CEG 4350/6350: Operating Systems P1: Links and Medium Size Files This is Part 1 of the project for this term

CEG 4350/6350: Operating Systems

P1: Links and Medium Size Files

This is Part 1 of the project for this term.  Our goals in this part of the project is  to (i) add the ability to store and retrieve medium  files, and (ii) to add hard and soft links in a file volume built on the simulated disk of P0. Large files are not necessary in this part.  This part deals with only one file volume at a time.  No mounting is involved.

You are expected to build on your own work of P0.   Do not use source code files of others or even those of mine but from prior terms.  The Project Expectations are all still applicable.

Be Considerate. Do make sure that you are not using up too much space (say > 10 MB) in your home directory.  The following will show your disk space usage:  du -s ~

1. Hard and Soft Links

From the lectures, you should know the definitions of hard and soft links. Resolve any missing detail in the semantics of links so that it matches with that in Unix. (E.g., if you cd via a soft-link to directory D, where should you be after a cd .. ?)

1. The i-nodes now need to have a link count field.
2. The i-node types are now: ordinary-file, directory, soft-link.

DO's and DONT's:

1. Do not permit hard links to directories.
2. Do permit soft links to directories.

2. Medium Size Files

We define medium  files as those using an i-node's (i) direct block number entries, and (ii) requiring single-indirect blocks.

Large files are those using an i-node's (i) direct block number entries, and (ii) requiring single-indirect blocks, and (iii) requiring double-indirect blocks  For bonus points, implement large files also.

3. A Simple Test Session

Implement the commands described below. All the commands of the project so far should be working as they did before, but now also should work for links and medium files;  so only the additional elements are described below.    In your testscript, demonstrate each new command and that the old commands work with links and medium files. Note that the addition of medium files does not bring in any "new" commands.

fs33% mkfs disknm

creates an initially empty file volume, as before, on the simulated disk named disknm.dsk.  Note that the i-node height now includes not only the fileSize field, but also the link count.

fs33% ln opnm npnm

creates npnm  as a new hard link to  opnm, and prints its i-node number.  It creates nothing new and returns 0 in the following "abnormal" cases: a) opnm is a directory; b) no ordinary file with opnm as its path name exists; c)  npnm already exists; d) npnm is an invalid pathname.

fs33% ln opnm .

creates a hard link named the same as the leaf name of opnm in the current directory and prints its i-node number.  Abnormal cases similar to the above apply.  For bonus points, add the flexibility that this command may omit the dot.

fs33% ln -s opnm npnm

creates npnm as a soft link to opnm, and prints its i-node number.  It creates nothing new and returns 0 in the following "abnormal" cases: a) opnm does not exist; b) npnm already exists; c) npnm is an invalid pathname.

fs33% rm pnm

removes the pathname pnm, which may or may be a link, and prints the resulting link count.

4. Turn In

All projects need to be submitted via Pilot.