HW9
released: 04/14, 9:00
due: 04/20, 23:59

Answer the following questions.
Submit your answers to Canvas assignments. There is an entry for this homework.


CS5600 File System (fs5600)

These questions are intended to reinforce fs5600.


1. Suppose fs5600 has a file "/dir1/dir2/file1".
   When a process read the file's information, namely executing:
   """
     struct stat;
     fs_getattr("/dir1/dir2/file1", &stat)
   """

   Question (3 points): [updated 04/26: was "2 points"]
   How many block reads to disk ("block_read") does fs5600 perform?
   And what are they (what info stored in these blocks)?
   (assume buffer cache is empty, meaning you have to read information from disk)



2. Suppose fs5600 has a file "/file1" and the file has 16KB of contents.
   When a process read 4KB from offset 2KB, namely executing:

   """
   char buf[4096];
   fs_read("/file1", buf, 4096, 2048, NULL);
   """

   Question (3 points): [updated 04/26: was "2 points"]
   How many block reads ("block_read") does fs5600 perform?
   And what are they (what info stored in these blocks)?
   (assume buffer-cache is empty, meaning you have to read information from disk)



3. Suppose a new file system fs5600+ has an inode as follows:

  """
  struct fs_inode2 {
      uint16_t uid;
      uint16_t gid;
      uint32_t mode;
      uint32_t ctime;     /* time of last file status change */
      uint32_t mtime;     /* time of last data modification */
      int32_t  size;
      uint32_t ptrs[1018];
      uint32_t indirect_ptr; /* inode = 4096 bytes */
  };
  """

  And the "indirect_ptr" is the indirect pointer in a Unix inode.
  It points to a block (4KB) that contains pointers (uint32_t) to actual data blocks.

  Questions:

  (a) how many pointers (uint32_t) can one block store? (1 point)


  (b) what is the max number of data block pointers in an fs5600+ inode? (1 point)
     [note: this number includes both pointers in "fs_inode2" 
            and the ones in the indirect block (the block
            that indirect pointer--"indirect_ptr"---points to).]

  (c) what's the maximum file size of an fs5600+ file? (2 points)