Re: [PATCH 13/19] vfs: Add a mount-notification facility [ver #16]

[Jann Horn]

On Wed, Feb 19, 2020 at 11:40 PM Jann Horn <jannh@xxxxxxxxxx> wrote:
> On Tue, Feb 18, 2020 at 6:07 PM David Howells <dhowells@xxxxxxxxxx> wrote:
[...]
> > +                       watch = NULL;
> > +               }
> > +               up_write(&m->mnt.mnt_sb->s_umount);
> > +       } else {
> > +               ret = -EBADSLT;
> > +               if (m->mnt_watchers) {
> > +                       down_write(&m->mnt.mnt_sb->s_umount);
> > +                       ret = remove_watch_from_object(m->mnt_watchers, wqueue,
> > +                                                      (unsigned long)path.dentry,
> > +                                                      false);
>
> What exactly is the implication of only using the dentry as key here
> (and not the mount)? Does this mean that if you watch install watches
> on two bind mounts of the same underlying filesystem, the notification
> mechanism gets confused?

Ah, nevermind, I understand this one now... this operation only
removes watches on this mount with that dentry, and so together, that
means it effectively removes watches by the full path.