On Wed 19-04-17 14:34:54, Vlastimil Babka wrote: > On 04/19/2017 02:16 PM, Michal Hocko wrote: > > On Wed 19-04-17 13:59:40, Vlastimil Babka wrote: > >> On 04/18/2017 11:27 AM, Michal Hocko wrote: > > [...] > >>> I am not aware of any such user. PageReserved has always been about "the > >>> core mm should touch these pages and modify their state" AFAIR. > >>> But I believe that touching those holes just asks for problems so I > >>> would rather have them covered. > >> > >> OK. I guess it's OK to use PageReserved of first pageblock page to > >> determine if we can trust page_zone(), because the memory offline > >> scenario should have sufficient granularity and not make holes inside > >> pageblock? > > > > Yes memblocks should be section size aligned and that is 128M resp. 2GB > > on large machines. So we are talking about much larger than page block > > granularity here. > > > > Anyway, Joonsoo didn't like the the explicit PageReserved checks so I > > have come with pfn_to_online_page which hides this implementation > > detail. How do you like the following instead? > > Yeah that's OK. The other two patches will be updated as well? yes > Ideally we would later convert this helper to use some special values > for zone/node id (such as -1) instead of PageReserved to indicate an > offline node, as we discussed. I have considered zone_id to be -1 but there is just too much code which uses the id to translate it to the struct zone * directly and that would lead to subtle bugs. On the other hand zone_id == 0 is not optimal but much safer from that POV. I will think about the safest way forward long term but my intention was to have something reasonably good for starter. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
