1. Nachos filesystem 0.01
Kang Zhang( jobo.zh@gmail.com )
2008-12-04

2. Agenda

3. Agenda
• History
• Installation
• Your task
• Implementation details
• Hints

4. History of Nachos
filesystem

5. History of Nachos
filesystem
• Nachos in C++
• Nachos in java( initial version)
• Nachos 5.0j

6. Installation of
phase 5

7. Installation of
phase 5
1) Download the patch from our
site.

8. nachos/
filesys/
Directory.java
Installation of
DirectoryEntry.java
FileHeader.java
RealOpenFile.java
FilesysKernel.java
phase 5
RealFileSystem.java
FilesysProcess.java
RealFileSystemUtil.java
BitMap.java
1) Download the patch from our
machine/
Machine.java
site.
Disk.java
SynchDisk.java
Lib.java
proj5/
nachos.conf
Makefile
test/
hl.coff
hl.c

9. nachos/
filesys/
Directory.java
Installation of
DirectoryEntry.java
FileHeader.java
RealOpenFile.java
FilesysKernel.java
phase 5
RealFileSystem.java
FilesysProcess.java
RealFileSystemUtil.java
BitMap.java
1) Download the patch from our
machine/
Machine.java
site.
Disk.java
SynchDisk.java
2) Merge these code with yours.
Lib.java
proj5/
nachos.conf
Makefile
test/
hl.coff
hl.c

10. Installation of phase 5

11. Installation of phase 5
3) Choose a phase to start with.(e.g. Phase 2)

12. Installation of phase 5
3) Choose a phase to start with.(e.g. Phase 2)
4) Merge proj5/nachos.conf with proj2/nachos.conf.

13. Installation of phase 5
3) Choose a phase to start with.(e.g. Phase 2)
4) Merge proj5/nachos.conf with proj2/nachos.conf.
5) Modify FilesysProcess.java and FilesysKernel.java

14. Installation of phase 5
3) Choose a phase to start with.(e.g. Phase 2)
4) Merge proj5/nachos.conf with proj2/nachos.conf.
5) Modify FilesysProcess.java and FilesysKernel.java
public class FilesysProcess extends UserProcess{

15. Installation of phase 5
3) Choose a phase to start with.(e.g. Phase 2)
4) Merge proj5/nachos.conf with proj2/nachos.conf.
5) Modify FilesysProcess.java and FilesysKernel.java
public class FilesysProcess extends UserProcess{
6) Merge test/ directory with your test/

16. Installation of phase 5
3) Choose a phase to start with.(e.g. Phase 2)
4) Merge proj5/nachos.conf with proj2/nachos.conf.
5) Modify FilesysProcess.java and FilesysKernel.java
public class FilesysProcess extends UserProcess{
6) Merge test/ directory with your test/
7) Run phase5 (win)

17. Installation of phase 5
3) Choose a phase to start with.(e.g. Phase 2)
4) Merge proj5/nachos.conf with proj2/nachos.conf.
5) Modify FilesysProcess.java and FilesysKernel.java
public class FilesysProcess extends UserProcess{
6) Merge test/ directory with your test/
7) Run phase5 (win)
$java nachos.machine.Machine -x hl.coff -[] nachosproj5nachos.conf

18. Installation of phase 5

19. Installation of phase 5
8) Done, it works!
nachos 5.0j initializing... config interrupt timer processor console
user-check
grader
hello worldMachine halting!
Ticks: total 551314, kernel 551000, user 314
Disk I/O: reads 18, writes 0
Console I/O: reads 0, writes 11
Paging: page faults 0, TLB misses 0
Network I/O: received 0, sent 0

20. Installation of phase 5
8) Done, it works!
nachos 5.0j initializing... config interrupt timer processor console
user-check
grader
hello worldMachine halting!
Ticks: total 551314, kernel 551000, user 314
Disk I/O: reads 18, writes 0
Console I/O: reads 0, writes 11
Paging: page faults 0, TLB misses 0
Network I/O: received 0, sent 0

21. Limits

22. Limits
• unsafe for multiple processes
• has limited file size(4k)
• flat directory structure

23. Overview of nachos filesystem

24. Overview of nachos filesystem
Nachos
FileSystem
OpenFile
StubFileSystem JVM Runtime
RealFileSystem
RealOpenFile StubOpenFile
Disk,Directory
SynchDisk ...

25. Overview of disk

26. Overview of disk
Hard Disk Driver
root
freemap filenodes
directory

27. Overview of disk
Hard Disk Driver
root
freemap filenodes
directory

28. Overview of disk
Hard Disk Driver
root
freemap filenodes
directory

29. Overview of disk
Hard Disk Driver
root
freemap filenodes
directory

30. Inside a file

31. Inside a file
Helloworld.coff
File info:
File length, etc.
File pointers:
Sector 1 Sector 2 Sector 3
Sector k
Sector n-2 Sector n-1 Sector n
INode FNode

32. Inside a file
File info:
File length, etc.
File pointers:
Sector 1 Sector 2 Sector 3
Sub
Sector k-1
sectors
Sub Sub Sub
sectors sectors sectors
INode FNode

33. Directory

34. Directory
• Directory
• Contains a list of directory entries
• DirectoryEntry
• Stores basic info about a file

35. File

36. File
• FileHeader
• Contains pointers to actual data on
disk.
• SynchDisk
• For concurrent access.
• RealOpenFile

37. Your task

38. Your task
• Remove restrictions on file size and enable
user to create files as large as the DISK
• Synchronize file access by multiple
processes to remove problems associated
with multiprogramming /
multiprocessing(Optional*)

39. Your task
• Remove restrictions on file size and enable
user to create files as large as the DISK
• Synchronize file access by multiple
processes to remove problems associated
with multiprogramming /
multiprocessing(Optional*)
* : I’ve not designed testcase for it. You need provide testcase by yourself.

40. Your task ...

41. Your task ...
• Allow file size to be modified after creation
• Implement hierarchical directory structure
• Implement some sort of performance
enhancement to your system (Optional)

42. Your task ...
• Design the api (rmdir,ls,mkdir) to prove
your implementation.
• ( You need modify syscall.h and start.s to support them, recompile the
libnachos.a is needed)
• (-1 is reserved by our Nachos test framework, don’t define api using
it)
• (be consistent with Unix style. E.g.Your file system should use / instead
of .)

43. Hints

44. Hints
1. Read the code before you start.

45. Hints
1. Read the code before you start.
2. Some functions need to be moved.

46. Hints
1. Read the code before you start.
2. Some functions need to be moved.
3. Take care of cross complier

47. Hints
1. Read the code before you start.
2. Some functions need to be moved.
3. Take care of cross complier
4. Be patient with the bugs. :-)

48. Questions ?

49. Thank you!