> > Right. After locking vfsmount_lock, mount_dironfile() should recheck
If the cost of ->enter() is low, then it shouln't really be a problem.
We can't use ->i_mutex for locking, and introducing a new lock for
this doesn't sound right either.
When the real superblock is created. It could even be the _same_
super block as the real one. There'd be just the problem of anchoring
the dir-on-file dentries somewhere...
Or with fuse the dir-on-file mount can just come from any mounted
filesystem, again possibly the same one as the parent. I do actually
test with this. The userspace filesystem supplies a file descriptor,
from which the struct path is extracted and returned from ->enter().