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 iy4Xcmvq Hv67enByXYR9CDsztRDsGze/IJluFl3vDINAlLYECwKh2woADYeyiP+Kjs8xFcMf/ioNvu2aGjmrmkgbtJjSxkdn2W+wB3r9MRHodTPua1wuHzhP10VJfgS5JTK4wnDlPIkIk4y7TswkfiC8ZhW7FGaxAZ16ehxzXHxVLIfSI/rFk+5aj3S6LonlX4t315y3EPN5k6G4fJE1RhkBfRzyHjMFsiE4bzK1hmDStwN71PtzLUF1u7ERflxM0yKglCk4RA6NgOOn1muPF600++/G6SM82zi23I1ag7+yK1+B2n4xIrsk7WijiOEotAStjnXpbaeBU6B5TvjgXt/4W+S438G6ScqdkMUbYbSKpsm8cLBpq/LdyWF96KZae23Ss/AQFgykK24g+g3oOkwKXN/jYtTgrvIC3J/WNvWXzPPkkM8onm2ym19Yr61AvdE4Hl5GwkYDFka+xfh+tczU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4 Feb 2026, at 15:31, David Hildenbrand (arm) wrote: > On 2/4/26 21:13, Zi Yan wrote: >> On 4 Feb 2026, at 14:55, David Hildenbrand (arm) wrote: >> >>> On 2/4/26 20:48, Zi Yan wrote: >>>> >>>> >>>> What do you mean? Changing memory failure code to only handle large_= rmappable? >>>> large_rmappable is a folio flag, memory failure code should see such= >>> >>> Did you mean "should not" ? :) >> >> Yes. >> >>> >>>> non-folio but compound things to begin with, IMHO. >>> >>> I would say that we could right now reject in memory failure code any= compound pages that do not have PG_large_rmappable set. >>> >>> I have the faint recollection that we don't set PG_large_rmappable on= hugetlb folios yet, so they have to identified as well. >> >> Right. My patchset[1] is trying to add it, since hugetlb is used as a = folio >> in most places and large_rmappable is a folio flag. >> >> >> [1] https://lore.kernel.org/all/20260130034818.472804-1-ziy@nvidia.com= / > > Still on my todo list :) Sure. Wait for your input there. :) > >>>> >>>> I think we need to be able to tell between raw page (compound or not= ), >>>> mappable page (compound or not, especially for those used with vm_in= sert_*), >>>> and folio. >>> >>> We can't identify (small) folios just yet. We'd need another page fla= g for that (just like PG_large_rmappable), and we all know how that ends = ;) >> >> Yes, I am thinking about removing mapcount in struct page to achieve t= hat. > > On my todo list :) Stupid CONFIG_PAGE_MAPCOUNT that is still around and= stupid partial-mapping handling. > > I worked on this after LPC but was distracted by PTO :D > >> And only pages used for vm_insert_*() and folios need mapcount. > > vm_insert_*() won't need it for non-folio things. Only folios. We just = have to teach the zap code to also leave the mapcount of these non-folio = things alone. IOW, identify them when we map/unmap as "not folio" and not= touch the mapcount. Oh, that sounds great. I thought I would need to convert all drive code that does vm_insert_*() to use folio. Basically, I hit __folio_large_mapcount_sanity_checks() on _mm_id_mapcount when I moved _mm_id_mapcount and friends from prep_compound_page() to page_rmappable_f= olio(). IIUC, __folio_add_file_rmap() can just return if a non-folio compound pag= e is encountered. Of course, remove part needs to do the same. > >> Code >> uses vm_insert_*() on pages would probably have a struct mappable_page= >> with mapcount. > > I don't think we'll need a mapcount for them. Only for folios. > >> >>> >>> With Willy's work we'll be able to identify folios reliably. >>> >>> How to deal with that vm_insert_* crap, especially for non-folio page= s, is also future work based on that. >> >> I think it might the other way around. memdesc does not have mapcount,= >> if we do not have a separate struct for these mappable pages now, >> what do we use at memdesc time? folio? > > Folios will have mapcount related information, yes. Long term, memdescs= will for sure not have any. > > Real fun begins once we start messing with refcounts. vm_insert_*() wil= l be "fun" on non-folio things. Yeah, maybe we will refcounts for every used memdescs. But who knows. Best Regards, Yan, Zi