On Thu, May 03, 2018 at 03:04:36PM +0200, Christian Brauner wrote: > >From a userspace perspective we often run into the case where we simply > want to know whether a given mountpoint is MS_SHARED or is MS_SLAVE. > If it is we remount it as MS_PRIVATE to prevent any propagation from > happening. We don't care about the peer relationship or how the > propagation is exactly setup. We only want to prevent any propagation > from happening. So what's to stop you from doing exactly that -- mount(NULL, "/", NULL, MS_PRIVATE | MS_REC, NULL) without bothering with statfs() in the first place? It's not like the damn thing had been costly - it's O(mounts in your namespace) with not to high constant, and in any case cheaper than allocating all of them back when you did clone(2). Confused... > The above case is what I see most often. A more specific use-case is to > differentiate between MS_SLAVE and MS_SHARED mountpoints. > Mountpoints that are MS_SLAVE are kept intact and mountpoints that are > MS_SHARED are made MS_PRIVATE. > > For both cases the only way to do this right now is by parsing > /proc/<pid>/mountinfo. Yes, it is doable but still it is somewhat costly > and annoying as e.g. those mount propagation fields are optional. Umm... And how would you get the list of mountpoints to feed to statfs() if not by parsing mountinfo? IDGI...
