On Wed, Apr 19, 2017 at 03:02:37PM +0900, Minchan Kim wrote: > On Tue, Apr 18, 2017 at 09:33:07AM +0200, Michal Hocko wrote: > > I do not follow. Why would you need kmap for something that is already > > in the kernel space? > > Because it can work with highmem pages.
That's copy_user_highpage(). If you want to define a new arch API copy_highpage(), feel free to make a case for it ... > > > Another approach is the API does normal thing for non-aligned prefix and > > > tail space and fast thing for aligned space. > > > Otherwise, it would be happy if the API has WARN_ON non-page SIZE aligned > > > address. Why not just use memcpy()? Is copy_page() significantly faster than memcpy() for a PAGE_SIZE amount of data?
