hammer2 - Starting refactoring PFS management in mount
* Start removing single-device shims.
* Adjust data structures. Rename hammer2_mount to hammer2_dev and
rename hammer2_pfsmount to hammer2_pfs. Refactor unmount.
* Integrate all available PFSs when a block device is mounted and
De-integrate related PFSs when a block device is unmounted.
At least one PFS (typically @LOCAL) must be mounted from a HAMMER2 block
device for that device's PFSs to be used. At least for now. We could
eventually trigger auto-mounting via the probe code.
* Add a synchronization thread abstraction for a PFS.
* Normalize chain->pmp to NULL for any chain which is part of the super-root
topology, for later sanity assertions.
* The ioctl to create a PFS now adds it (delete and snapshot do not, yet).
14 files changed: