TODOs in linux code reading
Index (aha)
https://lwn.net/Kernel/Index/
Four short stories about preempt_count()
https://lwn.net/Articles/831678/
An end to high memory?
https://lwn.net/Articles/813201/
(kernel doc) high memory handling https://www.kernel.org/doc/Documentation/vm/highmem.txt
On not getting burned by kmap_atomic()
https://lwn.net/Articles/111226/
The future of the page cache https://lwn.net/Articles/712467/