Implement Page Level Locking

[chotchki]

So I have a fully ready free space map but I can't avoid the locking issue anymore despite it also being the next item on the todo list.

So I started trying to bake in locks and I've hit my normal do I go for a read or write lock approach? I think I may have screwed up the lock manager design, oops too much in silos!

So what I really need in a lock manager is this:

• multi-threaded access
• ability to read page
• ability to write a page without causing collisions

I'm debating do I need to put a check-in / check-out layer on top of file manager.
So I could expose an api for the following:
Read - Easy
ReadForUpdate - This is the hard part
Ideally
Append - Needs to be serialized
//Ignoring Delete/shrink for now

I should treat this as a lesson for not implementing something outside the greater system and realizing I can't integrate it.