-Modify the file system to allow the maximum size of a file to be as
-large as the disk. You can assume that the disk will not be larger
-than 8 MB. In the basic file system, each file is limited to a file
-size of just under 64 kB. Each file has a header called an index node
-or @dfn{inode} (represented by @struct{inode}) that is a table of
-direct pointers to the disk blocks for that file. Since the inode is
-stored in one disk sector, the maximum size of a file is limited by
-the number of pointers that will fit in one disk sector. Increasing
-the limit to 8 MB will require you to implement doubly-indirect
-blocks.
+@item
+Inodes are immutable in the provided file system, that is, their content
+never changes between creation and deletion. Furthermore, only one copy
+of an inode's data is maintained in memory at once, even if the file is
+open in multiple contexts.
+
+@item
+File data doesn't have to be consistent because it's just not part of
+the model. In Unix and many other operating systems, a read of a file
+by one process when the file is being written by another process can
+show inconsistent results: it can show that none, all, or part of the
+write has completed. (However, after the write system call returns to
+its caller, all subsequent readers must see the change.) Similarly,
+when two threads write to the same part of a file at the same time,
+their data may be interleaved. External synchronization of the provided
+file system ensures that reads and writes are fully serialized, but your
+file system doesn't have to maintain full serialization as long as it
+follows the rules above.
+@end itemize
+
+@node Problem 4-1 Indexed Files
+@section Problem 4-1: Indexed Files
+
+The basic file system allocates files as a single extent, making it
+vulnerable to external fragmentation. Eliminate this problem by
+modifying the inode structure. In practice, this probably means using
+an index structure with direct, indirect, and doubly indirect blocks.
+(You are welcome to choose a different scheme as long as you explain the
+rationale for it in your design documentation, and as long as it does
+not suffer from external fragmentation.)
+
+You can assume that the disk will not be larger than 8 MB. You must
+support files as large as the disk (minus metadata). Each inode is
+stored in one disk sector, limiting the number of block pointers that it
+can contain. Supporting 8 MB files will require you to implement
+doubly-indirect blocks.