Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!tank!mimsy!chris From: chris@mimsy.UUCP (Chris Torek) Newsgroups: comp.unix.questions Subject: Re: SVR4 vs BSD (was AIX (is it unix)?) Message-ID: <19802@mimsy.UUCP> Date: 26 Sep 89 12:08:46 GMT References: <1702@naucse.UUCP><2499@auspex.auspex.com> Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742 Lines: 48 (`>>' comments are mine) In article <2499@auspex.auspex.com> guy@auspex.auspex.com (Guy Harris) writes: >Uh, what is RFS here? As of when I last had anything to do with S5R4, >AT&T's RFS was to be implemented in S5R4 basically as a file system type under >the S5R4 VFS mechanism. Oh. This I do not really understand, since the RFS mechanisms are pretty much equivalent to the VFS mechanisms, except that instead of vnode->vn_op(vnode, arg1, arg2) one writes (*fsswitch[inode.fstype])(inode, arg1, arg2) I.e., other than the vnode/inode/gnode/foonode differences found between all the different `virtual remote generic network filesystem interface definition specification ...' er, well, whatever, systems. I had supposed that VR4 was going to stick with RFS-style mechanisms. >>(modulo SunOS's ridiculous insistence that the local file system be >>stateless). >To what are you referring here? Things that got cleaned up since the code I looked at, perhaps? The VFS UFS code I saw (whenever it was that I was looking at it) did not bother locking parent directories in vfs_lookup, so that when it came time to write new entries, the state may have changed, etc. I.e., one could have a sequence where an `O_CREAT|O_EXCL' open could write over an existing file. >>Of course, the VM system is based upon a design done at >>Berkeley, and modified a bit at Sun. >Are you saying that the SunOS 4.0 VM design was done at Berkeley, and >just "modified a bit" at Sun? Well, actually, there was a fair bit of interaction (and not just from Sun), but the basic design (mmap+mummap, protection, mapped files) comes almost straight from 4.2BSD (where it came almost straight from Multics). There are areas where Sun and Berkeley might not agree (e.g., mmap for semaphored memory), but the user/system interface will at least be very similar. (The implementations are likely to be quite different.) -- In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163) Domain: chris@mimsy.umd.edu Path: uunet!mimsy!chris