R. Clayton (rclayton@monmouth.edu)
Tue, 5 Dec 2000 11:43:44 -0500 (EST)
For project 4, do we have to support both disk device and file system calls,
or do we scrap the device-oriented approach and use only a file system
approach?
I implemented the file system on top of everything else, so you can do that.
I don't know if it's worth the trouble to disable direct disk io, although I
can see why that would be desirable.
Because the user programs on the batch disks do either direct disk io or file
io, but not both at the same time, I'm thinking both uses of the free disk can
co-exist without problems. However, it isn't too hard to imagine situations
where that wouldn't be the case. For example, the file system could use linked
lists to keep track of free sectors, and the pa2 disk would trash the links.
If the file system checked the integrity of the free list during file-system
shutdown, it would fail for the pa2 batch disks.
If you're really worried about that sort of thing, you can assume the disk is
three sectors shorter than it actually is. The pa2 disks use the last three
sectors on the disk, and by skipping them the file system would then truly have
control over all the free sectors.
So: I would prefer if you provided both direct and file-system io, but if you
find it absolutely impossible to do, you should concentrate on file-system io.
This archive was generated by hypermail 2.0b3 on Mon Dec 18 2000 - 13:30:06 EST