Re: [PATCH] autofs4 - use lookup access intent to support recursive bind mounts

[Al Viro <viro@ZenIV.linux.org.uk>]

On Mon, Apr 28, 2008 at 02:38:25PM +0800, Ian Kent wrote:
> 
> On Mon, 2008-04-28 at 07:22 +0100, Al Viro wrote:
> > On Mon, Apr 28, 2008 at 02:14:54PM +0800, Ian Kent wrote:
> > > 
> > > Hi Andrew,
> > > 
> > > For autofs maps that recursively reference other map entries in their
> > > mount point path we need to ensure that these mounts are performed
> > > prior to the current mount request being done. We've used the access
> > > system call, made just prior to performing the mount, to make this
> > > happen. In the case of bind mounts, however, the lookup flags in 
> > > the path walk don't trigger a mount. To do this we need to also
> > > trigger a mount when we see the LOOKUP_ACCESS flag.
> > 
> > That's too fscking bad, since ->lookup() is about to lose access to
> > nameidata *and* flags for anything but the last step.  IOW, we'll need
> > cleaner solution...
> 
> Spell it out for me please!

->lookup() and friends are going to stop getting struct nameidata *.
->follow_link() obviously will keep it; ->d_revalidate() should
lose the sucker, but we might have to split it in two methods (which
is probably what'll be needed in your case).

At the same time struct open_intent is going to die, BTW, but that
won't matter for autofs, AFAICT.