the indirect block, the doubly-indirect block and the singly-indirect blocks it points to, and data blocks. make sure you understand why adding a doubly-indirect block increases the maximum file size by 16,384 blocks (really 16383, since you have to decrease the number of direct blocks by one). think about how you'll index the doubly-indirect block, and the indirect blocks it points to, with the logical block number. if you change the definition of ndirect, you'll probably have to change the size of addrs[] in struct inode in file. h. make sure that struct inode and struct dinode have the same number of elements in their addrs[] arrays.