> 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)
> 

  [Answer:
    7
    read root inode
    read root data
    read dir1 indoe
    read dir1 data
    read dir2 indoe
    read dir2 data
    read file1 inode

    note: no need to read bitmap or file1's data because this is "fs_getatt"
    which only reads (so no need to touch bitmap) and only reads file metadata
    (so no need to touch file data blocks).
  ]

> 
> 
> 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)
> 
> 

  [ Answer:
    5
    read root inode
    read root data
    read file1 inode
    read file1 data[0]
    read file1 data[1]
  ]


> 
> 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)
> 

  [ Answer:

    (a) 4096 / 4 = 1024

    (b) (1024+1018)

    (c) (1024+1018) * 4KB
  ]