On Wed, Apr 29, 2020 at 12:26:39PM +0900, js1304@xxxxxxxxx wrote: > From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > > Until now, PageHighMem() is used for two different cases. One is to check > if there is a direct mapping for this page or not. The other is to check > the zone of this page, that is, weather it is the highmem type zone or not. > > Now, we have separate functions, PageHighMem() and PageHighMemZone() for > each cases. Use appropriate one. > > Note that there are some rules to determine the proper macro. > > 1. If PageHighMem() is called for checking if the direct mapping exists > or not, use PageHighMem(). > 2. If PageHighMem() is used to predict the previous gfp_flags for > this page, use PageHighMemZone(). The zone of the page is related to > the gfp_flags. > 3. If purpose of calling PageHighMem() is to count highmem page and > to interact with the system by using this count, use PageHighMemZone(). > This counter is usually used to calculate the available memory for an > kernel allocation and pages on the highmem zone cannot be available > for an kernel allocation. > 4. Otherwise, use PageHighMemZone(). It's safe since it's implementation > is just copy of the previous PageHighMem() implementation and won't > be changed. > > I apply the rule #3 for this patch. > > Acked-by: Roman Gushchin <guro@xxxxxx> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Why do we care about the zone here? This only cares about having kernel direct mapped pages as far as I can tell.
