Improve mount performance #12
Description
SquirrelFS currently takes longer to mount than other PM file systems; we should add optimizations to improve this.
Possible optimizations:
- Perform system scan/index rebuild in parallel.
- Serialize indexes/allocators and store them durably during clean unmount so they do not have to be fully reconstructed. We probably want to use a checksum/crash bit to ensure that the serialized structures are consistent and correct before using them.
- This won't work in the event of a crash; we'll still need to do the full disk scan then.
- Reduce the size/complexity of in-memory data structures to reduce the amount of time it takes to set them up at mount.