On 07/24/2018 01:19 PM, Michal Hocko wrote: >> When creating a crashdump, I definitely need the pages containing memmap >> included in the dump, so I can inspect the struct pages. But this is a >> bit recursive issue, so I'll try making it clearer: >> >> 1) there are kernel pages with data (e.g. slab) that I typically need in >> the dump, and are not PageReserved >> 2) there are struct pages for pages 1) in the memmap that physically >> hold the pageflags for 1), and these are PageReserved >> 3) there are struct pages for pages 2) somewhere else in the memmap, >> physically hold the pageflags for 2). They are probably also >> PageReserved themselves ? and self-referencing. >> >> Excluding PageReserved from dump means there won't be cases 2) and 3) in >> the dump, which at least for case 2) is making such dump almost useless >> in many cases. > > Yes, we cannot simply exclude all PageReserved pages. I was merely > suggesting to rule out new special PageReserved pages that are denoting > offline pages. The same could be applied to HWPoison pages
So how about marking them with some "page type" that we got after Matthew's struct page reorg? I assume the pages we're talking about are in a state that they don't need the mapcount/mapping field or whatever unions with the page type... but I guess some care would be needed to not have false positives when the union field is actually used but happens to look like the new type.
