* while their top-lock is in CLS_HELD or CLS_CACHED states.
*
* - IO's are not reference counted.
*
* To implement a connection between top and sub entities, lov layer is split
* into two pieces: lov ("upper half"), and lovsub ("bottom half"), both
* while their top-lock is in CLS_HELD or CLS_CACHED states.
*
* - IO's are not reference counted.
*
* To implement a connection between top and sub entities, lov layer is split
* into two pieces: lov ("upper half"), and lovsub ("bottom half"), both