On 31.03.22 10:53, Christoph Hellwig wrote:

...

• page = vm_normal_page(vma, addr, pte);

• page = vm_normal_lru_page(vma, addr, pte);

Why can't this deal with ZONE_DEVICE pages? It certainly has nothing do with a LRU I think. In fact being able to have stats that count say the number of device pages here would probably be useful at some point.

In general I find the vm_normal_lru_page vs vm_normal_page API highly confusing. An explicit check for zone device pages in the dozen or so spots that care has a much better documentation value, especially if accompanied by comments where it isn't entirely obvious.

What's your thought on FOLL_LRU?