SVR4 vs BSD (was AIX (is it unix)?)

[Chris Torek]

(`>>' comments are mine)

In article <2499 at auspex.auspex.com> guy at 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 at mimsy.umd.edu	Path:	uunet!mimsy!chris