[linux-cifs-client] Re: mount options for selectively disabling parts of CIFS Unix Extensions

[Trond Myklebust]

On Tue, 2007-07-17 at 17:09 -0500, Steve French wrote:
> This is an interesting question for cifs in a few ways as well.  CIFS
> servers such as Samba can have different clients connected, some with
> "windows semantics" and some with "posix semantics" - even for handle
> based operations these semamtics differ for whether reads and/or
> writes on a locked range can fail.   If \\server\shareA is mounted
> twice from the same client with different mount options (in particular
> the new "nounix" mount option that I have been coding today, which
> disables support for the CIFS Unix Extensions), for reads or writes
> from the pagecache it could matter which handle is used - for that
> reason, they may have to be treated as distinct inodes or we may have
> to forbid a second mount to the same share from the same client unless
> a few key mount options ("forcedirectio" and "nounix" e.g.) are the
> same on each

Uncached i/o still doesn't help you avoid the kernel's use of cached
data. Anything from the references to inode->i_size that litter the
pagecache code to all the dcache references can be a real pain in these
situations.

Cheers
  Trond