Re: [PATCH] checkpoint/restart: refuse checkpoint on detached file

["Serge E. Hallyn" <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

Quoting Dave Hansen (dave-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org):
> On Thu, 2008-12-04 at 22:41 -0600, Serge E. Hallyn wrote:
> > 
> > @@ -158,6 +173,12 @@ cr_write_fd_ent(struct cr_ctx *ctx, struct
> > files_struct *files, int fd)
> >                 goto out;
> >         }
> > 
> > +       /* Make sure this isn't under some detached tree */
> > +       if (file_in_detached_tree(file)) {
> > +               ret = -EBADF;
> > +               goto out;
> > +       }
> 
> Looks fine to me.  This is racy, though.  Right?
> 
> There's no locking to keep the thing mounted for the duration of the
> checkpoint.

Oh, hahah, yeah.  We have the file pinned so we're not going to
lose any vfsmnt/dentries, but you're right, someone else could
come along and umount -l in the middle.

I suppose we could hold the namespace sem but it doesn't seem worth
it and could deadlock.

Patch withdrawn for now  :)

-serge