nopfn Feb 22, 2008

http://lwn.net/Articles/242625/


populate, nopage, nopfn이 fault 메소드로 통합된지 오래다.
사실 예전부터 nopfn을 언제 써야하는지 궁금했었다. 좋은 기사에 정확한 설명이 있어 덧붙인다.

http://lwn.net/Articles/200213/

Meanwhile, one of the longstanding limitations of nopage() is that it can only handle situations where the relevant physical memory has a corresponding struct page. Those structures exist for main memory, but they do not exist when the memory is, for example, on a peripheral device and mapped into a PCI I/O memory region. Some architectures also do very strange things with special memory and multiple views of the same memory. In such cases, drivers must explicitly map the memory into user space with remap_pfn_range() instead of using nopage().