Re: [PATCH 03/34] VFS: Add CL_NO_SLAVE flag to clone_mnt()/copy_tree()

[Valerie Aurora]

On Sun, Sep 26, 2010 at 10:42:05PM -0700, Ram Pai wrote:
> On Mon, Sep 20, 2010 at 08:03:44PM -0400, Valerie Aurora wrote:
> > On Sun, Sep 19, 2010 at 10:25:53PM -0700, Ram Pai wrote:
> > > 
> > > I understand your intentions, but I think you are making a wrong assumption.
> > > You seem to be thinking that if a slave-mount is cloned, the new cloned
> > > mount will also be a slave-mount and will hence receive propagations. As
> > > per shared subtree semantics, a slave-mount when cloned will create a private
> > > mount. Since your intention is to avoid generating any new mounts that 
> > > recieve propagations, you should be checking for shared-mounts and 
> > > slave-shared-mounts because these are the two kind of mounts that when
> > > cloned create new mounts that receive propagation.
> > 
> > No.  This isn't about the semantics of the clone mount operation.  It
> > is about the administrator creating a slave mount, unioning it, and
> > then being surprised when the unioned file system does not receive
> > mount propagation events.
> > 
> > Think of the source vfsmount tree as a set of command line arguments
> > for the union mount.
> 
> Ok. In that case,  you introduced a subtle change in the semantics of clone_mnt().
> As I understand it, the flags parameter of clone_mnt() are meant to be a modifier 
> for the cloned mount, not a filter on the source mount.

Yes, that's it exactly.

Do you have a suggestion for writing this a different way?  We can
move it all into copy_tree() and leave clone_mnt() alone, at the cost
of a little code duplication and some acrobatics around possible
loopback support.

-VAL
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