On Wed, Sep 06, 2023 at 05:03:34PM +0200, Mikulas Patocka wrote: > > IOW, you'd also hang on any umount of a bind-mount. IOW, every > > single container making use of this filesystems via bind-mounts would > > hang on umount and shutdown. > > bind-mount doesn't modify "s->s_writers.frozen", so the patch does nothing > in this case. I tried unmounting bind-mounts and there was no deadlock. You are making *any* mount destruction hang if the sucker is frozen. Which includes the things like exit(2) of the last process within a namespace, etc. And it does include the things like mount --bind /usr/bin/gcc /tmp/cc; umount /tmp/cc if /usr happened to be frozen at the moment. This is really not an option. > BTW. what do you think that unmount of a frozen filesystem should properly > do? Fail with -EBUSY? Or, unfreeze the filesystem and unmount it? Or > something else? It's not just umount(2). It's exit(2). And close(2). And AF_UNIX garbage collector taking out an undeliverable SCM_RIGHTS datagram that happens to contain a reference to the last opened file on lazy-umounted fs, etc.
