On Tue, Apr 18, 2023 at 07:34:14AM +1000, NeilBrown wrote: > On Tue, 18 Apr 2023, Jeff Layton wrote: > > > > The last thing we want in that case is for the server to decide to > > change some intermediate dentry in between the two operations. Best > > case, you'll get back ENOENT or something when the pathwalk fails. Worst > > case, the server swaps what are two different mountpoints on your client > > and you unmount the wrong one. > > Actually, the last think I want is for the server to do something that > causes a directory to be invalidated (d_invalidate()). Then any mount > points below there get DETACHed and we lose any change to use MNT_FORCE > or to wait for the unmount to complete. Of course this can also happen > during any other access, not just umount.... Any rmdir/unlink from another mount namespace where the mountpoint isn't a local mountpoint would lazily unmount the whole mount tree. You can't guard against this anyway.
