Kernel: Fix most of mutex + block race conditions

All block functions now take an optional mutex parameter that is
atomically unlocked instead of having the user unlock it before hand.
This prevents a ton of race conditions everywhere in the code!

kernel/include/kernel/FS/Inode.h

@@ -182,7 +182,7 @@ namespace Kernel
 
 	private:
 		BAN::WeakPtr<SharedFileData> m_shared_region;
-		Mutex m_epoll_mutex;
+		SpinLock m_epoll_lock;
 		BAN::LinkedList<class Epoll*> m_epolls;
 		friend class Epoll;
 		friend class FileBackedRegion;