Description

THE ASSIGNMENT MUST BE IN UBUNTU 19.10

The LionCloud Filesystem (lcloud)

You are to write the driver that will implement the the basic UNIX file interface using the memory system. You will write code to implement the filesystem, and make several design decisions that will determine the structure and performance of the driver. In essence you will write code for the read, write, open, close and other high level filesystem functions. Each function will translate the call into low-level operations on the device (see below).

The functions you will implement for this assignment are:

• LcFHandle lcopen( const char *path ); - This function will open a file (named path, e.g.,) in the filesystem. If the file does not exist, it should be created and set to zero length. If it does exist, it should be opened and its read/write postion should be set to the first byte (position 0). Note that there are no subdirectories in the filesystem, just files (so you can treat the path as a unique filename). The function should return a unique file handle used for subsequent operations or -1 if a failure occurs.
• int lcclose( LcFHandle fh ); - This function closes the file referenced by the file handle that was previously open. The function should fail (and return -1) if the file handle is bad or the file was not previously open.
• int lcread( LcFHandle fh, char *buf, size_t len ); - This function should read count bytes from the file referenced by the file handle at the current position. Note that if there are not enough bytes left in the file, the function should read to the end of the file and return the number of bytes read. If there are enough bytes to fulfill the read, the function should return count. The function should fail (and return -1) if the file handle is bad or the file was not previously open.
• int lcwrite( LcFHandle fh, char *buf, size_t len ); - The function should write count bytes into the file referenced by the file handle. If the write goes beyond the end of the file the size should be increased. The function should always return the number of bytes written, e.g., count. The function should fail (and return -1) if the file handle is bad or the file was not previously open.
• int lcseek( LcFHandle fh, size_t off ); - The function should set the current position into the file to loc, where 0 is the first byte in the file (loc is an absolute position from the front of the file). The function should fail (and return -1) if the loc is beyond the end of the file, the file handle is bad or the file was not previously open.
• int lcshutdown( void ); - The function should shut down the system, including powering off the devices and closing all files.

  The key to this assignment if figuring out what you need to do to implement these functions. You are specifically not given guidance on how to do it. You need to (a) maintain information about current files in the file system, (b) allocate parts if the memory system to place data, (c) copy data into and out of the devices needed to serve reads and writes. How you do this is up to you, but think carefull about it before beginning to code. What is important is that the code you write will be built upon the whole semester.

  The Lion Cloud Device Cluster (LionCloud)

  You will implement your driver on top of the Lion Cloud device cluster, which is a collection of virtual storage devices that communicate over a kind of virtual bus/network connection. You will begin by powering on the bus, probing to find out how many devices are available (there are a maximum of 16), then allocating space on the devices as the application creates and writes file data to the devices. Each device is uniquely identified by is device Id (whose type is LcDeviceId) which is discovered during the probe process. Each device has a two-level addressing scheme, where it has a number of sectors (s) containing blocks (b); therefore each device has s*b total blocks. A block is a region of memory of LC_DEVICE_BLOCK_SIZE bytes, as declared in the (see lcloud_controller.h header file.

  

   

• You communicate with the devices system by sending requests and receiving responses through a set of packed registers. These registers are set within a 64-bit value to encode the opcode and arguments to the hardware device. The opcode is laid out as follows:

  Bits   Register
  ------ --------------------------------------------------
     0-3 B0 - first 4 bit register
     4-7 B1 - second 4 bit register
    8-15 C0 - first 8 bit register
   16-23 C1 - second 8 bit register
   24-31 C2 - third 8 bit register
   32-47 D0 - first 16 bit register
   48-63 D1 - second 16 bit register
  

  To execute an opcode, create a 64 bit value (LCloudRegisterFrame) and pass it any needed buffers to the bus function defined in cart_controller.h:

  LCloudRegisterFrame lcloud_io_bus( LCloudRegisterFrame frm, void *xfer );

  All messages use the following registers:

  Register	Request Value	Response Value
  b0	0 when message sent to devices	1 when message sent from devices
  b1	0 when sending to devices	1 is acknowledge/success from device, any other value represents failure code from device
  c0	always the operation code (see LcOperationCode type in lcloud_controller.h)	The same code as sent.

  The operation code (LcOperationCode) indicates what operation is being requested (when sending) or completed (when receiving from the device). The following operations are available:

  Operation	Description	Remaining register use
  LC_POWER_ON	Initialize interface to the device cluster	All other registers (c1, c2, d0, d1) should be 0 on both send and receive
  LC_DEVPROBE	Probe the bus to see what devices are	All other registers should be 0 on both send. On receive, d0 contains a bit mask of present devices, where device there are a possible 16 devices, where the bit 2^x=1 indicates that device ID x is present. For example if the 2^4 (16) is present, then you know a device with ID 4 is on the bus.
  LC_BLOCK_XFER	Transfer a block to the device	c1 - the device ID for the device to read from c2 - LC_XFER_WRITE for write, LC_XFER_READ for read d0 - sector to read/write from d1 - block to read/write from
  LC_POWER_OFF	Power off the device	All other registers should be 0 on both send and receive