6 824 Spring 2006 6 824 Lab 3 Reading Writing and Sharing Files Due Lecture 7 Introduction In this lab you ll continue implementing the Frangipani like file server you started in Lab 2 You ll start with the code you wrote for Lab 2 and add support for reading and writing file contents You ll have to choose a representation with which to store file contents in the block server and implement the SETATTR WRITE and READ RPCs Continuing with the CCFS Server There are no new source files needed for this lab you will continue to implement functionality in your existing server There is a new tester which tests for reading and writing data correctly Download the lab tester files from http pdos csail mit edu 6 824 2006 labs lab 3 tgz to your home directory on one of the class machines pain wget nc http pdos csail mit edu 6 824 2006 labs lab 3 tgz pain tar xzvf lab 3 tgz Then copy the source files from your Lab 2 to the Lab 3 directory For example pain rsync av lab 2 lab 3 Lab 3 builds upon Lab 2 so make sure you pass the Lab 2 tester before proceeding When you re done with Lab 3 you should be able to read and write files in your file system For example start up the block server on one of the class machines frustration cd lab 3 frustration blockdbd 3772 Then start up the file server on another pain ccfs dir frustration 3772 root file handle 2d1b68f779135270 pain cd classfs dir pain echo hello a pain ls lt total 0 rw r r 0 root wheel 6 Feb 16 13 52 a pain cat a hello Cite as Robert Morris course materials for 6 824 Distributed Computer Systems Engineering Spring 2006 MIT OpenCourseWare http ocw mit edu Massachusetts Institute of Technology Downloaded on DD Month YYYY pain If you try the above commands on your Lab 2 file server you will get an error Your Lab 3 file server must support sharing the file system on other hosts via the block server So when you re done with Lab 3 you should be able to do this on a third machine e g anguish anguish ccfs dir frustration 3772 2d1b68f779135270 1 6608 root file handle 2d1b68f779135270 anguish cd classfs dir anguish ls lt total 0 rw r r 0 root wheel 6 Feb 16 13 52 a anguish cat a hello anguish Replace the fourth argument to ccfs with the root file handle that ccfs printed out on pain Your Job Your job is to implement SETATTR WRITE and READ NFS RPCs in fs C You must store the file system s contents in the block server so that you can share one file system among multiple servers For writes you should ignore the stable argument and always write the file to stable storage the block server You should wait for the put of the file s contents and attributes to complete before sending a reply to the client This behavior is equivalent to performing writes with the a stable argument set to FILE SYNC If your server passes the tester see below then you are done If you have questions about whether you have to implement specific pieces of NFS server functionality then you should be guided by the tester if you can pass the tests without implementing something then don t bother implementing it Please don t modify the block server or its client interface blockdbc C and blockdbc h since we may test your file server against our own copy of the block server Testing You should test your file server using the test lab 3 pl script The script tests reading writing and appending to files as well as testing whether files written on one server can be read through a second server To run the tester first start a block server frustration lab 3 blockdbd 3883 Then start two instances of ccfs with the same root file handle on the same machine anguish ccfs dir1 frustration 3883 1 72422 root file handle 2a868a18dad0f84e anguish ccfs dir2 frustration 3883 2a868a18dad0f84e Cite as Robert Morris course materials for 6 824 Distributed Computer Systems Engineering Spring 2006 MIT OpenCourseWare http ocw mit edu Massachusetts Institute of Technology Downloaded on DD Month YYYY 3 72595 root file handle 2a868a18dad0f84e anguish The directory argument for each instance is different but you should pass the root file handle printed by the first ccfs as an argument to the second ccfs Now you can use test lab 3 pl to test your file system by passing the two root directories that you just created anguish test lab 3 pl classfs dir1 classfs dir2 Write and read one file OK Write and read a second file OK Overwrite an existing file OK Append to an existing file OK Write into the middle of an existing file OK Check that one cannot open non existant file OK Check directory listing OK Read files via second server OK Check directory listing on second server OK Passed all tests If test lab 3 pl exits without printing Passed all tests then it thinks something is wrong with your file server You should re start ccfs before you run the tester If you run the tester more than once without re starting ccfs the tester is likely to see stale information cached by the NFS client for the second file system You don t need to solve this problem for Lab 3 but if you re interested the solution is to implement mtime and ctime for files and directories Hints You should continue to consult the NFS v3 specification for details on how NFS should operate You may also want to consult the book NFS Illustrated by Brent Callaghan SETATTR Here s how to extract the argument for the SETATTR RPC setattr3args a nc Xtmpl getarg setattr3args nfs fh3 a object the file handle that the client wants to set attributes sattr3 a new attributes the new attrbutes sattrguard3 a guard ignore this argument Here s an example of how to set the size and mtime attributes atime is similar to mtime fattr3 attr if a new attributes size set attr size a new attributes size val if a new attributes mtime set SET TO CLIENT TIME attr mtime a new attributes mtime time Here s how to generate a reply for the SETATTR RPC wccstat3 res nc Xtmpl getres wccstat3 Cite as Robert Morris course materials for 6 824 Distributed Computer Systems Engineering Spring 2006 MIT OpenCourseWare http ocw mit edu Massachusetts Institute of Technology Downloaded on DD Month YYYY res set status NFS3 OK res wcc make wcc old attr new attr nc reply nc getvoidres WRITE Here s how to extract the argument for the WRITE RPC write3args a nc Xtmpl getarg write3args nfs fh3 a file the file handle where the client wants to write uint64 a offset the offset to start the write uint32 a count the length of data to write stable how a stable ignore opaque a data handle for the data The last …