Re: [PATCH] don't invalidate non-directory mountpoints

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

On Fri, Oct 07, 2005 at 04:35:53PM +0200, Miklos Szeredi wrote:
> > > d_invalidate allowed a non-directory mountpoint to be invalidated,
> > > which is bad, since the mountpoint becomes unreachable.
> > > 
> > > I know it's racy wrt attaching/detaching mount, but AFAICS so is
> > > everything else that unhashes the dentry.  This seems to be an
> > > oversight when splitting out vfsmount_lock from dcache_lock.  To be
> > > fixed.
> > 
> > NAK.  That's a wrong way to deal with the problem and it's much older
> > than vfsmount_lock or dcache_lock (and affects directories too).
> 
> Sorry?
> 
> Directories are not invalidated if they have any other reference (like
> a mount, or any subdirectories which may have mounts).
> 
> So how does it affect directories?

The underlying problem is still there - parts of mount tree _can_ go
unreachable when remote object dies; trying to pin them down is hopeless
and the only sane way to deal with that is to dissolve the subtrees
of mount when that happens.