[linux-cifs-client] [PATCH 0/3] cifs: some random patches for 2.6.31

[Jeff Layton]

On Mon, 25 May 2009 12:42:42 -0400
simo <idra at samba.org> wrote:

> On Mon, 2009-05-25 at 06:14 -0400, Jeff Layton wrote:
> > On Sun, 24 May 2009 21:05:42 -0400
> > simo <idra at samba.org> wrote:
> > 
> > > Also on the mandatory issue, I wonder if applications
> > > ever check it in the real world. If not, then either way is fine,
> > > otherwise having the bit set would give precious hints.
> > > (Although I prefer the patch as it is rather than leaving permission as
> > > open as they are now).
> > >
> > 
> > I doubt applications ever look at this. If they do, then they also need
> > to pay attention to the "mand" mount option and I'm pretty sure that
> > checking that wouldn't be portable anyway. This change is really about
> > whether we want the kernel's VFS layer to enforce mandatory locking on
> > these files.
> 
> Yes if apps never look at it (as I believe too) then it is probably just
> useless to set the locking as mandatory, although in that case shouldn't
> we prevent sending advisory locks to the server if unix extensions are
> not negotiated ? (do we already do that?)
> 

Currently, we actually attempt to map posix advisory locks to windows
mandatory locks. There are obvious semantic differences here, so this
mapping is not perfect, but I think we do as well as be expected given
the differences. We could consider disabling this mapping somehow, but
in most cases people probably do want some sort of lock set on the
server when they set an advisory lock.

This is a pretty complex topic, but I think with this change we'll have
a sane set of default behaviors relating to the mode (well, as sane as
we can expect given the issues with Windows<->Linux semantics).

-- 
Jeff Layton <jlayton at redhat.com>