kernel support for open share modes

[J. Bruce Fields]

On Tue, Feb 15, 2005 at 06:31:10PM -0500, Michael B Allen wrote:
> Well I don't believe I said that exactly. What I said was that POSIX isn't
> sophisticated enough to properly implement a userspace network filesystem.
> 
> Specifically, when using only the POSIX APIs, there is a race condition
> between examining ACLs, share modes, or other file meta data, and acting
> on that information such as opening or deleting the target file.

I can make sense of that statement only if I read "network filesystem"
to mean "network filesystem that implements Windows ACLs and share
locks."  None of this is a problem for, e.g., a userspace NFSv3
server--as it uses POSIX ACLs and locks, it can rely on the kernel to do
all the necessary checks atomically for it.

--Bruce Fields